165 comments

Beating the Stock Market – With DIY Insulation

A Honda Odyssey with all seats including front removed, holds exactly 41 bags of insulation.

We learned that a Honda Odyssey with all seats including front removed, holds exactly 41 bags of insulation.

Well, I’m almost done rebuilding that house I have been working on since last fall. There was a big push through the electrical and insulation stages, and then I happily handed the place off to Agustin and his crew for drywall*, which is now in its final days as well.

Insulation was a big step for me, because I’ve been talking a big game throughout this project on energy efficiency. Sure, we have plenty of high-solar-gain glass on the South side, radiant heat, loads of thermal mass from interior concrete and brick features, and a metal roof to keep heat out in the summer. But all of this goes to waste if you don’t control the flow of heat between inside and outside – which means a tight air seal** and a lot of insulation where it counts.

Where it Counts

In most houses, the attic is the first place to seal and insulate. In the winter, your warm air rises and tries to sneak through the ceilings. In summer, the sun blasts down upon the roof and your ceiling becomes a radiant heater when it is least needed. And the area is especially large: in my long, flat house, ceiling is the dominant feature.

How Expensive is a Leaky Attic?

As explained in the old classic about Destroying your Heating bill, this depends on how fast it leaks, and what you pay for energy.  But using figures from where I live in Colorado is a good generalization, since it has a climate about midway between the cool and warm parts of the United States.

In the dead of winter, we might have an average temperature of 32F (0C) here. The days are warmer than that, but the nights are cooler, and in energy consumption it is the average that matters. If we maintain the interior of the house at 68F, it means we are keeping our house constantly 36F warmer than the outside.

Now comes the fun part: for every square foot of house that is exposed to the cold (or heat in summer), we have heat leakage. The speed of this heat leakage depends on the r-value of the walls and ceiling. Higher R-value is better. Skipping directly to the answer to the puzzle above, a 1000 square foot ceiling with just drywall (roughly R-1 insulation)** loses 36,000 BTU of heat per hour, 24 hours a day. That is about $260 per month of energy loss.

Adding another R-1 of blown cellulose, one of the cheapest and best kinds of insulation, cuts this in half. This amount of cellulose over 1000 square feet costs about 14 bucks. This is a silly theoretical example because that would only be about 1/3 of an inch of cellulose, an amount too small to apply practically. But it sets us up for the handy chart below. We’ll approximate the total annual heating/cooling cost by using my “Four Januarys” method, which usually works out well.

Insulation Return on Investment (ROI)

(values shown are per 1000 square feet of surface area)

R ValueExtra Cost to upgrade to this levelAnnual Heating CostAnnual Return on Investment for this upgrade
0$0 Infinite0%
1$14$1040Infinite
2$14$5203700%
4$28$260928%
8$56$130232%
16$112$6558%
32$224$32.5014.5%
50$252$21About 8%

Pretty interesting stuff: every time you double your insulation, your costs double and your additional lump of savings is only half as big. But even so, the math works out that you should still insulate your attic to at least R-50, because cellulose is so cheap. And this table is for a relatively moderate area of the US, a country with the cheapest natural gas in the world. In other countries (or  if you use oil or electric heat), this equation tilts even more in favor of better insulation. In other words, you can generally accomplish that almost-impossible feat of beating the stock market, just by insulating your own house. 

All this is why my friend Mike, who reads this blog, needs to get with the program and insulate the shit out of the leaky attic in his 100-year-old house before the next winter season hits – no excuses!

With all that theory out of the way, here’s what I actually did in my own house. Since I built my ceilings in vaulted style, there is no traditional attic. Just 14″ roof rafters with roof deck and metal roof screwed to the top, and drywall screwed to the bottom. With about 20 recessed light fixtures in this ceiling, there is lots of potential for air leakage. So I did this:

A cross section of my own roof. 2" of spray foam plus 12" of cellulose gives me almost R-60 total insulation!

A cross section of my own roof. 2″ of spray foam plus 12″ of cellulose gives me almost R-60 total insulation! With this method, you don’t need the plastic vapor barrier below the rafters.

Spray Foam Insulation

Here is my ceiling with 2" of the amazing foam applied.

Here is my ceiling with 2″ of the amazing foam applied.

When you want to go really hardcore on insulation, closed-cell spray foam is the way to do it. It is about 10 times more expensive than cellulose for a given amount of R-value, but it has advantages that nothing else can match: a perfect air seal, double the R-value per inch, and structural rigidity.

I started my roof insulation job with 2 inches of spray foam to seal the numerous gaps in the roof framing and create an airtight roof structure that needs no venting. I also had the foam contractor fill assorted cracks around the rest of the house, and spray all exterior joist bays in the crawl space. This was expensive ($2700 for the whole project), but it accomplished the most important part of insulating: stopping air leaks. You can buy do-it-yourself spray foam kits from Amazon and Ebay, but I found that hiring a local contractor ended up being about the same price (90 cents per square foot at 1″ thick), so the decision to outsource that task was easy.

Blowing your own Cellulose

Now for the most useful part of this article: contractors were bidding upwards of $3000 to blow the 12″ of cellulose insulation into that area beneath my spray foam. Cellulose is just shredded newspapers, so it is incredibly cheap. It is also incredibly easy to install. I calculated that about $700 of the stuff was needed in my place, which left $2300 to cover a day or two of labor.

Mrs. MM loads a 20-pound chunk into a homemade cardboard hopper (long story)

Mrs. MM loads a 20-pound chunk into a homemade cardboard hopper atop the blowing machine (long story)

Anybody with functional arms and legs can blow cellulose, so it is an ideal DIY task. You just follow these four steps:

  1. Buy the bags of stuff at the store. It looks like this, but the Lowe’s in my area has it at the ripoff price of $14.25 per 18-pound bag. The same stuff was $9.47 at Longmont’s Budget Home Center. Each bag gives you 20 square feet at R-38. I bought 71 bags for my house. Consider delivery, because the stuff is bulky.
  2. Rent the blowing machine. This is just a giant reversed vacuum cleaner with a hopper on top. Most building material stores will lend you one of these for free if you buy at least 10 bags of insulation.
  3. Round up your spouse and have each of you put on a good breathing mask. This stuff is dusty – too dusty for the crappy fabric masks, in my opinion.
  4. You climb up into the attic with one end of the firehose, while your spouse hangs around outside opening the bags and heaving them into the machine. Blow the light fluffy material evenly across your attic to at least a foot deep. Pro-tip: a good headlamp makes this easier. Use mobile phones to communicate (or a remote controlled power switch) so the attic person can turn the machine on and off.

 

Cellulose in a Vaulted Ceiling

Here I'm blowing cellulose into the vaulted ceiling, supported by fabric.

Here I’m blowing cellulose into the vaulted ceiling, supported by fabric.

My own job was a bit more complicated, since there is no attic. I picked up a huge roll of landscape fabric and stapled it tightly to the bottoms of the rafters with the help of a friend. Then I cut ‘X’-holes near the top of each bay and fed the blowing hose down to the bottom of the slope. Turned on the machine, and slowly filled each cavity from bottom to top. It was a bit of a pain, but in the end a rewarding day of high exertion and a worthwhile way to save a couple thousand dollars while learning a new skill.

To round out this (hopefully) well-insulated house, I caulked the interior faces of all multi-stud columns to reduce air leakage, used R-15 and R-19 batts as appropriate in the exterior walls, stapled up sheets of plastic vapor barrier across all walls before drywall, and glued up sheets of foil-faced rigid foam insulation in strategic areas where batts would not fit. I’m also adding a 1″ layer of rigid foam on the outside of the new wood framing before adding siding, which adds even more R-value and even more importantly will cut the thermal bridging effect of all the studs and headers.

If I have done my job right, we should end up with a house where the winter sun (plus the heat given off by the people and appliances) provides for most of our warmth needs, and simply opening the windows at night provides all of our summer cooling. But if I’m wrong and further tinkering is required, that won’t be such a bad outcome either.

 

 

* This is always a semi-religious experience for a Colorado housebuilder, as you typically get a word-of-mouth drywaller referral from another builder. An earnest Mexican guy comes out to appraise your project and gives you a very fair (yet very informal sounding) estimate. You’re not sure if you conveyed everything properly due to your respective lack of Spanish and English comprehension. But the next day, when you show up at 9am to make sure they are doing well, you enter a scene of blaring mariachi music, flying drywall panels and cutting tools, and a house that is already almost done. I’ve worked with every housebuilding trade and learned to do each of them myself over the years. But the speed and skill of Colorado’s Mexican drywall crews remains beyond my comprehension. Maybe it is an informal brotherly competition that arises just like in real sports, since hanging the sheets it is probably the most physical and athletic trade. Either way, these guys are the superheroes of construction.

**Airtight houses still need ventilation. In the olden days, houses were so leaky that you’d get more than enough fresh air just through the cracks. Modern houses fixed the leaks, but that caused indoor air to become stale: the various smelly and toxic gases from products, cooking, and humans build up and you end up with a building that can actually make you sick. In my climate, you leave your windows open for 6 months of the year, which leaves the 6 cooler ones to deal with. I plan to vent out the house during daylight hours (warmer), leaving it more sealed during winter nights.  Part of the strategy involves these silent Panasonic Whispergreen bath fans, which can be set to run at a very low rate without you hearing them.

*** Sounds pretty ridiculous, but it is not far off the truth for my new house when I bought it. It had drywall ceilings, and a 1″ thick layer of sawdusty wood fiber batts from the 1950s (labeled “extra thick!”). Then a vented attic right above. And even that was poorly installed with no vapor barrier and lots of gaps and holes in it. Net effect might have been R-2 or 3. I cringe when imagining this home’s previous 55 years of energy bills.

  • Mark Ferguson May 1, 2014, 10:12 am

    I always thought that spray foam looked awesome. I never really saw it much until I started watching Holmes on Homes show where he always used spray foam. I just met a builder in the Greeley area who uses spray foam on all his new houses. Cool article and break down of the costs.

    Reply
  • Joe Carnation May 1, 2014, 10:23 am

    A word of caution about cellulose insulation – it’s soaked in flame retardant, which is fairly toxic and will eventually turn up as tiny dust particles that get inhaled and absorbed through the skin. Try to use fiber glass or other forms of insulation whenever possible.

    Reply
    • Mr. Money Mustache May 1, 2014, 10:33 am

      I would disagree with the recommendation for fiberglass – it requires much more energy to produce, and tiny glass filaments are even worse for your lungs than borax and wood fiber. Besides, neither one will be present in significant quantities in the air you breathe, because you seal it in behind the drywall. More on the comparison here: http://www.healthyhouseinstitute.com/a-688-Cellulose-Insulation

      You could also use denim batts or something else, but I think everything needs to be fireproof to be used as insulation these days.

      Reply
      • James May 1, 2014, 11:10 am

        The only question I would have is whether the landscape fabric is fire retardant. I assume you checked that out, though, and to be fair there is a fairly small amount of that material — if it gets to the point of being ignited, many other safety measures must have already failed.

        Reply
      • Kenoryn May 1, 2014, 12:17 pm

        A friend recently installed this stuff in his new addition.
        http://www.ecobatt.us/eco_batt.html
        Looks like a good alternative to fiberglass and is apparently cheaper as well.

        Reply
    • Ms. Must-Stash May 2, 2014, 5:50 am

      We have a neighbor who is an energy efficiency auditor (and who did a great job auditing our house). He highly recommends cellulose because he says it performs better in extreme cold temperatures than fiber glass does.

      As MMM says, just be sure to use high quality breathing masks during your DIY installation and make sure everything is sealed up well – then there should be no issues with dust particle exposure over the long term. I can also personally vouch for this – we took our attic from R-12 or so to R-50 last year with cellulose – it’s great stuff!

      Reply
    • Evie July 10, 2014, 12:51 pm

      Actually, most cellulose is treated with boric acid, which is safe (you can even eat it!) And you should be more wary of blown fiberglass. Look up the manufacturer’s certificate with the safety information. I recommend Applegate cellulose Insulation.

      Reply
  • anotherengineer May 1, 2014, 10:27 am

    A very timely article as I will be blowing cellulose in my attic this month, though it is only 2 1/2 feet high at the ridge making it a tight fit. Any pointers? To build on MMM, in cold climates, such as up here in Alaska, insulating crawlspaces and basements is more critical due to foundation walls conducting away heat to frozen ground, which is why I put R-38 batts on the walls and R-30 on the periphery floor. Before taking on energy projects, research tax credit and rebate programs in your area. Alaska has a program involving a before and after energy audit and reimbursing up to $10k of your costs.

    Reply
    • Mr. Money Mustache May 1, 2014, 10:45 am

      To do that low-pitch roof, I would probably use the same technique I used for my vaulted ceiling: Start with the hose poked way down into the far corner, then turn on the blower. Slowly pull back the hose and leave a trail of nicely-distributed cellulose that fills up the whole space. This can be a tradeoff, since it blocks attic ventilation at the eaves. But with gable vents you could still get away with it, and I personally feel good insulation is even more important than roof venting.

      Reply
      • PatrickGSR94 May 1, 2014, 10:51 am

        With any normal ventilated attic, you need to use vent baffles on the underside of the roof decking to allow air to still get in from the soffit vents up to the gable/roof vents. Gable vents alone won’t do it, at least not by code.

        I’ve heard that you really only need a baffle every other truss/joist bay, but I personally would probably do them on every bay. They’re super-cheap (maybe $1, less than $2 each), just thin plastic or styrofoam pieces that you staple to the bottom of the roof deck in between the framing.

        Reply
      • Matthew May 1, 2014, 11:40 am

        Speaking of the eaves, would it have been possible to fill your bays after drywall installation via the exterior upper eaves? I think your approach is better for new construction because the landscaping fabric allowed you to see when the bay was full, but maybe approaching it from the exterior eaves might work well for existing construction?

        Reply
  • Bruce May 1, 2014, 10:28 am

    Yea Mike, get with the program or Mr. MM may be over to do it himself!

    Great post. So many ways to beat the stock Market if you pay attention to $ leakage and how to stop it.

    Reply
  • Paul Silver May 1, 2014, 10:29 am

    This is a job I want to tackle this year. I know our insulation isn’t as good as it could be, and energy bills are only going up.

    A friend suggested we get a carpenter (‘chippie’ over here in the UK) to lay an extra two layers of rafter-style planks in the loft first, criss-crossing over the existing rafters. The cellulose then fills in all the gaps, and you can still board over the top and use it for storage. You can get little stands that would do the same job, but they work out more expense than using good old timber.

    Reply
    • Alistair May 2, 2014, 1:54 am

      This is a good solution, going over the rafters prevents cold bridging. Remember to seal all the gaps on the ceiling at the edges, as air movement will draw heat up

      Reply
  • PatrickGSR94 May 1, 2014, 10:38 am

    Pro-tip for those blowing insulation into a normal vented attic space. If you have trusses, go around measuring your finished insulation depth at several points on the trusses, and make marks with something like bright orange spray paint. That will give you an easy indicator of how high the insulation needs to be from a distance away.

    Or if you have more traditional ceiling joists and roof rafters, cut some thin wood pieces, like paint stir sticks, to your finished insulation depth, and attach them to the side of the ceiling joists in several locations.

    This is also something I’ve been needing to do to my house forever. Very poorly built in 2003, with barely 4 to 6 inches of insulation in the truss-framed attic, and 6″ batts above the vaulted living room area.

    Reply
  • Pretired Nick May 1, 2014, 10:41 am

    I’ve got to look into the spray foam again. A few years back when I tried to have that done, I couldn’t find anyone doing it locally. I bet there are a few more companies doing it now that it’s been around a few years.

    Reply
    • Mr. Money Mustache May 1, 2014, 10:47 am

      Anywhere within an hour radius of Denver (and maybe other places too), RG Insulation does the spray foam around here at a good prices and quality level.

      Reply
  • Chattanooga Cheapster May 1, 2014, 10:42 am

    A seperate home energy question.

    Have you ever considered Solar Heating Panels? I’m considering buying or building some, but can’t really find the ins and outs of them.

    Reply
  • TheDude May 1, 2014, 10:46 am

    MMM would you mind giving me the name of the company you used for spray foam.

    Also (for those in northern CO) if you need enough bags of it. It maybe worth a drive to Cheyenne as they have a Mendards.

    Reply
  • Danny May 1, 2014, 10:48 am

    Lowes has ripoff prices, as in, too high? Looks like they might have lowered the price in response to your article! It’s $9.32 per 19 lbs now.

    Reply
    • Mr. Money Mustache May 1, 2014, 10:58 am

      Good catch, Danny – they vary their prices around the country, so your Lowe’s is charging the correct price, where mine (zipcode 80504) is ripping people off :-)

      Reply
      • Mark S May 1, 2014, 1:54 pm

        Your Lowe’s link shows it at $6.55 in Minnesota!

        Reply
        • Mr. Money Mustache May 1, 2014, 2:50 pm

          Whoa! That is some serious difference around the country. That could have saved me $210! Maybe the manufacturing plant is nearby … any other people seeing different prices?

          Reply
          • RMD May 1, 2014, 3:54 pm

            $5.99 in Shawnee, KS

            Reply
            • Rupert May 1, 2014, 6:47 pm

              Same in Michigan.

              Reply
              • Adam May 2, 2014, 7:17 am

                $5.99 in Ft. Wayne, Indiana, too.

          • Joe V May 1, 2014, 3:59 pm

            Yep, $12.14 in Ridgeland, Mississippi! Yikes!

            Reply
          • MCF May 1, 2014, 4:43 pm

            $8.48 in San Diego.

            Reply
          • Stacy May 1, 2014, 5:19 pm

            $12.15 in Ithaca, New York

            Reply
            • CTY May 1, 2014, 11:48 pm

              $9.46 in Bakersfield CA– but it says up to $4,500 rebate, could not view the details of the rebate though.
              If Lowes is a rip off for this stuff in CO that may be true around the country (despite a lower price); did anyone look for the rock bottom in their area? I checked a couple around me & they run real close to the same. I’d go with Lowes because they give 10% discount for military (tax + a little).

              Reply
          • Joseph May 2, 2014, 12:57 pm

            The pricing on lots of different types of insulation will be different across the US. Sometimes this might be because the distance from the plant increases freight charges and this effects the price but often the reason is simply that they have determined that the market in certain areas is better and they can charge more there.

            (I work for an insulation distribution company)

            Reply
          • janice Z May 2, 2014, 3:29 pm

            $5.44 in Chicago suburbs (Westmont, IL)!

            Reply
          • Bev Pelletier May 5, 2014, 12:34 pm

            12.33 in the Philly suburbs!

            Reply
          • Mark May 20, 2014, 9:16 am

            Looking online, our local Budget Home Center in Longmont is now charging $13.97 (as of May 20th 2014): https://store.budgethomecenters.com/inet/storefront/store.php?mode=showproductdetail&product=-1&link_id=-1&link_itemcode=1229749&category=

            Bummer.. need to get around 70 bags of this stuff.

            Reply
      • Rob May 4, 2014, 1:19 pm

        The Lowes pricing can be used to your advantage since most of these stores have a price matching policy, where the will beat a competitor’s price by 10%, if it is not a sale price.

        Reply
  • Andres Salomon May 1, 2014, 11:07 am

    Looking at your roof diagram, I’m curious – have you accounted for thermal bridging?

    Reply
    • Andres Salomon May 1, 2014, 3:26 pm

      I guess to provide additional details; I just read this blog post: http://www.buildingscience.com/documents/insights/bsi-063-over-roofing . Pretty amazing picture there of the melted snow showing where heat is escaping his roof. My concern would be MMM’s roof rafters acting as a thermal bridge, bringing your R60 down to something much lower (but still pretty good!). Though maybe the engineered wood is designed to counteract that? I really don’t know.

      Reply
      • Money Saving May 2, 2014, 11:09 am

        Ha – I’ve noticed that on my neighbor’s house and never really put two and two together. It seems like most houses with minimal attic air space would have this type of issue where the wood can conduct the heat. I wonder what the R value is of a roof joist?

        Reply
    • Nathan May 3, 2014, 9:13 pm

      Joe Lstiburek is great. Here’s a video he did that mustachians would appreciate: https://www.youtube.com/watch?v=rkfAcWpOYAA&list=WLK6yYMFQDwPggKN0uGNn3rg&index=3

      One problem I see with MMM’s roof structure is the double vapor barrier (spray foam + planned 6 mil poly before drywall.). In the event that water ever does get into the structure it won’t have a viable way out and will rot. Better to have just one vapor barrier.

      A layer of foam insulation seems to be standard directly under the roof deck now. It’s easy to install, adds another 20-30 R value, and will help keep condensation from forming on the sheathing.

      Reply
  • Peter May 1, 2014, 11:08 am

    Just did this myself in December, ended up using 81 bales of the stuff (I paid 20$ for the delivery haha). Was quoted 3000-5000 from a few contractors. Did it myself for about 1600 all said and done.

    The month over month comparison
    December 161 therms, Average Temp 12
    Janurary 142 Therms, Average Temp 9

    Look forward to see a year over year comapison.

    Reply
  • Stephen May 1, 2014, 11:12 am

    You should check out a concept called passive house which starting to catch on over here in Europe. Basic idea is that the house is so air tight and has so much insulation that a heater is rarely needed, most just use a small electric stand alone heater in the winter, if it gets really cold.

    Reply
    • Mr. 1500 May 1, 2014, 11:26 am

      Stephen, we have these in the states, but they are far and few between. Sadly, it’s probably a symptom of cheap energy.

      Anyway, here is an example of one that I used to live near: http://articles.chicagotribune.com/2013-02-15/classified/ct-mre-0217-passive-house-20130215_1_passive-house-river-forest-home-efficiency

      Reply
    • Willis Montgomery III May 1, 2014, 1:37 pm

      Passive homes are definitely the way to go. That said for the majority, retrofitting will be the only way to improve things on a time scale that makes sense for most home owners now. I would love to tear down my 1963 cape and build a passive house. From what I have read, building a similar sized passive home would be about 300,000k. My current home/land is only worth 220000, so will I save 80gs over the time I live there? Not sure, especially with lost investment opportunities. Crunching those numbers would be interesting though. I’m guessing with deep energy retrofits, one is better off modifying the existing structure. If anyone has actually done these numbers or something similar, I’d be interested to know how it worked (or is working) out. One thing seems certain, building homes the old way with wood 2x4s is just silly. SIPS and ICFs seem like the way to go. Thank you.

      Reply
      • biscuitwhomper May 2, 2014, 11:15 am

        Absolutely! I expect that most new homes will be SIPS 20 years from now. Again, this only applies to new construction, but for anyone building new, give SIPS a long, hard look. It has been out long enough that the bugs are worked out, assuming you have a good, factory-licensed installer helping you.

        Reply
    • Andrea May 8, 2014, 1:08 am

      Is mold not a concern? How does the house “breathe”?

      Reply
    • 205guy May 20, 2014, 2:28 am

      I recall at least one MMM article about thermal mass in concrete counters, etc. and he seems to have remodeled this new house for solar thermal heating.

      For airflow issues, he bring up the topic himself–open a window on warmer winter days. But there is an alternative: http://en.wikipedia.org/wiki/Heat_recovery_ventilation

      Reply
  • Jordan Read May 1, 2014, 11:15 am

    Landscaping fabric…now that is a cool idea. I was curious how you were planning on using cellulose with your ceilings and that pesky gravity stuff. I didn’t think you would wait until it was installed, but then I thought that maybe you had some type of mad genius plan, like a hinged roof that opened so you blow from the top down, or some type of vents to outside that go down each channel. But landscaping fabric is cool, too. :P

    Reply
  • Clint May 1, 2014, 11:17 am

    I want to add insulation in my attic this year. Can I blow cellulose over the existing fiberglass or would I have to stick with one kind of insulation for any reason?

    Reply
    • Peter May 1, 2014, 11:59 am

      You can blow it over existing fiberglass insulation. But you still need to air seal all cracks and penetrations that are under the fiberglass.

      Reply
      • TomTX May 2, 2014, 3:30 pm

        Well, sealing penetrations isn’t totally mandatory – it’s definitely a good idea, and I spent some time in my attic today with a can of (fire rated) spray foam chasing penetrations.

        You can definitely put cellulose over fiberglass – fiberglass is typically over-lofted by contractors anyway. Double fluffed, its insulating value plummets, but it costs the contractor half as much in materials. Allows too much convection. The cellulose will seal it in reasonably well.

        Reply
  • Mr. 1500 May 1, 2014, 11:23 am

    I love cellulose. With every house we have ever owned, almost the first thing we do is load the back of the Honda Element up with bats and fill our attic.

    One incredible benefit of it over fiberglass is it’s superior noise absorption properties. I saw this demonstration in person a couple years ago: https://www.youtube.com/watch?v=_AzxowD6if0

    Our current home had no insulation. After we blew cellulose into the walls, the sound of passing cars, excited children and barking dogs faded away.

    Reply
  • ERIU May 1, 2014, 11:33 am

    Thanks for doing this! I’m moving into a 1947 home in Wisconsin, and this is one of our top projects! I am a busy Mom with little kids, work from home, and the hubs travels a lot, so I’m enormously grateful that the you’ve done the rough calculations here for us!

    Reply
  • ELE May 1, 2014, 11:33 am

    Do cellulose batts exist?

    Our walls are plaster/lath and pretty cold in the winter. Short of cutting holes in the walls, is there any other way to get insulation in there?

    Reply
    • joe May 1, 2014, 3:42 pm

      Look at roxul. Mineral wool bats. Can buy then at Lowes home depot. Easy to work with.

      Reply
      • Chris May 5, 2014, 1:29 pm

        Just checked out Roxul, looks interesting, wouldn’t that require the walls to be removed? i also have plaster and lath, with the wall between me and my neighbor (its a twin house) being concrete.

        Reply
  • DIYMark May 1, 2014, 11:50 am

    Excellent post. I really enjoy the construction stuff and hearing about your progress. Keep them coming. There is an excellent Fine Home Building article on “Flash and Batt”, meaning pairing up spray foam and batt insulation (March 2011) for those that want to dig deeper. Compares costs versus efficiency of insulation strategies.
    I wondered if you followed up your leak abatement diligence with some true numbers. Have you performed a blower door test before/after? Let us know how you did.

    Reply
    • Mr. Money Mustache May 1, 2014, 2:56 pm

      Yeah! I will do one of those door tests on the finished product. I could’t do it “before”, because the house had huge open gaps to the outside before this foaming and before that it had no roof at all – so you wouldn’t have even considered heating it before this stage of the work.

      Reply
  • KMB May 1, 2014, 11:51 am

    I see an air duct in the closed cell foam picture. Is it for bathroom exhaust? Or do you have some kind of supplemental forced air system in addition to your radiant heat?

    Reply
    • Mr. Money Mustache May 12, 2014, 8:28 am

      That’s for my over the range vent hood. It was a tricky venting situation, since the range is on an interior rather than exterior wall.

      Reply
  • Dean May 1, 2014, 12:01 pm

    We just had our {state}-saves contractor in to give us a break down on what it might cost to better insulate our house (attic has old, compacted insulation. He said it was giving me an R 10 and needed “help”). The great thing about it is that they’ll pay for the material and the contractor to ‘install’ it. The down side is I have to remove my existing floor boards (attic space is used for storage) and the old insulation from the 1960’s. I figure while I have the space open, I’ll build up the existing space by 8″, allowing the contractor to blow in almost 18″ of insulation. My house struggles to stay at 65 in the winter, I cannot wait to see what this will bring :)

    Reply
  • Big Guy Money May 1, 2014, 12:07 pm

    Very interesting. We have a house built in 1927 currently and if we were going to stay permanently, we’d look into additional insulation (I was dismayed when we renovated our kitchen and I found tar paper as the only insulation in the walls. I live in North Dakota). As is, we’ll probably end up moving one more time within several years. I enjoy the DIY articles – extremely well done.

    Reply
  • insourcelife May 1, 2014, 12:16 pm

    Our house was built in the late 90s and we have a finished room in the attic (3d floor). Around it on the floor (i.e. open ceiling joists for the second floor) there is some type of blown in insulation sitting on drywall that is the second floor ceiling. The insulation is about level with the top of the ceiling joists. The roof rafters above are not insulated – just OSB and shingles. The roof is vented. Would it be beneficial to add insulation on top of that and if so how much? Trying to see if this is something I can DIY and if it’s worth it from the cost/benefit standpoint. Our temperatures are probably similar to Colorado but with milder winters and hotter summers.

    Reply
    • PatrickGSR94 May 1, 2014, 12:19 pm

      If your insulation is less than 12″ thick then yes you can benefit. Most likely your ceiling joists are 2×6 which means the insulation if level with the top is less than 6 inches, or less than R-19 which has been prescribed as the minimum for decades now (today most recommendations are at least R-30).

      Reply
  • Rob May 1, 2014, 12:18 pm

    This seems to be one area that’s often overlooked in the rent vs buy toss-up when considering a new home. Particularly frustrating in areas with housing bubbles and generally poor quality insulation (e.g. London UK). I have to make do with draft blockers and silly things like bubble wrap on the windows (which actually works quite well!)

    Reply
  • mjmphx May 1, 2014, 12:34 pm

    Hey MMM, thanks for the excellent article.

    I’m in sunny Phoenix, AZ, and have been considering the spray-on radiant barrier on the underside of my roof (a white-sand tar shingle, conventional ranch-type pitched roof, decent amount of room to work in the attic). I’ve currently got about 4″-6″ of blown fiberglass covering the ceiling, so that’s not terrible (though I’ve done a lot of work in the attic, and messed up the insulation some). Any thoughts on the cost-benefit of radiant barrier? It’s attractive to me as a heat-transfer guy (I’m in aerospace and it’s shiny, also a simple idealized thermal model said it cut heat flow by half or so), but I have little experience with longevity of aluminum-in-polymer-on-wood systems. Do you (or any other readers) have experience with that? The material is about $300 for my approx. 2000sqft roof (energyefficientsolutions.com – LiquidFoil), and the sprayer would be a rental, I’m figuring another $100 or so for that. We also may not be in the house that long, but that’s not a very sustainable way to think.

    Cheers,
    MJM

    Reply
    • Joseph May 2, 2014, 8:44 am

      As long as you keep the radiant barrier clean (no dust, webs, etc), it should last forever.

      Reply
    • TomTX May 2, 2014, 5:29 pm

      If you get a decent paint, aluminum-in-polymer-on-wood should last for a long, long time in your attic. 50 years+

      Reply
      • mjmphx May 6, 2014, 3:24 pm

        Thanks guys, I’ll start lining up materials and we’ll see how it goes!

        Cheers,
        MJM

        Reply
  • LittleMissCuz May 1, 2014, 12:52 pm

    We are going to look into insulating our house this year .. we have a cape .. no attic and very small space near the dormers. I have no idea how we are going to get in there other than trashing the ceiling drywall in the rooms upstairs but even still, if we make a hole in the drywall we will only be able to blow insulation into that baffle .. will we have to make holes all across the room?

    Reply
    • Mr. Money Mustache May 1, 2014, 2:52 pm

      Yeah, that is the traditional method: one hole in each joist bay, feed in the material, patch the hole. But for existing walls, you usually blow in heavier material so that it can settle down to the bottom. Not sure what that stuff is called as I’ve only used fluffy cellulose.

      Reply
      • TomTX May 2, 2014, 5:32 pm

        It’s also cellulose, they just use a higher-powered blower. Feed the hose through the cut hole as far as possible. Blow until it bogs down, withdraw about a foot, repeat. Packed cellulose.

        Reply
  • WageSlave May 1, 2014, 12:53 pm

    I read that the propellant used to deploy closed-cell foam is full of HFCs and terrible for the environment. While it’s great for sealing and insulating, the irony is that the environmental damage done by the propellant will never be offset by the HVAC energy savings.

    I could be wrong; this is based on hearsay from having lurked on green building websites and forums. Not to poo-poo on your project, but others concerned with their environmental impact might want to read up on this before jumping in with closed-cell foam.

    IIRC, I believe open-cell foam, while not as “good” as closed-cell, uses a water-based propellant and has basically no environmental impact.

    As a side note, I read that lots of people are wrapping their houses (new construction or “green” rehabs) with rigid foam board (e.g. EPS/XPS/ISO). There are companies that reclaim this stuff from demolitions, and sell it dirt cheap. You get the MMM-approved benefits of being green (recycling and lowering heating/cooling energy usage) and frugal (buying used is almost always cheaper).

    Reply
    • PatrickGSR94 May 1, 2014, 1:32 pm

      There are a number of closed-cell foam products today that use water-based or other environmentally-friendly blowing agents. From the Demilec Heatlok Soy 200 data sheet: “HEATLOK SOY® 200 PLUS is a two component, closed cell, spray applied, rigid polyurethane foam system. This product uses recycled plastic materials, rapidly renewable soy oils, and the blowing agent has zero ozone depleting potential.”

      http://www.demilecusa.com/tech-library/heatlok-soy-200-plus

      Reply
  • Done by Forty May 1, 2014, 1:02 pm

    MMM, I have the same sort of home with no attic, and only a small amount of space between the low pitched roof and the ceiling. Would the process be the same, in which we simply cut into the ceiling every 2 feet or so?

    I’m not that keen on cutting into the ceiling if I can avoid it. Would we be better off trying to widen the old vents under the soffits? They’re just circle cut outs into wood, with some screen material on the backing. They look a little too narrow for a hose to blow in the insulation, but with a smaller hose, we potentially could make them work as is…

    Reply
  • phred May 1, 2014, 1:12 pm

    Does blown-in cellulose settle over time, thereby causing the R-value to shrink along with it? Will it need fluffing back up every ten years or so?

    Reply
    • Willis Montgomery III May 1, 2014, 1:24 pm

      I had this done in my house in 2009. Compared to the thermal solar for domestic hot water (2005) and the PV solar array(2009), the blown in insulation had the fastest payback. The blow in insulation cost about $6000 for my 1400 sf 1963 Cape style house. After Massachusetts tax credits and Federal tax deductions, my final cost was $1500. That is, I never had to come up with the 6k, just the $1500 when the guys finished the job. Living on the over priced craptastic vacation nightmare land of Cape Cod with it’s 6 month depressing winters heating with oil and a bit of wood, the insulation paid for itself in about 2 years. It’s been 5 now since the install and the house is still warm and toasty. I used a borrowed IR camera and I saw no noticeable difference from the images the installer took 5 years before. So, if there is settling, I have not seen it. One recommendation: have your house sealed and insulated before doing PV or thermal. Insulation and sealing is super low hanging fruit. The biggest savings are definitely in transportation though. my 12 mile round trip bicycle commute that I do rain/sleet/snow/ice etc saves about 130 a month.

      Reply
      • littlemisscuz May 1, 2014, 6:12 pm

        How did the tax credits work? Did the company help in directing on how to apply for it? I live in CT .. how can I find out what my state offers?

        Reply
        • CTY May 1, 2014, 11:58 pm

          Your energy provider usually knows about all rebates & tax credits.

          Reply
        • Willis Montgomery III May 2, 2014, 6:08 am

          dsire.org is a good place to start. Rise engineering out of RI did the work. Great guys, I was pleased with the work. They did all the paperwork for the incentives.

          Reply
    • TomTX May 2, 2014, 5:35 pm

      It settles some, but it’s typically not a big deal. You can blow more if you like. Better than fluffing.

      Reply
  • WageSlave May 1, 2014, 1:15 pm

    That landscape netting is a clever idea. Do you know what the max weight it can sustain is?

    I’ve been reading and lurking on several green building websites, and some people with traditional attic space (i.e. a fair amount of volume), just go crazy with the cellulose. And why not, right? The problem becomes, at some point, the weight of the cellulose is too great to be supported by the drywall.

    So maybe the landscape netting (or something along those lines) is a good cheap way of adding structural support to the attic area so you can blow in a ridiculous amount of cellulose.

    Reply
    • Weegie5 May 2, 2014, 7:53 am

      I wouldn’t think the landscape fabric adds any structural support. Ultimately the weight of the cellulose (and drywall) is supported by the connections to the trusses (or studs in walls). If those connections (typically quantity & spacing of drywall screws) are of sufficient strength, there won’t be a problem. If it gets to the point of compromising the structural integrity of the trusses, you’ve probably gone waaaay overboard.

      A contractor named Matt Risinger has posted some great videos on his YouTube channel regarding air sealing and well insulating houses (anti-mustachian features of the houses notwithstanding). Here is one: https://www.youtube.com/watch?v=q4UrjGhB9T0 As you can see, there are some specialty products to hold in the insulation fill other than landscape fabric. OC’s is in that video; CertainTeed makes one too: http://www.certainteed.com/products/insulation/fiber-glass-insulation/317369

      Reply
  • Grant May 1, 2014, 2:08 pm

    Be very, very careful about installing a vapor barrier behind drywall. These barriers are designed to let walls dry either from the outside in or from the inside out (depending on climate) – but not both at the same time. Putting vapor barrier under the drywall is counter-productive if you already have vapor barrier installed on the outside of the house’s sheathing (which you almost certainly do, living in Colorado). The inside layer of vapor barrier will actually cause moisture to be trapped inside the wall cavity and will cause rot, mold, and other nasty stuff. I would suggest you speak to a building specialist in your area before you finish your drywall work.

    Reply
    • Ammon May 1, 2014, 2:43 pm

      Your point about avoiding a moisture sandwich is a good one. However, house wrap is an air and water barrier but not a vapor barrier, i.e. your walls can still dry to the outside. More info here:
      http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/brands/water-barrier-systems/products/tyvek-homewrap-superior-house-wrap.html

      Reply
      • Weegie5 May 1, 2014, 4:06 pm

        MMM didn’t specify whether his “plastic vapor barrier” was a vapor control layer like Tyvek or just plain old plastic sheeting. For his sake, I certainly hope it was Tyvek (or similar).

        Joe Lstiburek and Building Science Corporation are my go-to resource for knowledge on topics like this. http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers/

        ~James

        P.S. The arid Colorado climate is one of the more forgiving places if it was just plastic sheeting.

        Reply
    • sigpop May 1, 2014, 2:45 pm

      This problem bit me in the arse in our basement. I hung plastic up before studding out the walls. We have a bump-out and an access panel for the water meter. When I took the panel off I noticed some black mold forming behind the plastic. Now I’m in a jam: do I rip down walls or keep it sealed up?

      Our house is relatively new and we don’t have any water problems in the basement (knock on wood) even though we don’t have a sump pump. We do run a dehumidifier on occasion in the spring and fall. I did paint the walls with UGL Drylok before putting up walls.

      In hindsight I wish I would have not put up plastic, rather pull the studs an inch or so off the wall and cut in some vents to allow for easy moisture exchange. I only have two offices with walls so at least it isn’t the whole basement.

      Reply
    • eric May 1, 2014, 3:15 pm

      Here is an excellent explanation about why using plastic as a vapor barrier is a bad idea:
      http://www.greenbuildingadvisor.com/blogs/dept/building-science/what-happens-when-you-put-plastic-vapor-barrier-your-wall

      Reply
  • Golden May 1, 2014, 3:07 pm

    Nice project! Did you make any allowances for airflow around the recessed lighting? Or is it not an issue with fancy efficient lights?

    Reply
    • Bird May 4, 2014, 3:26 pm

      I’m wondering the same thing about recessed lighting. In my very limited experience I see IC recessed lights with regular fiberglass batt insulation.

      Reply
  • CincyCat May 1, 2014, 3:07 pm

    Great article! Any suggestions for insulating a finished attic in a space cape cod style home? Nothing I’ve found online sounds like it would work.

    The roof rafters appear to be only about 8″ (house was built in the 1940’s), and there is currently R-8 insulation that is stuffed between the rafters & the drywall that makes up the ceiling & walls of the rooms. (The wall insulation is stuffed between regular 2×4 studs, and is open to the unfinished part of the attic that we use for storage.)

    We know that this project would likely require a total gut & re-do of the space, but any tips from those who have BTDT would be greatly appreciated!

    Reply
    • Weegie5 May 2, 2014, 7:40 am

      Sure, a gut renovation is the best way to do it. Another approaches that can provide the energy savings without the entire reno would be to use a hole saw to cut into each stud cavity. From there you could blow in additional loose-fill fiberglass, mineral wool, or your favorite flavor of cellulose. Or you could pay a pro to come in a fill the voids of each stud cavity with a spray foam. The foam will likely provide much better air sealing than any loose-fill.

      When the filling is done, go back and patch & paint each of the holes. Keep in mind that this part will probably take at least as much time as all the cutting & filling.

      ~James

      Reply
  • Eric May 1, 2014, 3:48 pm

    Good job!

    It’s good to see the closed cell spray foam on the underside of the roof deck. That is one of a few code approved and building science proven ways of insulating an unvented cathedral ceiling.

    Another way to do this, which may have been more or less cost effective since you did your own roofing, is to tape the seams of the roof deck to create an air barrier, then cover the roof in 2 or more layers of rigid foam. The advantage is the structural roof deck stays warm and does not suffer from condensation and thermal bridging by the roof rafters is avoided. There are several places in Denver, and many others across the country, that have reclaimed foam board from commercial reroofing projects and about a quarter the price of new material.

    For other people that are interested in building unvented cathedral ceilings here is a good link:
    http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling

    And this is the holy grail of all building science information (Joe Lstiburek is the go to guy for all things building science related)
    http://www.buildingscience.com/index_html

    Reply
  • BarnacleBill May 1, 2014, 3:51 pm

    To those asking about Cape Cods or low roofs with small spaces: I had an 1899 first-floor (of 2) flat in San Francisco insulated with blown cellulose so I wasn’t heating the upstairs neighbors all the time. I had it professionally done. The contractor needed to drill three 2″ diameter holes in each joist bay. The building is about 18 feet wide. So there was a row of holes across the ceiling, which they filled and patched. Then I painted the ceilings. So it can be done. Apparently the pros fill a hidden space by pushing the hose in until it hits the far wall, then slowly pull it out as they’re blowing, and they listen to the sound and can feel the pressure in the hose to determine how much/how thick they’re blowing. It probably takes some practice but could be done by an amateur.
    Attic insulation should be the first thing you do to an old house, followed by air sealing and windows, then wall insulation comes in a distant last. Warm air wants to rise through the attic, not radiate out through the walls. When it’s rising, it’s sucking cold air in through walls and windows. But if you stop the rising air, you don’t get as much cold air being pulled in.
    I always laugh when I ride around Seattle and see houses with solar panels on the roof and old double hung single-pane windows. Solar panels might make you feel good about yourself but they’re pretty far down on the chain of cost effective energy savings. Insulation is at the top.

    Reply
  • Oh Yonghao May 1, 2014, 4:21 pm

    In January we had insulated our first house. Make sure that you get enough tubing with your blower to do the job properly. When I got the free rental from Lowes they only had one tube which was not enough to get to the back of the attic and instead I had to bring up some brooms and sweep the insulation over. In winter we found that using a van to house the blower worked very well, rented one from U-Haul for about $25. We had only lived there for 2 weeks before doing the insulation so we have no numbers to compare. I still see some areas where we could throw a few more bags up into it but we’ll have to see how the summer goes right now.

    Someone earlier recommended using bright orange paint or something similar in the attic, which I think is great. I’ve also thought of using string along with that so it is easier to see the level between marks.

    We kept our house at 65* and our heating bills were $105 for January and $100 for February. Now with April’s bill and nicer weather we have seen it fall below $50. Just running some numbers on here we look to be going from an average monthly cost of $61 in our 2 bedroom 700sqft 70’s duplex apartment to possibly $100 for total energy costs in our 2005 3 bedroom 1800 sqft house w/ 200 sqft finished garage with additional insulation added to the door. Roughly triple the sqft with less than double the energy cost. We hope to reduce this cost further during the next year where we’ll have a better chance to acclimate and will have grown in our knowledge of how to properly warm our house.

    A huge change to the garage was the door insulation, my bike is parked in the garage so I get to feel the temperature every day and it noticeably went from being in the mid 40’s to maintaining 50-60*’s after the door insulation went up. It has also stayed cooler now with the temperatures hitting mid 80*’s for the past couple days.

    Reply
  • GE Miller May 1, 2014, 5:14 pm

    I don’t know proper building codes (I’m sure you do), but how have you accounted for proper attic ventilation?

    Also – wouldn’t having wood sheathing with a vapor barrier on top and bottom (spray foam) create moisture concerns for the wood?

    Reply
  • Brian May 1, 2014, 6:22 pm

    Excellent post! I love your articles on energy efficiency.

    Out of curiosity, are you planning on using a film on your windows? They can reduce the heat gain in summer, reduce heat loss in winter, and reduce the thermal exchange.

    The book I’ve got says to do them even on new windows with Low E tinting built in. You can even install it yourself with some new skills. Would love to hear your thoughts on matter.

    Reply
  • HP12C May 1, 2014, 6:38 pm

    I’m not sure I understand the comparison to stock market returns. In the market, you (hope to) get your initial investment back plus whatever annual return Mr. Market gives you. With this project, you’re not likely to get your initial investment back on resale.

    Reply
    • Mr. Money Mustache May 1, 2014, 9:17 pm

      I’d expect that you should get more than your initial investment back in resale. You save documentation of the insulation you put in, receipts, pictures, and mention it in your brochure. You could also save your utility bills before/after.

      Just like a fuel-efficient car, an efficient house has higher resale value than a guzzler.

      Reply
    • PatrickGSR94 May 1, 2014, 9:31 pm

      I think the initial investment could be regained fairly quickly with the utility cost savings after just a few years, as compared to more standard construction.

      Reply
      • Sir Salty May 2, 2014, 6:05 pm

        Additionally, the returns MMM showed are on the expense side. Stock market returns (income side) are usually taxed at least at the long term capital gains tax rate. So best case 15%, which would push MMM’s 8% return up over 9%.

        Reply
  • Miketheaccountant May 1, 2014, 7:04 pm

    Great post! Here’s an even better deal for Massachusetts and Connecticut residents: Call Next Step Living and have this work paid for by the utilities. Subsidies range from 100% for air sealing to about 75% for cellulose and other weatherization work. Out-of-pocket costs for a typical $2,500 job are $600-$800.

    Reply
    • littlemisscuz May 2, 2014, 5:33 am

      Thank you for this .. I just scheduled an energy assessment with them.

      Reply
  • Zalo May 1, 2014, 8:35 pm

    What about using hay bails as insulation? They seem to be trending in sustainable house building; they are compostable, inexpensive, and I’m assuming they insulate well.

    Thoughts?

    Reply
    • TomTX June 5, 2014, 7:15 am

      I think that I dont want a flammable, compostable insulation in my house.

      Reply
  • Nick May 1, 2014, 10:07 pm

    Did you use radiant barrier plywood on the roof deck? What are your thoughts on it either way?
    Planning a large addition to our home soon, looking at options to maximize energy efficiency.

    Thanks.

    Reply
  • Blake May 1, 2014, 11:10 pm

    R60!!!! Thats crazy….
    /Quick google search later/

    Ahh another case of American imperial measurements.
    R60 is about R10 in SI units

    In Australia the government recommended R values vary between R2-R5 with R6 being the the best batts commonly available.

    Im not sure the roi is good but i’ve been toying with going for polyester batts for my large roof cavity. Expensive but none of the issues with fibreglass.

    Reply
  • Alistair May 2, 2014, 1:58 am

    I would be a bit worried about interstitial condensation, did you do a calc on this? Particularly around he cold joists. It would have been sensible to use a polythene instead of the landscape fabric, to prevent moisture getting into the void. But all non vented systems with cold bridges are sensitive to this.

    A foil and a second layer of drywall would be sensible in and rooms with high humidity like bathrooms and laundries.

    Reply
  • jestjack May 2, 2014, 3:07 am

    Thanks for the interesting article and the savings comparisons. It sounds like the project is coming along well. The only question I have is a lack of ventilation in the vaulted ceiling. I have pulled more than one job apart…especially bathrooms ….that didn’t have proper ventilation and as others have claimed mold, mildew and wood rot were present. Had a home inspector one time tell me …”the structure needs to breath”…Am I missing something? Did you do something else so that this is not a problem or factor? Please share this looks like a great project! Thanks again….

    Reply
  • Jake Peters May 2, 2014, 4:48 am

    I think I understand the phrase:

    I caulked the interior faces of all multi-stud columns to reduce air leakage

    But, if possible, a photo will really help me understand the air leakage aspect of the design of the columns.

    Also, I think the questions about “thermal bridging” are valuable, but not necessarily unique to MM’s roof, but any flat roof, where the roof deck itself is close to, or frequently supported by, the ceiling of the inhabited space (IOW, no trusses).

    Jake

    Reply
    • PatrickGSR94 May 2, 2014, 8:13 am

      Where you have door or window openings, there are typically 2 or 3 studs directly adjacent to each other and nailed together (king studs, jack studs, etc). You can’t insulate in between those, but there are typically small openings and cavities since the studs are never perfectly straight and flat. Caulking those gaps can help mitigate air infiltration in those areas.

      Reply
  • Kevin Harrell May 2, 2014, 5:23 am

    MMM:

    As someone who also just completely filled his attic with cellulose insulation (and am now reaping the cost benefits), I’m also someone who lives in a high radon area.

    As you may know, your county is a high radon risk area, and with that seriously low airflow (which admittedly is great for comfort and cost savings), I would highly advise you test your new home for radon before occupying it, particularly a “closed house” test. Post-insulation, my short term test showed slightly high levels, so now I’m performing a year-long test for confirmation, as houses tend to be more “aerated”, for lack of a better word, in the spring and fall, and perhaps for you, the summer as well since you open your windows to let out heat at night.

    I know there are some people who don’t even believe that radon is a risk (especially in non-smokers); however I prefer to err on the side of caution, and will install a remediation system in my house if the long term test continues to show high levels.

    Reply
  • Mark May 2, 2014, 6:40 am

    Great post, I’m also constantly looking to upgrade on these kind of things to get the normal spending down.

    HOWEVER, I do not agree with the article title -> Beating the stock market because it’s simply not 100% true. Stocks that have risen by 8% are things you can “easily” sell to get some liquid assets. However insulation that pays itself off 8% of the initial investment each year is not. You can’t sell your insulation to get some easy liquid assets and pursue another great investment that gets you more % than the insulation.

    Reply
    • PatrickGSR94 May 2, 2014, 8:18 am

      Say your energy upgrades consistently lower your utility costs by 30% each month. Once the initial investment is recouped via that savings, then you still have that money savings that previously went to utility bills that is now free for other things. Liquid assets, so to speak. Isn’t that like beating the stock market?

      Reply
  • Eric May 2, 2014, 8:21 am

    Can you imagine the cumulative economic effects if an entire City or Town did this? I might actually start a blog writing about how local governments can scale some of your ideas up to a community level.

    Reply
    • Mr. Money Mustache May 2, 2014, 10:49 am

      They are working on it – this is why there are so many tax incentives and other programs to encourage us lazy consumers, businesses, and government entities to upgrade our buildings. It takes time, mostly because people are very unaware/uninterested in building performance, just as they are unaware of their own car’s fuel inefficiency.

      One of my goals is for people to start getting excited about this stuff. It should be an absolute mark of prestige to have a house that barely consumes any energy – the equivalent of a fleet of Lamborghinis today.

      Reply
  • Bob Werner May 2, 2014, 9:50 am

    The real monetary benefit of a very low energy home is the increase in value of the property. Ex. A home that cost $100 per year vs. $1000 to heat and cool (sq ft same) would be worth a lot more. There are even energy efficient home loans that may be 1/2 percent lower in loan rates. In this example the home may be priced at around $10,000 to $20,000 more and still qualify for the loans based on homes of comparable square footage.. So your return on investment is probably in the hundreds if not thousands of percent.

    My 3000 sq ft home with a ground source heat pump and good insulation costs about $100 per month in the winter to heat. My neighbor’s cost about $300. My home is worth a great deal more because my energy cost to run it is so much less.

    Think of it as a car that gets 300 miles per gallon. People pay a premium for that

    Reply
  • Bob Werner May 2, 2014, 9:56 am

    PS. Don’t forget to blow door test before the dry wall is up. (or after if need be) This will identify any leaks. Then seal and caulk them. A big leaker is the gap between the floor and stud plate. (I figure you already know this)

    I haven’t kept up, but if your making the home as tight as I think you are, you’ll need a heat exchanger or at least an air intake of some sort. Otherwise you’re likely to be short on oxygen in such a small enclosure.

    Reply
    • Andres May 2, 2014, 2:24 pm

      I’ve been wondering how MMM is going to deal with this as well. Since he’s doing radiant heat, I’m assuming that he doesn’t have or want ducts running through the place. That means either having a well-placed Heat/Energy Recovery Ventilator combined with an open floor plan, or a bunch of them in each room. A few companies make them, though I haven’t researched price (google for “ductless ventilators hrv”).

      I’ve been looking into this stuff since I just bought a house from 1927 with oil forced air, and I’d *really* like to switch to a minisplit heat pumps/radiant flooring combination after doing some serious insulating. I’d like remove the duct work in the process, freeing up lots of space in the house (and no longer blowing old stale dusty air all over the house). However, how to properly ventilate those well-insulated spaces without ducts then becomes a concern.

      Reply
  • micha May 2, 2014, 10:05 am

    Did anybody else have trouble interpreting the investment returns on the chart? I think it is showing that for spending $14 you get to save $520 which is a 3700% return. (this is over 4 years, not annually as indicated in the chart.
    Do the investment return numbers seem like they are multiplied by 4? and the last one is more like 1.1% annual return which is not a good return. It seems like the cross-over for beating the stock market happens somewhere between R-16 and R-32 if you look at annual returns.

    Reply
    • Mr. Money Mustache May 2, 2014, 10:46 am

      Sorry for the confusion. I estimated total annual heating+cooling costs as being 4 x the heating cost in January (four Januarys method). This is just because my own energy bills tend to align this way. So it would indeed be $520/year and a 3700% return. Better returns in more extreme climates.

      Reply
      • Micha May 2, 2014, 12:02 pm

        Thanks for the clarification, I didn’t understand the 4 January rule as a yearly estimate.

        Reply
  • D Foltz May 2, 2014, 10:27 am

    Just a nitpick on your table of heat leakage through the roof:

    The R-value of an uninsulated roof isn’t zero.
    Even neglecting the (admittedly, pitiful) R-value of the building materials themselves, there’s a couple air gaps.
    Pulling out my heat transfer book and calculating an R-value for a roof-with-separated ceiling gives me R6 (+-2 or so) – about R0.5 from the top surface of the roof, R1 from the bottom surface, R3.5 from the top surface of the ceiling, and R1 from the bottom surface.

    Plus probably R1 from the OSB and drywall, so call that R7 +-2.

    Doesn’t change the conclusion much, but it might be worth fixing. (infinitesimal payback periods just look silly in a table)

    ***
    WRT heat loss through the vertical members connecting the ceiling and roof, they are about R20 and pretty small. I wouldn’t worry too much about hot (cold?) spots due to them.
    (The structural elements of the ceiling and roof, themselves, might matter a bit, but I think the ceiling is already built, so we won’t worry about the cost/benefit of using 2x3s rather than 2x4s to support the ceiling)

    Reply
    • Mr. Money Mustache May 2, 2014, 10:42 am

      Haha.. I knew I would get busted for that :-) … the uninsulated roof (line zero in my table) is actually supposed to be the case of having NO roof – just blasting your furnace out into the open sky.

      I do find it amazing to think that the 14″ engineered TJIs would only be R-20, though. In theory they will conduct through tiny warmer spots on the metal roof.

      Reply
      • D Foltz May 2, 2014, 11:08 am

        I think 14$ is a pretty cheap roofing job. I suppose sheet of plastic is about 14$ and gives you about R1… :-p

        ***

        Well, I didn’t even use an envelope for the R20 value. Let’s see here…
        14″*(1ft/12″)*(1m/3.28ft)/(0.12W/m^2 [softwood])= SI R value = 2.9
        2.9*5.67(SI R -value > US R value) = US R value = 17
        R19 including air gaps, OSB, drywall.

        Actually lower than that, because they are encased in another material (the insulation), but that’s 3D and I’m not doing writing up an FEA for this.

        But… the TJIs are what, 1.5″3.5″, spaced every 2’x2’? That’s about 1% of the area of the roof, so you’ll loose maybe 2-3% of your heat through them.

        NPV of 0.5$/year is what, less than 12 bucks? I can’t think of a solution which would have cost less than that.

        Reply
  • OhioDoug May 3, 2014, 6:33 am

    Any recommendations on an all brick 2nd story (all my living space is upstairs) home without any current attic vents? The entire exterior is 3-deep brick and the slightly pitched roof is straight above without any overhang for soffits. I think I can figure out the insulation part myself, just not sure about the venting. One bonus for me is that there are businesses below me that pay for their own heating, which will help a ton. I’m finishing up framing now and hoping to start insulation in early fall. I haven’t started research yet so this article is a great kickoff for me!

    Reply
  • Hobbes1 May 3, 2014, 7:15 am

    Thanks for this article. My wife and I have been considering this very topic lately.
    We have a two story, all brick (double thickness) home built in 1925. It has a full attic, with exposed rafters that are about 10″ wide, under a slate roof. I have seen numerous opinions online about the ability to insulate the roof on the inside but some ideas are conflicting.

    Any tips on the best and most cost effective manner to insulate our roof in the attic to a degree that we could proceed with turning it into living space? We don’t want to ruin (or replace) the slate roof but from what I’ve read, back in the day, the roofs were installed in a manner that allowed them to “breathe” but without soffit vents. We have a standard sized window at each end of the attic for more ventilation.

    Thanks

    Reply
  • EconNerd May 3, 2014, 11:01 pm

    The insulation ROI table is a nice example of diminishing marginal returns. Schools should teach econ w/ examples like that!

    Reply
  • James May 4, 2014, 11:21 am

    An important thing keep in mind when blowing insulation (be it cellulose or fiberglass) into a closed cavity, like the roof system mentioned in this article, is to fill that cavity at a high enough density (a dense packed install). If installed at too low of a density the insulation will settle and lose contact with the upper surface (spray foam on the roof deck in this case) and create an air space. This air gap makes the insulation less effective and in this case can create a misaligned pressure/thermal boundary where the air tight surface (spray foam) is not in contact with the majority of the insulation (cellulose). The spray foam serves as backup protection here and you should still see good results but it would be a good idea to air seal the ceiling plane at the drywall in addition. Caulk around the housings of can lights, plumbing vent stacks, fan housings, etc. For fiberglass , dense packed, is around 1.5 pounds per cubic foot. For cellulose it is around 3.5 pounds per cubic foot but should push closer to 4 for large cavities greater than 6-8″.

    To accomplish these densities a little math to determine a bag count is very important. Figure out the weight of the bags, the volume of the cavity to be filled, subtract framing, do a little dimensional analysis and you should know how many bags need to be installed. To blow at theses densities, a good machine with powerful blowers is necessary to accomplish this. I have no personal experience with store rental machines but the ones I’ve seen at box stores seem unlikely to be able to accomplish these densities.

    I’m not sure of the dimensions of MMM’s house but let’s consider a 1000 sq. ft ceiling with a 10″ space to fill. That’s 833 cubic ft. Subtract 10%for framing and such: 750 cubic feet. He got 18 pound bags… so (3.5lbs/cu. ft x 750 cubic ft.) / 18 lbs/bag = 145 or so bags. At a bare minimum this is how many bags should be used if this space was 100o square feet.

    When installing insulation in the method MMM used the netting fabric should bulge down between each rafter bay after installation and require a roller to make it flat prior to installing drywall. If the drywall can be installed without rolling the bays, it is likely not installed at a high enough density.

    I’m a huge fan of an un-vented roof system as described, I think the whole building industry should change to a similar style, just be sure to make it air tight and install insulation under your foam that will remain in contact with the spray foam.

    Reply
    • Mr. Money Mustache May 4, 2014, 4:02 pm

      Excellent stuff James. Looks like I didn’t dense pack it nearly that much – just blasted as much in there as I could fit. I’ll let you know how well it performs next winter. Still very glad I got the spray foam as a backup!

      Update: and based on your recommendation, I caulked all recessed light openings before putting on the trim kits. With the housings themselves being highly rated airtight ones, we should have very little air leakage into this ceiling!

      Reply
  • ElectricEagle May 4, 2014, 7:38 pm

    I’m surprised that nobody has mentioned fire risk.

    Cellulose insulation is an organic material which is treated with borates to reduce flammability. Even with this treatment, it can support a smouldering fire (who knows what you get if your cellulose is made-in-china and doesn’t have the fire rating that is claimed on the bag). When combined with flames that spread quickly through non fire-rated landscaping fabric, this could be a big deal.

    http://www.fireengineering.com/articles/2006/03/overhauling-when-cellulose-insulation-is-present.html

    The financial benefits of a well-insulated house are real and significant. That said, I think its worth springing for either silica (glass) or mineral (rock) insulation.

    Reply
    • PatrickGSR94 May 4, 2014, 10:25 pm

      The insulation is protected by the Sheetrock. Spray foam insulation is required to be protected by either an intumescent coating or noncombustible covering like Sheetrock. So it will also protect the cellulose as well.

      Reply
      • Electriceagle May 5, 2014, 8:50 am

        Many fires start inside the wall, near lighting fixtures or other electrical items. Besides, unless you use typeX, sheetrock is not fireproof

        Reply
        • paddedhat May 7, 2014, 5:09 pm

          Commodity grade 1/2″ sheetrock has a 1/2 hour rating. The only problem with your thinking on this issue is that not only do you have a rated sheetrock surface in the assembly, you also have IC rated, air-tight cans and a sealed ceiling/roof assembly. Therefore, your lack one vital component to generate and sustain your “smouldering fire” scenario……oxygen. Now, I’m not claiming that there is a vacuum and total absence of air in the space, but there is not enough to sustain an ongoing event. Had this same assembly been constructed with a fully vented roof, I would agree that the possibility of a sustained burn is much more likely. This btw, isn’t just supposition, but demolition. As I have observed “self-extinguishing” electrical fires on numerous occasions, while rewiring and replacing aluminum Romex. Finally, the flame spread rating of the landscape fabric, in this case is a non-event.

          Reply
    • PeterK2003 May 8, 2014, 9:22 am

      I would be much more worried about other thing catching on fire than treated insulation.

      The carpet padding in my house(early 80s most likely) was extremely flammable. After removing it I burnt it and it easily started with just a match and was an extremely hot fire in just a few mins. my house would have been gone before the fire company even got out the door.

      If you ever burned a piece of furniture(at least older ones). They are alarmingly combustible.

      Reply
  • Matt the architect May 5, 2014, 10:47 am

    My criticism is from the standpoint that your vapor retarder is on the wrong side. In northern cold climates you want the vapor retarder on the warm inside side seeing water vapor travels form warm to cold. In southern climates you want the vapor retarder like where you have it with the premise that you would be cooling more of the interior when the exterior is hot and humid. Our dew point calculator is having licensing issues in our office so I am unable to use it for you. My guess is the dew point is right about the location of the foam insulation.

    I would suggest doing this calculation or have it done because my 30 year gut experience is telling me you could be in trouble and all the money you saved will be use remediating mold.

    Reply
    • Mr. Money Mustache May 5, 2014, 10:57 pm

      Don’t worry – did the calculations, checked with the building department, built everything right for my climate, and passed the inspection. Remember I did start a custom house building company and I’ve been building things since I was a little kid! There will be no mold.

      Reply
  • Stephen May 5, 2014, 11:45 am

    I’ll add another check mark onto the people you influenced to do the insulation. I did the attic and it took about a day but we actually had no insulation when we bought our house. I still feel bad for the 50+ years of discomfort or high energy bills due to no insulation for the previous owners. Also, we were able to get a GA rebate that paid for over 1/2 the cost of the insulation so our out of pocket was about $160.

    Reply
  • Rob May 5, 2014, 1:04 pm

    In planning out the insulation & energy efficiency of our new build, I decided to hire a company to actually build an energy model of our home. I was planning R30 walls and an R60 ceiling. When we ran the modelling, it turned out than anything above an R40 ceiling was just extra expense that didn’t do much at all to lower my heating costs. Instead or spending that money insulating the ceiling we’ll be paying closer attention to the air tightness of the building and getting a good HRV. The extra cost for the up-front modelling paid for itself rather quickly.

    And on the spray-foam front, not all areas allow spray foam in the same way. The MMM example wouldn’t be allowed here in Calgary, for example. Here you still need to (stupidly) have a air gap for venting when you use spray foam, which adds even more to the expense! So we’re opting for rock wool in the ceiling instead and will save the spray foam for the really tricky spots like along the floor joists.

    Reply
  • Peter May 6, 2014, 9:08 am

    So i have an attic and there loose insulation of some sort filling the voids between to the joists. I would like to add more insulation but I would also like to be able to store stuff up there. So making the layer any deeper than the joists would hamper storage. So i guess the solution would be to add “Rafter Vent baffle”(think that is what you call it) and then tack batts between the rafters. Yes? No? Better idea?

    Related question. If I would get rid of my asphalt shingle roof and do a metal roof is the ventilation still needed?

    Thanks All.

    Reply
    • Joseph May 7, 2014, 6:33 am

      Well, technically there’s nothing wrong with doing it that way as long as there isn’t more than one vapor barrier (which shouldn’t be a problem if what’s there already is blown in). That being said, two separate thin layers of insulation probably won’t be as effective as one thicker layer. One way of doing it would be to heighten the joists by adding 2x4s. If you attach them along the joists you would add almost four inches. Then you could add more insulation and still store things up there.

      Reply
      • PeterK2003 May 7, 2014, 7:05 am

        ahhhh true that would be easier too…though I it would be a B#&*% to put all those 2x4s up there.

        I’m curious why 2 distinct layers would be less efficient. Like what would be the physics of that?

        Reply
        • Joseph May 8, 2014, 7:54 am

          To be completely honest, I’m mostly going off of what the “pros” in the industry around me have said without doing much research on my own, so I couldn’t be certain of the “why” in this situation. I was told it had to do with it being one solid thermal mass versus two layers with a transitional air pocket in between. At least that’s what one of the insulation salesman in my office said. When I talked to a guy who actually sprays foam he said that if they spray foam in the rafters they would completely rip out any insulation in the floor joists so as not to create a second envelope apart from the rest of the house. I think that had more to do with kraft faced batts though, since multiple vapor barriers could create moisture and mold issues in the space.

          Reply
      • TomTX June 5, 2014, 8:11 am

        I would put the 2×4 across the joists, not along. Actually, I did, though it was 2×6, not 2×4. Easier to install, and breaks most of the thermal bridging.

        Reply
        • Joseph June 5, 2014, 8:31 am

          True. I was thinking about it like batt insulation, which would need the boards to be installed along the existing ones to hold a thicker batt, but with blown insulation I suppose it doesn’t matter.

          Reply
  • maury young May 6, 2014, 10:39 am

    I’ve hesitated telling you about this because you’ve already started the house.

    http://www.strawbale.com

    Reply
  • paddedhat May 7, 2014, 5:20 pm

    Loved your take on the Mexican rockers. I had a kick Ass crew, Manuel and his posse, for about five years. They always had crazy tunes on the boom box and they would cook lunch on the salamander heater. I typically build modest places, with 100-110 boards, per. Manny would show up early, with four or five guys. The rock would be up, and the place would be swept clean by noon, with workmanship that was about as close to perfect as humanly possible. Anymore, when I hear a local clown whining about Mexicans being lazy, or doing shit work, I just shake my head. Those guys were the fastest and best tradesmen I have ever seen. It was about two years ago, when my good friend, and sheetrock company owner, hit Manny’s number on his speed dial, to schedule a hang job, only to find out that the whole crew went home. Our loss, and I hope they are all safe and well.

    Reply
  • Paul Ford May 8, 2014, 12:19 pm

    I love the number of comments the article is getting… and I’m hoping for some help. Basically, should I spray foam the attic floor or the underside of the roof deck? I have a 150 year old home with a ridge vent and a couple of box vents. No sofits or gable venting. The heating bills are out of control (12′ ceilings and 3k sqf) and I see that the previous blown in insulation has settled to the level of the roof joists. I’ve recently installed a 2nd HVAC system for split-floor control. The system is in a closet on the 2nd floor with all ducting run through the attic and registers penetrating the ceiling. I’ve later learned this may not have been smart, but with plaster on brick walls I didn’t have many choices to get conditioned air to the 2nd floor.

    So, if I spray the underside of the roof deck, I won’t get a great air seal because I doubt I want to cover the ridge/box vents… but it would be easiest application. I could then blow in cellulose to hit R60. I suppose I could consider rigid foam and great stuff for the under deck application. Alternatively, I can vacuum out the existing blown-in and spray foam the attic floor/joist area. This would have the benefit of sealing all the ceiling penetrations, but would be much more costly accounting for removal of existing blow in and operating around all the ducting. What say you?

    Reply
    • Cam May 11, 2014, 7:37 am

      Paul, you are right, routing the ductwork through the attic is not a terrific idea. Since it is there, you have to either insulate the ductwork or insulate the bottom of the roof deck. Otherwise the nice conditioned air in those ducts gets wrecked by the extreme temps in the attic. So you should consider doing the bottom of the roof deck and kill two birds with one stone.

      Reply
      • Mary G. May 28, 2014, 10:03 am

        I agree with Cam. Just to clarify – if the attic space remains ventilated, then insulation at the level of the roof deck has NO insulating value. In order to get your $$ worth out of insulation on the roof deck, the attic space must be brought within the thermal boundary and sealed off.

        A ventilated attic space is thermally similar to the great outdoors. Ducts belong indoors. If I were you, I would look at the layout and decide whether it would be doable to create a sealed, insulated space out of the currently ventilated attic or, alternately, whether it would be possible to add enough spray foam and/or cellulose so that the ducts are effectively covered with R-60. You are losing a lot more heat through those ducts than you are through the ceiling.

        Reply
  • Jocelyn May 9, 2014, 8:20 pm

    To echo your Colorado Mexican crew, I had a similar experience in California. Had to redo the fence in my backyard after a container truck went through it, nicely stopping a few feet from the house. The (old) Asian guy came, gave an estimate about half what others had quoted, but I couldn’t understand what he said, was not sure he understood we were speaking about the fence other then “yeah yeah, good good, no worry” (which had me worry…). Out of insanity we went with them. I have never seen a team work like that (and I did extreme remodeling a few times). Your mariachi induced transe description is very accurate. Now, 15 years later, I am looking to have a fence done (in Montreal) and I have no idea how to find such a fun, good natured, hard working and efficient crew. I am thus expecting that the experience will suck, as usual.

    Reply
  • TinaP May 14, 2014, 2:35 pm

    My insulation sucks in my 1988 home – I’ve wanted to improve it for years, but was never quite sure how without paying an arm and a leg to hire someone. And it’s not a huge house, so the savings wasn’t really out-weighing the cost. Can you use this spray foam and cellulose to “redo” insulation on an already established home?

    Reply
  • Andrew W May 20, 2014, 10:15 pm

    Dear MMM,
    I recently read an article in Fine Homebuilding (Issue 242; pp 54-58; March 5, 2014) about creating a balanced ventilation system within an airtight home. MMM, you mentioned your choice of the Panasonic bath fan as part of your ventilation strategy, but what, besides opening up windows, is your plan to provide your home with fresh air, especially during those cold winter nights? Have you considered either a HRV (heat-recovery ventilator), or an ERV (enthalpy-recovery ventilator)? You could add a supply-only ventilator, but that comes at the expense of losing the heated air inside your home.

    Love,
    Your Guardian Mustachian

    Reply
  • Andreas June 26, 2014, 9:00 am

    Hello MMM, great article – and yes, insulating your house is a phantastic investment. Here in Germany, energy is comparatively expensive, hence we had our house insulated some years ago. What I have learnt since is that insulating your house is not only a great investment, it also a kind of luxury that I wouldn’t want to miss anymore: The house is warm and cozy in winter, and it stays cool in summer – we hardly need to turn on our heating in winter, and in summer we have no desire at all for air-condition, even after long periods of heat (well, of what we call heat here in Germany).

    What we did was to not only insulate the attic. We also added facade insulation and covered the house from the outside with 15cm polystyrol plates, on which a thin layer of brick was added. Additionally, and very important to obtain the desired insulation effects, we exchanged all windows of our house. Previously, the house had 40 year old windows with double glazing, only. With such old, hardly insulated windows, all insulation attempts may be futile. We hence switched to state-of the art windows, i.e. with triple glazing and krypton gas filling. The effects are tremendous, and in spite of high cots it is a very good investment in the long run (at least considering the high energy cost here in Germany).

    Here are some informative links (sorry, the automatic translation in the 2nd link isn’t perfect, but the photos speak for themselves):
    – Windows: http://en.wikipedia.org/wiki/Insulated_glazing
    – Facade insulation: https://translate.google.de/translate?sl=de&tl=en&js=y&prev=_t&hl=de&ie=UTF-8&u=http%3A%2F%2Fwww.mein-eigenheim.de%2Fdaemmung%2Fitems%2Ffassade-daemmen-3-systeme-zur-auswahl.html&edit-text=

    Regards, Andreas

    Reply
    • Mr. Money Mustache June 26, 2014, 3:18 pm

      Wow, triple glazing and 15cm foam! Here in Colorado, most people don’t even bother replacing 100 year old SINGLE pane windows, because energy is so cheap (plus they are bad at math :-))

      Reply
      • Andreas July 5, 2014, 12:14 pm

        Hello MMM, well, double glazing has been standard here since I can remember. I don’t know any building here with single pane windows. Well, there are some buildings from before the world war that have single pane windows, but usually, these have double windows, each with a single pane.

        Our kind of insulation has become very common here: Many Germans are insulating their homes and upgrading their windows as interest rates are so low and as energy is getting more and more expensive all the time.

        For example, we would never measure our fuel in gallons and rather use liters, because our fuel prices for gallons would be too intimidating :-) I personally think it is a good thing that fuel and energy is getting so expensive, cause it gives an incentive not to waste it.

        Cheers
        Andreas

        Reply
  • Adrian July 7, 2014, 8:44 pm

    Do you have any recommendations on how to insulate an attic that has knob and tube wiring? The K&T is in good shape and replacing would be very difficult (access impossible at eaves, requires opening up walls and ceilings)

    We haven’t insulated the attic yet because 1) i like to hang out up there… well not. but working up there on lights and outlets is easier without insulation. 2) because of the K&T wiring. We have about 1 month of cold climate a year (about 35F outside temp). 3) we like the warm floors from the hydronic radiant heat and like to circulate a lot of fresh air in the house, so don’t mind the heat losses so much. We figure (perhaps wrongly) that if we insulated the attic, the air would get too hot if we had the radiant on as often as we like warm feet… 4) we plan to heat the hydronic water with a few solar thermal vacum tube panels. For now the heat uses btw $10-$30 of gas per month. Thanks for the great article!

    Reply
    • Evie July 10, 2014, 3:57 pm

      Blowing insulation around knob&tube wiring is against building code in many places…

      Reply
      • Adrian July 15, 2014, 5:48 pm

        Yes, exactly. It’s against code here too. If someone has done it, please share how you did it.

        Reply
  • Evie July 10, 2014, 3:55 pm

    The DIY approach may NOT always be cheaper than working with a contractor. In fact, many states incentive air sealing/insulation work, but you can only access the subsidies/rebates if you work with a certified contractor from a specific list and only if you get an energy audit first. For example, in Maryland (where i work), the utilities provide 50% rebates up to the cost of $2000. The contractors also get a much better deal on the cost of materials since they buy in bulk. Once you factor in the rebates and the cheaper cost of materials–the shear math works out in favor of hiring a contractor over doing it yourself.

    Reply
    • Oh Yonghao July 14, 2014, 11:02 am

      My experience so far looking up how much contractors cost they have this funny way of eating up the entire rebate. I’ve looked into it for solar and I could do it where it costs me nothing if I could get the rebates, but since I have to use a contractor the price skyrockets. It seems like most contractor’s find buying in bulk means more padding for their own pocket, being on the list means no competition, and the rebate means they just have to beat the price of a non-listed contractor after rebates.

      Luckily the insulation rebates did not require a contractor, and the home energy audit is a self audit. The only thing which would require a contractor is a blow test which is 100% refunded. YMMV.

      Reply
  • Joseph May 8, 2014, 11:51 am

    Yep, cardboard baffles, that’s what they use most. There are other options as well but that’s the cheapest. Do a search for “attic baffles” and you’ll get some other options as well. You could check out Accuvent by Brentwood. They run a little pricier but they have a good product and they’re absolutely convinced it helps cut down on costs associated with energy consumption as well because of how it’s designed to sit between the joists.

    Reply

Leave a Reply

To keep things non-promotional, please use a real name or nickname
(not Blogger @ My Blog Name)

The most useful comments are those written with the goal of learning from or helping out other readers – after reading the whole article and all the earlier comments. Complaints and insults generally won’t make the cut here, but by all means write them on your own blog!

connect

welcome new readers

Take a look around. If you think you are hardcore enough to handle Maximum Mustache, feel free to start at the first article and read your way up to the present using the links at the bottom of each article.

For more casual sampling, have a look at this complete list of all posts since the beginning of time. Go ahead and click on any titles that intrigue you, and I hope to see you around here more often.

Love, Mr. Money Mustache

Ads

$25 Unlimited Smartphone
The Lending Club Experiment
A $500 Signing Bonus... WTF?
How to Start a Blog

latest tweets