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The Radiant Heat Experiment (on a seriously low budget)

The house rebuilding project is going well. We’ve finished all the framing, and the higher ceilings and more open floorplan are hinting at a level of awesomeness that surprises even me. A picture from just this morning:

new_livingroom

Here is the new living room and the kitchen around the corner in the back. Old ceiling height was at the bottom of that steel beam. 2 more giant window openings still to come behind those plywood squares.

While I’ve destroyed and rebuilt quite a few houses for other people, this is the first one I have been fortunate enough to create from nearly scratch for my own family, so I am treating it as a bit of a science experiment. I want to build neat energy-saving features into it, but they need to be cost-effective and homegrown whenever possible.

Any old rich guy can hire the top architect and boutique builder to make him the latest LEED-Platinum superhouse to show off in Dwell magazine… at $1000 per square foot. But with energy cheap and skilled labor and high-end home materials expensive, it takes more thought and experimentation to save energy AND money at the same time. And one of these experimental projects is to build my own radiant under-floor heating system.

If you have never heard about this, you’ll want to tune in. The dominant heating method in the US right now is the forced air furnace – a big box in your basement that blows air (and dust) through a huge network of bulky air tubes so it can reach all parts of your house through floor vents. It works, but it is not elegant: they make noise, waste a surprising amount of interior space with ducts and chases, and are a hassle to install or upgrade.

When my small construction company was building some houses from the ground up a few years ago, the architect highly recommended that we use hydronic (radiant) heat instead of forced air. “It is a world of difference”, he said, “To have that silent warmth radiating at you through the floor instead of just blowing around some hot air.”

Unfortunately, when I got quotes from some plumbers for this type of heating system, the cost was astronomical: $35,000 or more, when a full conventional heating system was only $10,000 installed. Since these homes were being built to sell, on a tight budget to compete with other houses in the forced-air price range, I reluctantly decided to skip the luxury option. Plus, the passive solar design in our architecture would ensure that the furnace was used only lightly anyway.

Now, the picture has changed. I have learned to do my own plumbing, and new technologies have come down in price that make radiant heat much more affordable. After quite a few long nights of research and online training videos, I have bought all the necessary parts and we are about to put this sucker in.

What is Hydronic Radiant Heating?

Have you ever walked past a large brick building long after the sun goes down, and felt warmth all over your body even without touching the wall? How about feeling the heat from a hot bed of campfire coals even when sitting some distance away? This is radiant heat in action: a warm surface shines out infrared light (also known as heat), which directly warms your skin. With a hot campfire on a still mountain night, you can feel completely warm even when the air temperature around you is below freezing.

This same concept applies nicely to warming a house with hydronic radiant heat: warm water circulates in tubes under your floor, causing the floor to warm up and shine heat at you from all directions. There are no ducts and no blowing dust, and the system operates silently. And because the system is warming your skin directly at the same time it warms the air of your house, you feel warmer at a lower temperature setting, which allows you to keep the house cooler, saving energy. But the best part may be that you have constantly warm feet, wherever you go in your house.

So how do we build one of these systems? In a nutshell, you need something to heat the water (sometimes called a boiler), a network of tubing under your floor, and a pump to circulate that water through all that tubing:

components

While the concept is simple, my summary leaves out a lot of detail. When you look at the typical “boiler room” in a luxury house, there are all sorts of valves and sensors, and miles of meticulously soldered copper from the $35,000 plumber.  I mean, shit, does this look like an easy do-it-yourself project to you?

boiler_room

Me neither. This is why I have always gone with forced air furnaces in the past.

On top of that, hydronic heating is an art and science unto itself, with things like ΔT, GPM, BTU/hr, and R-value calculations involved. If you can get through all that, you’re faced with boilers that start at $2000, a complicated selection of parts that nobody except the experts really understands (you won’t be getting advice at Home Depot on building one of these systems), and all sorts of other hurdles.

However, after digging through all this rubble, I found a few simplifications that bring the cost and complexity of radiant heat way down, to make it a DIY-compatible project for the average handy Mustachian. The tricks I’m applying for my system:

  1. Using drinking-water-safe components allows an “open loop” system which requires fewer valves and allows item 2:
  2. Using a single tankless water heater for both hot water and house heating cuts out the $2000-$4000 boiler cost. I chose this extremely efficient Rheem Tankless unit that runs only about $1200.
  3. A single variable speed circulator pump eliminates most of the loss and loop size calculations by sensing the water temperature and adjusting its speed automatically (this also saves energy).
  4. Using a pre-made manifold from Rifeng allows easy multi-zone control and adjustment, without the need to ever mess with the tubing after you install it.
  5. And of course, everything is done in PEX, to eliminate the cost, slow installation, and boiler-room heat loss of copper pipes.
Disclaimer: Like all of my experiments, and indeed my whole lifestyle, there is some unproven stuff in here. I am using myself as a guinea pig, and there may be some trial and error, and even risk involved. Enjoy and learn, but don’t dive in as a beginner just to follow me (another beginner) blindly!

Boiling it all down, the system I ended up with is relatively simple, and I drew it out for you in this picture:

radiant_system_1600px

My proposed radiant heat system (click for larger)

So far, this is a work in progress. I have already run this by a system designer and received his nod of approval, and completed some of the installation, so I am sure we can get this to work. But there are surely improvements to be made.

The great thing about this blog is that there are many people reading right now (including professional plumbers) who have already done this, so if you have any suggestions on how to improve or simplify it further, it would be much appreciated and I will update the article as new information is received. I will also publish a second post when everything is done, to show a few of the steps in progress and the finished pictures.

Reader corrections so far:

  • Add the expansion tank before the pump, not after it as currently shown
  • Watch out for Legionella bacteria growth in an open-loop system like this. While rare, the bacteria is dangerous. Exactly the same risk exists if you have a tank-type water heater and keep the water under about 120F. Solution: make sure my tankless unit is hot (legionella dies above 122F, so perhaps 130 or higher), to exterminate bacteria. Also, drain or flush the heating loops during the offseason so the water does not sit stagnant for months.
  • OR, create two-loop system with a heat exchanger in between the two loops, so the heating water never touches the hot tap water. This requires oxygen-barrier PEX and an air eliminator. You can also buy tankless heaters with two independent loops: one for heating, one for potable water.
  • Add a check valve on the 3/4″ return line so cold water cannot sneak back into the manifold instead of going to the Rheem (I guess this could happen when the pump is off)
  • Actually, add a check valve on every loop, just to make sure there are no flow surprises and water goes the direction you want it to. Otherwise, cold water can be drawn through loops unexpectedly.
  • Many tankless heaters (including the Rheem I recommend above) are not warrantied for use in heating systems. This is fine for me, as I find warranties are generally useless anyway. But it is good to note.
  • Further criticism about this experiment showed up here on the forum of the useful site called heatinghelp.com. While the thread almost convinced me that I am an idiot, the thing is that a similar discussion forms somewhere on the internet about every single article that ever appears on this blog. Many plumbers spend their days cursing this site just because I recommend doing some of your own plumbing with PEX, for example. The problem is that my fellow tradesmen tend to use anecdotes rather than statistics to make these safety decisions. The experiment will go on undeterred, but I will make a point of doing some tests with my friend who works at the city’s drinking water treatment/analysis lab.

What About Cooling?

Every house should be designed to suit its own climate. Here in Colorado, we have intense sun nearly every day but much cooler nights due to our elevation 5000 feet above sea level. So the house has loads of South-facing windows to capture heat and more loads of thermal mass to smooth out day and night temperature swings.

In the summer, this picture flips around: the Earth tilts so the sun is nearly overhead (and the large overhangs I built onto the house shade the windows from the rest of it). You keep the windows closed during the 90F days and the interior stays cool. On summer nights, the temperatures drop below 60F, so you run a large fan blowing out the day’s heat to cool everything down and begin the cycle anew.

I find this strategy (along with not being a Giant A/C Wussy) allows us to live happily without turning on our A/C in Colorado. But there’s always a backup: most modern houses without ducts use a ductless mini-split air conditioning system for cooling. These can be more efficient than central A/C systems, because you only cool the rooms where heat is building up. I will add a system like this if necessary, but we will be sure to test out a summer without air conditioning first, since the place is likely to be even more comfortable than our current house, even without cooling.

As the final cheat sheet, here is my shopping cart from PexSupply, my preferred supplier of plumbing stuff. There are a few extra things in my shopping cart for building out the bathrooms, but in general this is a complete system for a 1500 square foot house: about $1100, with free shipping and no sales tax. Add in the water heater and you have a complete heat and hot water system that costs less than a single low-efficiency furnace.

 pexsupply_complete2

An efficiency upgrade to this system: I also purchased two boxes of aluminum heat reflector plates from Amazon which should improve heat transfer and efficiency slightly. Cost was $2.45 per 4-foot plate ($245 for each box of 100).

Update: After building the system with these, I feel it was highly worthwhile as it makes installation faster and cleaner, and improving heat transfer is a worthwhile goal with wood floors – while they work well, you do need all the heat you can get.

 

Update: One Year Later

This system is now up and running and you can read the results in the update article here:

The Radiant Heat Experiment – Did it Work?

 

  • Jill February 17, 2014, 6:20 am

    This kind of system is called underfloor heating in the UK; I had it installed last year in the ground floor of my house as part of a massive renovation (replacing a heat system from the 1970s). I also insulated walls and put in a heat pump to provide largely renewable heat at high efficiency and some solar panels.

    This is the first winter I’ve used it and it really does feel pleasant. There is a subtle difference in comfort between the ground floor (underfloor heating) and the upper floor (heated by radiators). It’s also nice to be able to place furniture in rooms without having to leave room for the large radiators that are normal in the British Isles, or even the wall vents typical of Colorado heating. I grew up in Colorado and wish I’d had this kind of heating there. The only disadvantage I’ve found so far is that it takes a long time to change temperature.

    I haven’t done the numbers yet for monthly costs, as utilities billing is usually done quarterly in this country for some reason.

    Incidentally, underfloor heating is also standard in Korea according to an American friend of mine who lives in Seoul.

    Reply
  • insourcelife February 17, 2014, 6:42 am

    My brother-in-law is rebuilding his 3,000 sq. foot 90 year old house in the Northeast doing everything from framing to electrical and plumbing himself and he chose to go with a similar radiant heat set up. He has a gas tank water heater in the basement and what looks to me like a thousand red Pex pipes attached – an even more complicated version of the 3rd picture in this post. It looks absolutely crazy to me or to anyone who’s seen thousands of feet of plastic pipes filled with water running under all the floors in the house. None of that looked like a DIY as one tiny mistake would mean a flood of water throughout the house. Good for you to try to simplify it. Are you doing separate temperature controls in rooms? Each room in my sisters house has its own thermostat for the floors – I’m sure it adds complexity as well because there are a bunch of Pex pipes in each bedroom closet behind the thermostats. I gotta say – radiant heat FEELS a lot better than our forced hot air… and you don’t have to dust every 3 days either.

    Reply
  • Dan February 17, 2014, 6:56 am

    Is the the diagram oversimplified not to provide a valve and drain on the return water line prior to the cold water input. I say this because you would likely want to completely separate the system in the spring, and drain/refill it in the fall since the water in your line will have turned rancid and unsuitable for consumption after several months of stagnation. Also, how will trapped air be removed from the system when the lines are filled?

    Reply
  • Mr Money Motivator February 17, 2014, 6:58 am

    Excellent post MMM, I am looking at doing just this in 12 months time or so.

    Nice to see you getting back to your old ‘how-to-DIY’ projects. I loved the one with the posh hotel style shower basin, that is also on my list!

    Reply
  • gargamel February 17, 2014, 7:18 am

    I wasn’t aware of the fact that radiant systems are the exception rather than the rule over there. Here in Austria we have been able to enjoy warm floors for quite a while. ;)
    Also the passive house standards seems to be way more popular in Austria.

    Reply
  • Conrad February 17, 2014, 7:21 am

    Good luck,

    When the tech was first coming out about 10 years ago I decided to do this, though we went an electrical system which was basically an electric blanket under the laminate floor I installed. 800+ square feet of the stuff. Installed it in the summer and took out old oil furnace off line and removed it fuel tank from the basement. Thought I was good.

    Then winter came. and yes our feet were warmer than the rest of us. But I ended up having to buy about 1/2 dozen space heaters that winter to make it bearable (and these are mild Portland Oregon winters mind you), and then we bought an electric forced air heat pump the next summer. (We went electric for possible future solar panel installation- which hopefully will happen in the next couple years).

    The pad system were about $4000, which have since been removed from the “grid” of our house, though they still reside under the laminate flooring. The electric heat pump with all the electrical upgrades (1920’s house) was about 12k. However we spend a lot less with the (electric vs oil) heat pump than we do with the oil. But really I’m not sold on the hear pump either even though we have it, lots of cleaning and replacing of filters. It’s kind of a pain in the ass.

    I knew of the water systems for radiant floor systems back then, but didn’t go that route (it was way more expensive then than it is now), It would be difficult in our old house. So I wish you luck, But unless you’re using concrete or stone for flooring, I wouldn’t expect it to heat the house much. You need something to trap the heat and keep it. If you go wood floors, the wood doesn’t hold the heat at all. Which was our problem- despite talking to the makers many times with their assurances that the system would work wonderfully..

    Also working in commercial construction, I have sees a few of these systems getting built on jobs that I’ve been on. And the ONLY times I’ve ever seen it on commercial buildings the PEX system is being buried in at least 6″ of concrete, sometimes more. And mind you 4-6″ slabs are the norm around here.

    Again I hope it works for you, and if it doesn’t you can at least rest assured that you spent a fraction of what I did for my own experiment.

    Reply
    • Roch Naleway February 18, 2014, 4:16 pm

      Some suggestions on what folks can do with electric resistant heaters:

      A baseboard or electrically heated home in Portland is not that expensive to retrofit these days. A ductless mini-split heat pump system is very cost effective and easy to maintain. A decent contractor can install a system for 1/2 the price that you paid 10 years ago: anywhere between $$3k and $6. Energy Trust of Oregon will provide a $800 incentive and Oregon’s Residential Energy Tax Credit will provide another $500-1,500.

      It will also cut the heating and cooling related utility bills by 50% or more. This corresponds to $800-$1,500 in annual savings for a home owner in the Portland metro area.

      Reply
  • Larry Folnsbee February 17, 2014, 7:27 am

    Great job MMM

    I live in a 90 year old house in western NY that I have been remodeling by myself for the past 28 years. I installed under floor radiant heat in my first floor 5 years ago. Pex Supply is my favored supplier too, although I did get quite a bit from Grainger due to a substantial work discount! Before, I had big cast iron radiators that I could not wait to get rid of as they took up so much space. Needless to say the warm floors make things so much more comfortable, and the cats love them too! Years ago when I installed a new bathroom in what was a second floor bedroom I used electric radiant in a 2″ slab. At that time I was much younger and hesitant to go hydronic due to my lack of knowledge. Also the electric had a much lower installed cost. I am still happy with that decision.

    I love working with PEX, and have since converted the whole house to PEX plumbing

    Can’t wait to see how this project turns out, but I already know you won’t be disappointed with the decision.

    Reply
  • Russ February 17, 2014, 7:40 am

    Hydronic heat certainly has its advantages, however one item I have not seen in the conversation is how to handle ventilation (i.e. fresh air), or how to remove dust. I agree that old, leaky and poorly designed forced air systems will introduce dust into the house as the return air ducting sucks from dirty air from crawl spaces and attics. A new, properly sealed, aerodynamic duct system with a high quality filter box will lead to better indoor air quality than a house with hydronic heat, which has no way of removing dust from the air.

    It is critical in energy efficient, air tight homes to install a ventilation system to provide the occupants fresh air, otherwise there will be a build up of pollutants and potentially humidity which can lead to condensation. Heat and Energy Recovery Ventilation is the best as it captures a large portion of the heat energy from the outgoing stale air.

    Reply
  • sarah February 17, 2014, 8:02 am

    I am working on doing this myself. Only I am installing solar pannels to heat the water and then pump it through the house. Thus, creating free hot water and free heat. :)

    Reply
  • Jason February 17, 2014, 8:30 am

    An important note about condensing boilers: Check your local codes. The moisture that is going to condense out of your flue gas (i.e. chemically identical to “acid rain”) has to be whisked away from your home in an “approved” manner. Also, your intake combustion air usually has to be piped in directly from outside (i.e. cannot use inside air for combustion) and there are rules for how far apart your inlet air and outlet flue gas vents are (has to be far enough away that you don’t draw flue gas back into the intake, but the lengths can’t be too different the combustion fan can get lopsided loads). (And keep flue gas far away from operable windows, and not above walkways [condensed water=freeze-slip-fall in our Colorado climate]).

    Anyway, just pay attention to the codes.

    Reply
    • Mr. Money Mustache February 17, 2014, 8:41 am

      Thanks John, I will definitely be installing the intake/vent PVC in the right way. They are going through the roof in this case, just because it turned out to be the easiest.

      Reply
  • Devin February 17, 2014, 8:32 am

    When I saw the fireplace picture and the title I was like ‘he is going to venture into leveraging his fire place into his radiant heating. Sweet!’ Then I read the article. Meh. I thought the goal from 2011 was to use no fossil fuels. Kidding. Good on you for the system design. It appears that the open system should work well. I have seen a few of these installed and they work extremely well with little maintenance. I was hoping you were going to expand the radiant system into your fireplace and leverage the thermal exchange by embedding your heating loop in there somehow. You even touched on the concepts that reinforce it in your article. Now that would be badassed. Who knows maybe you are secretly looking to complete that in later post and knock our socks off. I have been looking at multiple ways of creating an energy efficient home and this is possibly the next frontier. But it is it experimental and a little too complex for my liking right now. Involves in-line thermally switched valves and a hot water reserve to take advantage of the fire while it is going. Got way to expensive way too quickly. Efficiency at too high of a cost is just ridiculous. So I was secretly hoping you had some new insight and doing it at a severely reduced cost. Great article and I am sure you will be happy with the system and even happier that you learned something new. Hope all goes well.

    Reply
    • Mr. Money Mustache February 17, 2014, 8:40 am

      Nice idea Devin: I had definitely considered trying to connect some sort of heat exchanger to the high-efficiency EPA qualified woodburning insert I will be adding to that oldschool fireplace soon. The thing is, the floorplan of this house is so open (and it’s all on one level) that the fireplace can heat it all anyway. I will already have a few ceiling fans, so they will help speed up heat circulation.

      And I get free, clean wood scraps from my own carpentry business and those of others, plus the fact that this whole neighborhood is a forest of 100-year-old hardwood trees that regularly drop 400-pound limbs onto the street after storms :-)

      Reply
      • vwDavid February 17, 2014, 10:25 am

        If you are doing something wood burning, definitely start watching “Rocket Mass Heater” videos on youtube.

        Reply
      • JimGWC February 17, 2014, 3:38 pm

        I’ve heard good things about “Rumford” fireplaces. http://www.rumford.com/articleRumford.html

        I found the engineering principles alone made it worth reading.

        Reply
      • Mr. Mark February 19, 2014, 9:00 pm

        I was wondering if you could rig a heat exchanger between your floor heating outlet and the water heater inlet. No mixing of the water, just a boost to the intake water temperature for free.

        Reply
    • Kenoryn February 17, 2014, 4:16 pm

      Devin, wood-fired cookstoves often have an optional water heater on the side. That would take some of the figuring out of the equation. We are tentatively planning to have a solar domestic hot water/radiant in-floor heating system with wood backup heat through a wood-fired cookstove, which we would also cook on – just at the research stage right now! Unfortunately it is a lot more complex, but no fossil fuels.

      Reply
      • phred February 18, 2014, 12:09 pm

        In the past the water pipes coming out of a wood stove have frequently clogged closed due to mineral deposits resulting in KA-BOOM!

        Reply
        • Kenoryn February 19, 2014, 9:48 am

          Guess it would be a good thing to check on and clean now and then. I expect that during the summer you would be relying on your solar water heating, or possibly other backup, so you’d have an opportunity to disconnect that part of the system and clean it.

          Reply
  • Jenny February 17, 2014, 9:10 am

    What an awesome and interesting project. My apt in Tokyo has a system similar to this–hope you’ll love the results!

    Reply
  • Robert February 17, 2014, 9:14 am

    Nice project man! One thing I noticed is that your expansion tank is after your circulator. As in, you are pumping to it and should be “pumping away”. The link to the TACO lesson you shared explains why under the “Circulator Placement” heading of the Hydronics Step by Step course.
    Good Luck!

    Also in many areas you cannot use a Tankless water heater as a heat source, Check your codes.

    Reply
  • Greg February 17, 2014, 9:15 am

    The open system is a great way to keep it simple.

    Wirsbo used to make manifolds with adjusters at each loop, this allows you to fine tune each loop (each room for instance) so you can make different rooms different temps, even when they’re on the same pump circuit. I think this could also be done after the fact with ball valves if you want or need. Maybe your manifolds have this ability and it’s just not clear to me according to your illustration.

    Overall nice explanation.

    Reply
    • Mr. Money Mustache February 18, 2014, 10:52 pm

      Yup – this Rifeng manifold has the same thing. It is quite possible I won’t even need different zones after tweaking the knobs (just as my old single-speed, non-zoned forced air furnace does fine in the current house). It’s the Denver metro area after all, where you ride your bike all year. Heating isn’t a huge deal here.

      But I reserve the right to buy the actuators and add more thermostats if needed.

      Reply
      • Sara November 9, 2014, 5:14 pm

        Oh good! The idea of thermostats in each room was putting me off the system. I love a warm livingroom and a cold bedroom. Solved the problem!

        Reply
  • Jordan Read February 17, 2014, 9:16 am

    Awesome article MMM. If you need an extra set of hands one of these weekends, I’d be more than happy to exchange them (temporarily…I need them to work) for getting the opportunity to learn firsthand about this stuff.

    Reply
  • Martin February 17, 2014, 9:23 am

    Definitely think about solar pre-heat. If this guy can make passive solar work in the chilly north, you’d do well at high altitude in sunny Colorado (there are a thousand ways of doing solar water preheat, from simply a painted black bucket to high-end glass vacuum tube solar collectors).

    http://www.cbc.ca/news/canada/new-brunswick/fredericton-man-builds-300-solar-furnace-decreases-heating-bill-1.2527065

    Reply
  • AlexG February 17, 2014, 10:10 am

    Hydronic radiant heat is fantastic (full disclosure – I work for a manufacturer who sells PEX etc.). So kudos for heading down that road.
    However… previous comments have raised some very legitimate concerns about your system design (Legionella and water heater warranty being two of the big ones!).
    Check out the conversation on another forum that this subject has kicked off: http://www.heatinghelp.com/forum-thread/149762/how-prevalent-is-this#p1327837
    These guys have been in the business for many years and know what they are talking about…

    Reply
    • Weegie5 February 17, 2014, 8:11 pm

      One of the experts weighing in on this other message board is a guy named Mark Eatherton. He is local to you, MMM (Denver).

      There is a wealth of knowledge on the forums over at HeatingHelp.com, a.k.a. “The Wall”. For beginners, check out http://radiantec.com/retrofit/ for some good guides.

      ~Weegie

      Reply
      • Kenoryn February 19, 2014, 7:28 am

        Interesting that the people on the HeatingHelp forum are totally shooting down the idea of any open-loop system at all, while the second Radiantec link recommends it as the best type of system.

        Regarding legionella, it seems the bacteria begin to die at 120 degrees Fahrenheit, and the higher the temperature, the faster the kill. At 140 degrees Fahrenheit a few minutes is still required to destroy the population. In the proposed system, if the water heater is set to 140, it looks like the water will be disinfected twice: once before the heating loop, and once after, before going to the domestic hot water supply. If you wanted to be really sure, you could set the heater high enough and insulate the run coming from the heater such that the water would remain at 140 degrees for a few minutes, or find another method of ensuring that temperature was maintained briefly.

        Chlorine is also an effective treatment for legionella. Since MMM is on a municipal water system, presumably highly chlorinated like most municipal water systems, it will probably not ever be a problem anyway as it could be on a well system. This article finds that 99% Legionella kill is achieved after 40 minutes in water with low levels of chlorine similar to what would be found in a public water system. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC239530/

        Reply
    • Chris B February 18, 2014, 6:48 am

      I’m replying here, because this comment regarding legionella & the link to Heating Help needs more attention.

      I (a mechanical engineer by day) somewhat recently redid my heating system (mostly hydronic radiant now), and after much reading, calculating, building, and re-building, can safely say that “cheap” is not a word that should be used with this sort of system. My system looks a bit like that intimidating photo above :-) Despite my best efforts, I found that cutting corners leads to poor system performance.

      I’m a huge fan of this blog, but this post contains a great deal of misleading information. Hydronic radiant heat is not generally a diy project for the “average Joe”, and I think that there is a reason that installed systems are as expensive as they are.

      The legionella issue raised by others is my main concern, but a few other issues I see include:
      -relatively low mass system with many zones is likely to lead to short cycling of the heat source
      -during steady state operation, it will probably be hard to maintain a reasonable ΔT over the system loops, which will contribute to short cycling; since you’re using a tankless water heater, it might just not turn on (many of them require a suitably low inlet temperature)
      -I don’t see a way to remove air from this system(?)
      -Strange things may happen with water pressure/temperature when you have a large hot water draw while the system is calling for heat.
      -Depending on pipe geometry, you may end up creating a convection loop during the “off” season and heating your floors in the summer.

      I strongly advise you to – at the very least – move away from an open system approach. Maybe try to get your hands on a copy of “Modern Hydronic Heating” by John Siegenthaler, which is an excellent (text)book on the subject.

      Provided that you don’t make anyone sick, I’m interested in seeing how this experiment turns out. Best of luck!

      Reply
  • Chris Green February 17, 2014, 10:15 am

    MMM,

    I really enjoyed reading this article and seeing the picture of the popped roof. You have definitely created a dramatic space and am excited to continue seeing the progress.

    Reply
  • Brian February 17, 2014, 12:01 pm

    I am curious to how you are running thermostat/temperature controls for the zoning, pump, and heater. I am looking at doing this as a secondary system to my wood burning heat, however my only choice to heat the water is either electric or propane – which both run at a higher use cost, so being able to control the zones to minimize the on/off cycle of heating the water is where I am getting stuck in the design of the system.

    Reply
    • Roch Naleway February 18, 2014, 4:19 pm

      Brian,

      Consider a heat pump water heater if electric and propane are your only options. A heat pump water heaters uses 50%-65% less energy. If you need a lot heating capacity it is possible to set them up in series.

      Roch

      Reply
  • Chuck February 17, 2014, 1:13 pm

    Wish I could lay my hands on the research I did a while back. Imperfect recall, but the reflector plates really don’t add much. Like I said, imperfect recall, but you may want to do a bit more research on the plates before dropping $500. Otherwise, great looking project.

    Reply
  • Andy February 17, 2014, 1:13 pm

    MMM and Readers,
    As someone with basically zero construction experience (I am getting good at hanging things on walls and fixing toilet leaks though) I was wondering if anyone had some advice on getting my feet wet and picking up some of the basics. This type of article is fascinating, but well beyond my current skill level. I’ll be looking to buy a home in a couple years and aspire to be the mustachian type that can handle any job the house needs. Any recommendations on books or other sources of knowledge/experience for a beginner like me would be great.

    Thanks!

    Reply
    • Weegie5 February 18, 2014, 11:34 am

      Andy,

      Here are some resources I have found helpful in learning about residential hydronic (water-based) systems. (Disclaimer: I am a mechanical engineer and have spent my career working in commercial buildings, so I am mostly interested in how residential systems are different than their commercial counterparts.) That said, here are some resources to introduce fundamentals of residential hydronic HVAC.

      John Siegenthaler, P.E. might be the most highly respected residential hydronics guru in the country. His consulting/design firm, out of upstate NY, is called Appropriate Designs http://www.hydronicpros.com/ . He has written a couple relevant books, available for sale on his website. He writes a monthly column in Plumbing & Mechanical magazine, http://www.pmmag.com/topics/2661-john-siegenthaler-hydronics-workshop as well as in Radiant & Hydronics magazine, http://www.radiantandhydronics.com/authors/1925-john-siegenthaler-p-e/articles . One presentation he has given is available on the web, “Hydronic Heating for Low Energy Houses” http://www.duluthenergydesign.com/Content/Documents/GeneralInfo/PresentationMaterials/2013/Day1/hydronics-siegenthaler.pdf

      Another industry expert is Mark Eatherton of Denver. He is active on the HeatingHelp.com forum and writes a monthly column for Contractor Magazine, http://contractormag.com/author/mark-eatherton?page=0

      More related to radiant systems is the 2013 Radiant Heating Report, available from BNP Publications (with a free account, I believe): http://digital.bnpmedia.com/publication/?i=166040

      MMM’s link to the video library from Taco HVAC is good. Other (pump) manufacturers that might have similar content are Bell & Gosset (“B&G”) and Grundfos.

      Happy researching!

      ~Weegie

      Reply
    • Kenoryn February 19, 2014, 10:00 am

      Andy, I found the book “Tools and Techniques” by the Handyman Association of America to be really helpful. (http://www.amazon.ca/Tools-Techniques-Handyman-Club-Ame/dp/1581590253/ref=sr_1_2?ie=UTF8&qid=1392828810&sr=8-2&keywords=tools+and+techniques)

      It’s pretty much what it sounds like and includes an intro to basic plumbing, electrical and construction/carpentry.

      There are a lot of other similar books out there and I would get one of them for reference, and then start with easy low-risk projects to try out techniques, with the help of YouTube. The best way to learn is just to get experience. Another thing you could try to get some hands-on experience is volunteering for Habitat for Humanity or other volunteer building organizations.

      Reply
    • Anne-Marie February 27, 2014, 11:53 am

      I was you a few years ago, and I’m still nowhere near DIY radiant floor heating level. Start with a basic book such as the Reader’s Digest Complete Do-It-Yourself Manual. Use it as the base from which to tackle whatever projects come up at your current place–instead of calling the landlord, fix the leaky pipe yourself. There’s no substitute for learning by doing.

      If your current housing situation doesn’t give you enough scope for that, though, you can also develop tool- and material-handling skills by building standalone projects such as furniture. Also, let your friends with houses know that you’d like to help them.

      Reply
  • Neil February 17, 2014, 1:19 pm

    I’ll be interested to find out how this works for you. My condo (built in 1960) uses old style radiant heat, with baseboard radiators along the perimeter walls. It’s a closed loop system, so it has its own boiler. Since I’ve lived here (7.5 years), we’ve had to do a few modifications: new boiler, new circulator pumps, new zone valves (instead of the central control your system has, in ours, each loop is one apartment, and has a local thermostat controlled “zone valve” to control temperature.

    All of these are great and basically the kind of maintenance you’d be expecting after decades of service, though the circulator pumps seem to go quite frequently. But the most important cost saving addition we made was to add a glycol system to prevent pipe freezes, which won’t be available in an open-loop system. Prior to the glycol installation, we had 2-3 pipe freezes each winter. Thankfully only one pipe burst, but it was still $200-$300 to get a plumber out every time, usually in the middle of the night, to thaw the pipe and get heat flowing again. (I’m also not certain how one would thaw pex…passing an electric charge through copper causes it to heat up, which is very convenient) Glycol has basically inverted the pipe freeze issue, dropping it to one every 2-3 years.

    I’m also not sure if the dust result will be to your liking. I find that our home is very dusty, and the going theory is because of the lack of forced air circulation, which allows most dust to get pulled out through furnace filter and have clean resulting air. I’m also not sure about your climate, but forced air here has the added benefit of being able to connect a humidifier to it…dryness is a major problem in winter.

    I look forward to a follow-up review of the heating system once you’re in your new place. It sounds like a good experiment, at relatively low cost.

    Reply
  • Rmag February 17, 2014, 1:19 pm

    Hello,
    This system is very cool, providing a really good warmth.
    PE pipes seem adapted to the task, as metal pipes (copper, steel) tend to react with the gas dissolved in heated water. They are also less expensive and easier to operate during the building.
    Some “good building pratcices” (aka unified technical directives) in France include:
    _1 loop min per room
    _max temperature of the floor : 28°c,and a max departure temperature of 50°c
    _space between tubes shouldn’t exceed 35 centimeters. (depends of the type of pipe network : “snail” or “grid”).
    _cover the whole room with the pipe net (not too close of the walls or other futur constructions of course), so the water temperature can be lowered and the heat more equally distributed
    _insulating the floor under the pipes (so the heat won’t go on the ground)
    _when your radiant is “good to go”, proceed to nominal temperature gradually (10 days). This shouldn’t occur less than 14 days after you make the concrete screed (21 days is advised).

    For the cooling, here are some things to take into account:
    _If you plan to have a tilled floor, beware of water condensation (could become slippery)
    _Thermal flow is not favorable (cool air tend to stay on the ground)

    And of course if you don’t use a double flow CMV, you have to renew the air by other ways, to avoid moisture that could ruin the building (condensation in walls…).

    There are (many) other building specifications, but here are a few i remenber. Hope it helps.

    PS: sorry for the faults, i’m not a native english speaker

    Reply
  • Dimitri February 17, 2014, 1:28 pm

    I can certainly see some of the advantages of this underfloor radiant heat system, but when I lived in a house with radiant heat the dust accumulation was way worse than with central air. If you maintain and use good filters, the air is being cleaned as it circulates. Others here have mentioned central air blows dust around, but that is not my experience when comparing the two types of heating. But of course, the extra time you may have to spend cleaning the dust in your house weighed against the cost and environmental savings make that minimal. But I’m really curious why others feel this makes for less dust, not more?

    Reply
    • Mr. Money Mustache February 17, 2014, 5:13 pm

      You’re probably right on that, Dmitri – the constant filtering in a furnace does reduce dust, which I hear is mostly skin particles from the humans living in the house. On the other hand, the blowing air might push it up to weird parts of the house like shelves and loft areas, while with radiant heat it could all land on the floor for easy sweeping. I’ll have to let you know if I notice any difference either way.

      On the positive side, this will be my first house with ZERO carpet, which should be a nice improvement in cleanability (carpets and I don’t get along well).

      Reply
      • Chris February 21, 2014, 9:04 am

        MMM, do you have plans for whole house ventilation with an HRV/ERV or exhaust fan?

        Reply
      • Vanessa February 22, 2014, 6:45 pm

        Yeah, hooray for no carpet!

        And as someone who formerly had a dustmite allergy, in my experience ducted (forced air) heating is much dustier than non-ducted by a country mile. Loathed it. :)

        Reply
    • phred February 18, 2014, 12:10 pm

      Mustache could always plug a portable electrostatic air cleaner in each room

      Reply
  • Tom Kabat February 17, 2014, 1:37 pm

    Pipe sizing ideas: You show 1″ to the manifold and 3/4″ return. Why not reduce friction by having a 1″ return from manifold also. (include a 1″ tee where cold supply joins in and 1″ run to the water heater for low friction when pump is on and hot water is called by shower etc.) Then on the pipe out of the water heater, keep the 3/4″ section up to the tee that splits off the DHW to house as short as possible (less friction) and then have at least a foot of straight 1″ PEX before the inlet pump flange to allow the water to collect its thoughts and smooth its flow before it enter the pump. These ideas come from the Amory Lovins school of plumbing thought for optimized flow, capital and energy.

    Reply
  • eric darwin February 17, 2014, 1:42 pm

    All those south facing windows will let in heat. But most north american windows are designed to minimize heat LOSS, with the use of reflective coatings, etc. In contrast, European windows are designed to maximize heat GAIN from the sun, and depend on shading devices to keep out excess sun. Few north Americans design proper overhangs to keep out excess solar gain, and there is a problem as you go northwards that the sun angle and desired heating season dont match so an overhang that keeps out the highest sun is June 21 when the hottest sun lags that by 2 months.
    Therefore, mechanical sun shades are very useful. Awnings are the most common north american system, particularly retractable and maybe motorized awnings. Even better, from Europe you can get exterior Venetian blinds, made of metal, that allow you to block sun in too-hot weather but still let in light, and let in full sun in winter. As a do it yourself version, no operated by a remote, you can build variable louvres from parts from Home Depot, or a slidlng barn door on the exterior of the house where the barn door is really a trellis or louvres to block the hottest sun while letting in diffused light. You can also built a horizon trellis out from the wall above the window about 3′-4′ (look up exact distance for august on the ‘net) and put adjustable louvres on that, with parts available in the fence dept. at Home Depot.

    Reply
  • andrew fox February 17, 2014, 3:25 pm

    MMM,

    Have you considered the major disadvantage or radiant type heating systems, that they take a long time to get the house warmed up?

    I decided against radiant heat because I use my furnace like its a lightswitch. When I leave the house for 45 minutes or more I turn the thermostat down to 55 or off. It is a myth that it is more efficient keep the home warm than to let the temperature vary by turning the heat off when you leave. The problem with radiant heat is that it take a long time for the house to warm up, making it impossible to turn the heat off when you leave and still have a warm house minutes after you get home. I also sleep with a down comforter in winter and turn my heat OFF when I sleep, I turn it back on when I wake up, and its only takes a few minutes to warm up. My forced air furnace only takes about 5 minutes to raise the interior temp 5 degrees, 10 min for 10 degrees as so forth. For this reason I believe that radiant heat uses more energy and costs more to run than forced air heating. If you need your house to be heated to a comfortable temp 24/7 then radiant heat may work for you.

    Reply
    • Mr. Money Mustache February 17, 2014, 5:07 pm

      That is a good point, but I will still flip my system off whenever we don’t need the house warm. If we need the place to warm up quickly, we’ll just start the woodstove!

      Although it sounds very fancy, this radiant system will really be only the third-priority heat source in the house. First is solar, which should do the whole job for the 300 sunny days we get each year around here. Second is woodstove. Third is radiant heat, which is for when we are too lazy to have a fire, or sleeping or away on vacation.. plus to heat up those areas of the house a fire’s heat won’t reach.

      Reply
  • WageSlave February 17, 2014, 3:27 pm

    A question about your big south-facing windows: in the summer time, will you never open the shades/curtains?

    In other words, the same mechanism that will be so useful in the winter (free solar gain) will be your enemy in the summer. At a minimum I’d think you’d want to keep the shades/curtains drawn… but what if you want to let some natural light in? And also, what would you suggest if you live in a climate that has super hot and humid summers (in addition to super cold winters)?

    Another question: does the fundamental design of a system like this change in a two-story house? You’d obviously have to run a bunch of PEX up to the second floor… or would it be more efficient to simply install a second, independent system?

    Reply
    • Mr. Money Mustache February 17, 2014, 5:02 pm

      The 23 degree tilt of the Earth takes care of this, and it works especially well where I live at 40 degrees latitude: On Dec. 21st, the sun is at a 27 degree angle from the horizon, so it shines into all the Southern windows at a nice angle. In June, the sun is only 17 degrees away from vertical, so very little sun is trying to get in through those same windows. Then the house’s overhang takes care of that little bit.

      You have much more problem with East and West-facing windows, because the sun spends lots of time hanging out burning you from the sides on long hot summer days. So I hardly put any of those into this design.

      Reply
  • Jill Rolland February 17, 2014, 3:35 pm

    Why did you chose the water-based radiant heat instead of the electrical wires? I think someone else already asked about the potential for leaks with water as well as access?

    Reply
    • Mr. Money Mustache February 17, 2014, 4:55 pm

      Water is good in this case because it lets me use a natural gas heat source – gas heat is less than half the cost of electric heat at the usual prices, and even less these days because of a huge supply in the US.

      When plumbing with PEX, I find that leaks are not an issue – they just never, ever happen. With copper, I would occasionally have to re-solder a joint in when fiding up a big system for the first time, which probably just means I am a poor solderer. But PEX joints are all-or-nothing: if you can get the clamp on, the seal is good and stays good forever. They even withstand freezing, which I find pretty amazing.

      And, all of these pipes will be over a crawlspace anyway, which means easy access.

      Reply
  • Sean February 17, 2014, 4:16 pm

    I live in Colorado Springs and installed an “open direct” radiant in-floor heating system in my house 3 years ago. I designed it myself, and it works great! It is quiet, comfortable, energy efficient, and does not dry out the air like a forced air system. This last item is my favorite part of the system here in DRY Colorado.

    The Legionella thing is NOT a concern. Since you are regularly using and replacing the water in the system, it never stagnates for long enough to cause a problem. I had sooo many people warn me about this and other problems that it made me work even harder just to prove them wrong. I pulled a permit and had it inspected and approved by our local building department – no problem at all.

    I used all potable water grade components to build it (PEX, copper, stainless steel). I tried to make it a cooling system in the summer by running the water to irrigate the lawn through the tubes before it goes out to the grass. Unfortunately, this reduced the pressure too much to effectively water the lawn. I did use the aluminum plates for the 2nd floor “staple up” tubing – they seem to help extract the heat out of the tubes better.

    A few things to note: Your floors won’t be nearly as warm as you are expecting – especially if your house is well insulated and the system doesn’t need to come on that frequently. It doesn’t take much to warm the house, so the floors are only around 65 to 75 *F, which feels fine, but not “warm”. You will still get dust in the house – I can’t tell if it is more or less than with a forced air system. Also, all of the furniture in the house warms up due to conduction/radiation from the floors. This is fine except for the bed. I like to sleep cold, and sometimes the bed gets too warm even with the stat set to 66 *F (we keep our stats set to 65/66 *F all winter long – 24 hours a day).

    I still have all my sketches and layout drawings if you are interested. If you are ever down in the Springs, I’d be happy to show off the system. We live right next to Garden of the Gods.

    Best of luck to you. I am living vicariously through your projects until the time we have amassed enough cash to quit our jobs and do the same.

    Reply
    • CPS January 27, 2015, 12:37 pm

      Any chance you can post your sketches and layouts HERE?

      Reply
  • mg February 17, 2014, 4:23 pm

    Love your post. I like the built up option from here:

    http://ecorenovator.org/forum/geothermal-heat-pumps/484-homemade-heat-pump-manifesto.html

    I am going to go with the built up method but use pretty much the same components. I currently have a boiler hydronic install in a thin slab but find the standytime to defeat a large percentage of the benefits.

    Reply
  • AlwaysFixing February 17, 2014, 4:23 pm

    Great choice! There’s nothing like radiant underfloor heat. I experienced it in a resort about 20 years ago, and always assumed it was out of my price range. Amazing!

    I upgraded to a multi-stage gas forced air furnace recently. It’s not radiant heat, but what an improvement! Gotta love the tech working its way into hvac!

    Reply
  • mysticaltyger February 17, 2014, 5:05 pm

    This is SOOOOO true about radiant heat being wonderful. I lived in an Eichler designed house in California with radiant heat and even with the mild winters in the San Francisco Bay Area, those warm floors are WONDERFUL!!!!

    They are expensive though….but leave it to MMM to do it himself and figure out a way to make it inexpensive!!!

    Reply
  • jestjack February 17, 2014, 5:25 pm

    Cool project….just looking at the new framing with the steel makes my back hurt! That “demo” was a treat I’m sure…Real interested to see how the radiant heat turns out…with the pex….I’m thinking the controls are gonna be the big challenge. My thought is that with the passive solar from the windows and the adding of the high R-value insulation that new wood stove insert is gonna heat the new place just fine….probably could have gotten away withh electric baseboard as a back up. That’s the route I’m gonna take with a rental unit that has radiators with an oil fired boiler.(heating oil just went over $4.35 a gallon)…IMHO radiators aren’t all they’re cracked up to be…. Thanks for sharing your project!!

    Reply
  • Jan February 17, 2014, 6:40 pm

    I lived in Switzerland from 2005 – 2009 in a brand new apartment building with radiant floor heating. I had to get the building owner to come show me how to adjust the heat in each room, the controls were behind a panel in the built in cabinets in the hallway. That building had 8 inch walls and triple pane windows. It was wonderfully warm all winter and my utilities were low. Forced air heating was the hardest thing to adjust to when I came back to the US. I never noticed my apartment being dustier than any of my homes here in the US. When I returned to the US I bought a house built in the sixties, remodeled the bathrooms with Swiss bath fixtures, replaced the original water heater (1966) with a tankless one. Have thought about trying to retrofit heating under the wood floors but you need to determine if the wood floors will be OK. The wood floors in my apt were inch thick parquet, sort of like bowling alley lanes. I was told they do them that way so that the floors can be repeatedly refinished as needed. They build things to last 200+ years there.

    Reply
  • Saus February 17, 2014, 7:31 pm

    I lived in Korea for three years, and the underfloor heating is standard and utterly sublime. It was the most luxurious, magical feeling in the world to come home with the heat on. I am jealous!

    Reply
  • Cheryl Olive February 17, 2014, 7:51 pm

    Would it be possible to do radiant heating if my house is on slab?

    Reply
    • Roch Naleway February 21, 2014, 4:16 pm

      Yes, it is possible.

      Reply
  • Phil Robinson February 17, 2014, 8:34 pm

    Re-done two mains pressure HW systems recently and learned a lot, some of which might be relevant here.
    While the temp relief valve should be in the hot line as in your diagram, the pressure relief valve should be in the cold line – right after a non-return valve to prevent back-flow into the incoming mains. Your pressure regulator might have this non-return in it. Also, you might need a vacuum break for if you ever turn both the water and heat off – to prevent the system imploding as it cools and the water contracts.

    Reply
  • ross February 17, 2014, 8:47 pm

    I almost bought one of these for my rental properties but opted not to because its simply a rental. Anyhow, thought I would send it over since its a startup company who featured their product on kickstarter. Pretty badass if you ask me..http://myheatworks.com/

    Reply
  • Mark February 17, 2014, 9:23 pm

    My wife grew up in a house with radiant floor heat — she still raves about how warm it was even in bitter Wisconsin winters. We had seriously considered it for our home but it was just too expensive of an option for us.

    I really hope it turns out well for you. You will LOVE it!!!

    Reply
  • ewizzle February 17, 2014, 10:05 pm

    Fascinating post.

    My apologies if this has been mentioned already, but is there a possibility of utilizing a closed loop system with glycol (antifreeze) vs. water? Seems you could heat the loop to a higher temp and run the pump less, and this could potentially work for a cooling effect (condensation on the pex seems to be the major concern re: radiant cooling).

    Thoughts, MMM?

    Reply
  • Lorin February 17, 2014, 10:47 pm

    I love radiant flooring and recommend it to all of my clients (I’m an architect). It has a bit of a bad rep here in CA though as it was installed in most Eichler houses & then leaked terribly. But the new systems are much superior.

    I am more used to seeing these installed in concrete, though. The thermal mass allows the system to retain the heat so much longer that way (though there is a lag in heating it up) and distribute it evenly.

    Anyone have experience in using Warmboard? They’re plywood panels with pipes built in. It’s supposed to make install easier. Never used them myself.

    Reply
    • Rich February 20, 2014, 6:51 pm

      The pipes are not built in . They must be purchased seperately from the boards and site installed . 12″ spacing will require higher water temps than some comparable products that have an 8 inch spacing . Products with a graphite covering will distribute heat more evenly .

      Reply
  • StevoKeano February 17, 2014, 10:58 pm

    Nifty. In 1985 I installed a heat exchanger on top of my firebox (fire place) connecting the cross vent to the out doors. So, I’d start up a fire, open the cross vent and the pressure differential created by the flu caused a rapid breeze to enter throught the exchanger. Result, the room was toasty in a few minutes. This has another benefit of not drawing cold air in at leaky spots as it flows freely across the heat exchanger. Just a thought… ;-) The fireplace is still there at 1500 Lucas Terrace, Plano, Tx.

    Reply
  • matt mustache February 17, 2014, 11:24 pm

    All the solar talk is interesting and inspiring. I saw this story about a guy in Canada that put something together that you all may find interesting. A solar furnace using old gutters and aluminum cans (and it doesnt look crappy!).
    http://www.cbc.ca/news/canada/new-brunswick/fredericton-man-builds-300-solar-furnace-decreases-heating-bill-1.2527065

    Reply
    • Roch Naleway February 21, 2014, 4:17 pm

      Looks like a DIY air source heat exchanger.

      Reply
  • Raven15 February 18, 2014, 12:32 am

    I’d be a little cautious sending it back to potable water after a few days or months of downtime. Over that time dissolved chlorine and oxygen tend to dissipate, leaving unchlorinated anaerobic water with typical temperatures between 68 F and 120 F. Depending on the actual conditions, that sounds like a potential recipe for biological growth of virtually anything that grows in water and is smaller than 1/2″.

    Of course you’ve done way more research into this than me so you probably know already.

    Great site! Just found it a few weeks ago. I liked the early posts because it felt like I was more special, with only 12 commenters! I have my own 2-unit residence and was thinking about switching to Hydronic so I could replace a single water heater every 10 years, instead of a heater/furnace every 5 years. I had some misgivings, but with you as my guinea pig, maybe!

    Reply
  • Roddy Pfeiffer February 18, 2014, 12:55 am

    I am an American recently retired in China. We bought a new apartment in a high rise with radiant heat in the floors. I love it. Quiet, trouble free. No dust issues. This the predominant heating system here. My 2-BR unit has 4 zones. The Chinese save the cost of the heating system by having massive heating plants that supply hot water to many thousands of units. No individual furnaces here. You pay for the season in advance. A/C is by split system units. It’s all very energy-efficient. The older housing stock in the cities often use individual coal stoves, to the detriment of the air quality. These are being replaced, but it will take time. In rural areas, meaning half the homes in the country, they burn coal, wood, and straw. It’s very smoky. Your state-of-the-art system is the same as one I had designed (in my mind) when we were in the states. Radiant in the floors supplied by a common tankless WH for heat and bathing.

    Reply
  • Phillip February 18, 2014, 5:30 am

    One thing to do is look into what other countries are doing when it comes to energy savings. I live in South Korea at the moment, and traditionally the homes are radiant heated. This is something that Koreans have done for centuries. Currently, the floors are heated by water which is in a system much like what you designed so the water is also your drinking and bathing water too. It is controlled by a special thermostat which can separate whether you want to just have the tap water hot or the floors and tap water hot. I do not know how much is spent on the install of floors here. I just know Koreans are cheap, so I am sure it did not cost a lot.

    Reply
  • Brad February 18, 2014, 5:53 am

    Can somebody explain the point of the expansion tank in this system? Is it to trap and condense and steam that might be formed in the loop?

    Reply
  • cwebb February 18, 2014, 7:08 am

    Great Post. I have an old home with no subfloor and at some point I’m going to have to replace all of the original pine flooring. That would be a good time to add a subfloor and something like this. Hopefully by then the price will drop even more.

    Are you going to post an article that summarizes all of your energy saving changes to the new home when its done? I’m curious to know if you’ve changed out all of the windows, or if you just plan to insulate the old ones.

    Reply
  • Philippa Waterman February 18, 2014, 7:48 am

    Those huge windows will be fantastic ! The light will be amazing. Just one word of caution with the new heating system. You guys love the outdoor life and, in winter, after building a few snowmen, you’ll need a place to dry out gloves, hats and boots properly. Radiators work well for this, but warm floors are not so effective – a drying area with a radiant heat source up the side of one wall where you can hang stuff could work.

    Reply

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