Retrofitting Radiant Heating
I don’t have any ceilings and I want to keep the actual pine subfloor as the finish floor. Planning to do a Retrofitting Radiant Heating. I was thinking of one zone per floor. Anybody has any experience with that? How is the comfort? How about the heating bills?
I don’t have any ceilings and I want to keep the actual pine subfloor as the finish floor. Planning to do a Retrofitting Radiant Heating. I was thinking of one zone per floor. Anybody has any experience with that? How is the comfort? How about the heating bills?
As per “Master Plvmber”, radiant works best in a masonry floor. I am a builder who has used radiant heat whenever it was appropriate and have done both masonry and wood floors, often in the same project. It is true that wood is a poor conductor of heat, but to overcome that in a retrofit application we use the usual aluminum heat transfer plates, with an special aluminum foil scrim covering the plate assembly and then a foam insulation (blown in place expanding foam) over that. We have had very good luck with this approach. One of the problems with trying to drive the heat through the wood is that if you use higher temperatures, you will have problems with the wood. By utilizing a lower temp water, around 150 degrees, the wood movement has not been a problem. All the clients that we have done this for are very happy with the strong points of radiant, which are comfort and evenness of heating. Will you save money? Maybe, especially if you upgrade to a high efficiency condensing boiler with sophisticated controls. But even with your existing boiler you WILL get a lot of comfort…and that is worth a lot I belive.
I installed radiant heat over my existing subfloor using a DIY kit that specs 1/2″ hardiboard for thermal mass. This process added 1 1/2″ to the height of the floor:
http://florheat.com/
I avoided the total drag of installing between joists. I still have my existing 80% or so efficient boiler, and will upgrade to a mod/con boiler eventually.
In exchange I had to trim a couple of doors and retrofit a bit of trim, and eventually will have to retrofit my staircases.
I saw about a 30% drop in my gas bill. It’s not 50%, but with a more efficient boiler I feel like I can get to 40%. And it feels really comfortable.
If I were the OP I would ask myself why I am married to the pine subflooring. It will warp and cup, and is not appropriate for radiant heat. But radiant heat, particularly when installed with an eye toward efficiency, is worth it.
I’m a customer. I installed radiant heat in a 2 story addition to the back of a brownstone. I can’t speak to the cost of heating since it’s part of heating the entire house with gas fired hot water heat and not broken out separately.
I do want to emphasize the heat transfer plates previously mentioned. I used Thermofin extruded aluminum plates. I diy the floor material and the plates were easy to fit, easy to install and made the pex as easy to install as pex can be. The second floor of my new construction install looked very much like your open ceiling. My first floor is a slab on grade; 1/2″ polyisocyanurate insulation went on top of the slab and then the Thermofin (different model) on ply sleepers which were the nailers for the finished <3″ oak floor. Very comfortable.
You will get some movement in the wide plank but part of that is due to the usual low humidity in the winter. The heat from the radiant is no more than a sunny room with no a/c in the summer. When the heating season is over the floor will expand again.
It is key to comfort and running cost to insulate the house perimeter where the floors meet the outside walls and between the floors very well.
I don’t know why I’m getting involved in this thread. I guess that’s what I do….
Cmu is a naysayer in general and not a hands-on guy as I understand it, but most of what he cites in his posts comes from a substantial accumulation of book smarts and should not be discounted. I agree as he does his ignorance is limited 😉
He’s right to question that claim of 50% fuel savings because it just ain’t gonna happen, ESPECIALLY in a staple-up application, and making claims that it will is just plain irresponsible and misleading.
Keep in mind, radiant floor heating (RFH) is largely a European invention and when it starting becoming popular in the US, its recommended installation methods and materials was constantly changing every two years or so in an effort to get it to work with our construction methods. (my brother and I went to a school in Minnesota for RFH in the early ’90s and the books we kept from those classes are largely obsolete)
Most construction in Europe is masonry: concrete block, stone and tile. We build floors with wood, which is an insulator and a terrible conductor of heat.
That being the case, heating a wood subfloor from the bottom requires a bunch of parts and re-engineering that Europe has really never had to deal with and never figured for. What that re-engineering has amounted to is nice, warm, comfortable floors in most cases. What it hasn’t amounted to is greater efficiency or fuel savings comparable to RFH installed in masonry.
One of the above posters mentioned using Warmboard which is an outstanding, but prohibitively expensive product for most homeowners. That is exactly the kind of product derived from decades of engineering RFH to work in American homes.
In short, if you want toasty feet and want the staple-up, I say go for it. But if you think you’re going to save money or the environment or whatever other goal you may have in mind, drop a cast-iron or wall-hung radiator in that room and have a good boiler installed by people who know what they’re doing.
If you can keep the water temperature low a mod-con boiler with and indirect HW tank is probably worth the price especially if you can still get the rebates. Again you are not going to gain large savings vs radiators.
Be aware that not all master plumbers are qualified to install radiant floor heat. As well as thermodynamic experts
CMU, maybe in a textbook closed system it doesn’t matter how the heat is transferred, but here in the real world it does. And a brownstone is not a closed system, it has heat loss. In the open air pex tubing will not transfer enough heat. Concrete or aluminum plates are used to CONDUCT the heat away. Conduction is the reason masonry feels colder to the touch than wood at the same temp. It is more efficient at transfering the heat from your body.
What type of boiler or heater would you use? I also need to address the hot water for the house. Shall I use the same system?
it definitely does not save 50% by itself. maybe when you install it you make other changes like more insulation, new windows, etc. and it gives you the impression of a greater savings.
personally even if it didn’t save a dime, i’d do it (as long as there was easy access.)
it’s just so much more pleasant than any other type of heating.
“You have never used it yourself as you quoted and your ignorance on the subject is quite limited”
Yes, my *ignorance* is, indeed, *limited*. But my knowledge of the laws of thermodynamics and physics remain sound. What you’re saying is rubbish as any engineer would know.
In a closed system, it does not matter HOW you transfer the heat, it’s the same. There NO heat loss in ANY radiator, since it’s INSIDE the room. So the ONLY issue is the external efficiency (lower water temp. is reduced heat loss in the “boiler”, compensated somewhat by higher pumping loss as you have to move more water around. And, as I said before, the *perception of warmth* which can (but not does not force you to) lower the thermostat.
Please cite any study that says saving approaches 50%.
Hi birchwoodc, maybe I was too harsh on my last post, I really appreciate professional opinion like yours, but precisely to avoid comments like cmu, where just comments because has some free time, but not knowledge on the subject, I wanted to hear from real users.
Actually, since you were talking about the savings of using lower temperatures, does the radiant heat needs to be on longer because it uses lower temperatures or it doesn’t work this way?