The use of “Warm Board” for RFH.
Hornick
| Posted in Energy, Heating & Insulation on
Hi all,
I am undertaking the construction of a 2500 sq ft two story with approx 1400 sq ft on the first floor. I wish to RFH this portion of the home and “Warmboard” has been brought up as a possibility. It acts in place of the subfloor decking and allows the PEX tubing to fit into recesses. It is fairly cost heavy on the front side ($222 per sheet CDN) and the sheets are 4×8. As it is installed right to the joists there is no subfloor cost and they say you just do the rest of the business right over the top, tile, wood floor etc.
Has any one out there used or been using this product and could perhaps offer some advice.
Thanks,
Brent
Replies
i've seen it installed before the tubing went down... looked pretty impressive... but that's all i know..
Mike Smith Rhode Island : Design / Build / Repair / Restore
A good idea I have seen for floor heat if its not a slab on grade house is using a thin layer of concrete with 2x4 sleepers layed out every couple of feet. The walls are layed out, 2x4's are nailed to the decking and sleepers are also nailed to the deck. The tubing is layed out and a thin layer of concrete is poured on top and screeded level with the 2x4's. You can then nail wood flooring to the sleepers.
This works better than the stuff you are looking at because the tubing has some surface area direcly to transfer heat into the concrete. I also would bet it is a lot cheaper to install. You can use lighweight concrete or there is some other product made of gypsum they also use. You may need to beef up the floor joists a little.
John Siegenthaler has a great book on residential radiant heat.
Brent,
It is a very nice product. It gives excellent and uniform heat transfer. a couple of small points:
1) $$
2) Due to the nature of the board, some seams where two sheets of warmboard butt together need to be blocked from underneath. The grooves eat up some of the structural strength of the subfloor in certain directions. Sometimes this blocking can interfere with mechanicals.
3) Since it's so pricey, its tough to install this as a subfloor under cabinetry, kitchen islands, etc, places where heat will not be run. You'll need 1 1/8" material to match the height. Not a big deal, just something to think about. And usually another seam to block.
4) Your tubing goes where the warmboard says it goes. If you have high heat-loss rooms, such as a glazed sunroom, can the spacing and tube size of the warmboard meet the BTU loads required? Usually yes sometiimes no. "No" can be a pain in the rear.
5) Again, your tubing goes where the warmboard says it goes. Sometimes an architectural feature in the room, or part of the structural framing in a room, will break a run in the wb. With regular RFH tubing layout, you just zig-zag around it. With warmboard...it's a little more work.
6) Yo need to protect the wb and tubing from the trades during construction. Occasionally repairs need to be made to fix accidental damage by workers.
It's a great product and it offers excellent heat distribution. I really like it. But it can be both a timesaver and a time eater. I give it two thumbs. One up....and one a little bit down.
What ever happened to Barry?
Thanks Mongo,
From the video they sent it seems easily installed except for the added floor joists or the blocking required under the groves/seams not supported. There are several router templates that allow you to move the tube layout for some customization etc. The big question is its performance vs cost to installing light weight concrete or gypsum over the tubes and also the added structural framing needed to carry a poured floor.
I'm hoping to complete the 1 st floor with RFH and the bathrooms on the second floor also with RFH. The bedrooms would have high velocity forced air from a heat exchanger so I can also add air conditioning and meet the local code requirements for a waste heat recovery ventillator. decisions decisions .......
thanks again
Brent
Cost-wise, I'd say it's comparable to gypcrete.
Here (CT, USA), gypcrete is about $3 a foot. Subfloor $.75 a foot. Stapling tubing down, sleepers, blocking, etc, etc...when compared to the warmboard at about $4.50 a foot it's a financial wash.
Warmboard is "thinner" than a gypcrete floor.
Gycrete subs have ticked me off in the past.
Warmboard would be, in my experience, more (low-mass) responsive as a RFH platform than a gypcrete floor. You may want that, or you may want the "medium-mass" (my opnion) of gypcrete in your house.
Please dont think that in my previous post I was tearing down warmboard. I probably have an even longer list of minor gripes for gypcrete.<g>
In today's world, if I had to choose between the two, I'd go with Warmboard.
>I probably have an even longer list of minor gripes for gypcrete.
Me, too, and I have gypcrete here.
Right on, thanks for the responses,
I just got all the framing package, roof trusses windows etc back and things are financially in the good areas so the added cost of warmboard vs the rest of the will perhaps pan out fairly well. Time of installation is also a bit of an issue and the warm board appears to be alot quicker to get in and covered. I still have the cost out of the heating plant to make so I'll see where that takes me. Looking at 87000 btu heat loss calc. and hope to have indirect water heater. any takes on this?
Cheers
Brent
Where do you live?
I live in the Northern Ontario Canada. And just realised a big mathmatical error with my heat loss calculation. This error being a indoor room temperature of 70 F and an out door temp of -15 Celcius, Crap this the last temp should be 5 F. Back to the calculator..........65000 btu seems better???
Edited 2/7/2003 5:15:10 PM ET by BHORNICK
Check out Wirsbo's Quick Track. It goes on top of the sub floor. Adds 1/2" in height. It's very flexible in installation, as far as changing tubing direction and avoiding obstacles. Cost here is about the same as Warm Board, per sf. It can be installed at the end of the project, which reduces the risks of tubing damage. I put about 7000 sf in a home a while back, and it seems to perform well. The only issue I've seen with top of floor RFH, is increased shrinkage in wide plank wood floors, applied over it. Just something to think about, when considering finished floor options.
Brudogggie