Problem with Radiant Heating System

crr1223

Hi all. New here to this forum, but hoping someone can help. We recently had a two story ski house built with a very open concept on each floor. We had hydronic radiant heating put in throughout the main floor (single zone), with the basement (first floor concrete slab) fitted with baseboard heat. Because we wanted a open concept, the entire main floor was framed with engineered wooden trusses that essentially create one large enclosed cavity between the basement ceiling and main floor. The ceiling in the basement is drywall, and the main floor is plywood subfloor with an engineered hardwood flooring on top of that. The radiant tubing heats the entire cavity, but because the the drywall radiates more easily, the first floor is always 4-6 degrees warmer than the main floor (even without the baseboard heat on). The builder says he has built his last 10-12 houses in this fashion and has not heard of this being an issue before. He's been great to work with and wants to solve it for us. He thinks the only real solution is to rip down the the basement ceiling, insulate, and put it all back together. The other potential solution we considered is to cut floor vents into the main floor to allow the trapped hot air to vent up to the main floor. This would be a much simpler solution, but we're both skeptical it would solve the issue. I don't need it to be perfect, but would like to substantially reduce the delta T between the two floors. Any other thoughts/ideas would be appreciated. Thanks.

KC_Jones

Radiant floor heat should always have insulation under the tubes. There are different details depending on install type, but it is surely a requirement due to exactly the problem you are having. Insulation forces the heat to go which way you want.

Heat moves to cold and moves more readily to the path of least resistance.

I’m not an expert, but more details on the install type will help the more experienced give you advice on the insulation details you need.

ScottSecor

I agree with @KC_Jones. As mentioned the sheet-rock allows heat transfer better than the engineered flooring. You could pull the ceiling down as suggested and add insulation above the basement ceiling or you could add an "insulated ceiling" to the basement. Not ideal but maybe a drop ceiling, maybe fasten some sort of low density panels to the ceiling?

Are there area rugs on the hardwood floors? As you can imagine rugs certainly slow the flow of radiant heat as compared to bare hardwood.

With regard to the floor vents, I'm not sure they will work that well. Remember, you need to let air in to get air out. What I'm getting at is if you cut louvers in the ceiling below and the floor it might work better, but I would not want that setup in my house.

Jamie Hall

As @KC_Jones suggested -- the real problem is you are dealing here with radiant heat -- which is heating, probably pretty equally, the wood floor above it and the drywall below it. But... drywall is a miserable insulator (or, to put it another way, a superb heat conductor!) while wood is actually a pretty decent insulator. I can think of several ways to go after the problem, and it depends a lot on how far you have gotten with the interior. If the lower floor is still only partly finished, or unfinished, probably the best approach is to tear out the drywall, put insulation in, and put new drywall back up. However, if you didn't want that level of disruption, but had headroom to play with, you could put up 2 inches of rigid foam insulation and put another layer of drywall under that for finish. If you do the second, be sure to put in adequate furring to screw the lower layer of drywall to...

KC_Jones

How tall are the floor trusses in question?

I only ask because that may influence the recommendations for insulation under the ceiling. My parents house has them and they are ~24” tall which would be a big distance to have the insulation from the tubes.

Perhaps it doesn’t matter, just thought that could be an important detail to consider. Also the fact that the trusses aren’t solid on the sides of the bays, so that could make insulation a touch more difficult.

Does anyone have thoughts on doing blown in insulation? Since the bays are open in both directions I’m wondering if that wouldn’t be a less intrusive solution.