Radiant under carpet

Glenn Sossin_2

A proper heatloss with the right information tells you if there is a problem or not. Shooting from the hip and saying it can't/won't work is exactly that - not very accurate comments. That's why we have computer modeling. If we are taling about Fargo, North Dakota, with design temps of -25F (just guessing), I would agree we may have a problem with carpet - but we still do a heatloss to find out.

My house is 100% radiant, three of theb edrooms and my family room are carpeted. My bedroom has tray ceilings and the carpet is a pretty plush nylon. I used climate trak under all the carpets. I will admit, when I try to use the setback function of my thermostats on 10-15F days, I have an issue with response times - too slow for my liking. But generally, no problems heating the rooms.

My family room has a relatively thin burber but a 9ft wide French door unit at one end, and an 8x6 picture window at the other, with a valted ceiling. I knew, uprfront, that I was not going to get sufficient heat out under design load conditions from the floor- thats why I chose a berber. I did put some heat in part of one wall - in retrospect incorrectly, by simply looping the pex in the stud bays with a reflective bubble type insulation to direct the heat back into the room. We don't have any heat issues in this room.

As I have said in other posts, too often, we lose sight of the fact that we design to a worst case scenario which is rarely reached and we don't take into account potential heat gains. Simply put, that means we have excess heating capacity almost all winter long. It's just on the coldest of days that we may struggle to keep the temperature up.

Ed Lentz_2

I have a brother in law that swears that radiant under a carpet won't work. Says he was told that you can't put furniture on it without "special" feet on the legs, otherwise the pex would be crushed or the covering over the pex would be perforated. I told him the guy he was talking to was full of it. Who's right? He has a slab with insulation under it and about 380 sq ft with alot of windows. I think he is going to put in baseboard but I think the guy he is talking to is nuts.

jp_2

i was once

told by a concrete guy that the bluefoam board would crust under the weight of the concrete(basement floor), his example was furniture feet on carpet. at that point i realize it was no use to try to explain anything to him.

guess it depends on the 'tonnage' of the furniture.

Mike T., Swampeast MO

No way on earth that furniture legs could be a problem but carpet is another story...

If wall-to-wall carpet is used, such must be compensated for in the design. In general you avoid thick or plush or wool carpets and use thin pads with relatively low r-value. VERY easy to require a significantly higher supply temperature with carpet compared to other floors.

jp_2

well maybe actually

if they used warmboard, or something like quik trak then carpeted right over it, you could have a problem, never underestimate what people are capable of doing!!!

Unknown

the job I did...

Did a job turning from a screen porch into a year round room with a lot of windows, patio doors. Its was slab poured over slab.. Knowily the customer will have thick carpet for their seven kids to romp around on... Installed alum/pex AND cast iron baseboards with 2 stage thermostat... I stopped by during the coldest part of the winter.. Thermostat set at 72 and temp at 72.. Warm carpet no drafts from windows.. Kids all happy, customer happily wrote me a check...

hr

I'm not a fan of carpet and radiant floors

will it work? (heat the space on design days) it is all in the numbers..

One area to watch is the temperature the carpet pad sees on top of the subfloor.

Get to warm at that point and you may get some outgassing.

Not a lot of wiggle room if you miss the design, the subfloor, pad, and carpet have some not to exceed temperatures., Usually 140F for the subfloor and some foam pads below that temperature. Now add the carpet and pad r-value to determine your output.

The Rad Pad has some tables for quick calcs. It shows 1/2 foam pad at r-2.0 and 1/2 carpet at 1.4= R-3.4

The "radiant friendly" pads would be a good idea if you carpet over radiant.

hot rod

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Ruthe Jubinville_2

pad under carpet most important

check with carpet manufacturer as to what pad to use with radiant. It Heats very well under carpet if installed correctly.
Ruthe

Unknown

warmboard actually advocates this. they told me they tested using a "fat lady in high heels", but I think they were joking

Personally, I want something hard between tubing and floor surface, but there it is.

Glenn Sossin_2

Carpet & Climate Panel

Sometime around 2000, I went to a class training at Viega. They had cross sectional blocks of various installations in their training room. One them was climate panel with a very thin carpet - nothing like I'd ever seen before. It was maybe 3/8 of an inch thick almost like indoor/outdoor carpeting. I questioned them on the use of climate panel with such a thin carpeting. He told me this was the kind of carpet they used in Europe and had no problems with this type of installation.

I had a similar thought with the high heel idea, but I was thinking of the legs of French Provincial furniture, a dining room hutch, or the little wheels on a grand piano where several hundred pounds of pressure weight could be exerted over less than a square inch of area. He suggested, if we knew this condition might exist in advance, to lay down a layer of 1/8" masonite then the carpeting. This would minimize the R-Value addition, and still allow protect the panels.

Never did this, never felt the need. Other than a job with loose drywall screws laying on the exposed the exposed panesl with installed tubing, which of course resulted several piercings, I've never had a problem of this nature.

Unknown

true. though I do have to report that one of the contractors we work with has done several WB jobs using the ideal sponge rubber carpet pads we wish everyone would use, and no further underlayment. over time, the tubing grooves were noticeable on a couple of projects.

I'm not aware of any puncture occurances either. But, I don't want to be the guy who gets the call when someone drops a meat cleaver in the living room someday. Likely? not at all. but sooner or later, it's not a question of if, it's when. Maybe a few lifetimes, but still