I just found out about this forum – seems like a good idea. Anyway, I have a question for the group’s consideration, related to putting in flooring over a radiant heat system that is in the joists, attached to the bottom surface of 3/4″ Advantech. We’ve bought and are about to install a 3/8″ engineered wood floor that will float on the surface – here’s my question: given the 3/4″ subfloor and the 3/8″ of engineered wood, should I be concerned about the insulative value of those materials when what I want them to be is conductive?
As I’ve been thinking of this, I’ve thought of the following idea: would there be positive (or negative) value in drilling holes (1/2″ or so?) from underneath, through the Advantech, so that when I float the flooring above there will be a certain number of open pathways for the heat to rise through the subfloor and then through the engineered floor?
I’d be interested in reading your responses. Thanks, Don
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It should not be a problem. I often do 3/4 subfloor with pex tubing stapled up to the bottom side, and then lay 3/4 T&G hardwood on top.
However, I usually will put 3 1/2" of foil faced insulation under the tubing, with the foil face up to reflect the radiant heat. The tubing should be in contact with the 3/4 subfloor.
The only consideration is that the heat will take a while to raise the room temperature, but this is true of almost all radiant floor installations.
Bob, you don't advocate drilling holes (of some diameter, at some distance interval) to help the heat through the subfloor?
Holes will have little if any effect (except to possibly weaken the floor) on this installation compared to what you would get from properly insulating in the joist space. I believe you should leave a 2"space between the top of the insulation and the bottom of the subfloor so that the AIR in that space has a chance to heat up the subfloor itself, which will then conduct to the finished flooring. What temperature water will you be running in the tubes/ did you do a heat loss calculation?
Here are a 'couple of good links that you will find fascinating:
http://www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=1
http://forums.invision.net/index.cfm?CFApp=2
Edited 11/18/2004 9:32 am ET by johnnyd
Johnnyd-
We are planning to put in radiant in a home in NH mountains. Also planning engineered (floating) bamboo flooring and engineered cork for kitchen, slate for hallways etc. Any comments?
Is the book provided at the website you mentioned worth buying? ($5 s/h).
Also, have you used any remote systems to turn on the heat so the house is warm when you get there? By definition, radiant is rather slow to warm the house, esp in a very cold climate.
thanks
JohnnyN
Haven't read the book.
Plan on including the cork in your load calc, because the very fact that it is resiliant makes it more insulative than hardwood or stone/tile, but not as insulative as carpet/pad. It's a compromise...softer floor but still conducts heat better than carpet/pad, and also acts as a pretty good (dark color) heat sink for south facing windows. Smells strange, though. Hopefully temporary off-gassing. I got mine from this outfit:
http://www.infinitycork.com/home.htm
Is this new house a weekend get-a-way, or do you just mean while you are away at work and home every night? I've read about controllers that respond to messages via telephone lines, or I suppose a fancy programable t-stat, but for away during the day, home at night, just leave it set the same. With R38 ceilings, R25 walls, and sealed up reasonably well, cells instead of FG etc ect etc and maybe outdoor reset, you'll have such a stable system you won't have to worry about ramp up.
"As I've been thinking of this, I've thought of the following idea: would there be positive (or negative) value in drilling holes (1/2" or so?) from underneath, through the Advantech, so that when I float the flooring above there will be a certain number of open pathways for the heat to rise through the subfloor and then through the engineered floor?"
The whole point of underfloor RFH is that you are using conduction to move heat from the heat source to the flooring material. Drilling holes will not help in any significant way because there would be no convection through them. Using heat transfer plates will help, as will insulation below. The setup you describe is not a heat transfer challenge using conventional methods. Certainly nothing like carpeting.
Don't want to hijack Don's discussion, but I have a similar situation coming up--same floor system. But I also have a big north-facing wall with lots of glass, and I would like to get a curtain of heat across it. What is to be said for or against adding radiant baseboard heaters to the circulation system of the in-floor installation? With thanks to the pros out there.
You'll probably be wanting to circulate higher fluid temps through the baseboards than through the in-floor, so the heat source (probably a non-condensing boiler?) will probably have to supply 180* for the baseboards and somewhat less for the in-floor (~ 120*). But this, to my understanding, is commonly done with mix down valves that use return fluid to dial-in the in-floor temp.
Try the heatinghelp.com forum for very specific information on this application, although they will understandibly try to referr you to a pro for this kind of application, which is way more than straight-forward.
Unless your engineered flooring has materials that have insulatiing values, there is no need to put holes in your subfloor. Don is right in that Radiant Floors use conduction to translate heat to the room. It will be very important that the PEX tubing has the proper metal plates attached to spread the heat out over the floor, and that the joist bays are indeed insulated as Don also menitons, to direct the heat upwards where it is supposed to go. I would suggest you visit sites such as radiantec.com in Lyndonville, VT. for more info and illustrations on the installations. I've found them very helpful and they have an interactive form in which they will provide an price estimate for materials.
No need to worry...it will work. I installed pex tubing throughout both floors, on tp of it is 3/4 subfloor, and 15/16" thick wide pine. Works good.