Thursday, June 25, 2009

Buttoning up the radiant heat floors...

It's brutally hot and humid here in Kentucky now, which makes it an odd time to be discussing radiant heat, but I'd like to describe the final details of our radiant floors as we implement them.

I fired up the system this past winter and it worked great for heating the house and keeping our feet warm. In fact, the home-made aluminum transfer plates (10 to 15 cents apiece thank you!) were so effective that when we walked on the floors, we could feel exactly where the plates were located. But because we hadn't installed our ceilings yet, we had a lot of misdirected heat. The radiant tubing in the first floor inadvertently heated the basement, and the radiant tubing in the second floor made for hot heads on the first level of the house (with heat coming from the ceiling, it felt like talking on a 1990's cell phone for 2 hours). Before installing our finish ceilings, I took precautions to ensure that very little of our heat gets misdirected in our finished house.

The photograph shows what's above the ceilings in our timberframe house. To the left, you can see the PEX tubing affixed to the subfloor with aluminum transfer plates. The tubing runs left to right (and vice versa) in the picture, between 3x3 oak floor joists. The floor joists and the tubing are on one foot centers. (I used 3x3's instead of 2x4's, because I cut them on my own saw mill and this gave me two chances to saw the 3" dimension without bow or taper.)

In the middle of the photograph, you can see a layer of heavy aluminum foil stapled beneath the floor joists, but above the tongue and groove ceilings. This foil is made specifically for reflecting radiant heat and can be bought on the internet or at a box store. (We found ours at Lowes.) Even though a lot of web sites say that kitchen aluminum foil won't work, I'd bet that it would work. But the purpose-built stuff is better if for no other reason than it has "scrim" or fiber embedded in it and therefore does not tear easily. Because I was working alone, I used a few ceiling boards to hold up the aluminum foil while I was stapling it up.

In the right of the picture, you can see the (tulip) poplar tongue and groove ceilings installed beneath the aluminum foil. The ends of the boards merely sit on top of the timber frame beams. I avoided nailing any of them, so if at any time I want to remove the ceiling boards (to reroute electrical wiring or to repair radiant floors), I can simply slide the tongue and groove boards back out of the way. (FWIW, the poplar boards don't actually look bone white like the picture - they have a green hue which mellows to a nice buttery brown color in a few weeks.)

Well, that's it. Rinse and repeat.


Blogger Bob said...

What did you use for the transfer plate material and where did you get it. .

November 21, 2009 at 6:05 PM  
Blogger Thomas Massie said...


I included more info on the plates in this posting....


November 22, 2009 at 8:00 AM  
Blogger Bob said...

Thanks. Have you had any issues with noise due ti expansion of the PEX? I have been looking at the extruded product but they seem expensive compared to this option

November 22, 2009 at 9:43 PM  
Blogger Thomas Massie said...

I hear practically no noise. Occasionally I hear the floors make an unobtrusive "tick" when they are heating up after being really cold. But I'm pretty sure it is the wood flooring expanding / contracting. But I don't hear the pex or plates at all. I don't know how or why I have been spared.. perhaps the issue is exaggerated by some homeowners? Maybe my plates are magic? :)

For one thing, my pump is always on... I would say there could be noise if the pump was turning on and off, or if zone valves were coming on and off. I don't have my zone valves wired yet.

November 22, 2009 at 10:12 PM  
Anonymous Floor Tile Heating said...


Nice blog! Lots of people are considering radiant-heated floors because of that extra level of spa-like comfort. Before you decide about a heated floor, you should know some of the pros and cons of these types of heating systems. Thank you...

September 2, 2011 at 2:49 AM  
Blogger SCHAFF said...

I LOVE YOUR BLOG! Could you explain how you got your ceiling tongue and groove to stay? I zoomed in trying to figure it out. The firring strips under floor look like they are right on top of the 3x3's. I would also like to know more about your geothermal water heating. I am planning an off grid timber home in Wyoming. How much per square foot did your home cost you? Sorry if I am asking too many questions, I am intrigued. ;)

September 15, 2011 at 1:06 AM  

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