Placing thin gauge sheet metal down underneath luxury vinyl?

b1004u

Got an idea I wanted to run by some professionals before I dive in. I have an underfloor radiant heat system that I have had for about 12 years. It is in an old house, so the radiant was installed under the subfloor by stapling up 16" aluminum panels with a channel in them to hold the radiant tube. Each floor joist has 2 tubes of radiant running down it. Then, net and blow insulation was blown in to the floor joist (not foam spay, the cellulose stuff) so the heat would go up into the main floor, not down into the basement. I can attach some photos if necessary. The heating system has worked, but never made the main floor super toasty.

I am now remodeling my main floor, doing a number of things to make the system more efficient, such as upgrading my windows. I am also pulling up the old flooring, getting rid old layers of linoleum and such, and will be putting down Luxury Vinyl over the subfloor.

But, the other day I had an idea. What if I were to go to a sheet metal shop and buy large sheets of sheet metal, or aluminum, and lay them down spaced out between the subfloor and the vinyl?? Would this give the radiant system something more effective to heat up than just wood and vinyl? Is it a crazy idea?

mattmia2

Wouldn't make a difference. The heat would still have to conduct through the wood subfloor to get to the metal sheet. It also would probably be noisy as the metal moved around both from expansion and contraction and from you walking on it and it might eve cut through the vinyl as the seams between the metal sheets moved around.

hot_rod

probably not worth the cost, it may try to buckle unless you glue and fasten, a lot! Not sure what glue would hold vinyl to metal? And metal to wood?

Any idea of what the room heat load is? How hot of supply are you running?

EdTheHeaterMan

Your insulation may need to be upgraded to something with more R-value. I was told by a manuf. rep. for a tubing company, that you need at least 3 times the R value below the tubing as you have above the tubing. More is better! So if the sub floor and floor covering has an R value of 3 or 4 for example (say 5/8" plywood with 1/4" underlayment plus 1/2" foam carpet pad and a close pile carpet is above the tubing), then you need at least R-9 below the tubing, But I might use R-13 or R-19 if it fits. The radiant heat will radiate in all directions, up down, or sideways. So you want to insulate in the direction you don't want it to go.

hot_rod

As @EdTheHeaterMan mentioned, it’s all about r-value. Carpet and pad doesn’t belong over radiant IMO, If you have some in underperforming areas, rip it out!  Throw rugs with a thin anti slip pad can be acceptable 
It will always be the load that gets you. Mid 20’s BTU/sq ft is about all you can get from a comfortable radiant floor. If some rooms have loads above that, some supplemental heat may be need on design days

Without a heat load number for each room, it will be trial and error 

The rim or  band joist insulation us a huge leakage, spray foam it for r-value and infiltration sealing.

ratio

If there's several layers of old flooring that you'll be removing, that effectively lowers the R value above the heat, so more of it will want to go up. Also keep in mind that the more efficient the house, the less heat needed to keep it warm & thus the cooler the floor will need to be to provide that heat.

b1004u

Thanks everyone. I appreciate the input.

Yeah, I will be removing old layers of flooring to decrease the R value above, hopefully improving the heat transfer upwards. wish me luck!!!!!