Air space between slab and floor

mph

Intuitively, I think you're right about the two layers being better. I'll suggest to the builder that he go that way. I have plenty of latitude in my design to overcome the R2.5 total.

Thanks again,

Jeff

mph

Air space

I'm doing a job where in my heating design I allowed for R-2 floor coverings over a slab-on-grade. The builder is planning to install 3/4" sleepers with 3/4" plywood and then 3/4" hardwood flooring on top of that.

What effect will the 3/4" air gap have on the heat delivery? Will be there be a decrease in response due to convection vs conduction in the areas of the gaps?

Is there a way to calculate an equivalent R-value for this gap?

The builder is also considering skipping the sleepers, but putting two layers of 3/4 plywood under the hardwood. He says all of their door and window heights were set assuming 2-1/4" of floor build-up. Would this method allow better heat transfer because of the full contact between the flooring and the slab or would the increased r-value of the additional plywood offset any gains?

My tubing is on 6" centers; water temp calculated at 115 degrees.

Thanks for your input.

Jeff

Weezbo

moisture is the enemy ,your carpenter friend

would do well to consider.

merry Christmas.

lets hope you arent back over there in 30 below at Christmas" explaining away " i mean you well ,i just say things weird:)

Plumdog_2

Change the window and door openings

it would be easier. Unless maybe the siding is all on.

mph

C'mon quys, can't anyone help me on this?

Jeff

Matt_21

i don't know exactly

but i would think the 3/4" air gap would act like an insulator and rob a good portion of your heat. if he has to go one way or another, i think you would be better off with the 2 layers of plywood and then the hardwood. at least you can figure the r-value that way. you may want to give the manu. a call to see what they say about the air gap scenario.

Unknown

I agree with Matt. direct conduction is better than having to radiate through an airspace, given the conductivity of plywood at least. It's poor, but better than air I think!

Perhaps the spaces could be filled in with a thinset mortar?

hr

With

two layers of 3/4 ply, then 3/4 hardwood seems you will be up against 2.6 R value. Make sure you still get the load with that R.

I too would go with the direct conduction transfer of the "sleeperless" system.

I'm not sure you could calculate very accurately that air space, performance hit.

The nailing will be better for the hardwood installers with the double layer compared to the sleeper system

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"