air space between insul & underfloor plates?

hr

or a list of brands or products that are harmful? I hate to heqar these un substanciated rumors :)

As I watch spray foam go in it turns from a liquid to a foam block in seconds. I'd wonder how it could effect the tube in those few seconds? Once dry it doesn't even stick to pex tube, fdrom my experience.

I know there are many differents products used. One contractor in this area sprays a soy based product.

Judging by the resperitors the installers wear it has to be fairly toxic in the airborn stage.

hot rod

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tim smith

Air space between underfloor plates and insul

Opinions please, with plates and tube underfloor, shallow joists, air space between plates and insul or not? Thanks in advance, Tim. GC does not want to do ridgid!

Paul Pollets

Insulation

I like to leave 1-2" air space between the bottom of the plate and the insulation. R11 is still available, R21 if space allows. I use plain batts without foil, or kraft faced.

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tim smith

Paul, thanks for the reply

I usually like to leave some space but with plates I felt that the transmission is mainly being done by the plate and not the air space as in normal staple up. What's your opinion?

Wayco Wayne_2

Plates

dont need an air space like suspended staple up does, but... Is there a benefit to having an air space in that it might give a more even heat across the floor? I know I changed my kitchen from suspended to plates last Fall and I missed the eveness of the heat sacrificed for the ability to have more capacity per sq ft. WW

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jp_2

gravity lets you down

even if you try to push insulation tight after a while it will sagg under its own weight and you'll have an air space.

tim smith

Thanks all, hoping for even more opinions, Tim

jp_2

watch out for:

end of joist bay where it meets the outside rim joist. these ends should be insulated first, making sure there is full depth of insulation on the 'outside wall surface'.

if the insulation just goes to the end of the bay, when an air gap happens then you have no insulation at outside edge(gap area). this will wreak havoc on the floor heating.

hr

Spray foam

handles all the issues.

It's easy to build up a gob at the rim joist. It doesn't settle or absorb moisture. It seals all the infiltration points at the rim and plates to foundation, etc.

Excellent r value, easy to apply (have someone else do its

And it glues all the framing members together for a strong floor joist assemble. Good sound deadning too.

If it is a crawl space with concrete or block stem walls, spray them also!

For small areas you can buy DIY kits www.tigerfoam.com

hot rod

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Glenn Sossin_2

foam

I was at a Viega training last week. What a facility. Anyway, I heard from the instructor that some of these spray foam insulation products are not compatible with pex. Anyone else hear anything along these lines ?

Tom Hopkins

Edge insulation

Rim joist insulation is most crucial. I'll gladly pull the tubing away from the perimeter for added insulation. Spray foam (isocyanate?) solves better than any. Good R value and stops the dreaded infiltration.

Under plate insulation is a little trickier. Wayne, I'm sure you were shooting for lower circ temps as well as btu output when you switched to plates. With a modcon we all know lower circ temps = better efficiencies. As I understand plates we want to heat with conduction rather than convection. Striping, even with plates, is going to be evident with tight (spray foam or jammed up fiberglass) insulation below the plates. The important thing is the Btu's are going to the space above.

Sure, an air gap between the plates and the insulation below will allow a certain amout of convective and radiative (is that a word?) to bounce around between the heat source, the insulation, and the floor above allowing for more evenly distibuted between plate temps but at what cost? Even insulation absorbs Btu's.

As you might suspect I'm not an engineer. Common sense and practicality prevail in my way of looking at things. I have learned so much from this web site with guys like Hot Rod performing infrared camera tests on various installation techniques. Queries like "I thought my floor would be warm" from homeowners drive me nuts. If we can heat your home to a comfortable room temp with a "cool" floor, then somebody (or a few people) did an outstanding job of putting a package together. Hydronic design, construction techniques, and insulation competence come together with an energy efficient package that serves in the best interest of the end user.

That being said, I think, with no empirical data to back me up, that insulating as close to the plates is the best course. Spray foam the plates and surrounding floor and force the heat to go to it's control, the thermostat at the floor above.

Common sense (and sometimes brute force and ignorance) will prevail.

Alan(OnVacationInOregon)Forbes

Joist Bays

It might be the ultimate in insulation, but I like to leave my joist bays accessible since (it seems) I'm always running new wiring and plumbing.

John_162

Viega Training center

Glenn
can you elaborate on the Viega training center and how was the class?