Insulation for suspended tube

Mark Walnicki

per their Complete Design Assistance Manual (CDAM). I guess this makes this a suspended tube install?

Insulating the ends of the joist bay is a must, right?

The manual instructs to use a 2 inch air gap between the subfloor and insulation. What, if anything, happens if that is increased to 5" ? Must the 2" air gap recommendation be strictly followed?

Finally, they also say unfaced batts are fine to use for insulation, and foil facing is not necessary. To me it makes more sense to use the foil faced stuff. Does it really not matter, or is it better to go with the foil? Also, it would seem to me some sort of facing would always be needed as a vapor barrier, even if it were a tile floor.

Any thoughts and opinions greatly appreciated.

Andy N.

insulation

from my experience I would definitely insulate the ends of the joist spaces. This keeps the heat from transfering to the outside of the house. I have used foil bubble insulation and had good luck, the air gap was about 7" at some points where we insulated under the bridging, ductwork and plumbing. These areas worked just as well as the 2" air gap areas. I have also used unfaced r-19 with a 2" (more or less) air gap and had great success. The suspended tube method works surprisingly well with no striping, although water temps are considerably higher.

just my opinion,

Andy Nord

hot_rod

tight as possible

on the end insulation. I usually sub the insulating out to pros. I HATE working around insulation I have them use spray foam on any cracks and joints in the rim joist to stop infiltration, then at least 6" batt. The more the better. Insulatore generally have those large spray foam canisters wuth them for foaming around windows.

One GC I work for goes the extra distance and has the rim joist and crawl space foundation walls foamed with isoneyne (sp) That stuff really kicks the infiltration.

Remember heat travels to cold. The greater the delta T the greater the flow. Very important to insulate the rim joists as the other side of the 1-1/2" rim is outdoor temperature. Huge delta t there. Could be sub zero on one side and 140 on the other! Hard to over insulate!

Getting real hard to find aluminum foil batts anymore. Between the printing and the dusting issue, I feel the reflectivity is nil.

I'd try to stay close to the 2" on the air space, but as you know it's tough to gauge the space above the batts. If you use the wires to hold the batts in place merely push that wire support up 2" inches to get close to the 2" top space with R19 in a 10 or 12" joist. Or 8" batts held to the bottom of the joist gets you real close.

hot rod