Attic insulation question

belliott · May 20, 2012, 8:28pm

Since you guys concentrate on such things I am hoping for an opinion on the attic space pictured.
What you see is a new third floor addition with a cat 4 HVAC unit that is drawing inside air.

R30 batting as seen and baffles setup behind it from the soffit vents as far as I could tell .
These soffit baffles run to the ridge vent under the R30.

A couple questions I have is this now conditioned attic.(no vents from unit)

Why run baffles to ridge vent between the rafters?

Any big issues pulling air from in the attic with schedule 40 out the peak?

Condensation concerns with this setup?

Thanks in advance.

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ldapkus1 · May 20, 2012, 8:58pm

Was the contractor Polish?

mcyr · May 20, 2012, 9:30pm

Bob, this is similar to a cathedral ceiling in a living space.

The kraft face is not covered for a fire protection. I note that it is not a living space, but it would be considered mechanical space, right?

If the make-up air is coming from the attic, condensation will occur in colder months where ever the leakage is coming from. In which case, could be air being sucked in from the kraft faced staple flaps.

Is this an HRV unit.? Heat recovery Ventilator.

mcyr · May 20, 2012, 9:34pm

Bob, this graphic may help.

http://www.faryal.net/image/339-0.jpg

ldapkus1 · May 20, 2012, 9:38pm

The tabs aren’t even stapled to the rafter correctly. You’ll get air migrating between the rafters and insulation and condensation on the sheathing.

lkage · May 20, 2012, 9:53pm

Linas has a point. The vent baffles should be full width between rafters. Much air will be sucked in from the open ridge vent. (Why was it open to the attic with no insulation?
http://www.nachi.org/forum/attachments/f58/55444d1337545677-attic-insulation-question-dsc08623-1024x768-.jpg

belliott · May 20, 2012, 9:54pm

thanks Marcel,will use that graphic.
linas the staples were pretty tight with no sign of issues as this was built 2005 on a greysrone and brick listed as 50s by county.
what is wrong with the stapling?

mcyr · May 20, 2012, 10:14pm

I think he is referring to the stapling of the flap.
It can be done either way, but should be tight to prevent air leakage.

Allow friction to hold the batts in place. Or you can staple the flanges of faced batts to the inside or face of the joists. (Stapling on the inside is preferred by many drywallers because it leaves the edges of the framing members easier to locate. However, your local building codes may require you to overlap the flanges and staple them to the edges of the framing members.)
http://www.jmhomeowner.com/products/product.asp?category=FiberGlass&Product=KraftFaced:)

belliott · May 20, 2012, 10:27pm

larry Is there a way to check without pulling back the batting?
lol.
Full width makes sense however.

mcyr · May 20, 2012, 10:40pm

Bob, a more proper way is to cut 1" strips nailed against the rafters up tight against the sheathing and then pressure fitting a 1/2" Polyurethane board or equivilent against it and installing the insulation.
This method provides and airtight assembly and continuous vent unobstructed to the ridge vent for proper ventilation.
The air sealing is the key. Batt insulation is not the best product for air sealing when you have to rely on those flaps whether nailed inside the members or flat on the outside.
I have had much luck with this type of installation.

belliott · May 20, 2012, 11:39pm

I hope you are not suggesting spray foam after I saw this in the basement at the same place.

You guys think I have large reports just for the fun of it I bet.

P.s that is a shower drain trap.
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mcyr · May 21, 2012, 12:06am

LOL.