Insulation quotes in... now I have to decide

Momto3kiddosNovember 6, 2012

We are building a 5200 sq ft one story home in central NC (zone 4). Exterior walls 2x6 16" OC. All ducts will be in the sealed crawlspace, and all quotes below include sealing the crawl. Because of the large sq footage of roof and no air ducts in the attic, we are not interested in insulating at the roofline. We do plan to have a radiant barrier on the roof.

$11K = R-19 Rolled batts in walls, blown fiberglass attic to code

$15K = R-22 Asure-R Blown-in fiberglass in walls, blown fiberglass attic to code

$23K = R-18 3in closed cell foam in walls, 6in at ceiling level to code

Because of the numbers, we are leaning towards the Asure-R blown in fiberglass. Foam just doesn't seem to be justifiable. I like the continuous and consistent nature of the blown in fiberglass as opposed to batts.

Will I still need 1" XPS (R-5)or just zip sheathing? Also considering ZIP R sheathing instead(R-6)... any feedback on this would be great as it is a new product which combines housewrap, rigid foam, air barrier all in one product.

What else do I need to be thinking about? I appreciate all feedback. I have been learning a lot about insulation, but still do not understand much! Thanks in advance.

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LOTO

Just getting my bids in on my new construction and bid all 3 like you did....going with blown in fiberglass myself.

    Bookmark   November 6, 2012 at 11:43PM
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lzerarc

You are on the right track. Stick with the blown fiberglass. Foam almost never has a payback in walls. Spring for the exterior rigid and zip if you can. Zone 4 isn't a huge heating climate, but the xps will help your thermal bridge and tighten it up better. Best thing to focus on is air sealing. Your attic/ceiling is just as important as your walls, some think more. Reduce the amount of cans and if you do, use air tight and seal to the gyp. Also use air tight drywall.

    Bookmark   November 7, 2012 at 12:31AM
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worthy

The Oak Ridge National Laboratory's Zip Code calculator gives you a better read on cost effective insulation R values than Code minimums.

I've found exterior foam board and fg work well in a colder climate. ZIP R resembles Dow SIS but is new to the market and there are many questions.

    Bookmark   November 7, 2012 at 9:59AM
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energy_rater_la

I'd invest in foam sheathing to exterior
conventional insulation and air tight drywall
approach for walls. tape all seams of foam sheathing,
caulk or use sill seal under sole plates.

if your ducts are all in the crawlspace
then foam seal floors, and mastic seal
all ducts,return air, plenum connections, and supply
boxes to floor.

you should have a continuous vapor barrier on the
ground and ducts shouldn't be within 6" of vapor
barrier/ground.

will crawlspace be open or closed??

in the attic air seal all penetrations.
wire & plumbing penetrations, ICAT recessed
lights (insulation contact air tight) not IC
lights, seal oversized cuts for bath and stove
vent fans.
concentrate air sealing efforts at attic floor
to minimize air leakage into living space.
once air movement is stopped, then insulation
performs as designed.

invest in baffles in rafter bays to keep air
pathways clear.
chose one method of ventilating attic.
gable vents
soffit and rigde vents
of soffit and passive vents

best of luck.

    Bookmark   November 7, 2012 at 2:32PM
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