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Help - attic finishing - insulation

14 years ago

Hello,

We are looking at actually re-doing the HVAC system (gas forced hot air) in the attic of our cape cod and while doing this I want to address future needs for finishing the walk up attic into living space.

My question is about the insulation. It gets very hot up there in the summer (up to 110F). The previous owner put R-19 in the rafters and R-13 between the studs. They left the attic fan, which make no sense to me (why insulate if you are leaving a gaping hole in the roof). I removed the attic fan. The windows are also old and very drafty, but will get replaced.

On the opposite side of things it does not get very cold there in the winter, maybe 55 at most and that is unconditioned, yet the HVAC system is insulated and sealed.

Since the HVAC system is already in the attic, conditioning the space is a given and the system is sized for this already.

I know it costs less to cool than to heat, but I am wondering if we should expect to have to rip out the R-19 and do spray foam insulation to get a higher R value. Will basic code require R-30 or higher in the rafters (in New Jersey)?

There is also really old insulation in the floor joists "separating" the downstairs from the attic. Should we pull this all up and discard, or is it sort of a moot , since it does so little?

What other concerns should we be addressing here?

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Comments (3)

worthy
14 years ago
Your attic insulation is way subpar--walls and ceiling. You can increase the roof insulation on the interior or exterior (or both). For the walls, even high-density fiberglass batts are inadequate; fir out the wall. Change out single pane windows. And seal, seal, seal. While adding a supply duct, provide a cold air return.

Before you start using the attic space as living space, check out the structure. It may well have been designed for dead storage only, using 2x6s that give you a floor that bounces like a trampoline as you walk across the space.

Here is a link that might be useful: US Department of Energy Recommended R Values
pjcampo
Original Author
14 years ago
Thanks

I guess I got to reading a little bit and realize now that once a knee wall goes up and the ceiling is dropped down down below the ridge of the roof, there is tons of room to add insulation - so the only place where there would be poor insulation will be the distance from the knee wall to the ceiling.

It is indeed 2x6,but the spans are short. We will sister as necessary and use thick plywood floor I think. We'll have someone take a look at it.
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worthy
14 years ago
I was assuming cathedral ceiling and no kneewalls. I shouldn't assume!

Insulating Kneewall Attic Source:Roxul.com

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