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Re: GBlist: How much insulation to put in roof & in floor? -Reply




On Mon, 7 Jul 1997, Arnie Katz wrote:

> Date: Mon, 07 Jul 1997 14:00:04 -0400
> From: Arnie Katz <AKATZ@AEC.NCSU.EDU>
> To: greenbuilding@crest.org, london@sunsite.unc.edu
> Subject: GBlist: How much insulation to put in roof & in floor?           -Reply
> 
> For the floor: In a similar application(open crawl space, 2 X 10 joists,
> Chapel Hill, NC area) I used 9.5" R-30 with Tyvek across the bottom of
> the joists. In addition to the higher R-value, since the floor is exposed, I
> wanted to get the insulation up against the sub-floor. Typical practice
> using R-19 with tiger teeth, tends to create compression and lots of
> gaps. The R-30 filled the space entirely and stayed in place without
> mechanical support while I installed the Tyvek. Since I was using the
> sub-floor as the air-barrier, I wasn't terribly concerned with infiltration
> control per se. The Tyvek, hopefully, reducing "wind-washing" of the
> insulation, but was selected primarily as the least-cost, fastest,
> somewhat permeable material to act as a critter barrier. After seven
> years and lots of critters, it is still in place with no tears or holes.

Would it be worthwhile my adding extra joists on top of the old ones
to contain yet more insulation or would it be a waste of time & money?
 
> For the roof: I can't suggest what is optimal without knowing your
> ventilation strategy and a little more about the entire roof assembly. Is this
> to be a ventilated or unventilated roof? If ventilated, how do you plan to
> do that? Are you using a radiant barrier? If so, where? What is the
> roofing material? Are you using solid decking, or metal on open purlins?
> Is the ceiling to be sheetrock? If not, where's the air barrrier?

This is a tin roof [tin nailed to 1"X4" nailers spaced 16"OC attached
perpendicularly to the tops of the rafters]. There is ventilation up the V
grooves and between the nailers as well as along an inch or so space above
the insulation. There is no radiant barrier. The ceiling boards (1/4" AC
Fir Plywood) will be attached directly to the undersides of the rafters.


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