Latest Discussions : HVAC


05:18AM | 11/04/05
Member Since: 02/26/01
35 lifetime posts
I am building an addition on my 70 year old house. The addition is stick (2x6) on a CBS block foundation (w/ ventilating screens as per code) wall for the crawl space. Similar additions in my area (Northern Virginia) use R-30 batt insulation in the floor joist bays with straps or other support to keep the batts from falling out. I want to achieve the highest degree of R value given that my floor joists are 2x12.

I am considering using high density faced batt giving me an R value in the 40s then stapling window screening (I have a spare roll sitting around) to keep the batts up and the bugs out. My neighbor suggested using foamboard to keep the batts in (pink Owens Corning or blue boards a the local big box stores) since a 1 ½ inch board also gives an extra R value in protection and would seal out moisture from the batts. However, I think sealing the joist bay in this manner has the potential of locking in moisture in the joist bay.

Any thoughts on this and is there a better way. (BTW, the addition is small (8x21) but the 8’ joists have blocking so even though I have access and it’s a small job, each bay varies in length by an inch or so).

Thanks for any input.

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