need to get r49 in ceiling for inspector
hvtrimguy
| Posted in Energy, Heating & Insulation on
Hey all,
I had a pre inspection meeting with my local BI regarding a sunroom addition. the architect had r38 in the 2 x 12 ceiling but the inpector wants r49 since it is electric heat in the entire house. The architect proposed firring down the joists anothe 3 1/2″.
I alsked about foam and she said her program didn’t offer a significant dirrerence.
what is your take? stick with FG or look into spray in foam?
“it aint the work I mind,
It’s the feeling of falling further behind.”
Bozini Latini
Replies
You can get R49 with your rafter depth using spray in foam, which is R5 to R7 per inch depending on the material. Corbond is closed cell and you would need 7-8" of it to get R49.
FG is generally less than R4 and probably won't qualify, especially batts. You'd have to decide how you feel about foam applied to the roof deck, and make sure your inspector will accept an unvented roof assembly.
across the bottoms of the rafters you put up 2" of Thermax foil faced foam. This adds R7,2 per inch so you have R38 plus R14 min for a total of R52.
You add strapping on the face of the foam and screw through the foam panels into the rafters at 16" oc. This provides some help from radiant reflection and a solid connection for the sheetrock.
If the inspector does not have "a program" that recognizes the value of foam, it is worthless.
besides, convection loops in FG batts are so well recognized that this foam panel will do more than all the FG above it to reduce heat loss. It also stops thermal bridging.
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I dont see how a inspector can fail you on insulation, you just be cold and have to pay the bills, but it not a structrual or safety hazard.
Edited 11/17/2007 3:51 pm by brownbagg
There are places that have energy standards as one of the points.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
There are places that have energy standards
Mine would be one of those. You are required to provide a compliance sheet at the plan review stage, and the Compliance checker gets and equal shot at you plans as the other 8 (residential; 11 commercial) do. BI can redtag at the "pre drywall" inspection if you do not have the review-approved insulation in place.Occupational hazard of my occupation not being around (sorry Bubba)
NYS has an energy code that needs to be met. if the heat system was hot water based it would be fine to have r38. but electric heat requires r49. also more that 15% of surface area of structure in windows is an automatic fail. he is letting me go on this one since I spec'd triple glazed weathershield windows."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
New Insulation requirements
Common sense is not in the equation. Regulators are saving the Planet, so they think
Is the sheet rock simply attached through the 2" Thermax into the rafters with 3" sheetrock screws?
A bit of an old thread,
but the suggestion is to install strapping below the 2 inches of foam with screws that secure the strapping (and the foam) to the rafters.
drywall would then be screwed to the strapping.
Note that the drywall thickness dictates the screw length needed and that needs to inform the choice of strapping thickness.
You should be able to use polyisocyanurate board insulation. It starts off at R-9 at installation, but will eventually drift to R-7. I've never had a problem specifying it when space was tight.
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