Overcoming Fiberglass Insulation's 3 MAIN PROBLEMS

[Imhocep]

I have a question on how to seal the transition between the kneewall and the sloped ceiling on a cape code upstairs but I cant find a "contact us" button on your site? the short question is should i put something on the lower side of the sloped part between the bottom of the rafter and the foam vent to keep air from washing through through the insulation from top to bottom on the sloped part?

[HowToHomeInsulation]

@Imhocep Great question Imhocep! The cheapest way would be to cut pieces of 2" foam board into a shape that fits in between the top of the knee wall, the rafter cavity and the foam ventilation baffle. Then air seal around the gaps with Great Stuff.

[HowToHomeInsulation]

@Imhocep Another way to do it is to screw a sheet of foam insulation board on the attic side of the knee wall and notch out the rafters. Then air seal around it with Great Stuff. Do the same thing for the floor. Notch out the ceiling joists so you can block air from passing underneath the floor. This method guarantees an air tight wall, ceiling and floor. It will prevent air from passing through the fiberglass and short circuiting the insulation. Let me know if this makes sense...

[Imhocep]

@HowToHomeInsulation yes, it makes sense..ive already backed the kneewall with foamboard, so its too late for th enothcing part, but the first method you suggest is what I was hoping would be a good solution. Thank you for your advice and prompt reply! Your site is great!

[Imhocep]

@Imhocep also, i already did the "bottom" part, which was what made me think i should do something to the top!

[Imhocep]

@Imhocep I was wondering if using the foil faced bubble wrap might be easier and cheaper, by stapling it to the top of the kneewall, the sides of the rafters, and then up against the provents (not squishing it, but stapled to the sides of the rafters and layign up agaisn tthe vent), to make sort of a baffle, and use great stuff in the gaps and caulk along the sides? Itd basically be the same idea as the foamboard, but alot easier to instlal and work with?

[HowToHomeInsulation]

@Imhocep Yeah, any material that stops air and allows you to create an air tight seal will prevent the fiberglass insulation from being "short circuited" when the wind blows. Another cheap and easy way to do it is by filling garbage bags with scraps of fiberglass insulation and jamming them into the rafter cavities.