Sealing Around Soffit Baffles to Control Wind Washing
christian_330
| Posted in General Questions on
Hey guys, do you think there’s any benefit to sealing around the soffit baffles so air flow can’t enter at the top plate and ceiling joist right into the side of the ceiling insulation and decrease r value? Sealing around with foam would force the air to travel up the baffle into the attic and not creep into the cellulose or whatever I decide to use right?
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Replies
christian,
I don't think so, especially with cellulose.
You can see the degradation in R-value you can expect from the tables on page 56 of this report, they are pretty low. https://www.rdh.com/wp-content/uploads/2017/10/Van-Straaten-Windwashing.pdf
Is that an illusion? or is the bottom of the baffle picked way up off of the top plate? If so it looks like it would keep insulation away from where it should be...
That's a good catch -- ideally you want to insulate over the full area of the top plate.
Regarding air flow through those leaks, it probably won't make a lot of difference, since it's small. I personally would probably hit those gaps with canned foam anyway though for completeness -- it would be pretty quick going using a foam gun, and it would help to lock the baffles in place a little more securely too.
Bill
No that’s not an illusion. My roof pitch is so shallow that it’s really hard get any staples in there from the top to hold it down. If I pushed the baffle down far enough to get it to hold it down flush with the top plate on its own the baffle was basically protruding past the ceiling joists and insulation could blow into the soffit on the sides.
christian,
What a lot on insulators do here is use part of a fiberglass batt to help hold the baffle, and block the rafter bay so the blown cellulose can't leak out.
Mineral wool might wore better for this than fiberglass in a tight spot, because mineral wool is "stronger", for lack of a better way to say it. Basically mineral wool isn't as squishy, so it will stay in place better -- especially if it's partially there to hold something else in place.
If you pre-bend those baffles over a sharp edge prior to installing them, they'll be a tighter fit against the top plate and will allow for a better fill of insulation. The gentle curve you have in those pics is going to make for a pretty big un-insulated air gap above the top plate.
Bill
Ok, will see how I can address that. Thanks everyone.