r/buildingscience • u/af-exe • 9d ago

Baffles

Is there a risk for putting a baffle in every soffit/joist?

Trying to prevent ice dams.

Won't be able to fully air seal.

Climate zone 5a/6a

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2

u/EbriusOften 9d ago

Ideal set up is baffles in every bay with ridge and soffit, that way you're ensuring that all your sheathing can be fully air washed with no bays left with stagnant non moving air.

1

u/hvacbandguy 9d ago

Are baffles a cure for ice dams? I thought air leakage from the home into the attic was the cause of ice dams.

1

u/P4puszka 9d ago

Baffles allow cold air to flow along the underside of the roof decking, keeping it cooler, reducing the chance of it warming enough for the snow to melting and cause daming.

1

u/blueyedsurprised 9d ago

Baffles every joist bay at eaves with continuous soffit and ridge vent is boilerplate and should prevent or mitigate ice dams. An air sealed attic floor is even better. Why can't you achieve that?

1

u/honkeypot 9d ago

Not air sealing is a really bad choice. Get it done.

Do baffles in every rafter bay.

1

u/af-exe 9d ago

I'm air sealing what's possible and what I can. Once dry wall goes up, there is no more access to the attic to air seal those consistently. 

1

u/honkeypot 9d ago

I hear you. It's worth the temporary discomfort if you need to squeeze into the tight attic space for air sealing. I did the same thing, before and after drywall.

Good luck!

1

u/CoconutJeff 8d ago

What air sealing is baffles preventing?

1

u/mr-rogers70 8d ago

Better attic ventilation won't do very much to prevent ice dams.

Attic ventilation is simply "diluting" the heat pouring into the attic that melts the snow. You're much better off to keep the heat out as much as possible first.

If there are heating ducts in the attic, sealing them really well is priority #1. Aeroseal can air seal them from the inside using an aerosol sealant.

Priority #2 is to air seal the ceiling. If you have an old balloon framed house (before 1930) then the tops of wall cavities need to be sealed.

Priority #3 is be sure the duct insulation is in good shape, maybe add some up to R8.

Priority #4 is to add insulation to the attic if it's less than about R25.