Can I use expanding foam in roof eaves openings?

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Bratan

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Last summer I had huge wasp problem. They nested inside walls, gaining access thru some small openings near roof eaves. And eventually made it inside the house. Exterminator dusted the nest, but for for a month I had all those stunned wasps crawling inside the house in every room, it was a nightmare.
My top priority this year is to block those openings. Is it possible to just use expanding foam for this task? This is my first house so I'm not sure if it could create any issues later on...
Or maybe it's better to hire professional (what kind)?
 

Reach4

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Unless you decide to turn the attic into "conditioned space", you need to keep ventilation through the eaves. The main purpose is to help keep the roof cold enough to not melt snow and ice before the edge of the roof also melts its snow and ice. It also allows moisture to escape from the insulation.

You can use foam to block the space between the attic and the living space, but you can't just fill up the eaves with foam. If you were just blocking cracks, some kind of caulk might be more controllable.

What I would consider, I think, is to get your living space sealed by using a blower door test. http://www.greenbuilding.com/homeowners/testing-energy-efficiency-your-home The advantage is that it not only stops wasps, but stops air flow. That will save on heat and AC costs. You might even be able to get that subsidized. If you stop the air, you stop the wasps and more.
 

Dana

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A lot depends on how your roof deck/attic is vented. If the venting scheme needs soffit venting you can seal up the cracks/seams with expanding foam or flexible caulk then drill holes for round screened vent plugs.

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Wasps can and will bore through wood or foam. If you seal it up and the lack of venting raises the moisture content of the wood it becomes more attractive to wasps & ants, so it's important to figure out the venting scheme first.
 

Bratan

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Thanks guys! Sounds like it's not a good idea to use foam then... BTW wasps are getting thru openings for heating pipes (deep under the bathroom sink) mostly. This is very open concept house (20+ foot ceilings) so I don't think I can afford to completely seal it...
 

Dana

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Simply from a moisture control and heating/cooling energy point of view you can't afford NOT to take air-sealing seriously! It's the cheapest most cost-effective building envelope efficiency measure you can take, and it reduces moisture problem risks to boot when done right. It may even be subsidized by state & local efficiency programs.

If the 20' ceilings are cathedralized ceilings (rather than with an attic above) the roof & insulation stackup needs to be understood. Current code requires either a vented air space of 1" minimum between fiber insulation & the roof deck, OR insulation above the roof deck sufficient to keep the roof deck above a presumptive ~40F dew point temperature for the wintertime conditioned space air. If it's a code-min R49 total (for any NY location under IRC 2012), the minimum amount of that R that is above the roof deck is prescribed in Chapter 8 of the IRC. But the amounts will vary by US climate zone. NYC & Long Island and most of Westchester County are in zone 4A, but most of NY state is split between zones 5A & 6A.

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At lesser (or greater) total R values, Zone 5 needs at least 40% of the total R to be above the roof deck for dew point control, in Zone 6 it's half, but in zone 4 it's only 30%. But if there is an interior side vapor barrier (polyethylene sheeting or foil) the roof deck needs to be vented from below, which means soffit to ridge venting or other schemes.

Vented attics are much easier to deal with, but the attic floor/ceiling plane still needs to be air tight (but not necessarily vapor tight from a water vapor diffusion point of view.)

If a cathedral ceiling isn't properly vented or insulated and the roof deck is staying damp for lack of drying capacity, it becomes an ant & wasp magnet.
 

BrianZ

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I've got a similar issue. One roof overlaps another and at that spot the builder left a gap in the fascia. On the flat parts of the fascia this is sealed with wood containing soffit screens as shown above by Dana, but at the section in the picture they didn't do this, probably because its more difficult and would require an angled custom cut to fit the space. The gap is large enough for rodents to get in, and its a tough spot to work at.
 

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Dana

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In a warm humid gulf coast climate like Mississippi's where wintertime moisture accumulations are (almost) a non-issue, venting the attic to the outdoors brings more summertime moisture into the attic than it ever purges, increasing the likelihood of mold growing on the attic side of the ceiling gypsum in an air-conditioned house.

If the ducts and air handler are up there above the insulation (pretty much the standard for slab-on-grade or flood-able crawlspace foundations) there's an energy penalty being paid for that venting too. Though some think that venting the attic reduces the cooling load, those who have carefully measured it over the past 40 years have found otherwise.

Go ahead and close up the front doors to the lobby of the critter-condo with whatever method seems suitable. If it can be done with can-foam without creating aesthetic issues on the exterior, that's fine.
 

WoodenTent

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When you say they are getting into the house, do you mean the living space, or the attic? As others mentioned, you do not want to block the soffit venting into your attic. I'm assuming your house has some form of metal/vinyl soffits. The holes in soffit are made small enough to prevent bugs from getting in and out (at least ones that are able to get up there). So if there is other minor holes, then you can caulk those (if they are just from il-fit of soffit).

I would be more concern that there is pathways into the living space. This shouldn't be happening. I would go room to room, basement, hvac system and search for points of entry and address them.

Something is drawing them into the house in the first place. If your attic is warm and dry, they won't want to be there. So beyond just the holes, look for what might be causing them to want to be there. Food supply, moisture, free cable tv.
 
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