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I’m hoping to add some insulation and ventilation to our attic. It’s a 1954 with a 1991 addition. The second floor is warmer in the summer, the original part much warmer than the addition.

Current situation: Ventilation-one gable vent. New section has soffit venting. Old section has soffits just under 3 inches wide, with a couple of 2 inch round vents I previously installed. The rest has no venting, some rafter baffles though. There are limited soffits, there are 2 other gable ends.

Insulation-about 7 inches blown in on the ceiling and R13 batts on the kneewalls. The top of the stairs is the hottest, it had no insulation on the slant above the stairs or the backs of the walls that made the stair sides. I put an R30 there a few months ago. So, I’m thinking I put 2 inch round vents every X inches where there are soffits. Also make sure there are rafter baffles inside the attic at these locations. Possibly add a gable vent on the other end and/or front?

Then buy some more blown in and get the free rental and increase the insulation in the old part significantly. (the new part has plywood down and tons of stuff stored, the old part will never have storage)

General advice appreciated as well as:

How do I decide if/how many gable end vents to add? We’re 5 blocks from a great lake, it can get pretty windy here if that’s an issue. It appears there was previously a second gable end that was sided over.

How close should my round soffit vents be? I would consider doing some long straight vent but I can probably only cut a hole/strip about 2.5 inches wide and can’t find something that would work.

Thank you!

(soffit shown is about half of what the whole old section has. There's an 8 foot section on the back of the house, opposite and a 3 foot section on the opposite end.



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It looks like you have a ridge vent on the left already. The ridge caps look a little more "pronounced" than if there was no ridge ventilation. If there is no ridge vent then adding one would help a bunch. – Jack Jun 27 '14 at 13:58
Ideally, there would be a rafter baffle and soffit venting in every rafter bay, to prevent the roof deck from getting too warm (and melting snow, which could lead to ice damming). – littleturtle Jan 19 at 16:52

It looks like you have a ridge vent on the left already. The ridge caps look a little more "pronounced" than if there was no ridge ventilation. If there is no ridge vent then adding one would help a bunch.

Here is a section of a page from the 2012 IRC code stating the minimum requirements for venting. There are exceptions as well that should be in there too. It states 1 sq. ft. of vent for every 150 sq. ft. of attic. I can be reduced to 300 sq. ft. if you meet the exception. I think I read it right. But confirm it for yourself.

enter image description here

In the case of your one vent that was covered, it may have allowed snow to blow into your attic when there were high winds, then melt and cause drywall or plaster problems later.

If you feel you need to add more ventilation beyond the ridge vents, a continuous soffit vent will fit in that soffit space, it would be really labor intensive, but it would offer the most free air passage. compared to 3" rounds.

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