[mrdang]

Welcoming opinions:
I bought a periodically updated house from 1925 up here in Minnesota that has a 'mostly' finished attic- kneewalls are up, with panel access to outer (side)areas and insulation above middle living area. Needs a little joint compound and paint-THAT I can handle.
Here's the issue- behind the kneewalls on the sides of the house are the standard (2 front and 2 back) vents open to the outside. Part of me wants to cover it to help control the temp up in the middle-keep winter out. But I also know if the roof gets too warm I will get ice problems-but those areas are closed-off and extra r-30 rolled out at the attics floor level in hopes of keeping the heat down; no recessed lighting to worry about.
So I'm asking around and I am getting conflicting opinions... so I guess I'm asking for a few more?

[joypulv]

It isn't about the roof getting too warm; it's about letting moisture out before it condenses as soon as it's cold, dripping down walls and ceilings, and rotting wood and sogging insulation. In the winter you might get by with some sort of block if the vents are letting air blast in past them. A lot depends on how big they are and how many cubic feet of attic they are venting, and how much floor insulation there is over the entire attic, and does it have a vapor barrier on the underside. You could block off two and keep an eye on condensation.

[ballengerb1]

Does this home also have soffit vents to allow air to enter the attic at the eave? You must allow air to enter and to leave to carry away humid air and to keep the attic cold.Insulate as much as you can but do not close off any vents top or bottom.

[mrdang]

Joypulv, if I leave 2 covered, 2 uncovered (obviously one open for each side) do you think I should stagger them- front right side open, back left side open -or is it just a matter of the air going 'somewhere'? I was leaning toward leaving both the back ones open, being the east side (weather usually comes in from the west here)

[joypulv]

Decide based on where warm moist air works it's way into the attic, and where it goes OUT from there, not where air comes in from outside.

Kitchen and baths of course... but where water will condense in your attic is anybody's guess, so you will have to see what works. It's going to be the coldest draftiest spots. Presumably the vents. So if you tape insulation over 2 of the vents, go up in a few days and see if they are damp, and look for other evidence. Maybe leave a tiny bit of all 4 open instead.

I saw a house drip A LOT inside the cathedral ceiling after someone covered the soffit vents on the overhangs. Condensation happens quickly.

[ballengerb1]

Without know the sq/ft of the soffet vents and these 4 vents you guys are throwing dart in a dart room. Static air flow by convection is not determined by taking guesses. The homeowner is now trying to trap warm air inside rather than to prevent that attic air from becoming warm. More insulation not less venting is what is needed.

[joypulv]

I agree,