[dsec123]

hi! i'm in a 1 1/2 storey old post-war house, which means i have an attic space, and then two crawl spaces on either side of the second floor that run the length of the house.

the attic has gable vents and two roof vents and it seems like air is able to get in and out of it.

the crawl spaces are a different story. there is a very thin little perforated soffit that would allow a bit of air to get in, if it weren't for the fact that there is blocking in between the rafters along the top plate. there is also batt insulation stuffed between the rafters and the roof stays pretty warm during the winter, resulting in significant ice damming (this past winter was my first in the house). in the summer it feels like a sauna in the crawl space.

my plan is to remove the batt insulation between the rafters and put it along the knee-walls and in the floor of the crawl space to prevent heat from the house from transferring to the crawl space. then i was thinking about drilling a hole in the center of each piece of blocking to allow outside air to come into the crawl space. i figure in order to facilitate air movement, i would then need to either install a gable vent or another roof vent.

can anyone tell me what's the easiest vent to put in?

 

[Bud9051]

Busy so I'll just leave some reading. Your style home is called a cape, I live in one.
http://www.finehomebuilding.com/2012/09/06/two-ways-to-insulate-attic-kneewalls

Bud

 

[dsec123]

thanks for this! if i choose to insulate the knee wall/floor joists, do i also need proper ventilation? the article doesn't really discuss that.

 

[Bud9051]

If you insulate the kneewall and floor, yes, that space will need ventilation. it can either be continuous up to the upper attic space with those vents or you would want gable end vents as high as they will go in each side attic. Natural ventilation air flow id directly related to the difference in height between high and low vents. One or two feet provides very little air flow, unless the wind is blowing.

Bud

 

[dsec123]

okay, thanks again! because it's a 1 1/2 storey, air flow won't be able to get past the angled portion of the ceiling (which is packed with batt insulation).

so gable end vents as high up as possible would be the way to go? easier than installing roof vents?

 

[Bud9051]

As for the rafter bays stuffed with insulation, that is typically not allowed as moisture either passing through the drywall or up from the side attics will condense on the bottom of the cold roof. Thus either a venting channel above or rigid foam sealed in place against the bottom of the roof. Can't do that with drywall in place.

Sounds like you don't have a lot of room to work in either top attic or side attics. How long is the sloped section.

I have no data on long term issues, but there have been articles here in cold country about dense packing those channels with cellulose. You might want to talk about options from a cellulose contractor. They usually know what is approved in your area and they have very skinny workers to get into tight places.

Bud

 

[Gary in WA]

Welcome to the forums!

Where are you located?

Gary