Home>Discussions>INSULATION & HVAC>Ventilating old house with finished attic
4 posts / 0 new
Last post
pcknshvl
Ventilating old house with finished attic
pcknshvl

Here's the situation:

1938 Seattle house, with years of owners putting their "touches" on it. One touch included finishing the attic to make it a livable space. This meant putting fiberglass insulation in the rafter bays (2x4 framing) and sheetrocking over it. Don't know if the insulation has a vapor barrier or kraft paper facing.

We live in Seattle, in a 4C maritime climate. This means relatively dry and warm (not usually very hot) summers, and cool damp winters.

On warm dry days, even weeks of warm dry weather, we'll come home after a full day out or a vacation to a humid, musty smelling house. I was describing this to my contractor brother-in-law, and he asked if the roof is vented. It is not.

A recent house inspector confirmed this, and said this is likely the reason why we have the dampness and smell--with the stacking effect in the house, the warm damp air has no place to go.

(BTW, we have a crawl space, but it is clean and dry with proper vapor barrier, and the inspector said that it is not the problem.)

Here's the problem: we have no eaves or soffits, and no actual drip edges off this part of the roof because one side connects directly to a flat roof which we think was added to cover in a back porch to form a hallway and space for what is now the bathroom and a small bedroom, and the other connects to the front porch roof and the roof of an addition.

So: how can we improve ventilation? Completely reframing (and raising) the roof is one expensive option, but is there a compromise option? Would a few metal roof vents make a difference, even if there are no soffit vents nor, I assume, any space between the insulation and the roof sheathing? Can we avoid pulling all the drywall down?

Thanks for your input!

keith3267
Re: Ventilating old house with finished attic
keith3267

Do you have any kneewalls in this finished attic? How about a small attic at the top, it may only be 2-4' tall.

http://www.finehomebuilding.com/2012/09/06/two-ways-to-insulate-attic-kneewalls

pcknshvl
Re: Ventilating old house with finished attic
pcknshvl
keith3267 wrote:

Do you have any kneewalls in this finished attic? How about a small attic at the top, it may only be 2-4' tall.

http://www.finehomebuilding.com/2012/09/06/two-ways-to-insulate-attic-kneewalls

We have very short (2' or so) knee walls, and no small attic at the top. I have know idea if the knee walls are insulated.

Mastercarpentry
Re: Ventilating old house with finished attic
Mastercarpentry

Some pics of how the roof section interacts with the rest will help. In general, venting only high will reduce heat somewhat, but it takes airflow to reduce moisture. Based on the design and spaces you can use, you might need to get creative but there should be some way to get that needed airflow. It seems from your post that the rafter space is insulated without a way for air to go through above it. If that is the case either the sheetrock or roof sheathing may have to come off so you can add that.

Phil

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.