Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Is ventilation necessary when insulating rafters?


fourteener's Avatar
Visiting Guest

Posts: n/a

11-22-05, 08:28 PM   #1  
fourteener
Is ventilation necessary when insulating rafters?

I want to add insulation to my walk-up attic in an older house. We may eventually finish the attic also. Currently, there is R-19 in the floor of the attic with no room for more. It has tounge and groove floor boards. The roof is a hip roof with two hip dormers. The soffits aren't vented and neither is the ridge which is only two feet long. Will there be a moister problem when we finish the room if we insulate the rafters without providing any venting? The rafters are 2 X 6. I was thinking of adding another 2 X 2 for depth and using two layers of R-13 insulation. Does anyone have a better idea?

 
Sponsored Links
em69's Avatar
Member

Join Date: Jul 2005
Posts: 857

11-23-05, 05:01 AM   #2  
My concern is the lack of venting.

Do you currently experience large ice dams in the winter months near the edge of your roof?

 
fourteener's Avatar
Visiting Guest

Posts: n/a

11-24-05, 06:16 AM   #3  
fourteener
We just moved into this house in August and we just got our first snowfall of 2 or 3 inches. The outside temperature is around freezing. There is some snow on the roof, but it is melting off some, so I don't know yet if there will be a problem with ice dams.

 
em69's Avatar
Member

Join Date: Jul 2005
Posts: 857

11-24-05, 09:58 AM   #4  
You need a certain amount of roof venting, or else major problems will arise.

In the summer, roof vents help to keep the attic space cool which reduces A/C load.

In the winter, roof vents help to balance the cold outside air temperature with the warm air escaping from your home into the attic space. The roof assembly should be about the same temperature on either side.

Without roof vents, the warm rising air from your home will melt the snow on the roof and then it will freeze again, thus causing ice dams. These ice dams will build up on your roof edge (the soffit) up to a point where the melting ice cannot flow down the roof. Eventually it starts to go under the shingles and then into the attic.

 
Search this Thread