Expert: Paul S. Brown, AIA - 3/11/2009

Question
We have a 1924 colonial in Connecticut and we are in the process of getting quotes for blown-in insulation for our attic and walls.  The house is pretty much a box except for 2 areas on the 1st floor that extend beyond the 2nd level.  Therefore they have their own, independent roofs. I know that we need to insulate those roofs as well.  The only access would be through the existing 1st floor ceiling or outside through the roof.  Which one would be the best option and do we need to have the area vented?  Thanks in advance for your help.  I can send photos if you need them.

Answer
Hi Karen:
Good questions.
Which is the best option for access, through the roof above or the ceiling below?
I think it would be less disruptive to your home, to go through the roof from the exterior; as long as the contractor properly protects the work from the elements, and then re-roofs properly after blowing in the new insulation.  Another option might be through a sidewall in a second level room, if the roof of the lower level roof abuts at a height that would allow access.
Do you need to vent the lower level roofs?  Yes.  The contractor should install vents at the low end of these roofs in the eaves ("Soffit vents"), and should be sure to insert baffles that will prevent the soffit vents from being obstructed by the new blown-in insulation.  Then you will also need to vent these roofs at the upper end, to get good air flow through above the new insulation, so as to remove moisture that might build up in that space and condense on the underside of the cold roof, it it were not properly ventilated.
Be sure to get good quality soffit vents; on my house, the birds decided that those nice neat new holes in our soffits, with screens on them, looked like a great place to live.  With persistent effort, they were able to peck the screens away and move inside the attic space.  Very comfortable for them, I'm sure!
Good luck; I'm sure your project will go well.
- PB