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You are here: Experts > Home/Garden > Home Improvement/Repair > Roofing > Blocked Soffit Vents and Insulation
Roofing - Blocked Soffit Vents and Insulation
Expert: Tom Souza - 10/25/2009
Question
We live near Chicago and recently bought a 55 year-old, ~1200 sq ft ranch house with a relatively low roof. We are trying to install more insulation in our attic (there is currently ~3" of blown-in insulation). In the process, we found all kinds of references that you should not block the soffit vents, need to maintain air flow, etc.
While we have 14 soffit vents visible from the outside (each is 2 panels each 4" x 8"), the vents do not seem to have direct flow into the attic. There is a vertical pressed wood board mounted between the rafters which we initially thought was blocking the direct air flow (the pressed board is pretty much flush with the roof). This board is basically an upward extension of the wall, so the soffit area is apparently a separate triangular channel all the way around the house. In one location this vertical board is missing, and we could take pictures down into the cavity. But it looks like there is a board laying directly on the soffit. So, we used a small probe through the soffit vents from the outside and it looks like they are probably blocked by a board as well. When we tried using a leaf blower to force air into the roof through the soffit vent, the person in the attic could smell some fresh air but could not detect any kind of additional air flow either visually (i.e. no cobwebs or insulation were moving) or with their hand.
So, what do we do now? Since the soffit vents are apparently blocked, should we worry about opening them? Or should we assume that since the house is 55 years old (the roof itself is at least 7 years old) and the roof is in good condition, that we should just leave it as is and just go about putting in our attic insulation? Or is the air flow something that is critical and we should remedy before putting in our insulation?
Our original plans for the insulation were to put blow-in insulation to finish filling up to the joists (another ~3-4" of blow-in), and then rolls over the joists. We were going to use the rolls so that when we want to put up additional ceiling lights, etc we can roll up the insulation to find the electrical conduits and the joists to walk-on. This issue with the soffit vents has made us question whether we should be installing the insulation ourselves.
Answer
Hi Katherine
you did a very good job of explaining the situation.
with out seeing it it's hard to give a complete answer.
It seams the ventilation is working but not everywhere.
Adding more insulation should be ok as long as the air flow
flows as good as it is, be careful not to block any more vents.
you can always add venting from the top if needed. Basic rule of venting is
1.5 sq foot of venting to every 100 sq foot of attic space.
1000 sq ft attic space you need 15 sq foot of venting, some houses have
less and some have more. Extra things to consider out side walls are they
insulated, door ways, and windows are the the right type.
Good luck
Tom
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