Is An Attic Vent Required For Cedar Shingle Roof? - Building & Construction - DIY Chatroom Home Improvement Forum

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Old 10-25-2007, 08:42 AM   #1
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is an attic vent required for cedar shingle roof?

Hi - I am remodeling my attic

- the house is about 110 years old
- the roof consists of cedar shingles
- there is no attic ridge vent or sofit vents
- the shingles are nailed onto nailers that run horizontal across the rafters
- through that a good part of the shingles is openly exposed
- I am planning to put insulation up into the roof in between the rafters to make the attic a liveable space

I understand that I have to leave a space in between the insulatiuon and the cedar shingles for air circulation.

the disagreement between 2 contractors is the following:

1. I need to build in a ridge vent and sofit vent to allow complete air flow...

2. The other person says, that I can put the insulation all against the nailers (which are 3/4 inch thick), because of the nailers I have an airspace between the shingles and the insulation, also because of the nailers air can flow horizontally across the roof/in between rafters. He says that the cedar shingles breathe enough and even so their is no top level ridge vent enough air can move and leave the under the roof.

I understand that option 1 may be ideal, but obviously it is also intrusive and more expensive ...
do you have any views?


walenta is offline   Reply With Quote
Old 10-25-2007, 10:05 AM   #2
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Disclaimer that I am not a roofing expert, but practical thinking tells me that you need the vents. If the shingles had gaps enough to "breath", then you'd have gaps enough for bees and insects and major drafts to be coming through too. If they're not coming through, then I'd say there isn't enough breathing room. If you seal it off with no vents, tar shingles burn up fast enough, I can't imagine how fast wood shingles would last.


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Old 10-25-2007, 10:31 AM   #3
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The ridge and soffit vents are the correct way to vent the attic. There are two issues involved. The cedar needs to have venilation on both sides so it dries evenly. If the ventilation is inadequate the shingles will curl and it's useful life will be dramatically shortened. The other issue is without the proper ventilation you will get super heated air trapped under the shingles, penetrating into the living space causing you to spend more money to cool it. And this will shorten the shingles life.
Some contractors make recommendations because they don't want to bother with a certain aspect of a job, some do it out of ignorance.
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