fredhamel Posted September 11, 2011 Report Share Posted September 11, 2011 Hi guys, I'm trying to get some information on the net but I'm still a bit confused. I live in Canada. My house was built in 1963. In those days the soffit were made of plywood without any sort of venting. Later aluminum soffit were added over the plywood. And then soffit vents were added by piercing a whole trough the aluminum and the plywood. Click to Enlarge 42.19 KB I wonder if my roof gets enough ventilation. I just recorded the following temperature today: Outdoor: 21 celsius or 68F Indoor: 25 celsius or 77F Inside my roof: 36.7 celsius or 98F Does this temperature difference indicate a poor ventilation? Should I have the soffit entirely replaced by the modern style with small wholes everywhere? Thanks for you kind cooperation. Fred Link to comment Share on other sites More sharing options...
Marc Posted September 11, 2011 Report Share Posted September 11, 2011 It has enough ventilation if the relative humidity is low enough to prevent issues. I wouldn't pay much attention to the temperature of the attic air. Attic ventilation, if appropriate for your building design and climate, serves mostly to keep the attic humidity low. Marc Link to comment Share on other sites More sharing options...
Brandon Whitmore Posted September 11, 2011 Report Share Posted September 11, 2011 I agree that temp. has nothing to do with figuring out whether or not ventilation is adequate. Ideally, you want appx. 1 net sq. ft. of ventilation per 150 sq. ft. of attic floor space, and it's not that hard to calculate that out. If you have enough ventilation and notice moisture/ humidity issues in the attic, then you probably need to air seal the attic. Link to comment Share on other sites More sharing options...
Nolan Kienitz Posted September 11, 2011 Report Share Posted September 11, 2011 You also need to be sure that there is an "air path" from the eave (above the soffit vents) across the roof/wall framing and into the attic space and out the roof vents. Often insulation gets jammed into that space and blocks the air flow from the soffit vents into the attic space. Click to Enlarge 37.28 KB Link to comment Share on other sites More sharing options...
SNations Posted September 12, 2011 Report Share Posted September 12, 2011 The ratios used for roof ventilation are based largely on voodoo. I would say that you have enough ventilation if you have no moisture problems in your attic. Although you need to remember that things change over time, so what's fine now might not be fine next year. If you're concerned, you should work inside the house to prevent moisture from getting into the attic in the first place (source control), rather than worrying about removing it with ventilation. Link to comment Share on other sites More sharing options...
John Kogel Posted September 14, 2011 Report Share Posted September 14, 2011 I think the poster is worried about heat buildup in the attic, not moisture. I don't have an answer. We don't get heat up here in the damp North. [:-weepn] Link to comment Share on other sites More sharing options...
fredhamel Posted September 15, 2011 Author Report Share Posted September 15, 2011 Hi guys, Thanks a lot. I understand better now. Link to comment Share on other sites More sharing options...
Terence McCann Posted September 15, 2011 Report Share Posted September 15, 2011 It has enough ventilation if the relative humidity is low enough to prevent issues. I wouldn't pay much attention to the temperature of the attic air. Attic ventilation, if appropriate for your building design and climate, serves mostly to keep the attic humidity low. Marc Ice damming is a problem for us up North Marc in which case temperature trumps humidity (next to zero humidity in the winter anyway). Any ice damming problems Fred? Link to comment Share on other sites More sharing options...
Bain Posted September 15, 2011 Report Share Posted September 15, 2011 I'm aware of the conventional wisdom when it comes to roof venting, but I've seen lots of roofs that were inadequately vented, and the shingles were prematurely deteriorated and looked much, much older than they truly were. I don't have anything quantitative to reinforce what I'm saying but, in my experience, here in the quasi-South, maintaining reasonable attic temperatures is as important as managing humidity when it comes to venting. Link to comment Share on other sites More sharing options...
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