Rafter Baffles

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  #1  
Old 10-27-10, 02:28 PM
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Location: Virginia
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Lightbulb Rafter Baffles

I may be trying to go a little far with saving $$, but I was wondering if you could staple polyethylene sheeting (from soffit to a few feet up) on the rafters as a vent. Seems like the companies are producing all these ready-made baffles that do the same thing but will cost several times more.
I saw a comment on the internet about concern of condensation on baffles; however, the baffles I see are polystyrene, plastic, etc. and seem like they would all experience the same issues.
If it helps, I plan to lay insulation rolls across the attic floor and use vents as suggested along the rafters.
 
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  #2  
Old 10-27-10, 05:13 PM
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The devil is in the detail. Some plastic sheeting is perforated so moisture can pass through it. Pink or blue rigid foam has sufficient permeability to also allow drying to the outside. A 4 mil plastic sheet would be a solid vapor barrier, and thus potentially a condensation problem. I say potentially because the other ingredient is warm moist air leaking out of your house. If you take steps to air seal before adding additional insulation, you will greatly reduce your heat loss as well as reducing your potential for moisture issues.

If you go with the plastic, go crazy with a bunch of holes. Its primary purpose is to hold back the new insulation, so tons of holes will reduce any condensation problems.

Here is a link on air sealing from efficiency Vermont. It opens very slowly, but has great information.
http://www.efficiencyvermont.com/ste...ide_062507.pdf
 
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