Addition: Roofing options
I am planning on adding a sizable addition to my home and realize one of the areas that has the least insulation is where the trusses meet the wall.
Unfortunately my original home does not have raised heal trusses so I don’t think I can add that now. Also, after looking in the soffits some of my rafter bays are completely full of cellulose or stuffed with Fiberglass batts. I have not made it far enough into the cathedral attic to see if I have moisture issues at this time.
Are there any good options for this area or should I just call it a wash, add ventilation channels and load it up with spray in cellulose.
I would love to do a foam over top of the sheathing , but this will greatly increase the cost as I would have to re-roof the original structure and add the foam. The total roof area will be over 3000 sq. ft. as that is the floor area.
I am in Zone 4, St. Louis area.
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Replies
Mike,
Although your title mentions roofing, it seems that your question really concerns insulation.
There aren't many good options when rafters or roof trusses are so tight that there is insufficient height for adequate insulation above the top plates of your exterior walls. The usual solution (if you can't afford to install rigid foam above the roof sheathing) is the following:
1. Clean out all of the existing insulation from the work area. (You can temporarily pile this insulation in the middle of your attic.)
2. Install sturdy ventilation baffles directly under the roof sheathing. (Here is a link to an article with more information on this aspect of the work: Site-Built Ventilation Baffles for Roofs.)
3. Purchase one or more two-component spray foam kits, and install spray foam insulation from the top plate of the wall to the underside of the ventilation baffle. Continue installing spray foam until you reach the point where the rafter or truss provides enough room for code-minimum levels of cellulose insulation. (If you don't want to buy two-component spray foam kits for this work, you could hire a spray foam contractor instead.)
Here is a link to an article by a homeowner who describes doing this work: One Man’s Quest for Energy Independence — Part 4.