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Gus 12-26-2008 05:13 PM

Different attic vent. and insul. question
I purchased a 1940 2 story home 18 months ago. The house originally had a flat roof and according to the neighbor the PO was always fighting leaks. So finally they had a gable roof built over the flat roof. The house is a block house all the way to the newer gable roof. Until a week ago I had no way to get into this space, I cut an opening in the ceiling of one of the closets. There is essentially no insulation except behind the lathe and plaster in the ceiling that is about an inch thick, it does have a paper backing. There is two roof vents and no intake vents. All the sheathing on the gable roof had black all over it and covered in frost. The shingles are curling and the sheathing does not look too good either.

I want to blow in insulation into the space, but I don't want to miss any steps on the way. I was going to roll out a 6mil vapor barrier over the old flat roof and seal it to any protrusions and block wall that extends above the flat roof. Then I was going to blow in at least enough insulation for R30.

I know the ventilation also needs to be addressed, but I'm not sure how to remedy this. There is no overhang on the roof so there is no soffit behind the gutter (I hope I am using the correct terms). The roof will need to be replaced next year and probably the sheathing. The gable framing consists of 2x6's on 24" centers.

I can get dimensions and pics if that would help. I really want to get the insulation in soon to cut down on the heating bill.

Ed the Roofer 12-26-2008 09:07 PM

You most likely will need to replace the sheathing at the same time you do your roof, from the description of the mold infestation occuring so far.

For the Intake Ventilation for a home that has no soffit overhangs, the Smart Vent from DCI Products works extremely well, plus you will need to balance the ventilation by adding an equal amount of Exhaust Ventilation, best by using the Shingle Vent II Ridge Vent.

Smart Vent Description:

Smart Vent Installation Instructions:

Shingle Vent II Performance Comparison Chart:

Both products should be used 100% continuously for the best and maximum desired results.


Gus 12-28-2008 08:50 AM

Thanks for the info on the vents, that should work for my application.

Does it look like I am taking the right approach on the insulation?

Ed the Roofer 12-28-2008 12:56 PM

Wel, R-38 is recommended for our area. (I am around the NW suburbs of Chicago) So, if R-30 is the best and most affordable that you can get, that at least is better than what you have now.

Don'r forget to buy the insulation Baffle Chutes, also called, Proper Vents, which goes on top of the insulation near the eave edges, to provide a minimum of 1 1/2" of clear unobstructed air pathway from the Intake Vent, so it doesn't get impeded by any insulation blockage.

Also, you might want to check into SPF insulation. I am not as well versed in the idiosyndricies of that product, but if you search some of the insulation threads in this section of the forum, you will find a decent amount of information about it and links for more knowledge.


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