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Old 08-03-2015, 03:12 PM   #46
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If using ocSPF, 3-1/2"--5-1/2" is required for an air-barrier- depending on 1/2# or 3/4# SPF. You would also want a vapor barrier between it and the brick cavity to stop moisture or increase the thickness greatly for a moisture barrier there. OR just use ccSPF instead; 1-1/2" for air barrier.

Did you pull a section of soffit for an inspection access? To see if there is blocking over the wall or not; SPF against the blocking on brick side and into the cavity OR (no blocking; against the rafter rim board and in the brick cavity. Could use some scrap XPS at rim/blocking if less expensive- check cost. Cold also add some poly before spraying brick cavity. Are there exhaust holes in the mortar joints below the top row of units; will you be adding those... since stopping airflow with new SPF. Does the soffit extend over the brick or abut them... if over, just add some rigid XPS there also; no need for SPF. Are the lights rated IC- insulation cover- for temp. gain... light boxes should really be fire-rated foam (pp.42/47, 47/47; http://buildingscience.com/documents...ing-guide/view

Gary
PS, what size a rafters?
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Old 08-03-2015, 05:55 PM   #47
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So which is better to use open cell or closed cell for this application if I have to spray that much more of the open cell then I would probably be money ahead using closed cell what about putting ISO between rafters at back of the house there is only about 5 inches back there
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Old 08-03-2015, 06:10 PM   #48
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You don't need to spray everything. If you have the OC foam, you can apply that to the penetrations and top plates. You could sister in some skinned rigid foam at the outer wall where the bricks are and spray it in place.
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Old 08-03-2015, 07:00 PM   #49
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ISO there would work, a lot cheaper than SPF, either open or closed cell. Notice in the link on page provided; open cell is applied over the other air-sealing compound- caulk or sealant as they are not full of air holes/passageways in their composition- better and more effective than 4" of ocSPF stopping air AND moisture. Line the rim and some on the soffit board/top plate, between rafters, air sealing (first) as well on the exterior areas. Is the canned foam (cc) an option... figure it both ways to decide. Though GAPS & HOLES or what-ever (cc) is difficult to work with compared to WINDOW/DOOR (oc) that is detail -oriented.

Gary
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Old 08-03-2015, 08:26 PM   #50
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I dont have any foam yet but will the closed cell work as a vapor barrier for the brick as long as it is 1 1/2 inches thick
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Old 08-05-2015, 01:25 PM   #51
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Yep; http://www.sprayfoam.org/technical/faqs

Little different; http://www.energy.ca.gov/business_me...1_QIISPFv6.pdf

Gary
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