Envelope Renovation in 2A: Part 1- Attic
I'm going to break this down into 2 posts...attic and wall, with the attic/wall intersection here.
Brief background on existing conditions:
1970 2-story home (2500sf) here in Seabrook (SE Houston), a very hot very humid climate in a 110mph windzone
1st floor: 85% brick veneer on 2x4 stud backup and faced fiberglass batt insulation (sheathing/weather barrier unknown)
2nd:floor: is 12" Masonite lap siding attached directly to studs (yes...no sheathing)...again with the fiberglass batts
Attic: As is the case with every home in this area, the fancoil, furnace and ductwork are all sitting in the oven otherwise referred to as the attic. As if this isn't bad enough I can see the ceiling drywall from the attic access stair across the vast majority of the attic floor (iow...next to no insulation). It's no wonder it is almost impossible to keep the 2nd floor cool during the summer (having only one thermostat on the 1st floor certainly doesn't help either)
So addressing the attic...since the roof is relatively new my preference is to address the problem inside the attic. There is a continuous ridge vent but otherwise ventilation is handled by gable vents...no existing soffit vents.
Before pricing here is the plan based on reading several articles on the topic:
The attic is very shallow (6:12 pitched roof that is dropped 2' in the front with dormers) and there is an amazing array of completely haphazard kickers and braces holding up 2x6 rafters.
What I want to do...ignoring the random kickers and bracing...from the furring down-
*add 2x2 spacers to each side of rafters
*install 2" polyiso on the spacers leaving 1 1/2" clear venting channel) (R13)
*Install 2" closed cell icynene pro seal eco (closed cell spray foam) (R9.8) providing an excellent air barrier
*install 3" polyiso to bottom side of rafters (R19.5)
*install 2x6 insulated kneewall to match roof
*if at all possible I'd like to spray in a 2" layer of the closed cell foam to complete the air barrier the the exterior wall, then blow in the death triangle cellulose insulation leaving enough room for soffit ventilation to reach vent channel
Ideally I could get an engineer to evaluate the kickers and braces and clean up the remaining conditioned attic void. Since our HVAC system is way past it's life expectancy replacing that is in the plan as well...hopefully smaller and more efficient for not running in a 130deg attic. Also...as part of the hardie siding job my preference is to eliminate the gable vents and install cont. soffit vents to replace them.
Current 2012 Energy code would require R38 here and this would comfortably exceed that with R42.3 and would bring the HVAC system inside the conditioned space.
Are there any obvious holes or dangers here? Aside from energy conservation the other main objective is to improve the air quality of the home...since moving here 9 years ago my wife has developed allergies and asthma that never existed before.
Since we are replacing the HVAC system...what recommendations would you have on system replacement under these conditions (climate and indoor unit)
I'll get to the walls in Part 2
Thanks in advance for your time...
Posted Thu, 02/27/2014 - 10:30
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