Overwhelmed with Insulation Choice in NE Texas with a 3:12 pitch
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We purchasing a 3000sf 1950’s ranch style house in NE Tx. I really need your advice narrowing down the best insulation for us.
Problem: 3:12 pitch, no insulation and 2 wings of the house only have tiny access hatches that are blocked by ducts, and it needs a new roof in the next couple of years. Opportunity: we can seal up the openings and insulate it any way needed when we replace the roof.
Our goal is to reduce the utility bills and increase comfort in the home without breaking the bank. We’ve done several flips and are ready to start a construction company to do this current one as a launching pad into doing it as a business, as we can’t find any contractors here that address the science of ventilation and moisture.
There’s as much of the roof that runs East to West as there is North to South. It’s in Gardening Zone 8b. Windows will be replaced and insulated eventually. Chimney, exhaust fans and entries into the attic will be sealed with caulk or foam.
*We had 3 spray foam companies come out and every single one had different and strong opinions on how it should be done. $4500 was the quote. Some parts of the attic are so hard to get to I don’t know that it can be foamed correctly. Only one mentioned fire retardency. Only one mentioned foaming over the garage to stop the suction when we opened the garage door. Two said foam the soffits and one said to create a barrier over the top plate so the moisture behind the brick can get out. None mentioned it might void the shingle warranty.
*We could blow in cellulouse but to get above R 30 would leave NO room in the attic for maintenance. We have a decent amount of soffit vents and were thinking about doing a ridge vent when we replaced the roof but i read more vents at top than at bottom reverses the pressure/air flow.
*At this point we’re even looking at polyiso (or something) above deck so we can still access the attic. Is it true that we would not need insulation in the attic if we do this above deck. Can normal rafters support all this extra weight of two layers of decking and foam? How does the polyiso stand up to frequent hail? We would do metal or composition on top.
Thanks so much!
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Replies
Tonya,
Of the options you mentioned, polyiso above the roof sheathing makes the most sense.
Thanks Martin. Do you know it's cost compared to spray foam?
Tonya,
The only way to determine prices in your area is to get contractors to submit bids.
For more information on installing rigid foam above your roof sheathing, see these two articles:
Creating a Conditioned Attic
How to Build an Insulated Cathedral Ceiling
The question I had from those two articles was do you HAVE to use insulation between the rafters and the polyiso above decking, or can you just use polyiso?
Tonya,
You can put all of the insulation above the roof sheathing if you want. In your climate zone (DOE climate zone 3), the 2009 IRC calls for a minimum of R-30 insulation. If you install polyiso, you'll need about 4.5 or 5 inches.
Tonya,
if you choose to create a thermal control layer at the roofline...
(an encapsulated attic)
Be sure to find a way to create an airtight connection between the exterior walls and the underside of the roofdeck.
Also if you currently have non sealed-combustion appliances(furnace,wh, etc) in the house or attic ... you will need to replace them with sealed combustion or electric versions.
Thank you John. Are you saying that because our dryer, stovetop and water heaters, one furnace are older gas appliances, plus a chimney. That we might have to replace them if we did a unvented attic (spray foam or polyiso, etc)?