Icynene Spray Foam on Underneath Side of Roof Deck – Zone 5
After reading for months, getting 4 quotes from spray foam contractors in my area, and undergoing an energy audit, I’m in the process of finalizing plans for open cell half-pound Icynene application to the bottom side of the roof deck in the attic. This is a retrofit job. Within the attic is a furnace in a closed room vented directly to the outside. I have a few questions after I received the proposal today from the contractor
#1 – I currently live in Zone 5 (Chicago IL). I’ve received quotes for application of 6.5″” or R-23 and 10.5″ or R-38. The difference in cost between the two for the square footage I have is $12,500. Local code specifies R-38 for attics, however I’m unsure if this is applicable for all types of insulation, or conventional bat/blown cellulose. Assuming local code to not be an issue, how quickly (if at all), would I see the return on investment for the thicker foam?
#2 – The attic is unliveable space. There is currently a furnace room and heating vents running throughout the attic. Do I need to apply a vapor barrier to the foam after its installed? I’m not planning on covering the foam with drywall. The rafter bays are framed with 6×12’s.
#3 – The energy auditor recommended installation of an HRV due to alteration of the stack effect after the foam insulation. Is this reasonable? How would I test if I needed such a device? I’ve received a quote for installation of a Lifebreath RNC5TPD HRV system to be installed using the upstairs bathroom fan vents for $2,000..
#4 – The house has currently 3 furnaces (2 in basement – 1 supplying basement, 1 supplying 1st floor, 3rd furnace is in attic). Total BTU is 180,000. The house size is roughly 5,000 sq ft. After application of the foam, the house will likely be overpowered. Is this a consequence I’m going to have to live with, or are there any alteration that need to be done to the furnaces?
Thanks for any input anyone is able to give on these questions. Getting any valid opinions on these matters are helpful since there is often misleading and a wide variety of opinions people recommend.
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