Insulating My Non Cooled Attic
Hi, I live in Southern California and just moved into a home with some generous space in the attic. The home was built in 1967 and my plan for the attic is this:
Move the furnace from the 1st floor to the attic (I have confirmed this can be accomplished relatively easily). I would like to insulate between the attic rafters and use the space as storage or possibly add cooling to the space if we decied to use it as a kids play room etc. There are currently two gable vents in the attic. I understand that I have to install attic baffles to let the air come in through the eaves and out through the gable vents.
1) What is the best way and best material to use to insulate my attic? What R-value will I need to achieve?
2) Do I also need to insulate the joists between the attic and the 2nd floor? Would this add to the energy efficiency? Sound isolation?
Thank you!
Replies
IMHO.
IMH, DIY'er Opinion, Consider hiring a GC.
Insulation is climate specific, your venting needs are dependent on the size of the furnace, unless you provide outside air another way, your work spans numerous trades, you have to move a supply line to the furnace, multiple permits are likely required: etc...........
Is the attic to become part of the conditioned space? So many questions to be addressed.
I suspect that your work is more complex than your current expectation.
Good luck.
Work is always more complex than my current expectations. Thats probably why I am posting questions in this forum. It would be helpful if you might give me some direction on the venting information I previously asked about.
The furnace is currently getting air from the attic through ductwork. The main trunk line is alrady there though I will be installing new ductwork anyways. I will be extending the gas line and electrical service there as well. The attic will become a part of the conditioned space. I currently have gable vents through the side of the home. I suspect I will have to install a ridge vent or turbine vent in its place to properly condition the interior space.
I will post photos of this area in the future.
Thank you
Yeah, you have lots of issues.
There may or may not be enough room to do any of this. How big is the house and how tall is the attic in the center?
What are the dimensions of the rafters? You need about 4" of clear space above the rafters for the venting to be effective.
Do you live in a fire-prone area? If so there will be restrictions on installing vents. (Even if not you'll probably need to jump through some permitting hoops.)
More Info
There is plenty of room in the attic, easily convertable to a useful room (probably not code compliant). Id say the attic in the center is 7-8' high. Rafters are 2x6 - I understand that I should allocate 2" between the underside of the roof sheathing and the rafter baffles to vent the air from the eaves. I am in Mission Viejo, CA.
Keep in mind you'd need to lose at least a foot at the top to provide a vent "duct" to communicate with the gable vents. (You could reduce this somewhat if you switched to ridge vents.)
Almost certainly not code-compliant. And if you violate local fire safety regulations you'll lose your insurance, so be careful.
Unvented attics are permitted.
Make sure your ceiling joists will support any extra weight. Keep all your duct work inside the building envelope. The roof insulation will have to meet the required value.
From the Calif. Residential Code
"R806.4 Unvented attic assemblies. Unvented attic assemblies (spaces between the"
"ceiling joists of the top story and the roof rafters) shall be permitted if all the following conditions are met:"
"1. The unvented attic space is completely contained within the building"
"thermal envelope."
"2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly."
"3. Where wood shingles or shakes are used, a minimum ¼ inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing."
"4. In California Climate Zones 14 and 16 any air-impermeable insulation shall be a vapor retarder, coating or covering in direct contact with the underside of the insulation. See Title 24, Part 6, Figure 101-A—California Climate Zones."
"5. Either Items 5.1, 5.2 or 5.3 shall be met, depending on the air"
"permeability of the insulation directly under the structural roof sheathing. No insulation shall be required when roof tiles, wood shingles or wood shakes, or any other roofing system using battens and no continuous underlayment is installed. A continuous layer shall be considered to exist if sheathing, roofing paper or any continuous layer which has a perm rate of no more than one perm under the dry cup method."
"1. Air-impermeable insulation only. Insulation shall be applied in direct"
"contact with the underside of the structural roof sheathing."
"2. Air-permeable insulation only. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation with an R-value of R-4 shall be installed directly above the structural roof sheathing for condensation control."
"3. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable"
"insulation."
If you're still looking for options for insulation, try looking at univfoam.com. They have a variety of foam insulation panels that should work.
Fire proofing?
Given that a furnace is to be installed in the attic, wouldn't any foam insulation require a fire barrier like drywall?
As I tried to suggest before, a great deal of local building code knowledge is going to be required for this project.
Good luck.