Retrofitting an Attic
Hello. Long-time reader, first time posting!
We bought a 1993-built house in Fayetteville, AR (Zone 4a, also ~1500ft elevation if that matters). It has a very steep gable roof with two east-facing dormers that serve as the windows of the master bedroom upstairs.
As part of the inspection we discovered:
1) Roof is not ridge vented, but there are a couple gable vents and I believe soffit vents. There does not seem to be any condensation issues from what we can tell.
2) Bathrooms are venting INTO the attic.
3) One of the two HVAC units is in the attic. It’s original to the house and we are opting to replace it. Currently gas powered furnace.
4) Original blow-in insulation isn’t great, and could also stand replacing.
After lurking here for a long while, my general preference would be to bring the attic into the envelope of the home and purchase an electricity-powered HVAC system (maybe heat pump?) to replace the current one. I have a desire to rid the entire house of its use of natural gas, and see this a golden opportunity to do that with the HVAC system in the attic.
We will have the bathroom vents punch through the roof unless there is a better approach.
Last, and most pressing, concern here is insulation/encapsulation. It’s hard to suss out the appropriate recommendation about this as I read through older to newer articles here. I know sometimes roof line plays a role. What would make sense with the gable roof with the two dormers?
I initially got quotes for spray foam, but after reading some more, I have a bit of concern about the safety it, as I have small children (2yo & 5yo). Perhaps unfounded, but I’m not opposed to this if there is little risk and it is our only option.
Thanks,
-Kenny
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Replies
I'm assuming you have no way to move the HVAC equipment out of the attic, which would be the ideal option if possible. There are many reasons to avoid the installation of any HVAC equipment in attics. If you want to avoid natural gas, be sure to go with some form of heat pump. Electric resistance is NOT an improvement over natural gas in most gases regarding total energy consumption or fuel use.
If you keep the attic vented, a ridge vent is more efficient than gable vents, but gable vents can work. If you put on a new roof at some point, I would absolutely install a ridge vent at that time, and be sure to use a proper ridge vent and not one of the "shingle over a piece of foam" type "vents".
Spray foam is pretty safe if it's installed by a competent installer. People usually run into problems with inexperienced installers that mess up the mix as they're spraying, which can result in improperly cured spray foam and it's this "imporoperly cured" part where problems like persistant smells come from. Spray foam is probably the most common way to encapsulate an attic, but it's not always the only way.
You mention you have a "steep" attic. How steep is "steep"? Could you possible frame out a small mechanical room in there? If you could, you could seal up that room and leave the rest of the attic vented (taking care to keep the ductwork inside the building envelope as much as possible). If you go this route, you could use rigid foam and batts for insulation, avoiding the use of spray foam.
Bill
Thanks for the advice. I am exploring the idea of getting a room built, yes. We've just had issue getting access, so I'm not entirely sure how much space is up there. I might put a pause on all this until I can really examine things.
Would insulating the exterior of the roof sheathing be a better way to go (given that we might need to replace the roof in the next 5-10 years)? I have read that's a good approach, but don't know much of what to consider there. I imagine finding a competent installer is probably the most important part of that.
If at all possible, consider undoing the very poor choice someone made long ago to put the HVAC in the attic. Think mini split and wall heads.
If that seems impossible consider that gable wall plus the roof sheeting may have double the surface area of the attic floor. This surface area will likely loose more than twice as much energy as a well-insulated attic floor simply because almost no one will spend the money to put up R60 spray foam over that vast area given its high cost. Almost anyone can spread R60 on the attic floor with the free blower Home Depo will provide.
A conditioned attic is only a marginal improvement over your current situation given its larger surface area and lower R value and could be a step backward if the ducts are tight and the old insulation is thick.
Getting rid of the gas meter and its 20$ or so monthly fees could be a good idea but mostly that has to do with your local rate plan. Generally, if the gas is city gas from a network of pipes its costs is so low getting rid of it does not make financial or comfort sense but dumping propane is almost a no brainer.
I am sure most spray foam install go fine but the fact is every few months some poor soul posts a horror story and we never hear about problems with cellulose insulation.
Walta
+1
Oh wow I never thought of it that way. Amazing advice.
Also, for me, getting rid of gas is a health/sustainability measure. I would like to one day be fully self-powered with solar and other renewables. Not as concerned about that $20/mo either, but a token reward for achieving that goal, I suppose :)
Does it still make sense to spray r60 on the floor if you have 2x4 trusses? I'm trying to figure out how to fix my attic - no airsealing for the boxes in the ceiling and 4 inches of insulation and all the upstairs ductwork is up there. I feel like if I brought it up to minimum (salem oregon, so I think r-38) it would be super hard to ever go up there again to do maintenance, inspect the roof or do any kind of improvement from the attic.
Alex I do not think they can spray R60 and follow the manufactures instructions because it would be too thick even if it was possible no one that does math would do it because the foam is so expensive no one could live long enough to get a return on that investment.
“Super hard” is an opinion some people can’t trim their own finger nails and other run 100-mile muddy obstacle course for a day of fun. Working in an attic full of insulation is possible but not pleasant.
Walta
I agree with the general sense that air-sealing and insulating the floor is the way to go, along with moving the HVAC inside the envelope. But I'd want to get a better understanding of the master bedroom dormer configuration to have a specific recommendation for that.
As for the bath fan vents, they could go out the gable ends or through the roof. Gable ends is easier if the gable end isn't too far away.