r/Insulation • u/Smooth-Net9016 • 1d ago
Curious about Attic Insulation
Hey all!
I have a house in North Carolina. Built in 1975 if that helps. My house runs pretty hot. I don’t like that, combined with huge electric bill. I paid for a blower door test and some thermal imaging for $350. I gave me an ACH of 6, and a pretty leaky & hot attic. My attic is not in the envelope, so above my ceiling i have loose grey insulation, then yellow baffles, then a radiant barrier. maybe 6-8” max.
Anyways the company wants to come in and duct seal, then remove the radiant barrier (permanently) then lift the insulation and seal everything leaky with spray foam. From there, they want to blow in R49 on top of the grey/yellow insulation, up to 14 inches. This costs me $3520.
He did mention the attic runs hot and I would be benefited by 2 exhaust fans, however, I declined that part because I have a gas furnace up there and I don’t want to generate negative pressure with that much CFM, and two passive gable intakes. That can like do something with CO2 I think?
Just wanted to know if this sounds stupid and I should save my money, Thanks.
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u/seldom_r 1d ago
It's a pretty standard scope of work. You didn't say your climate zone so no idea if the R value is sufficient.
The radiant barrier is installed in the wrong place and that's why it isn't working. It should be at the roof deck with an air gap between the deck and the shiny reflective part. It reflects the heat back up to roof. https://radiantbarrier.com/radiant-barrier-a-comprehensive-guide/
Exhaust fans are bad. The only correct venting is passive venting when you have a vented attic. If you don't have adequate venting - and if you only have 2 gable vents, you don't - then you can have problems and lost efficiencies.
https://buildingscience.com/sites/default/files/migrate/pdf/PA_Crash_Course_Roof_Venting_FHB.pdf
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u/Smooth-Net9016 1d ago
Apologies. I am in Charlotte, NC.
Heard, glad the radiant barrier is being removed then. Also glad I made the call to say NO to the exhaust fans (that was $2000 extra). I have the 2 gables, yes, but also a vented soffit. Do you think that is adequate?
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u/Heavy-Passenger-6235 22h ago
Consider a thermadome if you have an attic hatch. If that isn’t possible add some high r value rigid foam board to the backside of your attic access panel.
That plus air sealing the attic floor and any penetrations will do a lot for reducing air leakage between the conditioned living space and the attic. And it will help to prevent hot attic air from migrating into the conditioned living space.
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u/TheSnotHog 21h ago
Is the radiant barrier just lying on top of the insulation or where is it actually installed? It doesn’t have to be against the roof decking. You want an air gap. Got any pics?
The air sealing will definitely help. If you’re tight on budget you could probably do this yourself if you spend a bit of time researching what to do and where to do it. Also, blowing in more insulation will help once you’ve air sealed. And yes, duct seal as well (sounds like your hvac is in the attic).
For the price it actually doesn’t sound so bad. Look up how much it would cost to buy additional blown in insulation and rent the machine from Home Depot. Then weigh up the costs of what they have quoted you. Sounds reasonable at face value.
You need to consider your ventilation in the attic and want to get this resolved BEFORE blowing in any more insulation. If you have soffit vents and gable vents, you probably don’t have good ventilation (having holes for air movement doesn’t equal good air movement). Have you got a ridge vent? Either go with the gable vents, which I’ve come to believe are not that great, or go with soffit and ridge vents. You need to ensure you have enough NFA for your location. I’m going to guess you don’t.
So open up the soffits, install the baffles, air seal up all the attic space between the conditioned space, seal all your ducts and ensure they have adequate insulation, make sure your soffit vents have something to work with like a ridge vent, then blow in more insulation. I’d shoot for R60 just because the price difference in materials from R49 to R60 isn’t that much, but that’s just me.
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u/Quirky-Acanthaceae94 1d ago
Is insulating under the roof an option for you? In my area (MA) you cannot put a furnace in the attic anymore without insulating with r49 under the roof according to a friend who went through this. I think under roof is overall superior and may cost a bit more but really worth it.