Proper insulation in 90 year old house


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Old 08-05-20, 07:17 AM
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Proper insulation in 90 year old house

My son and I are looking to buy a 90 year old house (built in 1931) that needs a lot of work. The plaster is separating from the lath in the 3 second floor bedrooms, so we were planning on pulling down the plaster and lathe, rewiring where needed, and reinsulating. They have walls that are sloped due to the barn-type roof style. The walls almost come to a point at the top with very little flat area, maybe a few feet. I'm assuming the sloped walls are 2x4 where they are vertical, but where they tie into the roof and slope up they're probably 2x6 right? Should we put baffles in the sloped part to keep an airway open to the peak? not sure what thickness of insulation we can get in there too.
 
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Old 08-05-20, 07:30 AM
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With little to no attic area it doesnt make sense to me to waste any space on ventilation. The best way to insulate would be to have it spray foamed. And the primary benefit will be in winter months to slow heat loss. It will still be unbearably hot upstairs. Insulation works to keep heat in as well, so you may find that the insulation might help keep the upstairs cooler each morning but eventually once it does heat up upstairs, the insulation will keep that heat inside longer in the evening.
 
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Old 08-05-20, 07:47 AM
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Yeah I grew up in a house living in the upstairs that was similar and it was unbearably hot in summer. I had doubts about the spray foam. I'd heard some real war stories about what happens if it's not installed correctly and that worries me a bit about that. See this video: Hidden risks of spray foam insulation
 
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Old 08-05-20, 07:55 AM
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Fear mongering. There are entire industries built around it.
 
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Old 08-05-20, 07:57 AM
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Yeah I get that, and I understand that if they don't put it on in 2" layers it can have a fishy smell to it. Just concerns me a bit is all.
 
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Old 08-05-20, 08:04 AM
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The upstairs would be similar to this video. What do you think about this option of rigid insulation? rigid insulation
 
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Old 08-05-20, 12:29 PM
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You can if you want. But you need to air seal all the edges as you install it or it's not very effective... and could lead to problems. Poor air sealing let's warm moist air hit the cold roof deck in the winter which spells problems. And the air space it pointless if you dont have soffit vents to let air in or an attic with ridge vent to let air out. The space simply becomes a place for frost to accumulate in the winter. In that particular house you are better off filling the cavity completely with insulation IMO.
 
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Old 08-05-20, 01:10 PM
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Okay, thanks. That makes sense. If you look at the photo of the house, there is very little soffit to begin with. The ones along the roof edges would be blocked by the roof rafters, so only the bottom corners of the roof would let any air in to begin with and only half of those rafters would actually go to the top I'm guessing. the others on each corner would be blocked by a roof rafter. So possibly fitting the rafters full with rigid foam or having sprayed foam would be the best option it looks like.
 
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Old 03-05-21, 07:22 PM
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Well we decided to go with the closed cell spray foam insulation. I think it was the best choice considering how difficult it would be to vent the roof otherwise. Now it needs no vent, nor does it need a vapor barrier. It's airtight. Looks like a cave up there now. We're going to do the main floor walls as well once we tear out all the drywall and old insulation and re-wire and re-plumb like we did upstairs. It's already 5 warmer upstairs now than it is downstairs. It used to be 10-15 colder. I ran a few heating ducts up there too, but didn't notice it being warmer till the insulation was applied. I don't think we'll need to augment with electric heat from what I can tell now. It's like one big Yeti cooler.


 
 

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