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Blown-in or batts un-insulated 1880's house

Greetings - I was reading through the Q&A about blown in insulation and vapor barriers for older homes, which prompted me to ask a few questions.

My 2 story home in upstate NY has very little insulation. The house has sort of a mansard roof, but it isn't. The outside walls on the 2nd floor are perpendicular but only about 4ft in height. The walls join the sloped roof. The sloped roof (about 10') extends up 45 degrees and meets the horizontal ceiling. The attic has about 1/2" of loose fill that my Dad put in in 1955. One bedroom (there are 5 on the 2nd story) has about 7" of batts above the horizontal ceiling. The house is balloon construction.

I want to insulate the walls, sloped roof, and ceiling in the bedroom we use (eventually the whole house). Since the sloped roof area should probably have an air space between the insulation and the exterior metal roof, would it be better to remove the 3/8" sheet-rock, put in an air channel between the rafters, insulation with vapor backing, and new 1/2" sheet-rock, rather than blown-in in the sloped roof area?

Since the house has balloon construction, blown-in insulation in the walls COULD find it's way all the way down into the walls of the unfinished basement. There are diagonal members (My Dad called them fire-stops) to keep the house "square". Since I'm on a diy budget, I'd rather NOT insulate the whole house right now... just the one bedroom. In my case, would it be better to rip off the sheet-rocked walls in the one bedroom we use on the 2nd story and put in insulation with a vapor barrier?

What do you do for a vapor barrier with blown-in insulation?

Re: Blown-in or batts un-insulated 1880's house

for the ceiling space, if you can access the attic without tearing out drywall go for it, simply take a trouble light up there and install through vents between the rafters to create a air space. then put batts between them.

for the level ceiling, install the through vents, then block off the stud cavitys with either card board or stuff batt insulation in, from there do blown in

for the walls you can take down the 3/8 drywall then put batts in but youll be looking at alot of debris to get rid of, doing blown in through the existing drywall works just as well. from there you can simply put a layer of 1/4 drywall up to make the walls a little thicker and it will create a smoother wall while covering all the holes drilled for blowing in the insulation.

in regards to a vapor barrier with blown in insulation. when the blown in is an afterthought there is no way of putting plastic up when the walls are already finished. however there is vapor barrier primer that is available , now the only thing is you wont be able to get it at a big box store. youll probably going to have to go to a paint supplier which is used by contractors. we use the primer when we have spray foam installed. as there are some instances where we cant use 8lb foam which acts as a vapor barrier, so we use 2lb foam and then use vapor barrier primer, we have to get this primer either through specific suppliers or sometimes its provided by the spray foam company

Sidney Fife
Re: Blown-in or batts un-insulated 1880's house

Batts are cumbersome and can either come loose or compact, in a weird space like the one you describe, thus losing their insulating ability. Also, fiberglass batting is irritating and is possibly a carcinogen.

Blown-in cellulose if problematic, even on vertical surfaces, since it compacts over time and if you have a lot of air in the rest of your house, it will permeate the atmosphere inside. Anyone with allergies or asthma will be in trouble, esp. if you have FHA heat.

I highly recommend a blown-in foam insulation like Icynene, or Soyfoam. You take off the drywall, blow it in and when it hardens, use a special saw to shave it down to the studs.

The only problem with this type is that you can't use it with knob & tube wiring (fire hazard) and if you plan to do any re-wiring, you have to cut through it.

It's best to hire someone to do it (it's very tricky) but you can buy do-it-yourself kits. They're more expensive than the other 2 types, but you'll get a MUCH greater R-value and the bonus that it provides it's own air barrier, while allowing moisture to escape to the outside.

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