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Insulating an attic that’s already been finished

ConfusedPA | Posted in General Questions on

Need some help. We recently purchased a 1926 brick sided house. The 3rd floor (attic) is finished with knee walls and crawl spaces accessible to the front and rear of the house.

The knee walls are anywhere from 5 ft tall in some places to 3ft tall in the hallways with the ceiling following the roof ridge line up to about 8 feet high from the floor then flattening out creating a ceiling that is a few feet below the ridge beam of the roof.

There is currently no insulation on the 3rd floor. except surrounding the 3rd floor bathroom. There is a few inches of fiberaglass insulation on the walls with baffles up to the ridge vent and more fiberglass stuffed below that baffle.

The 3rd floor layout is a T shape with a longer central hallway with bedrooms on both ends and a bathroom off center in the middle.

 There are ridge vents at both peaks, and some soffit vent intakes except in one section of the crawl space.  That “room” contians a hot water heater for the 3rd floor bathroom and has a powered attic fan. 

There is a tongue and groove floor in all of the crawspaces, no insulation below that in the joist bays. The rafters are 2x6s and the space between the finished ceiling and the rafters  get tight where the sloped section of the ceiling is, because they used 2x4s laid on their sides as cross tie nailers to hang the wallboard. 

There are radiators in the 3rd floor, (Natural gas fired boiler hot water heat) no ductwork/no central air.

There are windows in both bedrooms as well as the bathroom. 

I was looking at having either closed cell foam sprayed in the rafter bays and sealing off the soffit vents and filling the space below the the ridge vent there by going to a closed/unvented attic.  Or alternatively having blow in over the existing attic floor and adding insulation behind the knee walls, adding rafter baffles over the sloped ceiling line and just stuffing as much insulation up there as I can. There is now way i can reach R-30 value between the ceiling and roof deck in the areas that are sloped.  I can not afford to completely tear out and remodel the 3rd floor.

So would I be better off by having it completely closed cell spray foamed or just doing the best i can with blow in and baffles?  Or would it be better to not add any insulation at all?  I’m concerned that by adding insulation but not enough I could actually cause more issues then just leaving it un-insulated.

FYI I am in Cambria County Pennsylvania, which is climate zone 5 I believe.  I know that ideal code is r-49, but there is no way to achieve that with my layout at least not over the finished area of the attic.

Any help is greatly appreciated.

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  1. ConfusedPA | | #1


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