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Our townhouse used to have an "embedded" porch (under the attic, one wall living room, another bedroom, third wall shared with neighbor's porch, 4th the outer screened one). I removed the screening, substituted some glass sliding doors, and made it into a "sunroom". Added HVAC ducts. Now for insulation.
I can easily blow insulation into the attic over this space. However, the wall between my new sunroom and the neighbor's unconditioned porch poses a problem. Because of the difference in his and my house floor plans, there's a flat wall from his house extending up above that side of my attic. I can look down into the wall cavity between my room and his porch. Studs are 24" OC, and the gap is about 2-1/2". No cap over this, so I could easily fill the space with, say, styrofoam pellets. Problem is I need about 24 cu ft, and even at Walmart they'd cost about $150. Plus, you only get about R2 at best.
So, I'm looking for alternatives. Solid styrofoam sheets would cost about half as much, and have twice the insulation value, but they don't bend enough to get into the space and there'd probably be too much air movement. Most likely candidate seems to be something like blown-in cellulose, but the rental blower has a 4" hose that wouldn't work with my 2-1/2" cavity. My brother suggested using the blower to put a lot of cellulose in that end of the attic, then just shoveling it into the cavity with a snow shovel or such. I don't know if this would fill the cavity completely and evenly, or whether the narrow gap could result in empty spots.
Another idea I've been pursuing involves fiberglass batts pushed or pulled down into the gap. Pulling (bottom of batt taped to a wood strip, which would have a string or strings attached, coming out a hole bored at the bottom of the wall) seems more likely to get an even fill, but also more likely to tear the batt and require pushing from above anyway. The batts, intended for walls with 3-1/2" cavity, would be compressed by about a third, and therefore the R19 they normally have would instead probably be down around R12. Still, 3 times as good as the styrofoam.
Anyone have any ingenious suggestions?
Thanks!
I can easily blow insulation into the attic over this space. However, the wall between my new sunroom and the neighbor's unconditioned porch poses a problem. Because of the difference in his and my house floor plans, there's a flat wall from his house extending up above that side of my attic. I can look down into the wall cavity between my room and his porch. Studs are 24" OC, and the gap is about 2-1/2". No cap over this, so I could easily fill the space with, say, styrofoam pellets. Problem is I need about 24 cu ft, and even at Walmart they'd cost about $150. Plus, you only get about R2 at best.
So, I'm looking for alternatives. Solid styrofoam sheets would cost about half as much, and have twice the insulation value, but they don't bend enough to get into the space and there'd probably be too much air movement. Most likely candidate seems to be something like blown-in cellulose, but the rental blower has a 4" hose that wouldn't work with my 2-1/2" cavity. My brother suggested using the blower to put a lot of cellulose in that end of the attic, then just shoveling it into the cavity with a snow shovel or such. I don't know if this would fill the cavity completely and evenly, or whether the narrow gap could result in empty spots.
Another idea I've been pursuing involves fiberglass batts pushed or pulled down into the gap. Pulling (bottom of batt taped to a wood strip, which would have a string or strings attached, coming out a hole bored at the bottom of the wall) seems more likely to get an even fill, but also more likely to tear the batt and require pushing from above anyway. The batts, intended for walls with 3-1/2" cavity, would be compressed by about a third, and therefore the R19 they normally have would instead probably be down around R12. Still, 3 times as good as the styrofoam.
Anyone have any ingenious suggestions?
Thanks!
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