Adding some insulation to old brick house

mdelaurentisMarch 3, 2013

Hi,

I have a 100 year old three story brick twin house in Philadelphia. I ripped down a 4' x 8' section of plaster from the ceiling in the front room on the first floor. It was pretty much fully separated from the lath there, and I had electricians working in that area anyway. I'm getting ready to replace that section with drywall, and I'm wondering if it would be a good idea to add some insulation. I've attached a couple pictures and I'll try to describe the construction.

Most of the joists in our house run side-to-side, but in the very front part of the house, the ceiling joists in the first floor run front to back. Inside, they're notched and resting on a double side-to-side joist, then they go outside where they form the ceiling of the front porch. I can't easily tell, but I suspect they're resting on a steel beam embedded in the brick wall. I suspect this because there's a wide window maybe 16 inches below the ceiling. So the front-to-back joists don't terminate in the brick wall, they extend maybe ten feet out over the front porch. There's also a bay window directly above.

When I opened up the hole in the ceiling, I felt a strong draft coming in. There is a gap of a few inches between the top of the bricks and the floor boards above. Beyond that gap there is just dead space in the ceiling above the front porch.

Would it be a good idea to add some insulation before I close the hole up? There was a thin layer of blown insulation above the lath when I pulled it down. I've seen that blown insulation in other spots of the house, and as far as I know that's the only type of insulation we have anywhere. I could spray foam into the gaps above the brick and below the floor boards to seal it up, or maybe just put in a fresh layer of loose insulation. I could lay bats in there, but it seems like plugging up the gaps in the bricks would be the best route. I'm just not sure if there would be issues with moister. I've read that moisture can be a problem when adding insulation to houses that don't have it.

I'm not sure if it's even worth it though, since it's a pretty big house and this is a relatively small area.

Any feedback would be appreciated.

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mdelaurentis

Here's a photo of the area.

    Bookmark   March 3, 2013 at 12:29AM
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worthy

I could spray foam into the gaps above the brick and below the floor boards to seal it up

Perfect. You're air sealing, not insulating. Never put fibrous insulation behind those solid brick walls or in the rim joist area of any house. It will get wet, promote mould growth and not insulate or air seal.

Here is a link that might be useful: Insulating Old Brick Buildings

This post was edited by worthy on Sun, Mar 3, 13 at 9:54

    Bookmark   March 3, 2013 at 9:46AM
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energy_rater_la

if joists run from living space to porch roof, I'd bet
you have a situation like the one in the article
below. I've seen this in numerous existing
& new homes.

http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/54221/A-Sword-through-the-Ribs-of-the-Building-Envelope

what did you find out?

    Bookmark   March 17, 2013 at 5:42PM
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