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mincus · 02-10-13, 09:19 PM

I think that because they would be slowly gaining heat throughout the day, the rocks would still work. They have 8-10 hours to collect heat, even if not from direct sunlight. I know most thermal mass material you read talks about having it in the sun, but obviously that's not always possible. Some of the rock filled walls would get some sun, but not all. And no, I was not going to use an exterior wall

I think the only reason there would be an overall gain is because I use heat pumps. If I was using a gas furnace, it runs at the same efficiency day or night, and it likely wouldn't make much difference. However, my heat pump is far more effective during the day than at night. My overall idea is to build heat up during the day and be able to keep it through the night. This makes my heat pump run less frequently, and is easier on it by running it more during higher outside temps.

I do like your wall idea. However, I was planning on doing each room individually over the course of a couple years. So, doing spray foam would be hard, as would blowing in cellulose (renting the machine each and every time, etc). Wondering if I could use XPS foam, cut slightly smaller and sealed on the edges with canned spray foam. I know I've heard this technique for sealing rim joists. Would that work if I pull out the old fiberglass?

In doing this, are you renting a machine each time? What about the spray foam?

With regards to the electric boxes, I am reasonably sure that the wire in and wire out both go up to the attic for each of those boxes....although now that I think about it, maybe I'm wrong....seems like it would be a waste of wire. Assuming that is the case, moving the box out would not be hard at all. It would just be an inch or two higher on the new wall. I still have to investigate this more to make sure. Otherwise, I could just put in extra outlets and move the position of the current ones. This would of course require taking out the drywall, like you suggest. Now that I get to thinking, removing the old drywall is sounding better and better. It would allow me to put in the foam (increasing my r value for those first 3.5 inches), not worry about wires, tie my new wall directly to the old one at top and bottom, etc.

Any idea about how good XPS is at reducing sound compared to cellulose or fiberglass?

I would never hide a junction box. Had several of those in my old house and it made me quite angry!

02-10-13, 09:19 PM	#3
mincus Helper EcoRenovator Join Date: Feb 2009 Location: St. Louis, MO Posts: 42 Thanks: 0 Thanked 0 Times in 0 Posts	I think that because they would be slowly gaining heat throughout the day, the rocks would still work. They have 8-10 hours to collect heat, even if not from direct sunlight. I know most thermal mass material you read talks about having it in the sun, but obviously that's not always possible. Some of the rock filled walls would get some sun, but not all. And no, I was not going to use an exterior wall I think the only reason there would be an overall gain is because I use heat pumps. If I was using a gas furnace, it runs at the same efficiency day or night, and it likely wouldn't make much difference. However, my heat pump is far more effective during the day than at night. My overall idea is to build heat up during the day and be able to keep it through the night. This makes my heat pump run less frequently, and is easier on it by running it more during higher outside temps. I do like your wall idea. However, I was planning on doing each room individually over the course of a couple years. So, doing spray foam would be hard, as would blowing in cellulose (renting the machine each and every time, etc). Wondering if I could use XPS foam, cut slightly smaller and sealed on the edges with canned spray foam. I know I've heard this technique for sealing rim joists. Would that work if I pull out the old fiberglass? In doing this, are you renting a machine each time? What about the spray foam? With regards to the electric boxes, I am reasonably sure that the wire in and wire out both go up to the attic for each of those boxes....although now that I think about it, maybe I'm wrong....seems like it would be a waste of wire. Assuming that is the case, moving the box out would not be hard at all. It would just be an inch or two higher on the new wall. I still have to investigate this more to make sure. Otherwise, I could just put in extra outlets and move the position of the current ones. This would of course require taking out the drywall, like you suggest. Now that I get to thinking, removing the old drywall is sounding better and better. It would allow me to put in the foam (increasing my r value for those first 3.5 inches), not worry about wires, tie my new wall directly to the old one at top and bottom, etc. Any idea about how good XPS is at reducing sound compared to cellulose or fiberglass? I would never hide a junction box. Had several of those in my old house and it made me quite angry!