We're part of a real-time pricing program with our electric utility company, and a good strategy for offsetting electricity use during peak demand times is to pre-cool the house. The more thermal mass that our house has, the more effective the pre-cooling will be.
I've read about phase-change materials and the promise of Thermal Core PCM drywall, but it seems like the development into a commercial product isn't going to happen any time soon. I've seen various vessels filled with room-temperature PCMs for sale, but I have no idea how much I would have to buy in order to make a noticeable difference in thermal mass of a house.
Is there a practical way to add thermal mass to my house? I've heard of people suggesting adding large drums of water, though I'd be leery about doing so due to the possibility of structural damage and/or leakage. I also considered loading up our side crawl with bricks, but I'm not sure how much I could safely add without again running into structural concerns.
Best Answer
I have about 50 55-gallon drums stacked in my basement, all filled with water. They are stacked one on top of the other (bottom row/top row) along our north basement wall. I have two in floor-mounted fans, one pushing, one pulling, mounted in the ground-floor joist cavity (from above they just look like floor mounted cold air returns). During the day, the fans circulate the air around the house. Our furnace has a bypass door on the cold-air return that opens a door into the basement cold-air return. This way, during the summer the furnace fan (on 365 days a year) pulls all the intake air from the basement. With so much air coming from the basement, our 2 to 3 ton AC units run maybe 6 days in the entire summer.
The system is cheap to run (about 1/4 of our cooling costs with just the AC units). I got all the barrels for about $200, and I have emergency water for years if i need it. Plus, my house won't blow away in a gale.