Attic heat project designed from the bottom up

[Exeric]

It's easy for me to forget that this is still just an experiment. It's a risky venture in that if it doesn't succeed then it will be a lot of work for nothing. The only thing that makes me OK with that is it will be documented here and the larger society can profit from it, including all of you folks. You'll know better what does not work if this does not work. And you will also know better what roof area per inhabited space and what climate is required if it does work. But failure is only helpful to others when it is documented and publicized enough that others working in any given field know about it. Enough said.

Phase 1 is done - building the heat collecting system and recording the temperatures. With this latest cold snap I now know what to expect in terms of roof temperatures in the very coldest part of winter in this climate. It's been above average temps for most of the winter until the last three days. Three days ago it was 16 degrees below the 54 degree average high for this time of winter and the high never got above 38F. Weather was overcast and the roof temp never got above 50F. Yesterday was a few degrees warmer, clearer, but windy and the roof temp got to 68F. Not quite useable for what I want. Today was the real thing: eight degrees below normal high at 46F but clear and no wind. The roof got to 80F, and it stayed above 75F for 3.5 hours. So today was the threshold day for useability of roof heating for me. So it makes me very happy that a good solar day in the coldest part of winter "might" be useable. So far I've recorded only about 4 or 5 days when there was no useable high temperatures, all when its either too cold, too wet, or a combination of windy and dense overcast. Overcast or windy alone does not seem to preclude useable roof temperatures.



It actually got a little warmer than that 44F shown, but that 80.4F roof temp was the highest reading of the day.

[Exeric]

Phase 2 of this project is quite a ways off in time so don't expect many updates here until later. Phase 2 will require that I am actually able to bring that high temperature air down from the roof and that it does not deplete that renewable resource too much. I think Daox and Xringer both know that the radiation in the attic is a finite resource from their own work. I've compressed that radiation energy into a space much smaller than the entire attic. It has improved the quality of the heat (higher temp) but its hasn't stretched the resource itself. It is still possible that the higher temperature in the confined space up there quickly becomes depleted when it is actually pumped down into the living space. Only the actual bringing down of that air into my space will give indications. Again expect a year or more of other construction until I get to that point.

The other part that needs to be determined is if my plans allow for enough insulation to preserve that radiation resource. I'm not quite as worried about that, but still not sure. The fact is one could build a house like a thermos bottle and you could probably light a candle and have sufficient heat for the winter. It's just not feasible for most folks to build a house like that.

So overall I just want to make sure that everyone knows that I might or might not be breaking new ground here. When you try something new one never knows if it will work. That is the excitement of it and is what has encouraged me in this do far. Things are kind of boring when you only do what others have tried before. Time will tell how this experiment will turn out. If things go against me I'll report that too.

[jeff5may]

Good luck renovating the rest of the house. I know it will turn out well, considering the effort and skill you've put into all the projects mentioned in this thread. Take your time and put it together the way you want it. Phase 2 is much less important than the rest of your house.

[Exeric]

I'm glad you are able to read between the lines on where 99.9 % of my future work lies.

Best,
E

[Daox]

Have you been using this at all? Any other observations?

[Exeric]

Hi Daox, I saw your question just now. Better late than never and it's a good excuse for an update. No, I'm not using it this season because there's no insulation in the house yet and all that heat would just disappear into space at night. It's a pity too because I'll probably not see such a good solar thermal heating system as we had this year (drought in California, you know) in decades. Two months from the winter solstice and it has been regularly getting to 110F (43C) just beneath the roof. BTW, an interesting factoid, it seems there is a correlation between west coast drought and midwest and east coast frigid temperatures. The exact same thing happened in 1978 I believe.

Right now I'm just preparing for doing a dense pack of cellulose in the second bedroom, living room, and kitchen. I've put up ceiling drywall in the 2nd bedroom and living room and have yet to do the kitchen ceiling. I've put in 2x2s against the perimeter walls in all three rooms to provide thermal breaks. I've also put up the netting in the bedroom and living room. I just need to put netting up in the kitchen and do the ceiling drywall and then I'll do the perimeter dense pack and put drywall over the walls in all three rooms. I'm not going to do the taping and texturing myself though. Way too tedious for me and others can do it better and faster. I'll gladly pay to have it done. Once I have that done and a few things besides, I'll move into the second bedroom and do the final ripping and tearing on the bathroom and main bedroom.

I've routed a channel in the ceiling with ductboard between the garage and the nearest house hip rafter, but left the firewall in place for now. Once everything is done and the PV panels in place on the south facing roof I'll check if I'm still getting enough heat from the roof. There's a good chance I will because 2/3s of the west facing roof, the bathroom and main bedroom, have yet to have the black paint and radiant barrier put up. If it isn't quite enough then I'll just remove the part of the firewall separating the garage and ductboard channel I just put up. I can cut that out from the garage side so I don't need to trample the insulation.

[Exeric]

I suppose it might seem weird to add solar PV to a house with a good solar thermal system. Presumably the net metered PV would supply a good ASHP system but unfortunately I got educated late about these things and I had already installed a propane system connected to a built in propane fireplace. So the electrical will be used for general stuff plus AC, not heating. These things happen, that's why I've learned not to be harsh with other people after the fact. As they say, it could happen to you. Luckily weather around here should supply I'm guessing at least 75% of my heating requirements. Besides, who doesn't like the warm glow of a fireplace.