Using attic heat for the house

[Daox]

A couple of days ago, I stuck a thermometer up in my attic. Nothing fancy, just a wired unit that shows temperature. As its getting cooler, I'm finding the house cooling off slowly. I'd love to be able to get a bit more heat without having to turn on the furnace. So, last night I came home to find my attic at 92F (33C) at around 5pm and decided I was going to use some of that heat. I stuck a box fan into the attic access door and blew it down. Here is the very simple and quick setup.





Now, I'm not sure how much heat I really got out of it. The immediate area was definitely warm, but the room you see in the picture has a thermometer in the far corner and that didn't register any heat gain. However, when I went to sleep roughly 3.5 hours later the attic was still pretty warm as shown below.






So, it looks like the heat definitely has to be better distributed. I need a way to get it down to the first floor first. My first idea is to use the cutoff chimney in the attic! Its currently uncapped and probably making me loose a fair amount of heat in winter. I just haven't gotten around to putting some insulation around it yet.





To get it down to the first floor, I was thinking of using this vent hole that I had previously plugged up with foam. Its in my kitchen which is normally the coldest room in my house. Having some extra heat in there would be great.





So, I'm just kind of throwing out the idea to see what people think and get some suggestions. To get much heat I'd probably need a fair size blower/fan I'd imagine. I'm also not sure how long this will be useful? Will it be completely useless in winter? I guess we'll just have to see.

I also did a quick search on builditsolar and found this:
Attic based solar heting
attic temp logged data

These show that its not an original idea by far, and the temperature log of the attic I guess suggests that winter use really doesn't seem very viable. However, different climates and different types of construction will alter temperatures. So, I guess I'll wait and see.

[RobertSmalls]

That second link is very informative. It looks like the attic stays hot roughly from noon to 4pm, but it doesn't look like usable heat when it's really cold out. If you're only getting 4hr a day, three months out of the year, it's probably not great.

The attic would be a good location for the clothes dryer, though, assuming you do laundry from noon to 4pm.

[Ryland]

what about installing a heat pump? the attic should always be warmer then the outside temp.

[Patrick]

I would want some type of filtration on any attic air that I sent into the house. Too many bugs around here. And you don't want any insulation (especially if it's fiberglass) drawn into the house.

[knowbodies]

Wow, that attic looks strikingly similar to my except I've brought the chimney down to just below the floor level of the attic. If your chimney is as full of creosote as my was, I highly recommend against blowing any air down it. And definite seal any openings if you decide to remove anymore of it - the creosote and cement dust will create an enormous mess.

[Piwoslaw]

The first time I came across using attic heat was in John Seymour's book Blueprint for a Green Planet. Page 153 has a drawing of a solar house with a heat recycling pump, with the following description "This pumps the warm air that gathers in the upper parts of the house back to ground level where it is most useful".

If you have an unused chimney then go ahead and use it! It will save you the hassle and expense of running a duct between floors. Maybe make a circuit that checks temperatures and turns the fan on only when the attic is warmer than the kitchen? And Patrick is right about filtering.

Any chance of getting some insulation on that attic door?

[Daox]

Sorry, I haven't responded to a bunch of posts here.

Originally Posted by Ryland

what about installing a heat pump? the attic should always be warmer then the outside temp.

That would probably work very nicely, but I'd like to start out as simple as possible for now.

Originally Posted by Piwoslaw

If you have an unused chimney then go ahead and use it! It will save you the hassle and expense of running a duct between floors. Maybe make a circuit that checks temperatures and turns the fan on only when the attic is warmer than the kitchen? And Patrick is right about filtering.

Any chance of getting some insulation on that attic door?

Yeah, thats what I think I'm going to do. No filter for now. Its pretty clean up there so we'll wait to see if its a problem.

There is insulation above the door when its all closed up.

[Daox]

Originally Posted by knowbodies

Wow, that attic looks strikingly similar to my except I've brought the chimney down to just below the floor level of the attic. If your chimney is as full of creosote as my was, I highly recommend against blowing any air down it. And definite seal any openings if you decide to remove anymore of it - the creosote and cement dust will create an enormous mess.

Nah, the inside of the chimney is pretty clean actually, just a lot of cob-webs atm.

The attic got a good amount of cellulose blown in a while back, dust isn't too big and issue I don't think. If it is I'm sure I could filter it easily enough.

Thanks for the link skyl4rk. I just wonder how much heat there will be up there in winter. Robertsmalls says 4hrs a day which IMO seems like a healthy amount of otherwise free heat. Its hard to tell by those graphs though.

A heat pump wouldn't be a bad idea, but again I don't know how warm it'll be. All I have is the logged data from the first post. If the time window to pull heat is very small its probably not worth the work of trying to set one up.

Anyone got any info on an inexpensive data logger? I could use an arduino to make my own, but I don't have time right now for another project unfortunately. Most of the ones I've seen are very expensive for more than one channel logging ($100+).

[skyl4rk]

http://www.thermalattic.com/

[Daox]

Well, the house is still cooling off and I'm trying to hold back from turning the heat on. Tonight I came home from work to see the attic again at 90+ degrees F. So, I figured I'd give it another shot with an improvement. I found a piece of insulation to block the other part of the opening, so it should pull much more warm down. It does appear to be working quite a bit better now.