my unusual solar forced air heater, cut my heating bill

i'm using eve/attic heat to help heat my house.
ever go into your attic on a winter/spring day and find it warm or hot?
i use a 30" 40 watt fan to pump the air down and warm the house.
i used only 187kwh in march for my entire house! kept it toasty warm, ~78F for less than 6 cents/day.
.
Now i will soon reverse it and bring in cool air at nite to help cool it (next 2 months until humidity gets too high)

Excellent! Well done, Matt! But I don't think I would agree the -78F was "toasty"! :wink:

Imagine if you had some skylights in the attic, it would get even hotter up there. In summer, venting the warmest air from the ceiling into the attic helps cool it, and make the room more comfortable.

I did the same thing. Used a squirrel cage fan at the peak of my attic and ducted it to a stud bay that vents close to the floor in my house. I have it on a thermostat that kicks on at 85 degrees. Even though I have solar hot water panels all over the roof of my house, I still get quite a bit of heat out of the attic.

The project probably took me half a day to build and install. The fan I picked up at a yard sale for a few bucks.

Deron.

I used to work for a company in Berkeley that did solar thermal and pv systems. According to their engineers solar hot water systems are the most efficient, I'll wait for PV tech. to increase before I buy anything like that (like I could afford it).

I've always been interested in Stirling Energy's parabolic dish technology. I talked to one their engineers and Vegas once, and he said they had all sorts of problems with the technology. I also got to visit Nevada One which is their parabolic trough solar thermal power plant. It was amazing!!!

The technology to power the US with the sun is here today, its only a matter of the correct allocation of new energy funds, which will probably won't happen.

i don't see how solar hot water can be more efficient, which to me means cheaper to install and run.
.
My cost:
fan: $20(been using it for years as an exhaust fan; all i did was throw the reverse switch so my cost was 0).
Duct: $0. i used the box my heat pump came in.
Cost to run, $1 /mo, <$3 per year.
No chance of water leaks ever; what happens with old solar water roof leak; damage to interior?
.
thanks for all the comments!
.
As for my hot water,
i installed a convenient ON/off switch to my 40gal elec waterheater. cost $10 for the 20amp 220v switch; on for 7 min to shower, 45min to do dishes/laundry/shower.
Cost to heat water is less than $4 per month. Again i encourage u all to try to beat my costs over time, like 10 years or even 20 with any system.
If i had it to do over again, i'd install the elec water heater in the attic!

Matt Gruber said:

i don't see how solar hot water can be more efficient, which to me means cheaper to install and run.

Click to expand...

Thermal mass- it even works at night and for days when there is no sun. But I like your idea as it is cheap initial cost and also- I am not sure I would want water pipes in the attic. Sooner or later they will burst or leak. So then you have to put something outside and the cost keeps going up. In addition, it takes more energy to pump the water and you also would need glycol in my area. But water is not so good as compared to other ideas if you have the choice.

I looked at a house with solar heat when I first moved to this area. A guy had a big tank in the basement. He said that even if the sun did not come out for 3 days and no matter how cold it was, the furnace did not come on. I think this is where they get the efficiency. However, as you say, it cost a lot to install.

I was looking on the net and they even had a specially built house system based on your idea, except I think it was passive convection. It worked as they built massive heat collectors from mass in the ceiling area of the attic and circulated the air thru it. the home was built especially for this. http://www.geocities.com/davidmdelaney/thermal-cs/thermal-crawl-space-1.html This home in Ottowa Canada, has enough thermal mass to heat the home for 7 days!

I guess the only thing I would think that *might* be better, with your idea, would be to use your idea with an air to air heat exchanger. My house is only 10 years old and I think there is a lot of smells up in the attic e.g. formaldehyde etc. My wife I am sure would not like me ducting this air in the house, she's pretty sensitive - however, it does not bother me. Probably in homes that are much older, this would not even be an issue as most of the chemicals on the lumber would have gassed off.

Definitely in my area a whole house fan is very desirable in the summer and can save a ton of money. I have done quite a bit of research on this and I will probably install one this spring. the only thing is you need to be careful to not cause back drafts, so you need to make sure windows are open if you have gas appliances.


For those

EMF
i agree with a lot of your points.
1. SMELL- yes in 2005 a new roof really was bad for 1 year or 2. So i vote YES for a heat exchanger for others, for me i am chemical sensitive so i want continuous fresh air.
first few minutes there is an attic smell that clears up as the fan pulls in fresh air; inside air goes out the LR window.
2. pipes. i don't like water pipes in my slab or in the closet where the WH is. But, after 20yrs an attic WH MIGHT be ok, with a drain pan of course. I'm not sure if it would save $$, but i'd have more closet space.
3. attic exhaust fan is great! i tried a sears $200 30" fan for 10yrs, it was too noisey, so when it blew, i went with a ceiling fan. nearly silent and can run all nite cheap.

Money efficiency is more important than engineering efficiency. Ideally Id' have used a parabolic mirror to heat a fluid and run that through radiant floor. But the free sliding glass door panels I put up on the south wall of my house venting into the living room only cost about 50 bucks for a few boards, sealant, and vent grills. After a test, I spent 50 more on some sheet tin and black paint to make it heat the air better. So my hundred bucks saved me about 150 a month in heat bill all winter.

In a colder climate, of course, it might not have been efficient enough to work, but here in the desert, it worked great on days with a high of 40 F. I ran my heater daily for about 20 minuites in the mornings and then turned it off for the day.

High tech stuff is great, but everything in an earthship is low tech, and parts of it can be adapted to old houses if you just get creative. More insulation, more thermal mass, and more solar gain that only occurs in winter is not so hard or expensive to do.

Right. These are two different things. Efficiencies that is. If you had plenty of money you can do anything. What is better though and more fun probably, are these simple cheap and effective ways to lower your bills. Also, sometimes in exsisting homes you are kind of limited in what you can do - just due to the way your house is made.

I just got to thinking. A guy could run a cheap galvanized duct along the crest of his attic- that round stuff that you push together. Mount a fan in the ceiling and blow air into this ductwork thru flex. The ceiling air would be warmest anyway and would be good for this purpose. Then it would warm up even more as it went thru the duct and when it came out the other end you could return it to the house - preferrably low down near the floor if possible.

My house is a ranch style and sits with the back facing south- as this is what I like a back yard facing south. But, It also is the long side of my house so- the roof is facing south and real long. So, it would really catch a lot of heat with the shingles and radiate it into the attic.

In the summer, a guy could simply disconnect the fan from the duct and blow the hot air from his ceiling out into the attic vent if they were big enough, like a whole house fan does. Of course, you would have to open a window too- in order to cool down the house.

I need to try this at least in my garage to make it warm in the winter. It would be easy to try.

www.builditsolar.com has many, MANY projects like this, and every possible configuration has been tried by someone. Results posted, improvements tried, and various material choices priced and performances evaluated for consideration...a months worth of reading there!

Matt Gruber said:

i don't see how solar hot water can be more efficient, which to me means cheaper to install and run.

Click to expand...

I'm pretty sure he was just repeating what the engineers told him, that solar hot water was more efficient than PV doing the work of heating water.

Deron.

Yeah, PV to make electricity to make hot water would be pretty expensive heat. When I look at how much PV it would take to run my house, which is all electric, I don't even consider PV for the house heat or water heat. I would be nice to run the lights, tv's etc on pv. I'd like to make a simple pre heater for my water heater sometime soon, again out of scavenged stuff, or repuprposing my old water heater.