Another quick updated. I cut a hole in the insulation that I stuffed into the hole in the kitchen's chimney. I got the wire run down for the kitchen temperature sensor. I also made a damper for this hole. As you can see, it holds itself in place quite well just by the pressure of the air wanting to escape! So, a damper (or more) is REALLY needed otherwise I'll loose all the precious heat I'm trying to get.

http://ecorenovator.org/pictures/house443.JPG


Super fancy damper! I'll stick it in place with something so it doesn't fly off. In the picture, the hot air trying to escape up the chimney was enough to hold it in place quite well.
http://ecorenovator.org/pictures/house444.JPG

Next step was getting power to the fan setup. I had to add an outlet for it.

http://ecorenovator.org/pictures/house445.JPG

I've still been working on the system. Mostly, I've been troubleshooting little issues here and there. The switch from the benchtop version of the arduino differential thermal controller to the working version provided some hiccups that I'm still working out. While I was tweaking things, I also compensated for the resistance in the long wire run in the programming. Its too bad too, yesterday would have been a perfect day to run it.

Well, I found out one of my temperature sensors got fried. I think the wires got crunched together and it shorted out. I thought I had an extra on hand, but apparently not. Now, I have to wait for new ones to arrive...

Well, I got tired of waiting (and having many good heat harvesting days wasted). I came home today to a 93 degree attic! So, I setup the controller a little differently. It currently does not monitor the kitchen temperature. Once the attic gets to 23C / 73F it kicks on. Once it drops to 21C / 70F it kicks off. That is above the temperature the house is kept at (20C / 68F).

Currently, I am monitoring my kitchen's temperature to see what effect the fans have.

As for noise, there is a bit of electric motor hum that is coming down the chimney and the sound of rushing air a little. However, its quieter than when the furnace kicks on.

Well, it works. :)

Here is the logged temperatures. There are a few notes to go with it. Between 7:15 and 7:30, we were in the kitchen preparing diner, thus the temperature bump up where it had previously slowed. Also, after 8:00 I manually shut the fan off to see if the temperature decreasing trend would increase, and it seems that it did. Also note that the later time periods are not equal.

Here is a nice image to show what I mean.

http://ecorenovator.org/forum/attach...1&d=1302748687

So you're getting an extra 3°-4°F from the attic. Good job!
Does the warmer air from the kitchen also raise the temperature in other rooms?

I kind of watched my thermostat in the adjacent room. It did not seem to be effected by it much.

Very cool, Tim!!

That's awesome. You're using the roof as a solar collector.
In summer will you run the fan in reverse to pull hot air out of the house and into the attic?

Yup, the roof is my big 'ol solar collector. :)

I'd like to reverse the fans in summer. But, it kind of gets complex since I can't just reverse the fans. I'd have to come up with some duct work in order to reroute the fan's blow direction.

Heat Decay...
 

It's likely that some percentage of the heat you're recycling is coming from your house... either way this is a great project.

It reminded me, in certain respects, of some exergy analysis reports I have come across for some commercial European buildings, wherein the heat decay through a building was followed and utilized appropriately at various stages of decay... a whole new way to think about heat.

I'm curious if the heat build up in the attic that is added to your room heat, ever gets excessive, enough to cause you to over-ride the fan from the attic.

If that ever gets to be the case, it would suggest some heat storage for later use... like maybe an air-to-water exchanger in the attic, and a large water heater tank in the basement, to ease you through the chilly evenings.

Or maybe storing heat all the time for DHW preheat.

...anyway, great project!

-AC_Hacker

Good point, I could tell in my test that the fans weren't able to move the heat as quickly as I had hoped for. 2 degree F increase an hour isn't horrible, but there is a lot more heat up there. However, I like the simplicity of the system. Its cheap and easy. I'm quite open to ideas on how to improve it though.

As we move into summer, and heat is no longer needed for the house, DHW heating is a great alternative for using attic heat. I was thinking of running some PEX tubing up there as a simple preheater, and drain it for winter. If you wanted to get fancier, you could add a pump and thermostat to heat up a tank. With my acquisition of the solar hot water panels, it will not be needed. However, I'd love to see someone else do it.

Well, I got my new sensor the other day and soldered up the one I needed in the kitchen this morning. I also made a temporary mount for the sensor under the cabinet next to my fridge. This keeps the sensor out of the path of the warm air blowing in and should give an accurate 'room' temperature.

Now, I just need a sunny day where my attic gets up to temp to try it out. Its been so gloomy lately. Today is very sunny so far, but its really windy. We'll see if it gets up to temp or not.

http://ecorenovator.org/forum/attach...1&d=1303045718

Do you have those Heat Recovery ventilation systems that pump warm air from your roof space or attic , as we have them here in New Zealand ?? They have a differential and max and min settings so you are not blowing cool air down when its too cold up there???

I'm not sure what heat recovery ventilations systems you're talking about. This thread tells what I'm doing. Yep, it has a thermal differential controller controlling the fans.

I did make a few more tweaks to the differential controller the other day. Mainly, I was getting some noise over the long run of the wire going to the kitchen sensor. So, I added a 10 uF capacitor near the controller to act as a buffer. This smoothed out the signal and everything seems to be working great. See the thermal differential controller thread for more info.

I still need a nice sunny day to see if it kicks on though. The other day was nice and sunny, but it must have been too windy. As I saw, the attic only got up to about 65F yesterday.

http://ecorenovator.org/forum/attach...1&d=1303127991

Have a look at this link psl-heat transfer systems and this photo explains it .http://pyers.co.nz/psl-heat_transfer_systems.html

how do you insert photos in this ??

When I came home today I saw the fan was running. :) Unfortunately, I have no idea how much it helped. I think I'm going to connect my laptop to the arduino to do some data logging just to get an idea of how its working.

This looks like a heat recovery ventilator. They're used over here mostly in newer houses that are sealed better and need fresh air. They're a great idea, but this isn't what I'm doing with this project.

If you are trying to use photos that are already on the Internet,

• locate the URL of the photo
• copy it to clipboard
  
  http://ecorenovator.org/forum/attach...1&d=1303166376
• use the 'insert photo' button
• paste the photo URL to the dialog box

If you wish to include images that are NOT on the Internet,

• http://ecorenovator.org/forum/attach...1&d=1303166826
• Go to the 'Manage Attachment' button... it will open a new page
  
  http://ecorenovator.org/forum/attach...1&d=1303166860
• Press the 'Choose' button
• upload
• the URL of your photo will be there (right click) in 'current attachments'
• follow steps given at the top of this page

I like to center my photos, I think they look better, so I highlight the picture code and use the 'center' button...

-AC_Hacker

Here is the ventilation heat exchanger thread:
DIY ventilation heat exchanger
If you already have one, or are planning to get one, please share any info that might be useful.

Daox, have you noticed that this thread is already pinged by heat-booster.com?

I came home today to see the attic fan blowing. I'm still working on a data logging setup for it to see what is actually happening.

Get some / recycle some attic heat this weekend?

You betcha. I was gone this weekend, but now that its fully automated, it kicked in and heated the house at least on Sunday. When I came home it was still on.

Uploaded Pictures Test for Air Conditioner HP
 

I might have figured it out? We will see ?

http://ecorenovator.org/forum/attach...mweek3-001-jpg

Since tweeker bumped my post up I thought I'd give an update. The system and been working very well and I'm quite happy with it. Pretty much any sunny day (minus one day that was 20 mph winds) itll turn on and heat up the kitchen from the mid 60s to 69-70F.

I haven't toyed with the datalogging yet either. Its working, I'm happy. I'm okay with that for now. :)

Well, I had a bit of a hiccup with the system over the weekend. I actually wasn't even home, but came home Sunday night and the blower was blowing. However, I also saw that the damper in the kitchen wasn't pusheed up as high as it normally is. So, I went to check things out and sure enough, one of the fans wasn't turning. I'll have to pull it out and see whats going on.

The Chimney as Plenum
 

Is the chimney sound, i.e., a sealed plenum? That visible portion appears so, perhaps you even tuckpointed recently? I live nearby, in Milwaukee, and my chimney was built of cream city brick, once a popular local building material. I've had to replace bricks and mortar that cracked, fell out of and into the chimney, and also disintegrated into sand, due to the ravages of time, stack temps and combustion products from my oil burner. Perhaps even poor manufacturing and improper firing of the brick occurred.

Cream city brick, I've read, tends toward greater porosity than some other types, and positive pressure in the chimney may encourage exfiltration of particles. I've found small quantities of sand around the base of my chimney in the basement, and that suggests to me that some soot, a nasty eye and respiratory irritant, may also have been pushed into the basement atmosphere.

Had you considered lining the chimney with rectangular or round ductwork? Some lurking experts might comment about whether this would increase laminar airflow, reduce turbulence and surface effects from the brick, and perhaps cut down the time that the blowers need to run, thereby reducing electricity consumption. Perhaps the effort would not yield substantial efficiency benefits...?

I have not considered putting a liner in the chimney. I really don't think it'll do any good. The bottleneck of the system is definitely the outlet in the kitchen. The cross sectional area of the chimney itself is much larger.

Re: Using Attic Heat
 

Cool project, BTW. Do you have a thread or posting about how your chimney was rendered obsolete for heating purposes?

Nope, no thread. But, when I bought the house, they had just redone the roof. At that time, they had the chimney cutoff below the roof so they wouldn't have to deal with it. I'm sure it hadn't been used in quite some time.

Attic heat
 

Ahhh, so perhaps you have a newer natural gas-fired furnace that vents out the side of the house? Could the water heater be vented so as well?

The chimney bricks could be re-purposed for other construction and the chimney column space reclaimed for living/storage. Still, the brick visible in the kitchen photo is rather handsome...

These comments are in no way intended to minimize what I see as a clever and cool project.

I've entertained side-venting my heating unit and water heater to reclaim the space now occupied by the chimney. Tongue-in-cheek, I tell my my wife we could turn the chimney into a clothes chute...:eek:

Hi Daox - I've enjoyed reading your little project and have been interested in trying something like this as well.
I would like to know how you are filtering the dusty attic air that's being blown into your house. Or is it not too bad?

So far, I haven't used any filters at all. I just checked the kitchen opening and there is no trace of dust on the damper.

Hey Daox, check this out...
 

Hey Daox,

Check this out:


Here is a paper that didn't exactly utilize attic heat, but pretty close...

Combined PV - Air Collector as Heat Pump Air Pre-heater

-AC_Hacker

Sounds like a great idea to me. I think if I were to take this to the next level, I'd probably use a heat pump to allow more heat to be moved. The fans work good for heating one room, but there is a lot more heat up there that could be harvested.

Im curious to know when your attic is at 90 f, what the outside temp. is at the time and if it was a totally sunny day ? Im in northern Florida and ive never measured my attic temp. but i strongly suspect that it is at least 90 f up there when its 60 f. out due to the intense suns rays beating on my black asphalt shingles. This winter ill pay closer attention to that and just may implement something like you have to take advantage of the accumulated heat up there for the living room area where i spend nearly all my waking hours. During the summer months, i wouldnt be surprised if my attic is at 130 f. at 6 pm which has me thinking I should throw a 300' coil of 3/4" Pex up there for shower water (cooling down with some cold water of course) .

The ambient temperature varied quite a bit. The attic temp was much more stable. I'd say the ambient temperature was anywhere from 40 to 60F.