In reply to Robbie :
Over 20*. That’s excellent!
In reply to Robbie :
Over 20*. That’s excellent!
Find a thermometer for inside your garage! I’m super interested to find out how much spread there is between the outside and inside temps.
In reply to dculberson :
I didn't think we had any random thermometers laying around, but now that you mention it, I do think I have a couple old battery powered "digital" thermostats...
Maybe I can find some batteries and get them into position.
Phew. I think I can finally call this one done.
Finished out all the metal and flaps saturday. Sunday we had a really cold day, but clear sun most of the day. Here are the results!
About 9:30-10 am. Heaters are moving quite a bit of air:
Temp inside garage (30*): outside was about 8* according to weather app.
Here we are again about 2:30. Temp inside really close to 40*, outside got up to 13* yesterday - again, according to weather app.
And I checked again at about 4:30 when the sun went down.
First of all, you can see the flaps shut!
Outside was back down to single digits, inside dropped a bit:
Overall, I am very happy so far with that. This is an 840 sqft garage with average about 10-11 foot ceiling, so raising the temp from 30-40 on a 10 degree day is no trivial amount of heat!
WooHoo!
That's awesome! a 30 degree delta between outside and inside is great. I know it would be possible to spend years chasing your tail on efficiency gains, but I wonder if an improved flap could maintain insulation value at the openings but still open passively when heat builds up inside.
Whatever, free heat is free heat. I'm impressed. I have heat in my garage but only keep it around 50 degrees. Something like this would allow me to burn way less gas. Unfortunately my whole south wall is pretty much taken up with doors. Not enough wall to do anything like you've done.
So, my house was not doing so well without power, but my garage is working excellently! Well, much different set of expectations so not really Apple's to Apple's but ok.
Good sun today, all the vents are blowing lots of hot air.
Around 8 am I had an interior temp of 25 degrees in the garage and it's about 32-33 now. Been -16 or less outside all day. I'm very impressed with the performance today, and it is clear to me that the garage has a large thermal mass and good insulation. So if the heater had come online earlier in the fall, my average garage temp would probably be even warmer now.
I'm honestly really impressed with it today. I thought for sure it wouldn't be much above 0 in there.
In reply to Robbie :
Thats excellent!
That's really excellent. I have a perfect South wall on my garage for one of these.
I think I'm close to done putting everything back (and doing a huge dose of organizing my "bucketed" nuts and bolts).
This was a much larger project than I thought, but I am sure glad I did it!
The organization is a bonus.
dculberson said:That's awesome! a 30 degree delta between outside and inside is great. I know it would be possible to spend years chasing your tail on efficiency gains, but I wonder if an improved flap could maintain insulation value at the openings but still open passively when heat builds up inside.
I just remebered we had something like this in our Veal barn. It was a rectangular opening maybe 10" by 18" wide. Hinged at the top was a piece of 1" foam board. It weighed almost nothing so when the fans were on air was allowed in and when the ventilation fans stopped the foam board dropped down. Not terribly complex or expensive. The hinges seemed to stay clean and functioned without assistance over the years, surprisingly.
Very impressive results!
Why are systems like this not standard protocol in buildings?
Do you have a way of turning it 'off' in the summer? Or does the sun not really hit it?
ProDarwin said:Very impressive results!
Why are systems like this not standard protocol in buildings?
Do you have a way of turning it 'off' in the summer? Or does the sun not really hit it?
He'll probably be ok, the sun hits it in the winter because there are no leaves on the tree.
ProDarwin said:Very impressive results!
Why are systems like this not standard protocol in buildings?
Do you have a way of turning it 'off' in the summer? Or does the sun not really hit it?
The sun is at the wrong angle in the summer. Mine doesn’t put out any heat at all in yhe summer. There really is no downside to this.
In reply to ProDarwin :
Thank you - yes, I am quite impressed. For the summer, I have a couple things working for me. One is the trees. They will prevent a lot of the sun back there when the sun is shining 'sideways' i.e. morning and evening. Another is my roof overhang. There is about 20 inches of overhang above my panels. That means when the sun is at its highest point on dec 21 (lowest sun all year) I will have 7.5" of the panel shaded. Conversely, on jun 21 (the highest sun all year) I will have 67.5" of the panel shaded. equinoxes would have 23" of shade. Finally, I will cover up the top vents with something stiff like cardboard or foam board to prevent most of the air circulation as well.
As far as why this isn't standard practice, I have no clue. Doing this while the building was being built would've saved probably 20 hours of labor between both projects (the original construction and adding the panels). The extra cost of the panel material would be darn close to negligible after you subtract out the cost of the vinyl siding I wouldn't need to buy.
But speaking of the above - I think someone with a plastic/vinyl/polywhatever extruder (same machines they make vinyl siding and trim with) could make the vertical pieces that almost just snap together with the screen inside and the outer panels to make installation VERY quick. This is something I actually wanted to look into. Sooooooo - anyone know someone who works in the plastic siding design industry? SVreX?
Robbie,
Awesome job on a project that has had my interest for a while. I stumbled across the build it solar space heater article about 6 years ago and thought it would be a great addition to a garage but project prioritisation put this at the bottom of my to do list. I'm glad to see a member of an active forum document their builds, because I have a ton of questions/comments.
1. for the screens did you use the "solar screeen" like: https://www.homedepot.com/p/Phifer-36-in-x-25-ft-Charcoal-Super-Solar-Screen-3021116/100552677
It seems more pricy but I wonder if it would bump up the efficiency of your collector.
2. You mentioned keeping the back of the garage painted white to reflect back on to the scree for any rays that missed the first pass. I would like to offer a different perspective. Some percentage of what is reflected by the painted wall will be absorbed on the 2nd pass thru the screen and glazing but some will make it back out of the glassing and be lost back to the environment. If the back of the garage is painted black and absorb most of what's missed by the screen, that energy will heat the wall, and thus the garage via conduction or heat the air not in contact with the screen. We may be only talking a few percentage difference from today's state so if your attached to the astetic of white than it's probably not worth a change.
3. As the space heater is totally passive and functions due to convection you may end up with a large temperature spread from the floor to the top of your garage. This can be addressed with a fan, but that removes some of the passive nature of your system. Do you have any mesurments on how bad this spread is?
4. I know you stated you don't care about the BTU just the inside temperature, but i would be curious on the calculated BTU output of your space heater to understand it's return on cost. The build it solar barn was calculating 6000+ BTU per hour per 4'x8' bay. A 1500w space heater produces 5100 BTU an hour so your setup could be equivalent to 7*1500w*sunlithours. Even if you see an average of 3 hours a day I see that being worth 31.5 kwh a day. That works out to $150per month based on my DTE electrical bill (Michigan). Even if the BTU per hour numbers are optimistic I see this having a reasonable pay back period.
Thanks for sharing your build!
In reply to xxsportscar :
Thanks! So far I really like it. It's not the jungle in the shop, but so far this winter it has stayed between 40-50 in there, which is just fine with a coat and no wind.
I just used regular cheap screen (2 layers). Maybe different stuff could bump the effectiveness.
I sort of agree on painting it black, it may also bump effectiveness.
I don't notice an issue with hot up cold down. But, I usually stand in the garage so in need it warm where my head and hands are. Don't care as much about down by my feet. It is possible that I have a lot of heat up by the ceiling. I have an old ceiling fan I might install up above my work area to run only when I'm in the garage (it would also help me stay cool in summer).
I have no idea how to even start on a btu calculation, unfortunately.
I have a south facing enclosed porch with big windows.
It gets hot when the sun shines, not so much when cloudy,which we have a lot this time of year.
I just did a temperature reading, outside is 39/40f, on the porch 44f. It's cloudy.
I have toyed with different ideas to capture the heat but it seems most of the time I get the heat when I don't want it.
One day last week it it got to 80+ with abundant sunshine and outside high 40's.
I opened the house door for awhile. I should have had something to move the air.
Too much heat in the summer, have to open two windows.
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