Hot air wall design

[The master plan]

Ok not really a hot air wall but most of the wall is going to be covered with nearly 300sqft of black steel panel then glazed with Suntuf Clear Polycarbonate Roofing Panels.



I built the garage with this in mind and the measurements in the photo apply to that area and it is 5" deep into the wall. I figure adding 1/2" or so of foil faced insulation, leaving a collector design of 4 1/2" deep. The wall will be the back (inside) of the collector...so the air paths of the collector will be built onto this then covered with the black panels a small air gap then the glazing.

I think a guy could split it up into 2 main collectors maybe horizontally or vertically. Each with their own switch and fan maybe? Looking for ideas on a design of the air paths.

If I added some vertical copper tubing I should be able to heat a fair amount of water also. Or maybe install the black steel panels horizontally at a slight angle and make a easy drain back system on top the hot air system. Which brings me to the overall plan.


The idea is to keep the garage around 50F and any excess heated water from the system could be pumped to the house where I plan to install my heat pump and disconnect from the city heat. (Hot water heat) The house is small 500 sq ft. Almost done digging a 1000 gallon insulated water tank in the basement crawl space to act as a water source for the heat pump. That tank can be at a lower temp 40F to 60F would be great. I currently heat the house and my hot water in the winter with a wood stove, replacing the wood stove with one set up to heat mainly the water would work as a green back-up heat for both the house and the garage when completed.

I already have a gas boiler in the garage (will be converted to LP, there is no gas line on the property and its staying that way!) to act as a back-up heat source. The air from inside will be filtered and blown into the collector then the hot air from the collector will be blown over a radiator collecting some heat and storing it in a water heater, how large? Not sure yet. Then blown into the garage for heat.

I also have a water source heat pump all you do is add a furnace fan to it. It was a add-on in its time.


I have 1200ft of 3/4" pipe that is 7ft deep...under the slab and extending under the yet to be built driveway. The temp of that loop was 58F in Oct and 38F in Jan. When I do the driveway, I plan to install 2" of insulation and more pex to melt snow and ice at some later date maybe. (I have alot of pex for an auction. LOL) Maybe fire up the boiler or dump a small amount of heat from the system.

There is room on the lot for another 1200ft of pipe also. (total cost installed less than $400...Dad gets $100 to fuel his skid steer) I've read that putting some insulation above the loop acts as more earth and that could be done with the new loop. Of course this would raise the cost over $400 then.


Already have pex in the fiber stranded concrete 4" deep in the garage floor just 1" below the surface...The entire slab was poured onto 2" insulation, no part of the concrete touches dirt, the outside of the slab will have 4" of insulation and 2 rows of block will be covered in 2" of foam board insulation when done.




Walls are double 2X4 and 9" thick, will be dense packed with cellulose giving R30 or more. Garage measures 24' 2" by 24' 2" (The 2" is wall overhang for insulation)


Ideas comments??

[jeff5may]

Awesome setup! Depending on your heat source, this could slaughter your utility bills... unless you have tons of free wood. In that case, it would save your back lots of work.

[gasstingy]

I like your efforts so far and expect the results to be an order of magnitude beyond my garage / workshop. It's the never-ending project I work on between other priorities in my life.

Like you, I did the pex in the slab and extruded poly insulation under and around the perimeter of the slab, just not as heartily as you. I did 3/4" under the slab and 2" around the slab inside the perimeter of the block foundation walls. I did not go to the effort of filling the blocks with the beads like you did. What I am getting around to, slowly, is painting the blocks outside {100% completed} and inside {15-20% completed} and plan to glue 2" of the extruded foamboard on the inside face of the blocks and go over the exposed foamboard with some sort of waterproof finish. I haven't made up my mind on the material to use, yet.

One last thing, I sited the building as close to true south as I could get away with and added plenty of windows on the most southerly wall and a carefully planned overhang to block out the heat in the summer. I'm hoping the passive solar does the vast majority of the work heating the garage.

Wish you luck and I'll be lurking.

Mark

[AC_Hacker]

Sounds like wonderful planning and execution for both of you.

Only idea I have on the sun wall is that a couple of layers of expanded metal lath, with a small separation, might be better than a sheet of steel, there would be more surface area and therefore more heat transfer.

I'm a bit dubious about covering a loop field with plastic foam, however. Only about 2% of your ground heat originates from deep earth. 98% comes from the sun.

I think I would try to look deeper into that issue, and try to get past hearsay... see if you can find any science on that kind of thing, before you actually do it.

Best,

-AC

[Daox]

Any updates on that hot air wall?

[Daox]

Bumping again for updates.

[The master plan]

Update coming soon...My laptop Windows 7 crashed and had to replace my hard drive. Went with a solid state drive, super fast now. I lost my password in the process and took this long to "remember" my password. lol

[The master plan]

Been busy around here and pretty cold so haven't gotten very far on the wall but did get some more piece of the entire system. Found another geothermo heat pump(GT062), this one is going to go in the house. These suckers are heavy though!

So that gives me a heat pump for the garage and another for the house. Both are water to air, all I have to do is heat the water to around 50 degree's all winter long. Digging a 1000 gallon plus tank in the house for thermo storage. Also have a Gas boiler that will be converted to propane and plan on using that for "back-up" water heating when the sun isn't providing enough heat to the system. The boiler will probably be used to keep the slab warm in the garage anyway...so why not run a loop to the thermo storage tank at the same time to dump some heat?



The "new" heat pump works as an air conditioner also, has a 3 speed fan and 8 year old compressor. During the summer it would be dumping the heat from the house into the tank in the crawl space and it will draw that heat off in the fall when I start heating...how much better can that be?



I got about 3 cord of wood this fall and am down to about a cord or less right now. Maybe around 60 million BTU of heating for the winter going by heat content of the wood. Lots of air leaks going to be patched up this summer. I got one new window in and WOW talk about a difference! Going to be replacing a few more this summer also. So I am hoping it will take less BTU to heat next winter. Getting tired of hauling wood and the mess. Love the heat though. But there has to be a easier way.



I also talked to a guy last month here in town that had 12 solar panels that measure 3' X 8' and have dimpled copper plates and the water flows between the two sheets and around the dimples. Looks like a honey comb pattern from the outside. There are no tubes in this panel. I never seen one of these before and can't find any info on them. They are probably 20 or 30 years old but look in great shape. He wanted $3500 for all 12 but I couldn't swing that and declinded. Now he told me he has someone that wants six and I could buy just the other six.

Thinking I could mount those on the house and use them to heat the water in the large tank in the crawlspace that the heat pump will draw off. I get better sun on the house than the garage...but less space for panels.



So here's 3 square of black painted steel waiting for a "warm" day.



I got some of the back side insulation up for the solar panel going on the garage wall. Been to cold for me to work outside on it. But hope to make some progress this next week when its suppose to get above 0 F. Thinking of dividing it into 2 large separate panels. Both will have different fans and their own thermostat so either one, the other or both can be running at the same time. More pics to come when I start putting up the steel, I hope to get some testing in while its cold outside and the sun is low to see if this whole crazy idea is going to work...

[Daox]

It all sounds like great ideas to me. I'm looking forward to more updates.

[The master plan]

Brrrrrrrr.....been cold out lately.

So I got the pattern done for one panel, half the wall. (aprox. 150sqft) And one piece of the steel up. The rest should go alittle faster.



Started on the pattern for the other half(another 150sqft)...but it started getting dark and I started getting cold.



Plan is to blow air from the bottom up around and exit the tops of each panel in the middle. From there it will blow over a furnace coil to heat water, all I need is water at 50F or more. Then the air goes back to the collectors as a closed loop. At least for now, then after I get some testing I may add a way to draw in shop air. But then you'd have to filter it really well. With a closed system I won't get as much dust, smoke, dirt etc from the shop air on the inside of the collectors. And hopefully it will boost the amount of BTU's going into the water vs an open system.

There is a spot framed for a window but I am wondering how funny it would look in the collector? Would be nice to have the light from a south window also though. Not sure yet...

Side view of the whole mess. Black pipe in the bottom of the photo goes to the 7 ft deep 1200ft slinky coil under the garage slab and out into the driveway.



Just alittle of the insulation for the outside block. The whole garage bottom plate overhangs enough to fit this cut piece of 2" foam. Its buried almost as deep as the slab so the slab has 4" and the outside block has 2" of insulation. Expanding foam was used at the top of the pink foam also. Air tight as possible where you can, in a garage anyway. lol Then cover the insulation with Tuff II brush on coating to protect the insulation. Brown or matching tan?



The steel is painted on the the back, would rather have it bare. And after I placed the order I found out of course the black paint is 'energy saving' paint. Oops...

Worst case I'll take the panels back off and get them sandblasted front and back then paint the front with the proper type and go from there.