# Adding another solar air heater



## precaud (Aug 10, 2010)

In the fall of 2008 I converted my south-facing front porch into a 72 sq ft solar air heater, and the results have been excellent. Upstairs wood consumption dropped by about 1/3 and I no longer use ANY nat gas for heat. I posted some in-process photos in this thread:
https://www.hearth.com/econtent/index.php/forums/viewthread/24643/

I estimate that, on sunny days in winter, I get 50k-60k btus per day from this heater. It's working so well, I thought I'd add another one right next to it. So I'll share my process of building the second heater, which I started on July 5th.

The first photo shows the space where it will go. The walls of this house are thick (16 in.) masonry, so I won't be putting any new holes in. The idea for this heater is to bring cold air in through the basement window (bottom right), use a sub-flooring with partitions to distribute it evenly across the front glass, take the heated air into the house through the top 1/4 of the upper window with fan assist, and install a floor-level vent in a hallway 25 feet into the house to complete the circulation loop. When operating, it will heat upper and lower rooms at once.

As I discovered while building the first one, construction is painfully slow when building triangular spaces, probably 5 to 10 times slower. So this indeed is a labor of love.

The second photo shows the concrete slab poured, giving a better idea of what will be happening.


----------



## precaud (Aug 10, 2010)

The stuccoed walls are built to last, but are very uneven. 2x4 frames with shims are Tapcon'ed into the walls to make the outlines parallel and vertical. What in the world did folks do before Tapcons were invented?

The triangular vertical beams are milled on a table saw from 4x4 doug fir. Big fun. The bottom one is a redwood 4x4 just in case moisture finds its way in. The beam across the arch is a 2x6. Thanks to careful frame layout, everything is vertical and square at the top. {Phew.}

This heater will be about a foot taller than the first one, or 8' x 10'. The old porch wall blocks part of the early morning direct sunlight, so ultimate heat output will probably be just a bit more the first one, I'm guessing around 60k-65k btus/day. But since the walls will now be insulated, consider that we are also moving about 120 sq ft of massive masonry wall inside the heated envelope. So the ultimate impact on overall house heating is much greater than just the btu numbers would suggest.


----------



## precaud (Aug 10, 2010)

And now for my least favorite part - the roof. It will only have a 6º slope, but that will be plenty for such a small roof.

A 6º roof slope on the approx. 65º / 35º structure makes for some ridiculous angles in the places where they converge...

And that's where it stands as of today. Next step is to cover and seal the roof. I plan on using modbit roll roofing, it's easy to work with and I think I have enough of it left over from the last heater for this one.


----------



## billjustbill (Aug 10, 2010)

precaud said:
			
		

> And now for my least favorite part - the roof. It will only have a 6º slope, but that will be plenty for such a small roof.
> 
> A 6º roof slope on the approx. 65º / 35º structure makes for some ridiculous angles in the places where they converge...
> 
> And that's where it stands as of today. Next step is to cover and seal the roof. I plan on using modbit roll roofing, it's easy to work with and I think I have enough of it left over from the last one for this job.



Ask your local roofing supply about Ice and water shield going down first, instead of normal roofing felt.  With the two side walls being your house, keeping water out on a low slope roof is the the main long term issue to keep your solar air heat going and keeping out black fungus.  You might consider adding the slope of the roof to match your Latitude, so you could put an 80 watt PV panel or two to power the storage battery and 12v-24v blower so there's no inverter needed.  If you'll do this, then the $1500 max tax credit you only get once can be transfered to the unlimited 30% tax credit of a solar electric system.  When there is a low sun or no sun day for making electricity to power the blower, your air heater wouldn't be adding much heat anyway.

What type and cfm size of blower are you going to use?  What kind of collector plate and glazing?  There are many DIY versions on the web, but here is a commerical air heater that uses soda cans.  With their thin walls, not only is the heat transfer better, but the heated air never comes in contact with the glass....

http://www.cansolair.com/

I built a 40 gallon batch heater back in the mid-80's using wood as the main framing.  I always worried about the amount of heat it had.  After four years and a major hailstorm, I removed it when the new roof was put on.  If I were to do it again, for water or air solar heat, I would use metal studs, fiberglass insulation, and the correct foil-faced foam insulation inside the heater itself.

Hope you will keep taking pictures of your progress and posting them.  Great project!!

Bill


----------



## precaud (Aug 10, 2010)

billjustbill said:
			
		

> Ask your local roofing supply about Ice and water shield going down first, instead of normal roofing felt.  With the two side walls being your house, keeping water out on a low slope roof is the the main long term issue to keep your solar air heat going and keeping out black fungus.



Thanks for your suggestion, Bill, but I have never seen fungus of any kind here in New Mexico. The roof I did two years ago has been leak-free so I'm comfortable doing this one the same way. The roof area is small (half of 84" x 64") and south-facing, so water/snow clears very quickly. No need to go crazy on the construction.



> You might consider adding the slope of the roof to match your Latitude, so you could put an 80 watt PV panel or two to power the storage battery and 12v-24v blower so there's no inverter needed.  If you'll do this, then the $1500 max tax credit you only get once can be transfered to the unlimited 30% tax credit of a solar electric system.  When there is a low sun or no sun day for making electricity to power the blower, your air heater wouldn't be adding much heat anyway.



The roof is already built, not about to change it... The electricity needed to run a small fan for six hours a day is so miniscule, it's not worth putting money into PV panels to power them. Intellectually satisfying, but economically hard to justify.



> What type and cfm size of blower are you going to use?



Very little is needed from the fans to assist the natural convection - only 50-75cfm. Haven't decided exactly which fan(s) to use yet.



> What kind of collector plate and glazing?



Suntuf polycarb glazing, two layers of black aluminum screen for the collector. Black vented aluminum soffit is an interesting material but noone in this area stocks it. I guess there are not many soffits in New Mexico...



> There are many DIY versions on the web, but here is a commerical air heater that uses soda cans.  With their thin walls, not only is the heat transfer better, but the heated air never comes in contact with the glass....
> 
> http://www.cansolair.com/



Yes, I looked at that a couple years ago and it looks like a pita to make and not any more efficient than the screen.



> Hope you will keep taking pictures of your progress and posting them.  Great project!!



I certainly will!


----------



## precaud (Aug 18, 2010)

Be glad you weren't born a roof. The most under-appreciated part of any structure.

I put the roofing on this weekend. SBS modified bitumen roll roofing. Dirty, difficult work, and every detail has to be exactly right or it will leak. We had a thunderstorm last night and it passed the test with no leaks. And I haven't even sealed along the termination bar with PU caulk yet.

In 30 days, after the roofing cement cures, I'll paint the SBS with 2 coats of white elastomeric roof coating. That stuff lowers daytime rooftop temperatures bigtime and extends the life of the roof.


----------



## billjustbill (Aug 18, 2010)

A tight roof on and after a rainy spell is a reward all its own!!

One of the things I learned about the using the white elastomeric roof coating is that the one I used on my 16'x 44' patio roof, required a clear primer to be rolled on first.  Be sure to read the brand's requirements.

The other thing is that the one place that cracked and peeled, despite the expensive primer and putting on the second coat at 90 degrees to putting the first one on.  I rolled the second coat on within the manufacturer's recoat time, but it was where I left a place that thicker than the norm two-coat thickness.  The drying and weathering of the extra thickness caused it to shrink more and caused cracking in that area.    I believe that extra thickness in the coat was either at the beginning of the job when I had plenty of coating, so I rolled it on thick, or at the end of the job when I had some left over and rolled the it on "For good measure".... ;>)

Hope this helps,
Bill


----------



## precaud (Aug 18, 2010)

Bill, I currently have about 2,000 sq ft of modbit roofing that I have coated, and the only problem areas I see are those where the substrate has issues. I've used two different Henry products and one from Lowes, and after 3 years I don't see any significant difference between them. I pressure-sprayed the surface before applying, and coated in the early morning before temps had risen. So far, so good.


----------



## Jags (Aug 18, 2010)

Great project Precaud.  Keep those pics coming.


----------



## precaud (Aug 22, 2010)

I removed the top half of the window. It was very interesting tearing it apart and seeing how they built things back in the 1930's - iron weights on ropes nailed to the window frame for slide counterweights, and still functional after 80 years of use. Given the tools of the day, their work was amazingly precise, except for the squareness issues again... but they knew how to fudge them inconspicuously.

The top 12" is now an oak plywood hatch door that opens inward to let the heat in, the remainder was fixed in place. It will get covered with polyiso so finishing on the outside is not needed. The bottom sliding window is still operational, as it will be the only possible "service entrance" once the front is closed off.

Then all the frame gaps were caulked with expanding PU foam.

Next we start dealing with the interior.


----------



## precaud (Aug 30, 2010)

Made good progress this week. It is primed, caulked, the floor manifold (not shown in the pic) is cut to rough shape, and most of the insulation is installed. I'm hoping the good weather will hold so I can hang the rest of the fiberglass and get it covered!

It turns out I made one significant error. The concrete lip extends 5.5" in front of the glazing mounting plane, and the roof drip edge is 3" in front. So it drips onto the lip, which, of itself, is OK. Problem is, I forgot to slope the lip forward so the water runs off. So... it puddles there when it rains. Not good. The best idea I've come up with is to put a sloped flashing there to keep the water off the concrete completely. If you have a better idea, please let me know.

On the first one I built, I was able to get the glazing up and then finish the interior at my leisure. Not this time. With no easy access from inside the house, the interior of the heater must be finished first and the glazing goes on last. Everything has to be right the first time. I liked it the other way better.


----------



## semipro (Aug 31, 2010)

Great project Precaud.  I love seeing this sort of work.  The work I'm doing on my house now is much less fun...fixing water damage.  It amazes me the difference in building techniques between dry areas like NM vs. wetter areas like where I live. 

Is there a surface that goes over the fiberglass batt?  If so do you plan to paint that surface black for better heat absorption?  Maybe your glazing is not clear so it won't matter as much.


----------



## precaud (Aug 31, 2010)

Thanks Semi. Yes, not having to deal with consistently high moisture levels makes things a bit easier. Good luck with your repairs.

The batts get covered with black polyethylene sheeting. If the weather cooperates, I'll be getting to that today.


----------



## precaud (Sep 6, 2010)

Insulation is complete and the covering installed. The intake manifold is partitioned to distribute the air is evenly across the front, and is braced well enough to withstand my weight on it. If it weren't for that, foil-faced polyiso would have been a better material to use. But the interior will need to be cleaned every few years.

I took a different route to deal with the front lip drainage issue. The thought of living with the sound of water dripping on metal flashing was not appealing at all. So I cut grooves into the cement every five inches and dished out channels from the areas where water was standing. Not elegant, but it solved the problem.

Only three more steps before the polycarb goes in and we close her up.


----------



## precaud (Sep 19, 2010)

Everything is prepped and ready to go. The double screen is in, intake manifold installed, outtake manifold is in (hard to see it in the pic, it's above the window and insures that air is drawn from the heater at the very top, where it's hottest.) The intake manifold supports my weight easily, and crawling into and out of the heater through the window is not as difficult as I thought it might be. When I'm in my 70's I might feel differently about it...

The forecast today is for 86 and calm - couldn't ask for better weather for installing the polycarb.


----------



## Seasoned Oak (Sep 20, 2010)

If that works well imagine a sun room along the south facing part of your house, mine is about 24Ft long and 6 Ft wide. It warms a 3000 SF home on a sunny day and at night when it gets colder in the sun room than the indoor temp (about 77) i simply close the door to keep from giving back the heat at night. Worls like a charm ,and no moving parts (except the front door).


----------



## precaud (Sep 21, 2010)

Well the polycarb is installed and she's all sealed up. Functionally it's ready to rock, just a few exterior cosmetic details remain to take care of - coating the roof, removing masking tape, some gravel in front, little stuff. High chance of heavy rain is forecast for the next 24 hours, so I get to see if it's watertight. Since the roof already passed that test, it should be no problem.

Though I haven't cut the hallway floor vent yet, I opened the heater vents today to carry off the chemical offgassing (very nasty smells). Even with the longest possible loop length - house front to house rear, down the stairs, basement rear to basement front, and in - it thermosyphons very well. So I'm going to hold off on the floor vent and see how this arrangement works once it gets colder out. This would pull more heat into the kitchen at the north end.

I think I'll step away from this for a couple days, this thing has dominated my life since early July and it's time to take the blinders off and reacquaint myself with the rest of the world...


----------



## precaud (Sep 25, 2010)

These pics are interesting, taken from the same place and cropped as equally as possible, showing the south side of the house before the project started in July 2008, and as it is now, with 154 sq. ft. of solar air heating in place.


----------



## begreen (Sep 25, 2010)

Nice job precaud. Thanks for the visual documentation. Looks like you won't be heating with wood until December with the new setup.


----------



## PapaDave (Sep 25, 2010)

Yep, I love seeing these "how I did it" threads. 
Nice job, and let us know how it works for you when it starts getting cold.


----------



## 4acrefarm (Sep 25, 2010)

Looks great, if it works half as good as it looks i'd call it a success.


----------



## billjustbill (Sep 26, 2010)

precaud said:
			
		

> These pics are interesting, taken from the same place and cropped as closely as possible, showing the south side of the house before the project started in July 2008, and as it is now, with 154 sq. ft. of solar air heating in place.



Very nice and professional looking!!  How much do you have in materials?  Are the pictures showing the shadows in the before and no shadows in the after shots taken in the same month and time of day?

I'd bet that in the next 12-24 months, you'll have a couple of 100 watt solar PV panels on each solar heater to power the blowers....  ;-) 

Bill


----------



## precaud (Sep 26, 2010)

Thanks guys. I've been basking in that "post-project contentment", which will last until I finally start cleaning up the messes I made...  

The color coat on the stucco above the first heater will get done next year, I have some other stucco repairs to do and we'll get them all at once.

Total bill of materials for the second heater, about $550. I didn't have to buy any tools for this one so that helped keep the cost down.



> Looks like you won’t be heating with wood until December with the new setup.



I hope so BG, but methinks that may be optimistic, we'll see. No doubt the burning season for the Quad upstairs will be shorter on both ends, and maybe slightly fewer fires once winter arrives in force. But not the X33 in the basement. I'll probably start having fires down there sometime next month. Once ground temps start dropping the basement is a giant btu sponge, even with the walls insulated.


----------



## precaud (Sep 26, 2010)

billjustbill said:
			
		

> Are the pictures showing the shadows in the before and no shadows in the after shots taken in the same month and time of day?



No, the first one was taken early July 2008 in the morning, when the project started. The other was taken a couple days ago in the afternoon, hence the shadows are different.

EDIT: I've replaced that photo with one taken about mid-day.



> I'd bet that in the next 12-24 months, you'll have a couple of 100 watt solar PV panels on each solar heater to power the blowers....  ;-)



Could very well be!


----------



## billjustbill (Sep 26, 2010)

precaud said:
			
		

> billjustbill said:
> 
> 
> 
> ...




Thanks for the answers.  Great job!!  And remember, keep those reciepts and estimated labor costs to put toward this year's 30% tax credit...  Heck, with the tax breaks, Federal and Local, I'd bet you'd get enough to pay for those PV panels.... ;>)  Or at least that's the excuse you can use to tell your wife...

Here's a thought that might really help you with how much heat you'll bet getting.  Look for a thermometer that shows today's highest temp and lowest temp.  Might help if you log your readings and keep record of what it does other than the amount of wood and energy used you would normally know ....

Well done,

Bill


----------



## precaud (Sep 26, 2010)

Thanks Bill. Somehow I think the IRS might take issue with "estimated labor costs" on a DIY installation, don't you?


----------



## billjustbill (Sep 26, 2010)

precaud said:
			
		

> Thanks Bill. Somehow I think the IRS might take issue with "estimated labor costs" on a DIY installation, don't you?



It's something to consider.  When we had 30 minutes of non-stop golf ball size hail several years ago, it took its toll on everything including the 8' tall cedar fence facing the storm and even split  and broke out the ends of many other pickets. The whole cedar fence was only 3 years old.  In the process of having the insuance company's rep go over all the damages, they included replacement cost for the pickets that had the ends split or splintered in the rest of the fence from those big chunks of round ice.... The insuance settlement also included tax, and labor charge, too.

I got a fence company to come give me their estimate for repair and replacement.   The labor was almost as much as the materials, but it would be months before they could get to it.  So, I took their estimate, bought the materials myself, and installed all the new pickets and replaced the ones split.  The insurance company paid me for my materials and my labor base on that estimate. With my time, care, and application of ample sealer, plus the extra thought in matching the pickets on the whole new sections of fence, and installing it "right", the fence may have been a little better....  In the end, I simply used my labor to buy more cedar fence pickets and repaired a larger and longer section of the fence to the right in the photo.  It was a Win-Win solution.  30% of your labor, plus 30% the materials might just cover most of your cost for these solar heaters.  Every BTU saved after the expenses are paid makes Payback and ROI in less than two years and that much sweeter.....

 Even if you had to pay $50 each to get them out there and give you a cost, I'd think that with a couple of professional estimates on paper, our friends at the IRS would consider your labor as good as the professional and include that cost in the 30% tax credit...  Just a thought.


----------



## precaud (Sep 26, 2010)

Bill,
Yes, I understand that when dealing with the insurance companies. But the IRS is a different matter; it has to fit within the rules, although I know that many in Texas that have a different view of that... 

At any rate, solar air heaters do not qualify under the current "alternative energy" program; "Qualifying property includes solar water heaters, geothermal heat pumps and small wind turbines." They basically want you to install larger, less-cost-effective systems, ones that require licensed contractors and have a longer payoff period.

For tax deductability, my system falls under the "enhanced residential energy property credit", which covers energy-efficient windows, heating, insulation, and the like. It's only a 10% credit and the maximum tax credit is $1500 total for 2009 and 2010.

PS - that's a lovely back yard scene you have there! Shades of green vegetation which simply do not exist here...


----------



## billjustbill (Sep 26, 2010)

precaud said:
			
		

> Bill,
> Yes, I understand that when dealing with the insurance companies. But the IRS is a different matter; it has to fit within the rules, although I know that many in Texas that have a different view of that...
> 
> At any rate, solar air heaters do not qualify under the current "alternative energy" program; "Qualifying property includes solar water heaters, geothermal heat pumps and small wind turbines." They basically want you to install larger, less-cost-effective systems, ones that require licensed contractors and have a longer payoff period.
> ...



Thanks for the kind words about the green colors...  I took that in early April, just after a 3" rain.  The raised beds and trellis show some this year's onions and potatoes.  Now, I've been watering the big old tomato plants and planted some squash and cucumbers  in hopes for productive Fall garden.

I see your point about the IRS guidelines.  In view of how some of the older campus principals would "Pencil Whip" some of their reports to Central Office, I always joked with the other school adminstrators about me being 100% correct on my textbook counts and my IRS taxes.....   I never had to worry if it's done right, the first time.

 I've been slowly and economically gathering PV panels, charge controllers, and old C-span satellite dish mounts to make several 4-panel tracker mounts for a 25% better panel output. With my focus on PV solar array to be up and running by December 31st, I'd forgotten about how solar heat is different from solar hot water, too.  I used most of my $1,500 toward the installation of a Lopi Freedom Bay, so I know how quick it get used up.


I like this website.  http://www.energystar.gov/index.cfm?c=tax_credits.tx_index It keeps all things in line and easily shows what is left that the IRS will allow.  You'd think with all the 200' diameter, million dollar wind turbines put in the state, that Texas would have a Much Better Renewable Energy program....  It doesn't, in fact, it except for $75 gas to electric credit one tiny Co-Op offers, or one or two large electric companies paying for their customers to rent out their roof space for solar panels,  Texas has one of the WORST....

What kind of Winter temps do you have there in New Mexico?  Many days below freezing?

Please keep this group updated as your experiences continue.


----------



## precaud (Sep 27, 2010)

> I see your point about the IRS guidelines.  In view of how some of the older campus principals would "Pencil Whip" some of their reports to Central Office, I always joked with the other school adminstrators about me being 100% correct on my textbook counts and my IRS taxes.....   I never had to worry if it's done right, the first time.



Attention to detail is a good thing...



> You'd think with all the 200' diameter, million dollar wind turbines put in the state, that Texas would have a Much Better Renewable Energy program....  It doesn't, in fact, it except for $75 gas to electric credit one tiny Co-Op offers, or one or two large electric companies paying for their customers to rent out their roof space for solar panels,  Texas has one of the WORST....



I'm not surprised. NM's electric company has been dragged into it kicking and screaming and fighting it all the way. Promote it in their marketing and fight it in the legislature, that has been their tactic.



> What kind of Winter temps do you have there in New Mexico?



https://www.hearth.com/econtent/index.php/forums/viewthread/56906/#641857


----------



## precaud (Oct 31, 2010)

Thought I'd give a first report on how the system is working. Last week we had a cold snap, and the first three days were solid overcast. Obviously a solar heater gives you little or nothing on those days; twice I had to light morning fires, and once in the evening. The following three days were a little colder (mid-20's lows, high-40's highs) but skies were clear. On those days, house temp was 67-68 in the morning. Usable heat output started by 9:15am (DST), at noon house temp was 70-71, at 2pm it was 74, and peaked at 4-4:30pm at 79-80F. At that point the temps slowly decreased to 72-73 at bedtime (10pm-ish), 67-68 the next morning, and the pattern then repeated.

So far, so good. I'll give another update in a month or so, as outdoor and, more importantly, ground temps go down. But based on what I've seen so far, my guess is that, as long as the sun is shining, no supplemental heat will be needed. I am very interested to see how much impact this will have on wood consumption.


----------



## PapaDave (Oct 31, 2010)

If your house is staying that warm, you're not burning wood or turning on the furnace, wood consumption has GOT to be less. 
Those are the temp swings we're seeing right now, and I'm having fires morning and evening to keep the house around 70ish.
Really appreciate the update, and looks like your ROI will be pretty quick. Besides that, think of the time you'll be saving not dealing with the wood as much.
Nice job.


----------



## precaud (Oct 31, 2010)

Thanks Dave. Though I'm hopeful about reducing wood consumption, I'm not as confident about it as you are. It has to do with what I think is the impact of ground temperatures on this house (and probably any house with an uninsulated foundation). I think that is why wood use is always higher in late winter than early winter. For example, for Santa Fe, November and March are pretty well matched as far as average high and low temps, but the ground is much warmer in November. And I always burn much more wood in March than in November.

And at the same time, the solar heaters are becoming less efficient as the sun gets higher in the sky. The sun angle in March is the same as September, so there's less solar gain. So for me the jury is out on wood use until late in the season. But I'll post updates approx. monthly. I prepped just slightly less wood this year than last, so it will be an easy compare.

For now, unless this La Nina pattern breaks, winter may never show up here...


----------



## precaud (Dec 1, 2010)

Another monthly update. The heaters continue to perform incredibly well. But as expected, as ground temps go down, the house sinks more heat into the earth, so it doesn't hold heat as well. Afternoon temps peak at 74-75F, and fall more quickly.

For example, yesterday was sunny, nighttime lows were 15F, highs were 36F. Inside, I awoke at 5am to 65F, burned one mid-size load in the Quad to take the chill off. By 8am the heaters start producing useable heat. By 9:30am heaters are above 95F and their fans kick on. By noon, house temp is 71F, heaters are at 108-110F. At 3:30pm house temp was a very comfortable 74. Just before 4pm, heaters drop below 95F, fans turn off, and heater vents are closed. Went to the health club, returned 6:15, house was 68F. Burned two mid-size loads in the Quad to maintain temps, 70-ish at bedtime (75 in living room). Sleep. Rinse. Repeat.

The outlook: For the next couple months, the heaters are operating at max efficiency due to low sun angle, but wood consumption will likely be about the same as last year. So the heaters won't lower wood use in the coldest months, but are certainly making the house more comfortable. As I had guessed before, lowered wood use will come primarily in the shoulder seasons.

Next report will be around the new year.


----------



## precaud (Jan 2, 2011)

Another month passes, so it's time for an update. And the timing couldn't be better, we're getting our annual new year's cold blast - sub-zero the last two nights, daytime highs in the teens. This is about as cold as it gets here. The good news is, when it's cold, it's usually clear and sunny conditions (clouds hold in heat - no clouds, heat escapes), so the solar heaters shine when it's coldest out. The temperature pattern was about the same as I described in my last post, except set back an hour (we're on standard time now). It's 9:45am as I write this, I burned one load in the Quad at 6:00am this morning, the solar heater fans have just kicked in (they're set for 95F), it's 8F outside and 72F in the living room and 66F mid-house already. Yesterday the high was 17F and it was in the low-to-mid 70's mid-house from about 11:00am on, with nothing but the solar heaters.

So needless to say I'm extremely pleased with how well these things are working. If the sun is shining, no other heat is needed, so they're sized just about right for the space they're heating.

I still have to wait on saying if wood consumption is down or not. Experience says the real challenge will come in March/April, when the sun is higher in the sky (less solar heat) and ground temps are still cold. See ya next month.


----------



## spirilis (Jan 2, 2011)

Kudos!  Would love to do something like this myself someday.  Maybe my next house if it doesn't have an HOA


----------



## precaud (Jan 2, 2011)

Lots of acronyms in my head, but not that one. What's an HOA? I'm afraid to guess!


----------



## spirilis (Jan 2, 2011)

precaud said:
			
		

> Lots of acronyms in my head, but not that one. What's an HOA? I'm afraid to guess!


Homeowner's Association ... Yes, you should be afraid :D

My HOA requires that any minor-to-major change to the property (even digging a firepit) requires their committee to approve, a process that takes at least a month.  I'd have a field day trying to explain this one.

Of course, maybe it's worth a shot... one of those framed-in wall-hung furnaces right square on the south end of the house between the two big sliding glass doors would work, except for the fact that it's the part most visible by everyone in the neighborhood... Nah I doubt they'd approve it.

OTOH, if I built a short slanted assembly that sits on the deck below there, they might not know what it is (and might not care).  Hmmm...


----------



## PapaDave (Jan 3, 2011)

precaud, I understand your trepidation in delaying the inevitible, but if you would have otherwise been heating the space with wood, and you are now not, it stands to reason that your wood consumption is less. This year, at least....when the sun is shining. 
Sounds like those things are the cats pj's. I've thought of doing that for the shop. I have a 30' s/w facing wall that gets sun (when it decides to shine) from about 1-2 in the pm, and might negate the need for a furnace most of the time. I hate turning the furnace on when I go out there to work.
Waiting for the next installment.  :coolsmile:


----------



## precaud (Jan 3, 2011)

spirilis: Oh dear, _that_ HOA... so sorry. There are different designs that are more discreet in appearance. Maybe you could get one of those by their scrutiny.

PapaDave: I honestly don't think it's inevitable. I have pics of my wood pile at various stages last year, and so far this year's use looks about the same. Comfort levels in the house are much better, though, and that there is no denying.

It's questionable whether it's worth it or not to harvest a couple hours' sun per day. Alot would depend on the design and size of the heater. Just like other things (say, woodstoves...), the larger it is, the longer it takes to warm up. It all comes down to thermal mass. In your area, before you throw money and effort at it, I'd consult with people in your area who have done it.


----------



## jimbom (Jan 9, 2011)

Precaud,  Thanks for your great pictures and for sharing your project.  Jim


----------



## precaud (Feb 4, 2011)

Time for the monthly update. For most of January, the weather was milder than normal with full sun, and the solar heaters were able to supply most of the daily heat needed upstairs, with only one or two loads of wood in support. A couple days with highs in the low 50's/lows in the low 20's required no wood heat at all. Those temps seem to be the threshold for this house where additional heat is not needed.

But the last three days temps plummeted, and have been the coldest yet this season (-22F last night), the first two with no sun. Despite burning an extra load of wood each day, the house gradually gave up its heat store to the cold, and it was 62F mid-house this morning (no overnight fire). Seeing we would have full sun today, I burned one load of wood early morning. By 9am, the solar heaters were producing usable heat, by 9:45am the fans kicked on (95F) and by noon the mid-house temps inside were once again at 70, topping out at 72 late afternoon (high of 14F outside). So even with the worse cold snap we've had, these heaters can heat the entire house to very comfortable temps.


----------



## PapaDave (Feb 4, 2011)

precaud, thanks for the update. 
When does your heating season generally end? I can't wait for the end of season synopsis.


----------



## precaud (Feb 4, 2011)

Papa, for the last couple years, tax day (April 15) coincided with the definite end of heating needs upstairs, though it was pretty sporadic the last few weeks. Jan and Feb were the months of greatest wood use. I'm hoping these heaters will trim a couple weeks off the end - that's what happened at the beginning.


----------



## begreen (Feb 4, 2011)

precaud said:
			
		

> Time for the monthly update. For most of January, the weather was milder than normal with full sun, and the solar heaters were able to supply most of the daily heat needed upstairs, with only one or two loads of wood in support. A couple days with highs in the low 50's/lows in the low 20's required no wood heat at all. Those temps seem to be the threshold for this house where additional heat is not needed.
> 
> But the last three days temps plummeted, and have been the coldest yet this season (-22F last night), the first two with no sun. Despite burning an extra load of wood each day, the house gradually gave up its heat store to the cold, and it was 62F mid-house this morning (no overnight fire). Seeing we would have full sun today, I burned one load of wood early morning. By 9am, the solar heaters were producing usable heat, by 9:45am the fans kicked on (95F) and by noon the mid-house temps inside were once again at 70, topping out at 72 late afternoon (high of 14F outside). So even with the worse cold snap we've had, these heaters can heat the entire house to very comfortable temps.



Excellent! -22F is damn cold! Gotta love that solar gain on a 14F day.


----------



## precaud (Feb 4, 2011)

BeGreen said:
			
		

> Excellent! -22F is damn cold! Gotta love that solar gain on a 14F day.


Absolutely. Much like sizing a stove to a house, this was the test of the sizing of the solar heaters to the house, and it's just about right.

One of my summer projects will be to build a solar air heater for my lab in the basement. That will put a significant dent in wood consumption down there, and heat it even on the weekends when I don't make fires down there. To fit in the available space, the heater will have to be horizontally displaced, a substantially different design than these two.

And if the stock market keeps going vertical, I might have to sell something and spray foam on the outside walls. My results so far are with zero insulation on the walls...


----------



## begreen (Feb 5, 2011)

How thick is that adobe?


----------



## precaud (Feb 5, 2011)

17" thick, but it's mostly doubled-up pentile, a red clay brick that was made by the state penitentiary back in the 1920's-30's. Still quite massive, though. A layer of foam on the outside would move many tons of mass inside the thermal envelope and make a huge difference.


----------



## precaud (May 22, 2011)

Well the results are in, and they are very good. Here are two pics of the wood supply for the upstairs at season's end, for 2010 and 2011. The second solar heater cut my wood consumption by 60%. So I won't need to cut/split any wood for the upstairs this year, though I may add a little just to be on the safe side.

This summers project is to make a horizontally-displaced solar air heater to heat the basement.


----------



## PapaDave (May 22, 2011)

I feel vindicated. :cheese: 
That's excellent, precaud. Man, ...60%.


----------



## precaud (May 23, 2011)

Yes Dave, your premonition was much closer than mine, no question. My mistake was about the impact of ground temps on the heating needs upstairs. It doesn't affect it as much as I thought it does. It does affect the basement; wood use down there was only a little less than last year. Piping some solar down there for next winter should reduce wood use down there significantly.


----------



## PapaDave (May 23, 2011)

Do you have an idea how to do that yet (piping to the basement)?
I'm interested in your solution.


----------



## precaud (May 23, 2011)

I know I'll have to make two large holes in the wall into the basement.     It's a daylight basement so it will all be above ground. Beyond that, I'm just forming an overview of what will be needed.

A horizontally displaced heater does not benefit from natural convection, and has to be 100% fan-driven. So from a noise perspective, the larger the hole, the better (lower air velocity in the pipe and slower fan speed).

There are some interesting ideas for horizontal collectors that use aluminum downspouts as heat exchangers.

Since the basement has a longer season of heating needs than the upstairs (by 2-3 months), I will angle this heater upwards to increase it's solar collection, and cover it in the summer months.

My guess is, it will be easier to build than the previous two!


----------



## precaud (Dec 7, 2011)

There is always an element of uncertainty going in to extreme weather, wondering if the system will perform well as it has in the past. The last 36 hours has been another real test, with a cold, sunless day of snow followed by temps plummeting, bottoming at -5F at 3am this morning, followed by a clear, cold day today (20F high). Yesterday it snowed all day and the woodstoves carried the heating duties; burned two loads upstairs in the AM, three downstairs during the day, and three more upstairs in the evening (none overnight). In the AM it was 64F, and seeing it would be sunny, I burned one small load upstairs to take the chill off, and by 8:30am the solar heaters were producing. (That's about a half hour later than usual, besides the extreme cold there was a light fog to burn off). By noon it was 70F upstairs, and 73F at 3pm. So once again I am relieved, the system really performed well, and showed that it is well-sized to the house.


----------



## PapaDave (Dec 7, 2011)

Jeez precaud, if you keep this up, you'll find a way to stop using the stove too.
Is that what you REALLY want? :lol: 
Nice to have options, eh, and to have created them yourself to boot!


----------



## precaud (Dec 7, 2011)

PapaDave said:
			
		

> Jeez precaud, if you keep this up, you'll find a way to stop using the stove too.
> Is that what you REALLY want? :lol:



Help me find such a way, Dave, and I'll jump on it! Actually, nah, no self-respecting pyromaniac could ever give up their stove(s). 



> Nice to have options, eh, and to have created them yourself to boot!



Yes, that is satisfying, and it's great to have a success story to be able to share. And that is what I want to do now, to encourage others to go down this path. For if you look at where this house started 5 years ago (no insulation, $300+/month nat gas bills) and where it is now, you have to say; if it can be done to this place, then it can be done almost anywhere.

But very few people are thinking along these lines, even in locales where solar is a complete no-brainer. Example: there's a guy who redid the roofing on my garage/warehouse ten years ago. He lives a few blocks down the street and knows more about construction than I ever will. Last week I ran into him at the grocery store, he commented about seeing the heaters being built over the last few years and wondered how they were working. When I told him, he was floored. Most people view passive solar as something to play around with, and not as something that they can seriously use to carry the bulk of their heating needs.


----------



## Redskins82 (Dec 14, 2011)

Interesting!

It looks like you should have extended your roof a little farther out to shade the glazing during the summer when the sun angle is high. 

I've got approximately 5' X 7' solar heater attached to to the south side of my trailer and it helps. It's paid for itself and I don't even live in a region that gets a lot of good sunlight during the winter. I might build another one that is not mounted on the side of the trailer. It would be a well insulated box shaped like a cold frame filled with black cinder blocks or rocks. I could draw air from the floor inside the trailer into the bottom of the box and flow air out of the back of of the box near the top back into the trailer. This type of design might work well for your basement. Some designs put the box inside the basement. Check out the part of this article about rock bin storage of heat. http://home.earthlink.net/~jschwytzer/solar.html


----------



## precaud (Dec 15, 2011)

Redskins82 said:
			
		

> It looks like you should have extended your roof a little farther out to shade the glazing during the summer when the sun angle is high.



Yes, that was my one error in building this, covered it in post #10. But it hasn't been a problem.


----------

