solar air heating collectors
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Seasoned Oak
Minister of Fire
All i did was close in a south facing porch 6x24 Ft with some surplus windows 6@ 3Wx8T Ft Gave me 144Sq Ft of window area. Cost about $400 for the windows and some lumber. Can get up to 100 in there if i dont open the door to the inside soon enough,(by 11AM)even in winter. At the time i was heating with oil and it reduced the heating load a whole 250 gal tank of oil per season. In my next house ill just build a greenhouse style solarium on the south facing side
isipwater
Feeling the Heat
This sounds wonderful!! I would like to build a passive solar addition on the southwest part of my house in Massachusetts.
One of my fears was that it would not produce enough heat in the winter, living in a cold climate state. Sounds like you are getting plenty of heat.
My other fear is that it would produce too much heat in the summer. Has that been a problem for you? I have read you can use roof overhangs or awnings to block the summer sun.
Please post a photo if you have time. I would love to see what your passive room looks like.
Seasoned Oak
Minister of Fire
No problem in summer .sun is directly overhead so, you dont want one of those curved glass transparent roofs. I also have windows on the sides that open so in summer they remain open,and can regulate the heat in spring and fall. You will want to keep this room separate from the main house so you can close it off at night as the temps plummet with all that glass and will siphon off all your gains in short order. WHen the sun goes down i simply close the steel insulated door between the sun porch and the main house to retain all the heat gained during the day.
jebatty
Minister of Fire
For electric hot water heaters only:
1) if on a basement concrete floor, probably any floor, raise off the floor with 2 layers of 2" foam underneath (R20)
2) wrap the entire tank and top with at least 6" fiberglass, then cover with foil wrap insulation to seal all air leaks and for appearance (R19+); you can wrap the entire tank, no gaps
3) make U-shaped heat traps to prevent thermo-siphoning of hot water into both the cold and hot water lines
4) put pipe insulation on all the hot water pipes you can get at (don't insulate the heat traps)
I did mine about 10 years ago, cost for insulating materials may have gone up since that time, but these things reduced electricity for hot water by 50% (hot water heater on a separate meter and easy to see usage change)
Seasoned Oak
Minister of Fire
The new hot water heaters are very well insulated from the factory. The biggest factor IMO is not turning the temp up too high.
If you have to add cold water for a shower the temp is set too high. Big savings and less standby loss can be had keeping the temps down.
If you have to add cold water for a shower the temp is set too high. Big savings and less standby loss can be had keeping the temps down.
This is a little off topic, but it's driving me nuts so I'm gonna say something...
There is no point in heating the water if it's already hot. It's just a "water heater," not a "hot water heater."
I know this is the internet and by saying something like that I'm just opening myself up to getting a bunch of replies from a bunch of trolls, but I had to say something.
There is no point in heating the water if it's already hot. It's just a "water heater," not a "hot water heater."
I know this is the internet and by saying something like that I'm just opening myself up to getting a bunch of replies from a bunch of trolls, but I had to say something.
My wife complained because I set the temp to be shower ready with just a hair of CW. She likes to have it at scald and then mix in the CW. She's responded somewhat to my explanation but still grumbles a bit.
Seasoned Oak
Minister of Fire
Seasoned Oak
Minister of Fire
The enclosed sun room is a collector that you dont really see. I like solar solutions that are sort of invisible. I have a cement foundation wall under my sun porch and i d like to cover it with glass so it would look like more windows but in reality it would be a solar hot air collector.
I agree that sunspaces can be very effective solar collectors, not to mention giving the whole family some extra daytime living/playing space.
I did some testing on how a sunspace collector compares to a good quality commercial collector, and depending on how the sunspace is designed, the sunspace can provide just as much space heating per sqft of glazing as a commercial solar thermal collector.
You get the highest space heating output from the sunspace by minimizing thermal mass in the sunspace and by insulating all the surfaces that are not glazed. Couple this with a good fan and duct system to move the heated air from the sunspace to the living space, and you have a really effective solar space heater.
This is a bunch of collected info on low thermal mass sunspaces: http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#LowMassSS
and, this is the testing that gives the performance: http://www.builditsolar.com/Projects/Sunspace/LowMassSunspace/TestsLowMassSunspace.htm
They are amazing -- you can be sitting inside your collector having a cup of coffee and checking the Hearth Forum while the same collector you are in is providing 90+F air to your house for space heating when its 10F outside!
Gary
Circus
Feeling the Heat
Dec/ Jan Home Power Issue 158 has samples of low thermal mass sunspaces. The author seems familiar
semipro
Minister of Fire
Jim, why no insulation on the heat traps?
BTW, I believe loop heat traps work equally well and and don't take up as much lateral space as u-shaped ones.
I'm not sure how effective they are but these heat traps are available also.
I just bought a cheapo at Lowes and it came with those installed. Check Your WH so you don't double up (don't know if it would hurt anything though).
Seasoned Oak
Minister of Fire
Mine is as simple as it gets,no moving parts. I simply open the door between the sunroom and the main house when the sunroom temp exceeds that of the house. And close it when it goes below. About 10 hours on a sunny winter day. The house stays above average temps for another 3-4 hours after that. Effectively 12 hours of free heat. Main house(3000Sqft) heat not needed during those hours.
Circus
Feeling the Heat
You won't even need to open a door if vented. Thermal air collectors work fine without fans but losses go up from operating at higher temperature.
Seasoned Oak
Minister of Fire
Door opening of 17.78Sq ft keeps a lot of air moving. Plus vents leak heat at night when the sun porch is 25 degrees.
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jebatty
Minister of Fire
I didn't use insulation because I wanted to make sure the hot water rising out of the hwh cooled by the time it rose to the top of the traps to insure no siphoning. Maybe it would work fine with insulation. No reason why loop heat traps would not work, so long as siphoning is stopped. The commercial [picture] devices may work, but my hot water heater had those and I still had siphoning, thus put in the heat traps.
I think your right Jim, it not clear if they would work if insulated. As for the other kind, they have a ball that can get stuck in the wrong position....I have loops on mine, no moving parts to fail.
A stuck check valve and thermosiphoning prob cost me >$1000 on my old hydronic heating system before I figured it out. HVAC guys wanted $600 to change the valve out, I decided to just close a zone cutoff valve during the warm months.
A stuck check valve and thermosiphoning prob cost me >$1000 on my old hydronic heating system before I figured it out. HVAC guys wanted $600 to change the valve out, I decided to just close a zone cutoff valve during the warm months.
semipro
Minister of Fire
Hmm. It seems that leaving the heat traps uninsulated would actually allow the temp to equalize across the loop and weaken the effect that makes them effective. The first reference I could find recommended insulating the whole loop. http://www.energycodes.gov/moodle/mod/resource/view.php?id=583
Mine are easily accessible and insulated. I think I'll take my IR gun and do some tests. Could be they work whether insulated or uninsulated.
The off the shelf heat traps I referenced earlier have plastic flap valves in them sort of like an artificial heart valve. This type doesn't have the check balls.
Mine are easily accessible and insulated. I think I'll take my IR gun and do some tests. Could be they work whether insulated or uninsulated.
The off the shelf heat traps I referenced earlier have plastic flap valves in them sort of like an artificial heart valve. This type doesn't have the check balls.
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Sounds like that works really well for you.
What I found in the testing was that if you want to optimize the sunspace for producing space heating for the house you can get a lot more house space heating by 1) minimizing thermal mass in the sunspace, 2) insulating all the sunspace surfaces that are not part of the south glazing to reduce heat loss, 3) having as much south facing glazing at a good winter angle as possible, 4) double glazing is also helpful.
The difference in space heating output for a sunspace that follows these rules and one that does not is a lot. On my test sunspace I measured its heat output with a dirt floor (lots of mass), no wall insulation, lighter colored (bare wood) walls, and before a complete job of sealing was done, and compared this to the heat output after insulating the walls, ceiling, and floors, better sealing, dark surfaces. The heat output of the heat output of the optimized space was nearly 3 times the non-optimized -- this may seem like a lot and it certainly surprised me, but if you do some rough calculations on what the lack of insulation and warming the mass in the sunspace costs you, it comes pretty close to the same number. The measured efficiency of the optimized sunspace was 55% and the efficiency of the non-optimized was 20%.
This page goes into excruciating detail on the actual test: http://www.builditsolar.com/Projects/Sunspace/LowMassSunspace/TestsLowMassSunspace.htm
If you take the steps to optimize the sunspace for house heat collection, then you will almost certainly need some form of forced ventilation to move the heat to the house. On my 200 sqft test space, it took fans operating at an actual 650 cfm to remove the heat from the sunspace in good sun winter conditions -- if you don't have the enough flow rate, the sunspace gets uncomfortably warm and you lose some of the space heating potential. The heat output per hour in good sun conditions for the 200 sf sunspace was up to 41,000 BTU/hr -- kind of like a 60K BTU/hr house furnace operating at 70% efficiency!
The downside of optimizing for space heating is that the sunspace will go cold very quickly once the sun goes off of it because it has no mass to store heat, and it will not be a good place for plants in cold climates.
I'm not saying by any stretch that everyone with a sunspace will want to take the steps to optimize it for house heating, but just saying that if you do, the gain may be a lot more than you might think (certainly a lot more than I thought it would be).
Gary
Seasoned Oak
Minister of Fire
I do have the ceiling well insulated as well as the side walls. I dont have a lot of thermal mass,just flat black ceramic tile on the floor with cementboard under it. The room only overheats (80-100) if i keep the door to the main house closed. when i open it the sunroom rarely goes over 75-78 in winter.The air moves constantly warm air flowing into the main house and cool air flowing along the floor out into the sun room. This gets the main house up to about 78 and it takes me well into the evening hours for the house to fall into the low 70s and require any kind of additional heat. The fact that the sunroom does NOT overheat in winter tells me i dont need any additional artificial forced air devices.
Thought this might be of interest to this thread:
http://www.cbc.ca/news/canada/new-b...olar-furnace-decreases-heating-bill-1.2527065
Sort of like a solar hot water panel but using air. Not sure how he keeps it from bringing in cold air at night? A sunroom seems preferable to me if you have the space - no fans, can close it off at night, presumably more solar gain.
http://www.cbc.ca/news/canada/new-b...olar-furnace-decreases-heating-bill-1.2527065
Sort of like a solar hot water panel but using air. Not sure how he keeps it from bringing in cold air at night? A sunroom seems preferable to me if you have the space - no fans, can close it off at night, presumably more solar gain.
Seasoned Oak
Minister of Fire
They can be made to look pretty nice, or at least not to ugly...
http://www.builditsolar.com/Projects/SpaceHeating/DHWplusSpace/Main.htm
http://feherhome.dyndns.org/solar/
http://www.builditsolar.com/Projects/SpaceHeating/SolAirColWithDHW/AlAirCol.htm
http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm
Some of these are putting out 30K+ BTU per hour.
It seems to me that one of the promising areas that has not gotten much attention is integrating solar air heating collectors into the south walls of new construction homes. When you account for the material saving to the wall (eg no siding) the cost could be near zero and it would not take any kind of specialist to build it -- it could be just another part of the carpenters job and add a new profit center for the local builder.
But I agree that if your house is well set up for it, there is probably no better solution than a low mass sunspace on the south side of the house -- it can provide a lot of heat, make the house look better, and adds some value for everyone in the family and when you go to sell the house.
Gary
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