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Passive solar as source for in-floor air-based heating?....

 
pollinator
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Curious about this company out of Canada that does in floor heating using heated air instead of fluid as most hydronic systems use.  Was wondering if anyone had experience with their typical build and also if it might be able to use passive solar for daytime heating of air space, the air volume of which might be pumped through the system when warm enough, thereby heating the concrete slab for radiating off at night.  Was also wondering if air heated via RMH might somehow also be used at night to continue to 'feed' warmed air to the insulated slab.  Thoughts or experiences?

http://www.legalett.ca/frost-protected-shallow-foundations-icf-floors-air-heated-radiant-systems-passive-house-passivhaus-net-zero-energy-buildings-leed-concrete-slab-on-grade-insulation-homes.html

 
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I am not a pro, but I'd do water.  Water solar systems can be enhanced with additional panels easier and augmented with boilers.  Air systems would be difficult to augment with a fuel based furnace, lest there is a "high-velocity blower" involved, due to the small diameter of the pipe/duct. Water systems do need special care and maintainance in areas prone to icy conditions.  
If you want an air based system, consider a well Insulated, sealed sunroom-type collector. (Think...4-10ft wide, running the length of your southern-exposed wall.
Some ideas.... builditsolar.com ...
 
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When I was a kid, a long time ago, my parents bought a new home that had several innovative ideas.

It had "perimeter heating" and parquet floors.

We had a forced air heating system. The heating vents were in the floor along the edge next to the wall.

This was just like the heating systems most houses have though the air ducts were under the floor rather than in the ceiling.

That idea is a lot like a RMH bench without the forced air.
 
Paul Stockton
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Here's a good article from the builditsolar.com website I commented about earlier....

https://www.builditsolar.com/Projects/Sunspace/LTMSSGuide/LTMSSGuide.htm
 
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I certainly think it would be worth doing some calculations for feasibility. Usually passive solar uses directly heated mass, but sometimes has ducted air with a fan to a thermal store - that's quite common in greenhouse systems I believe. This would be the same thing, but more 'engineered' for want of a better word. I certainly think you could supplement the heat requirement if you had a good solar collector/air heater. You'd have to work out whether it was worth the extra complexity.
According to the link, the pipes used are either 2 inch or 4 inch diameter, so larger than typical water systems. It has what seems to be a central pump/heater unit (electric heater or hot water exchange). You'd need the typical bypass when the extra heat was not needed, or block off the airflow (or have subterranean tubes to access cold air....). Thinking about this system, another idea may be to combine solar water heating with the heater unit. I don't know whether they might consider this as an option.
 
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For what it is worth, I recently purchased 2 Australian made hot air heaters which are block boxes with polycarbonate 'glass' fronts and thermostaticly operated fans.
they retailed for about $A3500 each.
I paid $A250 each because they did not work effectively.
I am now trying to see if there is anything to be done to get them working.
 
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I have a plan to do something similar to the OP's idea.

This summer I tore down a 40x60 quonset hut and plan to rebuild it next summer I plan to paint the lower 8 feet of the 60 foot long south wall black and cover the entire 8x60 foot area with double pain windows.  With any luck the entire wall will act as a large solar heat collector.  Then use a solar panel to power a fan to blow heated air from the glazed area into a small heated workshop inside the building.  The workshop will be at least partially insulated.  I expect it will get uncomfortably warm in there any time the sun shines.  So eventually I want to bury drain tile in the floor then blow the air from the solar collector though the tile to heat up the floor so the floor acts as a thermal mass.  In the summer the panels would be shaded by the roof overhang and possibly be covered with shade cloth.

I don't expect to keep it 60 degrees  all winter but I do hope that by the time I get home from work in the afternoon the shop will be heated up and will continue to stay warm for several hours after dark.  I would consider it a major success if I can keep the workshop above freezing ALL winter.

I have done a lot of experimenting with solar heat and I think my idea will work.

 
John Weiland
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J Hillman wrote:.......I expect it will get uncomfortably warm in there any time the sun shines.  So eventually I want to bury drain tile in the floor then blow the air from the solar collector though the tile to heat up the floor so the floor acts as a thermal mass.  In the summer the panels would be shaded by the roof overhang and possibly be covered with shade cloth.

I don't expect to keep it 60 degrees  all winter but I do hope that by the time I get home from work in the afternoon the shop will be heated up and will continue to stay warm for several hours after dark.  I would consider it a major success if I can keep the workshop above freezing ALL winter.

I have done a lot of experimenting with solar heat and I think my idea will work.



I really like this vision, JH!  I've been thinking of doing a similar thing on a smaller scale on the south side of an outbuilding that currently is uninsulated, but I would be curious about heating up a heat sink by day to be released into the outbuilding later in the day.  Your idea of letting the sun charge up your thermal bank and then release it into your shop in the early evening sounds like a very doable scenario.  With the deep frost that we get here (~5 feet), I'm also thinking of how best to protect the 'banked' heat with below-ground insulation, noting that insulation placed horizontally from the foundation of the heat collector might work as well as the same amount of insulation placed vertically.   See https://framebuildingnews.com/below-grade-insulation-part-1/

Thanks and good luck with your build!
 
J Hillman
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John Weiland wrote:

I really like this vision, JH!  I've been thinking of doing a similar thing on a smaller scale on the south side of an outbuilding that currently is uninsulated, but I would be curious about heating up a heat sink by day to be released into the outbuilding later in the day.  Your idea of letting the sun charge up your thermal bank and then release it into your shop in the early evening sounds like a very doable scenario.  With the deep frost that we get here (~5 feet), I'm also thinking of how best to protect the 'banked' heat with below-ground insulation, noting that insulation placed horizontally from the foundation of the heat collector might work as well as the same amount of insulation placed vertically.   See https://framebuildingnews.com/below-grade-insulation-part-1/

Thanks and good luck with your build!



Obviously adding insulation under and around the perimeter will help keep it warmer, but it also requires a LOT of digging and moving dirt.

Last fall I built a simple greenhouse and have gone through one winter with it.
The south wall is all double pane glass, the north wall is R 15 insulated garage door panels.  The east and west walls are both about 1/2 R15 and 1/2 double pane glass.  The roof is a single layer of poly plastic covered by sheet metal(the metal is the roof, the plastic is to seal up the big gaps and make it more air tight).

I think it is 9'x16'.  And I had 12 barrels of water in.

I think our lowest temp was -42 last winter and according to the highway department the roads that are plowed all winter maxed out their measuring devices for frost depth, so more than 12 feet.  Although we had so much snow that areas that were undisturbed may have very little or no frost.

The ground in the greenhouse never froze all winter.  The frost crept in from the outside walls towards the center but I don't think it ever got more than 6 inches in.

Better insulation in the walls and any insulation in the ceiling would have made it even better.  Digging a trench  a foot or 3 deep around the perimeter and putting in sheets of Styrofoam into the trench would have also helped a lot.  As would thermal curtains at night.

We have thought of building a solar heat collector and blowing heat from that into the greenhouse to warm it up even more.  The heat from the solar collectors could be blown through drain tile buried in the floor.  

While burying the drain tile it would also be a good time to build a in ground rocket mass heater for those days when the sun just isn't enough.

We don't want to put too much into this greenhouse because of the way it is built there is only so much we can do to it and eventually I want to build a much larger earth sheltered greenhouse.  And we are currently building a large sunroom on to the house we are building that we plan to use to help heat the house and partially as a greenhouse.

Have you seen the youtube videos on the guy in Nebraska who is growing citrus in a earth shelter greenhouse by storing excess heat from all summer in the ground to use in the winter?  https://www.youtube.com/watch?v=ZD_3_gsgsnk
 
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