Solar Thermal - Adding heat to crawl space

72 Posts
Sep 19, 2008 08:53 pm
Solar Thermal - Adding heat to crawl space

I have a crawl space on a house built about 10 years ago.

It is in excellent condition, with very little moisture concern ... and only needs a little minor touch up on the ground cover/ moisture barrier and entry door.

I am considering doing roughly this:
1. Re-do floor moisture barrier ... lay down new 4-8mil plastic, well overlapped
2. Replace entry door with something fairly air tight
3. Close off cross ventillation during winter months
4. Add some thermal mass below main living room ( large rocks? )
5. Pump in Solar heat in to this space

I believe that this, plus some passive solar heating , will greatly reduce my heat pump's load.

I'm hoping to find a path to 100% Solar Heating ... but would be very happy with 50% with this start

I want to use a ground mount collector, for flexibility ... and I do not want it mounted on the house directly.


So, am I on the right track? Suggestions?

 
462 Posts
Sep 20, 2008 11:52 am
Re: Solar Thermal - Adding heat to crawl space

Kieth, you could also consider adding a sunspace along the foundation of the crawlspace. Basically use the foundation wall as mass and add an insulated pad of cement extending from the foundation. Paint the concrete black and add a small greenhouse type structure from which cold air from the crawlspace can be drawn into and hot air can be pumped out of and back into the crawlspace.
 
72 Posts
Sep 20, 2008 05:58 pm
Re: Solar Thermal - Adding heat to crawl space

Tom,
This sounds very interesting ... do you know of any links that show details of this method?

In particular, I'm very interested in anything that can be more aesthetically appealing ... it may help sell it to my wife!! :-)
 
462 Posts
Sep 21, 2008 11:28 am
Re: Solar Thermal - Adding heat to crawl space

Kieth, the best way to get your wife to agree on using some passive heating is to make her pay the utility bills. Then maybe she will agree to do things that will save money, despite aesthetics. I do not know of any links that show the method I mentioned, but it is pretty straight forward. Basically a small green house structure. Figure the foundation and the base would form an "L" shaped structure then add glazing along the diagonal closing it in. You can build it so it can be removed or so it is permanent. You could also use it as a hot box in the spring, if you have a garden, by installing the glazing so it can be opened and making the interior accessible.
 
72 Posts
Sep 21, 2008 12:30 pm
Re: Solar Thermal - Adding heat to crawl space

Tom,

I like your suggestion more and more, but I trying to visualize the best way to get the hot air in to the crawl space ... from the 'green-house/collector'

Am I close with this description ...

Would there be a large pipe near the apex of the structure, going in to the crawl space?
Where the apex of the structure is at the same height as the top of the crawl space.
 
And then a same size pipe going from the crawl space / near the base ... and in to the base of the structure.

And if so, I'm guessing some sort of flow valve to keep it all going one way.

And finally ... A small solar powered fan to pull the hot air flow in to crawl space. This would force the passive flow control valve to only open when the sun is shinning enough to power the fan ... and assumingly heat the structure air space.

the pipes should be insulated and flexible and detachable for summer break down of the structure?


... in my case this means a 3 foot tall collector structure. which leads me to thinking 3 foot wide and 6 feet long. for a 3x6 concrete base. In case it factors in, My foundation is brick covered concrete block, and the house is vinyl sided.

Would the structure need to be glass covered? Or could it be plastic instead? For easier break down and storage during warm to hot months.



also, with all that said ... do you think the simple black pad contact with the foundation be enough of a heat transfer that air movement not even be necessary?
 
462 Posts
Sep 22, 2008 11:02 am
Re: Solar Thermal - Adding heat to crawl space

Kieth, sounds like you pretty much got it. As far as the fan installation location goes, as you said, bring the glass structure up just over the top of the foundation wall. This should allow you to drill into the framing into the crawlspace. Drill two holes, probably 3-4" one at either end of the sunspace. Mount the fan in/over one of the holes. You can leave the other alone or use PVC pipe or dryer duct to blow or suck the warm or cold air from whatever location you want.
 You can even add a hole or duct in the room above to deliver hot air into that space also.
 Good idea to use a small PV to power the fan. (Radio shack has decent 12 volt fans). You can add a thermostat in line also to make sure the air is hot enough. (Use cooling mode).
  As far as the black surface. Just use foundation sealer. This will also aid with moisture problems should the glazing structure be a little leaky.
 Glass or plastic, whatever you got. Double up if you can. Find some old doors or windows.....
 Also check your sun angle for maximum gain...think about using snow a a reflector.....
 
72 Posts
Sep 22, 2008 08:57 pm
Re: Solar Thermal - Adding heat to crawl space

Excellent,
Thanks for the idea.
now, its a matter of whether or not I can make it appealing enough for my wife 'to allow'. :-)
 
1 Posts
Sep 23, 2008 02:06 am
Re: Solar Thermal - Adding heat to crawl space

My God, sounds realistic, but who is gonna invest in it man ?


---------------------


Save power Save Money
 
72 Posts
Sep 23, 2008 06:51 pm
Re: Solar Thermal - Adding heat to crawl space

huh?
 

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