[permaculture] Re: permaculture Digest, Vol 11, Issue 31
pci at permaculture-inst.org
Wed Dec 31 16:40:46 EST 2003
At 12:03 PM 12/31/03 -0500, you wrote:
> 1. Re:Greenhouse design (Claude William Genest)
>Greenhouses overheating are an issue even up here in Northern Vermont.
>What I've been thinking is: Since the sun is high in summer, low in winter
>and heat rises, then why is a glazed ceiling necessary at all ?!
>Why not a solid insulated roof with say a couple of solar wells/tubes ?
>This would lower construction and maintenance costs, increase heat in
>winter and block out sun in summer....
This is exactly what we do in New Mexico where it is a balmy 13 degrees
Fahrenheit right now. I have about one-third of my roof in triple layer
calcium carbonate (plastic glazing), which I have to cover with 50% shade
cloth in summer to prevent overheating. I need the extra light because I
am growing tropical fruit plants and they need the extra sun from
overhead. It works fabulously in winter, with affordable heat loss at
night. I have loads of mass surrounding the greenhouse in the form of
adobe walls and slab floor. Overheating can also be controlled by venting
at the roof peak. I have two large vents with ceiling fans below that pull
hot air up and out the vents, which I close in winter, and reverse the fans
so they blow warm air down to the floor.
PO Box 3702
Pojoaque, NM 87501
505 455 0514 phone
505 455 2003 fax
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