Thermal mass, opinions?

wertach zone 7-B SCOctober 22, 2011

I'm ordering a HFGH, 10 X 12. The greenhouses that I have had before were built, by me, from scratch with the north side heavily insulated. I'm too old for such a big project now..... I always used black 55 gallon barrels filled with water for thermal mass.

This new (to me) house has a lot of huge granite rocks that I could use instead. Since I have never used rocks, I'm wondering what are the pro's and cons of one over the other.

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stressbaby(z6 MO)

Hi wertach,

In my opinion, with a 10x12 HFGH, the amount of required passively managed thermal mass, rocks, water or otherwise, that you would need in SC to make a noticeable difference is not worth the space it would occupy in a small greenhouse.

The thermal mass will be giving up its heat as soon as the temp differential favors loss of heat into the GH. Generally that means that the mass is losing heat by mid afternoon and by 10pm when you need it, there is not much left.

If I were you I would put up >= 1" of reflective foamboard on the north wall. Maybe you could use the stones as flooring.

    Bookmark   October 24, 2011 at 7:53AM
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gardener1(6)

without insulation between the floor and the stones. the stones will draw the heat out of the greenhouse and into the ground. Trust me mine does. Im getting ready to insulate my floor.

    Bookmark   October 28, 2011 at 11:18PM
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who2ted(Z6/AZ)

@gardener1- how do you plan on insulating the floor, my floor is dirt but I could build it up.

    Bookmark   October 29, 2011 at 12:28AM
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cuestaroble

Before you insulate your greenhouse floor, you may want to read the article at the attached link.

Here is a link that might be useful: insulating greenhouse floors

    Bookmark   October 29, 2011 at 10:37AM
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who2ted(Z6/AZ)

great, I am not going to worry about a floor, thx.

    Bookmark   October 29, 2011 at 12:44PM
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gardener1(6)

sorry i jumped to conclusions I was told thats where I was losing my heat. I am new at this and still learning. Now I will concentrate on the ceiling. And thanks for setting me straight.

    Bookmark   October 29, 2011 at 2:05PM
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wertach zone 7-B SC

I disagree stessbaby, I'm in zone 7 of SC and we rarely have temps much lower than freezing. The scratch built Gh's that I have built before had water barrels under benches. They did however have the north side heavily insulated, no glass on the north side.

The temps would stay above 40 inside when the temps dropped to the low 20's or lower outside without any extra heat. If I had cloudy days with cold temps I would light my Coleman lantern and it would stay warm!

    Bookmark   October 29, 2011 at 2:21PM
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stressbaby(z6 MO)

Wertach,
Questions:
What size GH have you built before?
How many gallons of water did you have?
What was your elevation?

    Bookmark   October 30, 2011 at 5:42PM
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wertach zone 7-B SC

Stessbaby, My elevation is around 800' , lat. 34.62, long -82.2.

The GH I was talking about was about 14'X 20', 12' high. I had about 700 gallons of water. I used thick glass shatter resistant panels that came from a store front.

I wish that I still had the pictures of it, so that I could post them. But I lost them AND the greenhouse when I divorced! I really miss that greenhouse!

    Bookmark   October 31, 2011 at 12:32PM
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stressbaby(z6 MO)

So for me, 13 55 gal barrels wouldn't be worth the space in a 14x20 house. I have 3 44 gal barrels in a 20x23 house (for rainwater) and for me, even those take up too much space! Different strokes...

Thanks for the info.

Robert

    Bookmark   October 31, 2011 at 6:14PM
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wertach zone 7-B SC

Thanks for your response Robert. I'm not looking for quantity in my GH, just quality and economy. Heating a GH with fossil fuels or electricity costs too much in my opinion.

I only have 2 mouths to feed! I want to grow some lettuce and stuff for fresh salads, without worrying about salmonella. Use it for starting tomatoes, peppers, ETC. Extending some tender veggies later in the fall.

When I was younger, and had my really great greenhouse, I had tomatoes almost year round. I had a tomato that lived for 3 years! It might have lived longer, but I had to move.

I drove by about 6 months after I sold the house and the new owner had tore it down!!!!!! I felt really sad!

    Bookmark   November 1, 2011 at 2:54PM
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cheapgardener(5)

THIS IS A LINK TO A VIEW OF MY THERMAL FLOOR AND IT WORKS SOME PEOPLE THINK I HAVE LOST MY MARBLES BUT I KNOW WHERE ALL 30 GALS. ARE

Here is a link that might be useful:

    Bookmark   November 1, 2011 at 9:45PM
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