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.

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.

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

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

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

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.

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!

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

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!

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

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!

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: