Big greenhouse versus several small ones - more heat retention???

I have just purchased a second-hand greenhouse that is 12m (38ft) wide and 24m (~75 ft) deep. It is two gables (6m) wide, and modules of 6m deep, and so it would be possible to divide it into four smaller greenhouses (we need to re-skin the plastic anyway).


I see various advantages in having smaller greenhouses scattered around our 8 acre property, which are movable with a bit of effort, (not the least being that I would not have to pay $800+ and a g to a lot of effort for a building consent if the structure is portable. On the other hand, I am wondering if I would loose less heat in a from a larger greenhouse, than from smaller ones, as there is less surface area. At that size, does it not matter much? I plan to use passive heat as much as I can in the form or compost boxes, duckweed and fish tanks, and seedling frames attached to walls
(which will also weigh down and anchor the greenhouses in place). I also plan to put a rock stove thermal mass in at least one for summer vegetable growing, and may double skin it in plastic.

Annie

In my experience, heat gain AND heat loss are much quicker in a smaller house. The heat gain can be very rapid and plants can be cooked quite quickly. With less air/moisture, that he will go away very quickly too. In the end, I'd recommend keeping the hoophouse as big as possible to have a better temperature buffer.

Greenhouse are usually used for vegetables or sensitive tropical. Both of which I think should be kept near to the house vs far away.
Multiple smaller greenhouse have a greater surface area and so will lose heat alot faster than just one big greenhouse.

Having say 3 small greenhouse would however give you some redundancy so that if one fails you still have 2 to use.
And repair 1 small one per year is alot more manageable than one big one in terms of labor and money.

If you have the money to make up for the greater heat loss go for 3 "smaller" greenhouse.

I would say one larger greenhouse, designed and insulated as well as possible, with as much thermal mass as possible added to help moderate temperature swings.

So Annie, where are you? What exactly are you trying to cover? What do you want to do with the greenhouse/hoophouse?

I think that a big factor here that applies to big and small greenhouses is temperature moderating factors like barrels of water, stone walls,also venting devices automatic or manual,etc.

I would say that large or small greenhouses are equally likely to have wide temperature swings without these moderating factors. (At least passively heated types)

My little greenhouse made of recycled windows has consistent, slow temperature changes due to automatic vents, a stone floor and the fact that the floor is
below the surrounding soil level.

I've gleaned a lot of useful information from the Eliot Coleman book "The New Organic Grower'. There was also a two hour lecture up on youtube a while back where he discusses all things greenhouse. Certainly the 4 season harvesting that he is using in his unheated polytunnels use no thermal mass but instead make use of row covers and seasonality.

Has anyone replicated or expanded on the methods used in the greenhouse @ Solviva? I often wonder how they could scale up with the help of high human/animal energy potentials so characteristic of small Northwestern farms...

http://www.solviva.com/visit_solviva.htm#top
http://www.windward.org/internship/solviva2.htm (especially this "Earth Lung" concept?)

Cris Bessette wrote:I think that a big factor here that applies to big and small greenhouses is temperature moderating factors like barrels of water, stone walls,also venting devices automatic or manual,etc.

I would say that large or small greenhouses are equally likely to have wide temperature swings without these moderating factors. (At least passively heated types)

My little greenhouse made of recycled windows has consistent, slow temperature changes due to automatic vents, a stone floor and the fact that the floor is
below the surrounding soil level.

It doesn't have to be one or the other. You can have a large greenhouse and use plastic sheeting to divide into sections. If you dig down instead of build up it allows for a more stable temperature year round, kind of like your basement. This depends on your area and depth of the water table. Also climate battery is a technology used in areas with severe weather, like Canada. http://rfhs-greenhouse.blogspot.com/2010/03/ready-steady-go.html

Zack Fife wrote:

It doesn't have to be one or the other. You can have a large greenhouse and use plastic sheeting to divide into sections. If you dig down instead of build up it allows for a more stable temperature year round, kind of like your basement. This depends on your area and depth of the water table. Also climate battery is a technology used in areas with severe weather, like Canada. http://rfhs-greenhouse.blogspot.com/2010/03/ready-steady-go.html

That is why I mentioned the recessed floor and rocks in my greenhouse- the basement effect. The basement never goes below 55F or so and never about 70F in the summer, so I know exactly what you mean. If I had the money to build a "climate battery" like in the article you linked, I would be on it for sure. So, until then, I'll keep going with my poor-man's versions.


I would love to live in an "underground" house with the South side a bank of windows- which would double as my greenhouse.

Have you tried freecycle and Craigslist? With a lot of business closing down(sad fact) I've seen lot's of stuff going cheap as of late. Even a whole commercial green house for 12k here in colorado.

Zack Fife wrote:Have you tried freecycle and Craigslist? With a lot of business closing down(sad fact) I've seen lot's of stuff going cheap as of late. Even a whole commercial green house for 12k here in colorado.

I get recycled construction materials from friends sometimes, but most of my "parts" come through Habitat for Humanity's local Re-Store.
Freecycle around here was pretty lame the last time I looked at it.

I get recycled construction materials from friends sometimes, but most of my "parts" come through Habitat for Humanity's local Re-Store.
Freecycle around here was pretty lame the last time I looked at it.




I keep hearing about the habitat for humanity stores. How good are the deals?

Zack Fife wrote:


I keep hearing about the habitat for humanity stores. How good are the deals?

I imagine it varies depending on the store and who is working there on any particular day. (and obviously, the stuff that people donated)

For instance, I picked up (44) 7x7" glass bricks the other day for $1 each. They are used and I need to clean bits of concrete off, but still pretty nice. ($4-5 each new)
Last week I picked up 10 double pane windows for about $5 each. I'll have to frame them, but they are in great condition otherwise.
I got a sliding glass door and frame for about $15, and two 4 ft tall custom made triangular windows, double pane for about $10 each.

Just some examples of what I've bought.

Of course they have all kinds of stuff- electrical fixtures, house wares, furniture, kitchen stuff, tools,etc.
I try to go in at least every other weekend to look around as people donate stuff all the time and the good stuff gets bought up fast.