Thermal mass

Inbox :: Message
From: Jane Saylor
To: Jane Saylor
Date: Mar 13, 2025 19:19:08
Subject: Heat mass for my greenhouse
I have 2,000 gallons of water in ibc tanks painted black on the east, west, south sides and top,  in my greenhouse. 28x12 feet. The north back wall will have spray foam insulation professionally installed. There will be 28 triple pane glass doors from old coolers like at grocery stores. These will be caulked well. One of the center tanks will have a water pump attached to black pipes strapped to the back wall to be warmed by the sun and go back into the same tank for additional heat absorption. I will have hanging baskets from the ceiling for plants and plants on the floor. Possibly on top of gravel or concrete. I am in growing zone 5 a. How much heat will this create?

Hi Jane;
Welcome to Permies!
Where are you located?
Do you want to make this a 3 season greenhouse or year-round?
With that much glass, do you have a plan for ventilation?

If you want a year-round greenhouse, look into building a masonry stove (RMH) inside.

Jane Saylor wrote:Inbox :: Message
From: Jane Saylor
To: Jane Saylor
Date: Mar 13, 2025 19:19:08
Subject: Heat mass for my greenhouse
I have 2,000 gallons of water in ibc tanks painted black on the east, west, south sides and top,  in my greenhouse. 28x12 feet - I am in growing zone 5 a. How much heat will this create?

Might be just a technicality, but one way to look at this might be for calculation on how many BTU's you can store, Which in simple math, each gal would be 8#'s (pints a pound, the world around)  and each gal raised 1 degree in temp, simply would be 8 btu.  Problem here is just how warm you want your water to get.  

Fish involved?

Others can correct me, but in simple terms, the weight of other mass also going up 1 degree, can be considered as 1 btu stored.   i.e. 8000# going up 10 degrees, for 80,000 btus stored.   So you can see, going up 50 degrees starts to add up.

I know there are info sites on expected HEAT BTU's to gain through various glass vs plastic vs anything else.  And of course the actual amount collected.  

As Tom stated, Ventilation would seem to be a key concern during warmer times.

Best of success.

Scott

Just a quick go around with a calculator says you lose 35% or so in floor area to the ibc's, that's getting to a pyrrhic win. I'd go with T. Rubino for a RMH and a couple three at the north end for a buffering mass, the RMH would mitigate condensation too with a fan

A "pyrrhic victory" refers to a victory that comes at such a great cost, in terms of casualties or resources, that it's essentially a loss, or at least a victory that is not worth the price.

Jane, your design has some commendable features.  Would you consider wire shelving on at least two sides? This could give you more plant space over the water tanks