A & D are square foot measurements. However, square foot can be easily converted into the metric measurements such as square meter. - Millet (630-)

Thanks Millet , I needed to be sure on what should I convert prior to make that formula.

Thanks Again!

1 square meter = 10.765 square feet. Then just follow the mathematical formula to get BTU's required. - Millet (630-)

My 40,000 gallon pool has some stored heat. I wonder how long it could keep a greenhouse above 45*F in my zone 8b/9a? I could use the filter system and diverter valves to pump the water through heat exchangers with fans. I run the pumps anytime the temps drop below freezing to protect the equipment so heating a greenhouse would be a bonus. With a solar cover on the pool I could recoup some of the nightime temperature losses and my pipes are buried with a long 75' run which also buffers the losses. Has any one heard of anyone using a pool for heat?

Water as solar heating inside a greenhouse (or any where for that manner) can supply heat. By definition: when 1-lb. of water drops 1 degree F. it gives off 1 BTU of heat. Therefore, when a 55-gallon drum of water (551-lbs. of water) placed inside a greenhouse loses 4 degrees F. during the night, it gives off 2,304 BTU of heat into the greenhouse. I use 100 black 55-gallon drums as benches in by greenhouse, which normally provides 220,400 BTU/night = 1,542,800 BTU/week of free heat. Plants setting on top of the barrels greatly benefit from the heat coming off the drum,s and grow like crazy. You can see my greenhouse set up under the Greenhouse sub forum on this site. -Millet (6300-)

link

Millet what is the best to use when you have to choose between barrels made from metal sheet or pvc type ?

Thanks