GREENHOUSE : BTUs / cubic foot / hour?

Question

trying to calculate

BTUs / cubic foot / hour

for a poly greenhouse with 4mm doublewall ends and sides in zone 8 (never lower than 10 degrees F). need to be at least 60 degree F at night.

Answer 1

http://www.littlegreenhouse.com/heat-cal...

http://www.greenhousecatalog.com/greenho...

http://www.extremehowto.com/xh/article.a...

http://hortweb.cas.psu.edu/courses/hort4...

ps: many crops do fine with lower air temps if the pots are heated by putting them on a heated bench.