how should i heat my cold frame?

Question

I will be installing a 48ft. polyhouse soon and growing perennnials from seed. This will protect the seedlings, but the month of april in northern michigan is too cold. I'm thinking of a couple of electric space heaters with thermostats set at 68-70 degrees.

Answer 1

I think that if you are going to the expense of installing this sized polyhouse and growing from seed then you would be better off looking at undersoil cable heating.
It may be expensive as a purchase but will do more good than above ground heaters which will cost more to run and incur much in the way of wasted heat loss.
By doing this you will heat the soil and the air just above ground and where the heat is needed most

Answer 2

Hmm, this could be a problem. the space heaters are expensive to run, and the heat is not well distributed. use of some fans to distribute the heat may help. You might want to get the pole type space heaters this gets the heat where you need it a bit better. still heating 48 ft with only a couple of them probably won't work. 48 by what? or 48 square feet? 48 square feet is not large and could be heated easily. you may have to set the temp higher than that so the colder areas are warm enough.

Answer 3

That sounds excellent if you see to safety over the electric and they do not heat directly on any plants, and you can afford the energy used by their operation.

Answer 4

if you havent built it yet consider a concrete floor with radiant heat. at 48 ft. it would be considered a greenhouse not a cold frame