Safe, dependable greenhouse heater
I want to put heat in my greenhouse, that will be built soon. It will be 12 x 16. As I live in zone 4/5 and 5800 elevation I can't use just the barrels of water as they won't heat up enough to be able to plant early. I'm trying to think of some way though to heat the water as I think that method would save on total cost. I also would like the safest way to heat so what happened to Indygerdener won't happen to me. Any suggestions? Oh, the north wall will be solid and the rest will be insulated used windows. The roof will be fiberglass because of snow load. I will use the greenhouse to start later planted seeds and I plan on an in-ground planting bed for tomatoes and heat loving plants. Would soil heating cable help raise the temperture of the in- ground beds so I could plant in it earlier? Sorry for so many questions in one post.
generally one is 'restricted' as to choice of heating by what's available.
the bad news is, it's going to take a certain number of BTUs to keep the place heated - and it doesn't make any difference in the required BTU if the heat is coming from solar, wind, gas, oil, hamster wheel, etc.
"heat energy" is typically cheapest natural gas then propane (large tanks) then oil then electric altho oil and electric often switch depending on KW-Hr costs in your area and who has started (yet) another war in the mid-east.... up that way you may get cheap - er, less expensive.... hydro-electric power out of Canada?
you can rig up a home-spun solar panel for your water drums. the light diffusion of corrugated fiberglass roof will work against you - would work better if you could locate the collector in direct sun.
I had a nominal 12x20 lean-to glass to ground; back wall was 'the house' - house was 'all electric' / heat pump so I used electric baseboard heater strips - mounted along the perimeter. at 8 cents KW-Hr cost me about $400/year to heat at 52'F min. - I had an elapsed time clock on the power relay to the baseboard heaters - so I knew how many hours the heat ran; from the wattage could calculate the usage/cost. the baseboard heater units had steel shells; they rusted; they were in place and operational 20 years later when I sold the house - longevity seems to be okay.....
you do not need to heat the greenhouse to 80'F for seed germination.
build a small enclosure, heat that to 80'F. after they seeds sprout / etc you can / should raise them on in a much cooler environment.
my experience with soil cables is all bad. sorry.
once the sun is stronger and the ambient temps are up, you will not need any supplemental "soil heat" inside - you will need some method to vent the excess heat.
the bad news is, it's going to take a certain number of BTUs to keep the place heated - and it doesn't make any difference in the required BTU if the heat is coming from solar, wind, gas, oil, hamster wheel, etc.
"heat energy" is typically cheapest natural gas then propane (large tanks) then oil then electric altho oil and electric often switch depending on KW-Hr costs in your area and who has started (yet) another war in the mid-east.... up that way you may get cheap - er, less expensive.... hydro-electric power out of Canada?
you can rig up a home-spun solar panel for your water drums. the light diffusion of corrugated fiberglass roof will work against you - would work better if you could locate the collector in direct sun.
I had a nominal 12x20 lean-to glass to ground; back wall was 'the house' - house was 'all electric' / heat pump so I used electric baseboard heater strips - mounted along the perimeter. at 8 cents KW-Hr cost me about $400/year to heat at 52'F min. - I had an elapsed time clock on the power relay to the baseboard heaters - so I knew how many hours the heat ran; from the wattage could calculate the usage/cost. the baseboard heater units had steel shells; they rusted; they were in place and operational 20 years later when I sold the house - longevity seems to be okay.....
you do not need to heat the greenhouse to 80'F for seed germination.
build a small enclosure, heat that to 80'F. after they seeds sprout / etc you can / should raise them on in a much cooler environment.
my experience with soil cables is all bad. sorry.
once the sun is stronger and the ambient temps are up, you will not need any supplemental "soil heat" inside - you will need some method to vent the excess heat.
Thanks for the good advise. There is 220v to the shop which is only12 feet away and Mike is a good elec. so we could wire baseboard heaters up. I plan on keeping them in the house under lights until I up-pot them and then move them into the small enclosed area you suggested, with recommended heat, for them. We have planned on opening the windows and using at least one box fan to keep the greenhouse cooler in the summer.
the baseboard heaters run about 250 watts per foot - 12x16 you could get 8 ft each end + 8+6 long side, 30 ft * 250 watts = 7500 watts roughly 35 amps at 220v - the shop leg needs to support that - #10 wire + breaker. you'll need a 110v power relay to switch them on and off.
plus a separate 110v circuit for control & lighting/etc
plus a separate 110v circuit for control & lighting/etc
I have a small 6x8 greenhouse and used a portable oil - radiator type heater over winter. I would also throw a furniture moving blanket over the top. Seemed to do alright at a cost of about $2 a day or so on medium. The heater would run about 7pm till 7 am.
I did like the fact that it gave out heat gradually and fairly evenly.
I did like the fact that it gave out heat gradually and fairly evenly.