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Old 30-12-2009, 04:07 AM posted to rec.gardens
jeff jeff is offline
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First recorded activity by GardenBanter: Jun 2009
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Default Greenhouse heating question

Dan L. wrote:
In article , jeff
wrote:

Steve B wrote:
In another newsgroup, there's a discussion about heating a greenhouse.
Electric heaters were mentioned. Also kerosene, but comments were made
about fumes and stickiness. Someone recommended a plain propane barbecue.
It was stated that the CO2 would be good for the plants. I was wondering
about the CO produced, and what the levels would be.

What is the best/worst ways to do supplemental heat in a greenhouse?


I don't think propane will be a good value. When I ran the numbers
here, electric was cheaper than propane. Bear in mind that electric
heaters are 100% efficient, and propane will not be.

I've got a small "greenhouse" 8' * 8' here that I have been
experimenting with.

My thoughts so far have been to minimize heat loss and to maximize
thermal storage so that night temps don't fall as far. I've had a few
hard freezes and no damage, so far, to my tropicals with no supplemental
heat. I'm thinking of adding some insulation.

You may also think about heat lamps, a little easier to put the heat
where you need it, and less sensitive to drafts as you are heating the
air only indirectly. Hot air goes out with the draft.

Jeff

Steve



Hmmm ...

Do plants need Oxygen as well as CO2?

The root growth for new plants... I believe needs Oxygen more than CO2.
If one puts a propane barbecue heater inside the greenhouse this may
be bad for the plants because the heat would use up the Oxygen.



I don't think many greenhouses are so well sealed that the O2 inside
was much less than that outside.

If I
went with a propane heater it would be a camper/garage style heater in
which the heater is outside and blows the heat inside the greenhouse OR
has an exhaust vent to the outside. Electric mats under the plants are
probably the best way to go. Electric is also nice for the over head
watering systems. Electric can be a problem if the greenhouse is not
near a power source. So therefore... propane.


Perhaps.

A 20lB tank has 360,000 (if burned at 100% efficiency).
If the tank is $20 then at most 18,000 BTU/$

Electric at 10 cents kWh is 32,400 BTU/$

You'd want to buy propane in quantity to make it affordable. Of
course, a propane heater can kick out a lot more heat. But you also
don't have the control and options that you have with electric.

I think we don't know enough about the OPs requirements yet.

YMMV.

Jeff

Cross posted on edible as well.

Enjoy Life ... Dan