newbie needs help

[psyc1210]

HI again peps just got done up dating my cp so you know where im from still looking for some help for my new greenhouse i think my big fear is going to be how to heat it can you use gas heaters? Oh by the way the size of the greenhouse is 9w 12L 9H thanks for the e-mail you 2

[Cynthia, Prescott, AZ]

How cold does it get? I have two 1500 watt electric milkhouse heaters in my 8 X 12 X 8h, insulated GH, that sees 10F in winter so far. Gas heat will need to be a vented heater, and my husband's calculation put electric heat cheaper than propane considering half the heat going up the flue. I have a propane Southern Burner (no electricity required) that I keep the pilot burning on all winter as a back up heater should the power go off too long. Note that if you use more than on of these 1500 watt heaters, you will need 2 circuits, as one 20 amp service will not handle 2 of these.

[slippery_biscuit]

What type of glazing does your greenhouse have? Plastic sheet? Single wall fiberglass? Glass? Twinwall polycarbonate? How well it is insulated during cold Maryland winters will help determine your heat requirements.

[psyc1210]

allready i see this is going to be more difficult than i thought! But anyway thanks for the help! the GH is twin wall poly im not sure if im going to leave the floor earth or concreat. do you use both heaters? im hopeing i can get by with one. the wether hear is crazy one week its 60/70 the next its 20/30 but for the most part it hovers around 30 or 40 in the winter! thanks for the help!

[digitalgate]

wait till you feel Mineapolis weather. Today 80, tomorrow 20. today 30 tomorrow -10 or -20
Heat was a big problem for my mini greenhouse. Water condensed on the glass window and
form 1 inche- ice at the foot of the glass panel- INDOOR! Ice form indoor! Can you beat that!
of course when spring arrive the ice melted and i wll have wet carpet.

[Account deleted by Request]

Originally Posted by jimdandy

allready i see this is going to be more difficult than i thought! But anyway thanks for the help! the GH is twin wall poly im not sure if im going to leave the floor earth or concreat. do you use both heaters? im hopeing i can get by with one. the wether hear is crazy one week its 60/70 the next its 20/30 but for the most part it hovers around 30 or 40 in the winter! thanks for the help!

Propane heat works just fine in a greenhouse, it gives off CO2 and water vapor. You will need some sort of auto on/off switch to maintain your optimum temp. I worked at a nursery here on the island and all our poly houses were heated with propane heaters.
One thing about earthen floors though. They are good for helping to maintain humidity, but they are excellent breeders of all sorts of fungi, disease, and pests. Eventually we poured new concrete floors over the dirt and saved a whole lot on chemical treatment. One floor solution that I just remembered is to level your dirt floor, cover it with heavy duty polyethylene (at least six mil), then put down a layer of pea gravel (stone that is roughly one quarter to one half inch in diameter). This is cheaper than concrete (at least on Nantucket) and when sprayed down in the morning, it greatly increases the humidity in your greenhouse. It is also much kinder to your legs and back.

[Cynthia, Prescott, AZ]

During my winters, both electric heaters come on, but if you are OK with 50F and are usually around freezing or above outside, I think just one may work. I had to add a second heater because I was going down to 40F with just one. It has been below freezing at night here for the last month+, down to 18F often, and down to 13-14F occasionally so far this winter.

Double wall polly is probably pretty good, but if the GH temp is still going lower than you want, you can boost the insulation value of you walls with bubble wrap from a shipping store, lining the inside, put up just for winter, and removed and thrown away in spring, as the shipping type will only last 6 months. It is also great at diffusing light so that you can go with less or no shade cloth during winter. I just added the mylar lined insulation material on the north end to up the insulation value there AND to prevent radiation losses where I can.

One place that made a big difference is in heat loss thru the vents, a big heat loss area, where I baffled the vents, requiring the heat to go down hill before leaving the GH, which hot air is not known to do. Course this only works because I have the cooler and a vent fan to actively force the hot air down the tube-like baffling when the GH gets to hot (day time in winter). I had the cooler/vent fan off for a couple of days last winter and did severe damage to a lot of plants hanging in the southwest end. I have a solar powered vent fan from Harbor Freight that I will be installing soon to give protection for a power outage while the baffling is up for winter. In summer, I have a heat motor that opens the 2 vents on opposite sides of the GH to give some minor protection for a power outage.

My temporary GH:
Temporary Greenhouse Photo Gallery by Admiral Schnitz at pbase.com