Very, very cold!

[fanaticactus]

At least for this time of year...just not ready to accept this arctic air and wind. I know most folks are in bed by now (12:45 am), but I just finished watching an overtime football game. The outside temp might get down to a single digit by morning, but right now it's between 12-13F/-11C and the greenhouse with heater going (set at 48F/9C), it's holding at 37F/3C inside. Although I'm sure one night will be OK at that temperature, this will be a real test for the setup. I might have to run over to the GH tomorrow and boost the thermostat a few degrees. I have a few cacti in there that really don't like it below about 40F/about 4.5C

[sabotenmen]

Yeah, strange fluctuations this time of year. Watch the weather forecast and keep an eye on the thermometers, Fanaticactus!

[fanaticactus]

The minimum temp last night reached 7F/-14.5C (?) outside, and the GH dipped to 37F/3C. This is the earliest "cold snap" I can ever remember. I guess I'll have to bump up the thermostat today; one night under 40F in the GH is OK, but I don't want a repeat. On the other hand, when I was in college in upstate NY, one Thanksgiving (1966, I think) I rode down to just north of NYC with a friend in a Pontiac convertible (top down). The temperature was in the 70s, there was an "air inversion" alert for NYC, and people were spending Thanksgiving in shorts and teeshirts!

[majcka]

Wooowwww!

You have as we call it a "Siberian cold". We didn't reach that cold a whole last winter. No sir!

I wish you and your GH a good luck. I think you might need it.

[cactushobbyman]

You may find that turning up the thermostat may not result in higher temps. The heater's BTU's maybe too small to maintain the temp to the size of your greenhouse. I'm looking into a heater just to keep my greenhouse at or above 33 degrees. I have a 10 X 12 and the roof peak at 10 feet. Just over 1000 cubic feet of space to heat. Record lows in my area is 17 degrees. You may need to use a heating/air conditioner calculator to figure out the BTU's required to keep your greenhouse at your desired temp. In my area minimum would be about 1000 watts electric heater. But again, we average 300 days per year above 28 degrees. Good luck and stay warm, today's high 61.

[oldcat61]

I'm very happy with my oscillating heater from Home Depot. GH is 8.5 by 12.5 but is a lean-to. Also my husband threw clear plastic over it because of a small leak we keep chasing. Guess that's making a double wall kind of insulation. The mamms are blooming, so it's not blocking much light. It was 16F last night, the heater was on medium heat, low fan. Got down to 64 at 4AM. I'll let it go lower when blooms stop. Let us know your progress. Sue

[fanaticactus]

You may find that turning up the thermostat may not result in higher temps. The heater's BTU's maybe too small to maintain the temp to the size of your greenhouse. I'm looking into a heater just to keep my greenhouse at or above 33 degrees. I have a 10 X 12 and the roof peak at 10 feet. Just over 1000 cubic feet of space to heat. Record lows in my area is 17 degrees. You may need to use a heating/air conditioner calculator to figure out the BTU's required to keep your greenhouse at your desired temp. In my area minimum would be about 1000 watts electric heater. But again, we average 300 days per year above 28 degrees. Good luck and stay warm, today's high 61.

This is very good advice for all who read this, CHM. I was on top of the situation enough to calculate the BTU output of the heater and my needs for an 8x10 GH with double thick polycarb walls & roof and an insulated floor before I purchased it. The greenhouse supply website provided a handy calculator just for this. The tower quartz heater has a 5120 BTU rating, which was slightly above the cubic foot interior measurement, giving me, I hope, a bit of a "cushion". The heater has two settings: 750 and 1500 watts; I have it set at maximum output at 1500 watts. And today I bumped up the in-line thermostat to 52F. We'll see how that goes tonight. Believe me, our winters are not normally this cold for an average. We probably average somewhere in the mid-20s for the whole winter with perhaps two or three really cold spells, when it gets down to single numbers or below at night. But those are short lived. You are absolutely correct, though, on the importance of the BTU rating when considering a GH heater. The type of construction of the GH can make a tremendous difference as well.

[mg2007]

The cold is coming all the way to northern Alabama. Tonight we may have some freezing rain and snow accumulation. Tomorrow night, the low will be 20. Compare that to last winter, when the lowest temperature the whole winter was 18! I am testing several species of cactus to see which will tolerate our winter as long as they are sheltered from the rain, but this may be a colder than usual winter!

[fanaticactus]

And the same for us up here, mg2007. This is way earlier than usual to get this kind of cold even up here. And now I see on Sunday the temperature is predicted to be only 17 during the day and falling to -1 at night. Right now we have snow (no more than an inch), but it's supposed to change to rain around 2:00am. I'm hoping this just means an early winter and maybe February and March won't be too bad.