Greenhouse Heat solutions

[stewarjm192]

Hey good Nuts,
I live in upstate NY, with lows that dip to about 0F at their lowest, so a solid 5b.
Ive had a cmall 200sqft cold frame, made with 2x4 lumber and wrapped in 6mil plastic for the last few years to provide protection from that cold. I added a small oil-radiant heater when I got some less hardy species like trident maples, chojubai, etc. The heater kept that space at about 28 degrees on the absolute coldest days, which I was happy with, given a few heat mats for more sensitive items.

This winter, I moved and bought a 16x8 cedar frame poly greenhouse kit from Lowe's that nearly doubled my space. I also worked on a few spruce and fir in the fall, and have been trying to keep that 400sqft between 34 and 40ish degrees. I have had to add a small propane heater to supplement because the space is either too drafty or too large for the original heat source to work, given my new, smaller tolerance for temperature range.

A few things, I seem to blow out my Amazon-purchased thermostats, as they seem to be under-rated for the 1500-watt heaters I'm running on them....any suggestions there for a beefier thermostat that can handle 1800 watts maybe?

Also, what are some other things I can be doing to more efficiently retain and supply heat in that space?

TIA

 

[BrianBay9]

Use a heat sink. I used to use 55 gal plastic barrels of water as bench supports. The heat during the day and slowly release the heat at night. Other materials could be used for the same effect.

 

[harshadg]

I've outlined my experience setting up the greenhouse here.

While not quite as cold as where you are (I'm in zone 6b), we've had a few single digit days here. Things that made a material difference - adding insulation and buckets of water. I used foamular boards, cardboard, additional 6mil sheets, bubble wrap, and trying to seal all gaps. Note that the floor of my greenhouse is insulated from the pavers underneath using foamular boards. I leave the snow/ice on and around the greenhouse (it tends to seal the gaps), and don't really open the greenhouse unless absolutely necessary. The foamular boards are perhaps the single most important factor in my setup.

I have the inkbird ITC-608T which is rated for 1800W and I have a 1500W ceramic heater (with tipover protection) set on low (900W). The probes are buried in the substrate in two pots, and the program is set to turn on the heater when temps drop below 25F. See the temp data in the attachment alongside from the app I wrote. The dashed line is ambient, and the blue corresponds to the temp in the greenhouse. Gaps in data correspond to when my computer (currently the receiver for the bluetooth signal) was out of range/ asleep/ off and not failure of the sensor. (Currently working on a solution for uninterrupted signal acquisition)

Hope this helps.