Small semi heated cold frame, think it will work?

harleysilo · November 14, 2014

Hi all!
The kids convinced me to make a tiny test green house for this winter/early start next year. So with no research i built this for one of our raised beds. It's 3' tall in the back, 2' tall in the front with 2 tops that open.
I still need to make a small vent that opens with one of those temperature actuated openers.
It's only one layer of 6mil plastic, i could add a second layer but I’d cover up my screws preventing easy removal. I could get some large bubble wrap and staple that to the outside however.
I have a basement waterproofing system that consists of a sump, and gutters that run inside my foundation, but under the slab. They collect rainwater which is gravity feed out of the house. The sump and gutters have a blower fan that suck air through which keeps humidly down and vacates Radon gas if there was any there. I redirected this 24/7 airflow to the green house via a corrugated pipe. The air blowing out is consistently about 60 degrees. Half the air comes through the gutters, the other half is air pulled from the unfinished basement which comes through the walls (older house) or from the upstairs area.
This morning it was 23 degrees, inside the greenhouse it was 33 degrees. Perhaps adding a light bulb would be enough to keep it warmer, or doubling up on the plastic creating a dead air space, or the bubble wrap would help. I don't have enough room for some sort of solar heat sink.

Think we'll have much luck this winter?

So far we've planted Radishes, carrots, broccoli, various lettuces and spinage. We bought some already sprouted Kale and stuck that in too. I also rounded up all the strawberry plants and replanted them in there. I guess next year we'll try and turn this bed into only strawberries.

November 14, 2014	#1
harleysilo Tomatovillian™ Join Date: May 2007 Location: Woodstock GA Posts: 418	Small semi heated cold frame, think it will work? Hi all! The kids convinced me to make a tiny test green house for this winter/early start next year. So with no research i built this for one of our raised beds. It's 3' tall in the back, 2' tall in the front with 2 tops that open. I still need to make a small vent that opens with one of those temperature actuated openers. It's only one layer of 6mil plastic, i could add a second layer but I’d cover up my screws preventing easy removal. I could get some large bubble wrap and staple that to the outside however. I have a basement waterproofing system that consists of a sump, and gutters that run inside my foundation, but under the slab. They collect rainwater which is gravity feed out of the house. The sump and gutters have a blower fan that suck air through which keeps humidly down and vacates Radon gas if there was any there. I redirected this 24/7 airflow to the green house via a corrugated pipe. The air blowing out is consistently about 60 degrees. Half the air comes through the gutters, the other half is air pulled from the unfinished basement which comes through the walls (older house) or from the upstairs area. This morning it was 23 degrees, inside the greenhouse it was 33 degrees. Perhaps adding a light bulb would be enough to keep it warmer, or doubling up on the plastic creating a dead air space, or the bubble wrap would help. I don't have enough room for some sort of solar heat sink. Think we'll have much luck this winter? So far we've planted Radishes, carrots, broccoli, various lettuces and spinage. We bought some already sprouted Kale and stuck that in too. I also rounded up all the strawberry plants and replanted them in there. I guess next year we'll try and turn this bed into only strawberries.