Sam is interested in the temperature management inside the hoophouse where we are overwintering greens. Four seasons farming!
The hoophouse’s plastic cover does part of the job. Then there is an internal low hoop of heavy duty row cover over the raised beds. He has also hung silver-backed bubble wrap from the internal hoophouse frame to reflect light down onto the plants on sunny days.
To give an indication of the difference it makes on a cold day, I recorded some temperatures on February 9, 2020:
| Time | Conditions | Thermometer Location | Temperature |
| 6:30 am | Sunrise | Outside | 1 ℉ |
| In hoophouse | ? | ||
| Row cover down | At soil level | 19 ℉ | |
| 9 am | Sun | Outside | 8 ℉ |
| In hoophouse | 37 ℉ | ||
| Row cover down | At soil level | 28 ℉ | |
| 9:30 am | Sun | Outside | 9.3 ℉ |
| In hoophouse | 51 ℉ | ||
| Row cover raised | At soil level | 50 ℉ | |
| 11:00 am | Sun | Outside | 12 ℉ |
| In hoophouse | 72 ℉ | ||
| Row cover raised | At soil level | 71 ℉ | |
| 7:30 pm | Dark | Outside | 19 ℉ |
| In hoophouse | 20 ℉ | ||
| Row cover down | At soil level | 30 ℉ |
Conclusions:
- The hoophouse and the row covers definitely both help. On a 1 degree night, the temperature at soil level was 19 degrees.
- A manual effort is required to lift off the row covers when the sun is shining. This shows in the difference at soil level between 9 and 9:30 am. With the row cover down at 9 am, the row cover was keeping in the night’s cold even though the temp in the hoophouse was rising quickly. With the row cover raised shortly after 9 am, the temps in the hoophouse and soil level equalized.
- After the sun went down, it was 19 outside, 20 in the hoophouse, and 30 at soil level, showing the row covers really retain some of the day’s heat.
Sam wants to automate the lifting of the row covers (and other aspects of this process when we get a greenhouse). But for now, it’s been an interesting science project and we are still eating a small amount of greens.