Indoor Heated Grow Bench

Grow plants in your basement with little effort

Heating a greenhouse in the winter can be awfully expensive. I had to figure out how to cut my growing costs and decided to move my seed starting into the basement. What started as a simple operation with a heat pad and a few lights has grown into a fancy hot water heated bench.

My grow bench

Building a heated grow bench

My outdoor greenhouse bench uses copper pipe with boiler antifreeze and my indoor uses plastic PEX tubing with water. If I had to do it again, I would only use PEX as it appears to have a better heat transfer than copper. Also, the bench works more efficiently indoors as the basement temperature does not fluctuate. The indoor heated propagation bench exceeded my expectations.

The temperature inside my basement stays around 50 -55 degrees during the winter months. The Inkbird thermostat has a probe that is insert right into the soil and set at 75 degrees. The warmth of the soil increases the ambient temperature around the plants to 65-70 degrees creating the perfect environment for growing seedlings. There is a small USB powered fan to move the air and a Christmas light timer to regulate the lights. I keep my plants in the basement until mid-March then move into the greenhouse.

The bench dimensions are 8’ X 2’ and can hold 8, 1020 flats. With 72 cube inserts, over 500 plants can be grown on the bench. There is a 6-inch wall around the flats to keep heat in and holes are drilled into bench to draw fresh air up into the growing area. There are 7 hot water tubes that run the length of the bench and the circulation pump is controlled by the Inkbird thermostat. The Inkbird can be programmed to keep the soil at the exact temperature and runs about 35% of the time. We set the hot water heater at 120 degrees Fahrenheit.

Lighting

We found using the LED lights purchased at Harbor Freight to give more light than any other light tested. When using a light meter, it gives us about 80% of light which is 30% more than using LED full spectrum lights. Half the bench is full spectrum, and the other half uses the Harbor Freight lights. We rotate the plants between the two types of lights every other day.

Overall, we are incredibly pleased with our propagation benches. It is was an expensive endeavor that took a lot of trial and error to get it right. We are going to add misting nozzles to our outdoor bench for cuttings and plan to build 2 more in our basement. Raising plants in our basement until mid-March and using our heated bench in our greenhouse almost eliminates greenhouse heat. Last year, we heated our greenhouse 2 nights instead of the usual 2 months.

The bench consists of:

  • 2-gallon 1500watt hot water heater
  • A circulation pump
  • 60 feet of ½ pex tubing
  • 6 LED full spectrum lights
  • 3 LED white shop lights
  • An Inkbird 308 thermostat
  • Assorted small plumbing parts
  • Lumber needed to create the 8’ X 2’ bench
Heating tubes for the bottom of grow bench
2-gallon hot water heater with circulator pump

Heating tubes for the bottom of grow bench
½-inch pex tubing running throughout the bench