Heating Solutions for Your Indoor Grow
By Shannon McKee 2 July 2021
When winter is in full swing, you may notice that your growroom is just a tad too cold for your plants. It may be time to look into adding a heating source. No matter if your growroom is set up in an outdoor hoop house, greenhouse, or your basement, there are heating solutions that will work to keep your plants at a pleasant temperature that will keep you growing all season long.
Soil Heating Mats
One of the first options available for heating your growroom is focusing on heating the soil rather than the air. Soil or seedling mats sit underneath your trays and pots to provide the warmth that growing plants need. These soil mats are a great option when you want that ideal soil temperature between 75-85°F but can’t imagine trying to keep the heat in your home or greenhouse at that temperature. Some people only think of this as a germination mat, but it’s valuable for heating plants that have already germinated.
Compost Generated Heat
It may sound crazy, but you can use compost to warm your plants. This option is one way to create a heat sink and is excellent for greenhouses and hoop houses. You can dig a trench inside of your greenhouse, and cover it with a type of removable walkway so it’s not a problem.
This compost will heat up thanks to your daytime temperatures and will release this heat later in the day. Plus, you’ll get the bonus of having all that black gold ready to add to your garden. Just keep in mind you’ll have to carefully consider where you’re going to put that mainly open compost pile.
Another heat sink idea is to store water around your greenhouse or hoop house. You want the water storage to be placed in an area where it can be heated by the sunlight during the day. Then, during the night, the heat energy will be released into the surrounding area as the water cools off.
This option offers the benefit of having water on hand for your garden, but you have to make sure that you add the water back in as you siphon it off. Removing the water means that you’re eliminating heat storage space.
A good starting place for this method is a 55-gallon barrel, but you can use whatever water storage containers you have handy. To help get the most heat absorption, use dark materials for your tanks.
Electric Room Heaters
A popular option is an electrical room heater. There are some horticultural options that are made explicitly for greenhouse heating, but others do use regular room heaters. This type of heater means that you’ll need either an extension cord or outlets in the area where you plan on using the heater. Keep in mind that you have to use these types of heaters appropriately; you don’t want to create a fire hazard because your heater was too close to flammable materials.
One thing that you need to keep in mind when using any of these heat sources is to circulate the heated air throughout your space. You don’t want hot and cold spots popping up in your greenhouse. Plus, this helps with the condensation that can happen when heating an area in which you’re watering or growing plants hydroponically. Some heaters will have a circulation method, such as a fan, built in, but you’ll have to determine if you need additional circulation for your set-up.
While insulation is a passive heater, it can make your efforts more worthwhile. Insulation may not be appropriate in every situation—like covering up greenhouse windows for insulation, as you’ll then be blocking the sunlight from coming in—but there are other areas where adding some insulation can come in handy. Gardeners that grow in basement areas or different rooms inside of their homes may find that merely adding insulation goes a long way towards keeping the chill out of the room and the heat inside.
The temperature that you need in your growroom is going to depend on what you’re growing and your current set-up. Once you determine what temperature you need to try to reach, you’ll be able to personalize your heating plan based on your needs. You may find that you need to mix and match some of these options to get the right level of heat in your growroom.