How to Install a Greenhouse Heater

What You'll Need
Greenhouse heater (any of various types)
Electrical feed to the greenhouse
Insulation in the walls and ceiling
Power drill and bits
Extension cord
Wall and ceiling ventilation (gas, propane and paraffin heaters)
Connection to house gas line, or propane tank

A greenhouse heater is essential if you want to work well into the autumn in your greenhouse, or overwinter plants there. Look over the installation tips for various kinds of greenhouse heaters to choose and install the type that will be most beneficial for you and your plants.

Step 1:  Choose the Type of Heater

Propane, gas and paraffin heaters will all need ventilation as they burn fuel and release moisture into the air. Install floor and ceiling openable louvers, and keep them closed when you are not inside the greenhouse. Avoid running these heaters when you are not in the greenhouse. Ensure you have direct-current electricity available to run an electric heater. In an insulated greenhouse, electric heaters on a suitable thermostat can be left to run when the greenhouse is unoccupied.

Step 2:  Select a Suitable Size

For a gas or electric greenhouse heater, you need to know the size of heater yu need in BTUs (British Thermal Units). Determine the BTU size of heater by multiplying the square footage of your greenhouse interior (length times width) by 100 to get the maximum BTU strength of the heater you will need. For a gas heater, divide the BTUs by 100 to get the gas flow in cubic feet per minute (CFM) you will need to operate the heater.

Step 3:  Choose the Location for Your Heater

Most electrical and gas, propane and paraffin heaters come in stand-alone floor models. Make sure they are standing in a well-aired spot, away from boxes and not under tabletops. Some thin-strip electric heaters need to be installed on a wall near the ceiling, along with a protective cover to prevent contact with the strips. The strips can reach a temperature of 175 degrees Fahrenheit, so install the strips and covers well out of the reach of small children. Fan electric heaters also need to be installed near the ceiling, so they can circulate and cool warm air, and reduce mold buildup.

Step 4:  Install

Connect a gas heater to the gas main line. A gas feed should have been installed in the greenhouse when it was built. Obtain a propane gas cylinder from hardware stores and building supply centres. Paraffin is readily available at camping goods dealers, and other hardware centers. Choose the electric outlet closest to where you wish to install the electric or fan heater. Secure the heater to the wall or ceiling in its mounting brackets, with the power drill and suitable screws.

Step 5:  Test

Turn the heater on and test its performance. If it is causing the greenhouse windows to steam up excessively, lower the heat setting. Keep the indoor temperature well above 32 degrees Fahrenheit (freezing temperature) during the winter months to protect your plants, fruit and vegetables from frost damage.