Greenhouses are amazing for their traditional purpose of growing plants and extending the growing season in cold climates, but did you know a greenhouse can also be used to heat your home?
A greenhouse attached to a home works as a passive solar heater by collecting the heat of the sun during the day and transmitting heat into the home.
Some homes are built with attached sunspaces, conservatories, or solariums, which are a similar idea but are usually intended as extra living space. The primary use of a greenhouse is growing plants, and if it is attached to a home, passive heating is a bonus.
Passive heating with a greenhouse
Heat that is collected by a greenhouse during the day can be transferred into a house through windows or vents, or with fans for increased heat flow. At night, the windows or vents can be closed, depending on the greenhouse design, to retain the heat in the house when temperatures drop outside.
By using some sort of thermal mass inside the greenhouse, heat can be retained longer, keeping the greenhouse from freezing in even the coldest climates. Examples of thermal masses for heat absorption include bricks on the house, planting beds in the greenhouse, or black water containers.
An inexpensive greenhouse can heat a home
An attached greenhouse can be very large and expensive, but it doesn’t have to be. Below is an example of a small, inexpensive greenhouse design that heats a home in a cold climate. This lean-to greenhouse was built very simply using polycarbonate panels and 2 x 4 boards on a concrete footing.
See this video for details on how this greenhouse heats the house and requirements you’ll need to consider if you choose to build one yourself.
Here are some examples of how this greenhouse provides heat on a very cold day, along with a breakdown of savings. As you can see, on a day that is only 7 degrees Fahrenheit, the temperature inside the greenhouse is over 90 degrees.
Costs for building a greenhouse like this one can vary significantly, depending on the materials used. This particular example has 5-layer greenhouse panels that are extremely efficient at retaining heat, but can also be very expensive when purchased new. These panels were purchased from a reclaimed building materials store at a big discount.
This video breaks down construction details and cost savings, including heating bill comparisons from before and after the greenhouse was built:
Another beautiful example of passive heating with a greenhouse is the off grid Montana cabin we recently wrote about. It has a large greenhouse/sunroom addition that is used along with the wood stove as the cabin’s heat source.
Depending on your climate and the amount of sun you get, you may need a backup home heating source if you build a greenhouse for passive heating. A greenhouse is still a great way to provide supplemental heat to your home and a place to grow plants. It has the added benefit of providing cleaner air to your home by circulating air that has been filtered by your greenhouse plants.
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