Get Passive Home Heating With An Attached Greenhouse

This Addition Can Provide Year-Round Benefits When Done Right

Greenhouses are a must for getting the most from your garden in cool climates, but they’re a significant investment both in materials and labor. Using them to generate passive solar heat is a great way to offset that cost.

A small attached greenhouse is not only a boon to your kitchen but, when built onto a south-facing wall, is a solar-powered heat source that can keep you cozy through autumn all on its own and even help out on frigid winter days. Depending on the latitude, these additions can even allow year-round gardening.

By placing the greenhouse around a door or window, it’s possible to raise temperatures to 30 degrees above the outdoors and potentially save hundreds on heating bills! Circulating air allows the greenhouse to heat the house during the daytime and, optionally, heat the greenhouse at night. Ideally, there should be both a basement and a main floor window or vent open to the greenhouse. A fan can blow the warmer air that rises to the ceiling into the house while cooler air enters from below. A pair of ducts can circulate the air if only one window is available. In addition to heat, this will add oxygen and moisture to the home and ventilation for plants.

But the greatest benefit may be the delight of being able to walk out the door into a warm green space when the rest of the world outside is cold and bare!

Designing the Greenhouse

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Some hardware and building material stores offer kits, sometimes called lean-to greenhouses, but it’s not hard to build an affordable greenhouse with 2×4 lumber and polycarbonate panels. To get the most out of an attached greenhouse in winter, it should be against a wall facing directly south or very close to it for maximum sun exposure. There should be nothing obstructing horizontal light from entering the greenhouse, such as sheds and evergreen bushes. Deciduous trees that offer shade in the summer and drop their leaves to allow in winter sun are ideal.

Proper construction is as essential as correct location in order to prevent drafts and ensure durability. Triple wall polycarbonate, while costlier, is a lightweight solution that offers excellent insulation and resistance to wind and snow. Recovered window panes provide a cheap, environmentally-friendly alternative. If using single pane glass, an interior plastic layer is necessary for insulation. Concrete provides a solid base while being an excellent heat absorber.

To maximize the benefits of solar heat, heavy objects, such as concrete and stone, are useful to retain heat and release it overnight. Many greenhouse owners use water drums, as water is one of the best elements for storing heat. Dark paint also helps increase heat absorption.

An add-on greenhouse should be treated as part of the house and built to last. A comfortable and aesthetically pleasing interior makes a greenhouse a perfect place for both plants and people.

Things to Consider

While greenhouses have many benefits, they also come with challenges, and it’s best to do research and be prepared. Pests are one of the most significant concerns, and as devastating as they can be, it’s never a good idea to use chemical pesticides in an enclosed space connected to the house. Beneficial insects like ladybugs are one solution, but can’t be relied on when the weather gets cold, and they may depart altogether when it’s warm. Another alternative is to intermingle vegetables with pest-resistant herbs. If things are looking hopeless, January offers the opportunity to hit reset by opening the greenhouse door and letting the cold take care of things.

Another challenge for new greenhouse owners is anticipating the wildly fluctuating temperatures that changing weather and seasons bring. Keeping careful track of the thermometer for the first year will provide a reference for anticipating future threats to vulnerable plants. Lack of drainage can also cause problems. Incorporating a drain pipe and plastic barrier into the floor during construction will keep moisture away from the foundations.

While many homeowners are looking into photovoltaic panels for energy independence, they have downsides such as cost and complexity. So it’s good to remember there are simple ways to derive energy from Mother Nature that are not only ecologically sound but add to our quality of life.

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