Build a Greenhouse: The Amazing, Low-cost, Multipurpose, Solar-heated Greenhouse/Guest House

For less than $4,000, you can build a greenhouse on this 240-square-foot plan that will also serve as a small, comfortable guest house.


| October/November 2009



buid a greenhouse - greenhouse/guest house

This greenhouse was designed to be used as a guest house or studio.


PHOTO: KENTON KNOWLES

The idea behind my greenhouse/guest house concept is to build a greenhouse that has everything you need to live, and not a centimeter to waste. But you don’t have to use it as a greenhouse. It can be a guest house or an energy-efficient small home. The design is flexible, so you can incorporate whatever recycled materials you can find. Even if you buy some of the materials and hire a bit of help, you can build a greenhouse for about $3,800.

If you plan to use the building as a greenhouse, use insulated, wood-framed windows that aren’t coated with low-e or solar film, because the coating limits heat gain. Adequate thermal mass and a well-insulated floor and walls are necessary to store enough heat for a couple of days without sun. Thermal mass, such as concrete, brick or stone, helps moderate heat, tempering the thermal swings throughout the day and night.

To make a guest house, include a loft large enough for a double bed upstairs — the warmest part of the building — for cozy winter nights. In summer, the soffit design encourages airflow in the loft to keep it cool. To live totally off-grid and harvest water, install a metal roof at an angle appropriate for optimal solar performance for your area. To find this information, go to the Astronomical Applications Department of the U.S. Naval Observatory. (Click “Data Services,” then select “Altitude and Azimuth of the Sun or Moon During One Day.”)

Because the greenhouse/guest house is so small, you shouldn’t need a building permit in most locations, but check with local authorities before you build your own greenhouse. The maximum size of a building allowed in my county without a permit is 10-by-12 feet, so the greenhouse/guest house is designed to those dimensions.

The Benefits of the Greenhouse/Guest House

  • Salvaged materials keep costs down.
  • Lots of glass on the south wall provides light and heat for a winter greenhouse and/or solar heat for living space.
  • Wide overhangs shade the south side in summer, and soffit vents provide natural cooling.
  • Inexpensive DIY solar collectors on the roof transfer heat to the radiant floor via an automotive heating core.
  • Small footprint may make this structure exempt from building codes.

How to Build Your Own Greenhouse

To build your own greenhouse, start with a level building site, but make sure the site slopes enough to drain water from the building. Then cover the area where you’ll build the greenhouse with a weed barrier and gravel.

Make a 10-foot-by-12-foot grid (on center) of concrete deck pads — three rows of four pads. Put a 10-foot rot-resistant 2-by-4 (flat, not on edge) on the short rows. If you don’t plan to move the building, instead of deck pads use permanent concrete piers that are deeper than the frost line. After building the greenhouse, I moved it onto concrete barriers (used to divide traffic during road construction) and attached the greenhouse to them with hurricane clips, wedge anchors and 2-by-4s.

mikemills82
3/13/2016 12:42:39 AM

I used the plans on WWW.EASYGREENHOUSE.INFO and built my own greenhouse VERY cheap and easily! It was the best decision I've ever made. To my family and I, it just made economic sense to build a DIY greenhouse. We spent a fraction of the cost of buying an expensive pre-built one that just have to be assembled anyway...why pay inflated prices for material? The guide on that website is so very easy to follow and it doesn't matter if you're a total beginner like us. We were on a very small budget and found so many wonderful plans for our greenhouse...it was hard to pick just one, but the one we chose is terrific! We actually built the one that is featured on the website's homepage. I love growing fruits and vegetables for my family all year round! There's no such thing as out of season for us anymore! I finally have the greenhouse of my dreams and it was VERY affordable!


deanna berman
1/1/2010 1:26:53 PM

Hi I have an 8 foot children's playhouse and I would love to convert it to a solar/passive solar greenhouse. I would love some advice from the author of "Build a Greenhouse: The Amazing, Low-cost, Multipurpose, Solar-heated Greenhouse/Guesthouse" Thank you Deanna Berman, ND Ecovillage at Ithaca Ithaca, NY






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