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Build a Passive Solar Greenhouse

The "Red Greenhouse at Skye Hill" by Angela Kantola

In 2007 when my husband, Don Wallace and I bought a home in Deer Creek Canyon in the foothills above Littleton (elevation 7,300'), we began thinking about ways we might best live with the land and about "making home paradise." We started growing vegetables in a couple of fenced areas on our gentle south-facing slope and were soon thinking about how to extend our short Colorado foothills gardening season. Attracted to the design of rectangular passive solar greenhouses, we took a course entitled "Sustainable Greenhouse Design" offered by Penn and Cord Parmenter at the Denver Botanic Gardens in early 2012. The course covered the basics of passive solar greenhouse design, including the use of stored water as thermal mass and simple math formulas that guide design (much of which is based on the principles in the book  by Bill Yanda and Rick Fisher entitled The Food and Heat Producing Solar Greenhouse: Design, Construction and Operation originally written in 1976, revised in 1980, and reprinted in 2016).

We knew we didn't have the skills to make this an all-DIY project and were fortunate to find Steven, the fantastic artisan/contractor(and husband of one of my colleagues) to build our year-round, passive solar, 15' x 28', 400-square foot greenhouse. Although the Parmenters now sell plans for their greenhouse designs, in 2012, we had to improvise a bit. Don stayed on top of material orders and preparation and Steven figured out how to make it all work. And it turned out beautifully. We've been growing Swiss chard, lettuces, herbs, tomatoes, spinach, snap peas, cucumbers, and flowers since we began operating the greenhouse in 2013. Winter nighttime temperatures rarely drop below 40F (and usually are in the 50s or above). The lowest temperature to date was 35F for some hours in this January's ultra-cold snap (and still most of the tomatoes still survived!).

Key features that regulate the greenhouse temperature are: 1) thirty-one 55-gallon steel barrels for a combined 1,650 gallons of passive-solar-heated water; 2) three metal Venturi-effect roof vents plus window venting; 3) a deep masonry insulated foundation; and 4) glazing of 10mm twin wall polycarbonate (roof) and double-pane glass (verticals).  

Our biggest lessons learned have been: 

  • The importance of a very knowledgeable builder; 

  • The wisdom of building the greenhouse big enough to include hang-out space (we just can't beat a "vacation to sunny Florida" only 30 feet from our back door in the middle of a Colorado winter!); 

  • An understanding that the inside of a greenhouse is a year-round tropical climate that requires ongoing management of humidity and insects;

  • Realizing that our greenhouse is an ongoing, joyous journey of learning and discovery.  

The greenhouse has wood framing, and though well painted, we did experience some wood rot that required significant remediation in 2020 to 2021. Our dear contractor returned for those repairs, but sadly passed away in the fall of 2020. Steven's son, Dylan, who had helped with some of the repairs, completed the work in 2021. We are daily thankful for their fine craftsmanship and the privilege of having such a delightful year-round growing space.


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