The Greenhouse

We are located at an elevation of 5700 feet above sea level, just southeast of Denver, Colorado. Our greenhouse is located on the side of the house with a South-east exposure. Temperatures range from 100° F in the summer (1-3 days) to -30°F in the winter (5 days). Our greenhouse is designed to conserve heat and minimize our heating bill. It adds an average of $30 per month to our natural gas bill. It is also color coordinated with the house for the local architectural committee. The roof is corrugated greenhouse fiberglass and the side walls are flat greenhouse fiberglass.

We opted not to use the double pained fiberglass due to its stiffness. We are in the hail capitol of the world and get hailstones 3 inches in diameter. We have had hail storms that got me a new roof on the house but the greenhouse survived with only minor starring on the fiberglass. A friend who had the double pained fiberglass had holes in his greenhouse roof.

The size of the greenhouse is 13 feet by 16 feet. All of the wall space that does not need direct light is solid with R-11 insulation (Gray area walls). In the summer we cool using a swamp cooler as seen in this picture in the lower left corner. It blows cool air under the benches and is exhausted through the vent you see above. It fully exchanges the air every 30 seconds when in full operation.

The temperature range inside the greenhouse is 58° F during the night. The heater is a high efficiency oversized natural gas heater. We calculated the heat needed in BTU's for a night of -30° F, then bought a heater double that capacity. It easily kept up with the coldest night I have recorded of -39° F even with me opening the door to come in and check on things. Notice some of the things done to conserve heat. The shade cloth is located inside the greenhouse to trap more heat near the plants. (Note: it is far easier and cheaper to cool using a swamp cooler that to heat using a heater) Also as shown below, all walls are either insulated or lined with 6 mil greenhouse plastic.

The swamp cooler kicks in at 80° during the summer and 85° in the winter. When in full operation, it exchanges the air every 30 seconds in the greenhouse. We also have a single misting nozzle in front the the swamp cooler to add additional cooling and humidity to the air.

All of the fiberglass walls and roof are lined with 6 mil UV resistant greenhouse plastic. It is secured using the white plastic stripping stapled onto the wood beams as shown. This helps seal the greenhouse and provides about a R-4 insulation rating on the fiberglass walls and roof. All joints are caulked to minimize drafts from the outside cold air.