Greenhouse - Reducing Heating Costs I

The following is the first in a series on tips for reducing greenhouse heating costs.

Reduce Air Leaks

>Keep doors closed - use door closer or springs.
>Weatherstrip doors , vents and fan openings. For example, a 48" fan louver that fails to close properly leaving 1" gaps, allows 23,000 Btu/hr of heat to escape.
>Lubricate louvers frequently so that they close tight. A partially open louver may allow several air changes per hour. Additional fuel is needed to heat this air. Shut off some fans during the winter and cover openings with insulation or plastic to reduce infiltration of air.
>Repair broken glass or holes in the plastic covering.

Double Covering

>Line sidewalls and endwalls of greenhouse inside with poly or bubble wrap to achieve the thermopane effect. Install double wall polycarbonate structured sheets to get insulation effect and reduce recovering labor.
>Use poly with an infrared inhibitor on the inner layer for 15% savings. Payback is 2-3 months.
>Add a single or double layer of plastic over older glasshouses to reduce infiltration and heat loss by 50%.

Energy Conserving Blanket

Install a thermal blanket for 20%-50% savings. Payback is 1 year. Tight closures should be maintained where curtains meet sidewalls, framing or gutters. Use a U-shaped trap to prevent heat from escaping overhead. Heat and water lines should be insulated or located below the blanket.

Foundation and Sidewall Insulation

>Insulate the foundation - place 1-2" polyurethane or polystyrene board to 18" below ground to reduce heat loss. This can increase the soil temperature near the sidewall as much as 10 degrees during the winter.
>Insulate the kneewall or sidewall to bench height. Use 1" to 2" of insulation board. Applying 2" of foam insulation to a 3' high kneewall on a 28' x 100' greenhouse will save about considerable amount of fuel.

Reprinted from "Greenhouse Energy Conservation Checklist" by John W. Bartok, Jr., Agricultural Engineer, Natural Resources Mgt. & Engr. Dept., University of Connecticut , Storrs CT