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Greenhouse Energy Audit.
Greenhouse Energy Audit
Walk-through checklist for finding energy waste, plus retrofit ROI calculator. The biggest savings are usually under your nose.
Highest-ROI retrofits
| Retrofit | Cost | Annual savings | Payback |
|---|---|---|---|
| Energy / thermal screen | $3-6/sqft | 30-50% heating | 2-4 years |
| Single → double poly | $0.30-0.50/sqft + labor | 40-50% heating | 1-3 years |
| North-wall insulation (R-10 polyiso) | $2-4/sqft | 5-15% (significant in N-S oriented) | 3-5 years |
| Foundation perimeter insulation | $3-8/linear ft | 5-15% (huge for slab + concrete pony walls) | 2-5 years |
| Repair/replace torn glazing | Material + 1-2 days labor | 10-30% (depending on damage) | < 1 year |
| Weather-strip doors + vents | $50-200 | 3-8% | < 1 year |
| Boiler / furnace tune-up | $200-500/yr | 5-15% | < 1 year |
| Heat pump replacement of resistance | $8K-25K | 50-70% of electric heating cost | 5-10 years |
| Lower night setpoint by 5°F | $0 | 15-25% | Immediate |
| DIF strategy (cooler nights, warmer days) | $0 (control change) | 10-20% | Immediate |
| Root-zone heating + lower air temp | $3-6/sqft | 30-40% heating | 3-5 years |
| Move to bench-top growing | $5-15/sqft | 10-20% (heat just where plants are) | 4-8 years |
Walk-through inspection
- Glazing condition. Tears, holes, missing panels, gaps at seams — note locations + severity.
- Door + vent gaskets. Light visible around closed door = air leak. Light visible around vents when closed = air leak.
- Inflation gap (double poly). Should be 4-6"; inflated tightly. Touching = no insulation benefit.
- Heater / boiler condition. Soot? Rust? Last service date? Combustion analyzer reading?
- Thermal screen. Present? Deployed correctly? Fully closing nightly?
- Setpoint reality. What's the thermostat set to vs what's actually held?
- Equipment time. How many hours/day does heater run in coldest week?
- North wall. Insulated? Most greenhouses lose 15-25% through north-facing surfaces alone.
- Foundation perimeter. Insulated below grade? Concrete + cold ground = major heat sink.
- Air infiltration test. Smoke pencil at door, vent edges, glazing seams on a windy day. Air movement = heat loss.
- Thermal imaging (best). Rent or hire IR camera; cold spots glow blue. Single best diagnostic.
Whole-greenhouse benchmarks
| Greenhouse type | BTU/hr/sqft floor (peak winter night) |
|---|---|
| Single poly, no thermal screen | 50-70 |
| Double poly inflated | 30-45 |
| Double poly + thermal screen | 20-30 |
| Glass + thermal screen + insulated north wall | 15-25 |
| Modern high-tech "energy" greenhouse | 10-18 |
| Passive solar / earth-bermed | 5-15 |
If your greenhouse is significantly above these benchmarks, retrofits will pay back fast.
Free under CC BY 4.0. Cite as "OAT Greenhouse Energy Audit (openagriculturetechnology.com)".