What Winter Heating Really Costs, by Greenhouse Type

8 mm twin-wall polycarbonate, R-1.7/U-0.59 center-of-glazing (manufacturer and retailer datasheets, Palram ThermaGlas class), zero thermal-bridging penalty for the aluminum frame — deliberately generous, aluminum bridges heat aggressively. Airtightness baseline 1.0 ACH, the methodology's dome baseline. Gable geometry, 12′ × 20′, 5′ sidewalls, 3′ ridge rise — identical to the single-glass gable preset of the same footprint, so the glazing is the isolated variable; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years; polycarbonate panels typically carry a 10-year warranty and panel replacement is not modeled — both favor this structure. Corrections welcome.

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing, which covers 8 mm twin-wall as well as 6 mm. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

8 mm twin-wall polycarbonate, R-1.7/U-0.59 center-of-glazing (manufacturer and retailer datasheets, Palram ThermaGlas class), zero thermal-bridging penalty for the aluminum frame — deliberately generous, aluminum bridges heat aggressively. Airtightness baseline 1.0 ACH, the methodology's dome baseline. Gable geometry, 16′ × 30′, 5′ sidewalls, 6′ ridge rise — identical to the single-glass gable preset of the same footprint, so the glazing is the isolated variable; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years; polycarbonate panels typically carry a 10-year warranty and panel replacement is not modeled — both favor this structure. Corrections welcome.

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing, which covers 8 mm twin-wall as well as 6 mm. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

8 mm twin-wall polycarbonate, R-1.7/U-0.59 center-of-glazing (manufacturer and retailer datasheets, Palram ThermaGlas class), zero thermal-bridging penalty for the aluminum frame — deliberately generous, aluminum bridges heat aggressively. Airtightness baseline 1.0 ACH, the methodology's dome baseline. Gable geometry, 21′ × 48′, 6′ sidewalls, 5′ ridge rise — identical to the single-glass gable preset of the same footprint, so the glazing is the isolated variable; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years; polycarbonate panels typically carry a 10-year warranty and panel replacement is not modeled — both favor this structure. Corrections welcome.

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing, which covers 8 mm twin-wall as well as 6 mm. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

CoverLite 6mm twin-wall, U-0.62/R-1.61 center-of-glazing, zero bridging penalty (disclosed as generous), 1.0 ACH, half-ellipse 10'×8'×20' geometry

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

CoverLite 6 mm twin-wall, U-0.62/R-1.61 center-of-glazing (same datasheet as the seeded 10×20 kit), zero thermal-bridging penalty for the steel frame — deliberately generous. Airtightness baseline 1.0 ACH, the methodology's dome baseline. Half-ellipse geometry, 14′ span × 9′ ridge × 28′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, matching the seeded kit's basis. Corrections welcome.

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

CoverLite 6 mm twin-wall, U-0.62/R-1.61 center-of-glazing (same datasheet as the seeded 10×20 kit), zero thermal-bridging penalty for the steel frame — deliberately generous. Airtightness baseline 1.0 ACH, the methodology's dome baseline. Half-ellipse geometry, 20′ span × 12′ ridge × 50′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, matching the seeded kit's basis. Corrections welcome.

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

CoverLite 6 mm twin-wall, U-0.62/R-1.61 center-of-glazing (same datasheet as the seeded 10×20 kit), zero thermal-bridging penalty for the steel frame — deliberately generous. Airtightness baseline 1.0 ACH, the methodology's dome baseline. 30×48 is a standard commercial-grade arched footprint; half-ellipse geometry, 30′ span × 12′ ridge × 48′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, matching the seeded kit's basis. Corrections welcome.

Glazing solar transmittance 0.80 (decimal, normal incidence) — the twin-wall polycarbonate class figure Growing Spaces publishes at approximately 80% in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Single glass; U-1.15, Bartok's single-layer value (Greenhouse Management engineering tables), zero frame or lap-seal penalty — generous to lapped single glazing. Airtightness baseline 1.0 ACH, the methodology's dome baseline (older glass houses commonly run leakier). Gable geometry, 12′ × 20′, 5′ sidewalls, 3′ ridge rise; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 25 years (industry-cited 20–30 year range for glass structures). Corrections welcome.

Glazing solar transmittance 0.91 (decimal, normal incidence) — the midpoint of the 90–92% single-pane glass range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a glasshouse is credited materially more solar gain per square foot of growing area than the dome — the transmission advantage the same page describes, priced here without the diffusion penalty it also describes. No angle-dependent optical adjustment is applied to either structure.

Single glass; U-1.15, Bartok's single-layer value (Greenhouse Management engineering tables), zero frame or lap-seal penalty — generous to lapped single glazing. Airtightness baseline 1.0 ACH, the methodology's dome baseline (older glass houses commonly run leakier). Gable geometry, 16′ × 30′, 5′ sidewalls, 6′ ridge rise; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 25 years (industry-cited 20–30 year range for glass structures). Corrections welcome.

Glazing solar transmittance 0.91 (decimal, normal incidence) — the midpoint of the 90–92% single-pane glass range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a glasshouse is credited materially more solar gain per square foot of growing area than the dome — the transmission advantage the same page describes, priced here without the diffusion penalty it also describes. No angle-dependent optical adjustment is applied to either structure.

Single glass; U-1.15, Bartok's single-layer value (Greenhouse Management engineering tables), zero frame or lap-seal penalty — generous to lapped single glazing. Airtightness baseline 1.0 ACH, the methodology's dome baseline (older glass houses commonly run leakier). Gable geometry, 21′ × 48′, 6′ sidewalls, 5′ ridge rise; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 25 years (industry-cited 20–30 year range for glass structures). Corrections welcome.

Glazing solar transmittance 0.91 (decimal, normal incidence) — the midpoint of the 90–92% single-pane glass range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a glasshouse is credited materially more solar gain per square foot of growing area than the dome — the transmission advantage the same page describes, priced here without the diffusion penalty it also describes. No angle-dependent optical adjustment is applied to either structure.

Double 6-mil poly, air-inflated; U-0.70 per Bartok's greenhouse engineering tables (Greenhouse Management), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. Gothic profile approximated as a half-ellipse, 12′ span × 7′ ridge × 20′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; film carries a 4-year UV warranty and replacement cost is not modeled — both favor the tunnel. Corrections welcome.

Glazing solar transmittance 0.77 (decimal, normal incidence) — two 6-mil film layers at the single-film figure Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing (85–90%, midpoint 0.88): 0.88 × 0.88 = 0.77, consistent with the 76–80% commonly cited for inflated double poly. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Double 6-mil poly, air-inflated; U-0.70 per Bartok's greenhouse engineering tables (Greenhouse Management), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. Gothic profile approximated as a half-ellipse, 20′ span × 10′ ridge × 24′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; film carries a 4-year UV warranty and replacement cost is not modeled — both favor the tunnel. Corrections welcome.

Glazing solar transmittance 0.77 (decimal, normal incidence) — two 6-mil film layers at the single-film figure Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing (85–90%, midpoint 0.88): 0.88 × 0.88 = 0.77, consistent with the 76–80% commonly cited for inflated double poly. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Double 6-mil poly, air-inflated; U-0.70 per Bartok's greenhouse engineering tables (Greenhouse Management), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. Gothic profile approximated as a half-ellipse, 20′ span × 10′ ridge × 48′ long (a standard NRCS-class tunnel footprint); full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; film carries a 4-year UV warranty and replacement cost is not modeled — both favor the tunnel. Corrections welcome.

Glazing solar transmittance 0.77 (decimal, normal incidence) — two 6-mil film layers at the single-film figure Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing (85–90%, midpoint 0.88): 0.88 × 0.88 = 0.77, consistent with the 76–80% commonly cited for inflated double poly. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Double 6-mil poly, air-inflated; U-0.70 per Bartok's greenhouse engineering tables (Greenhouse Management), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. 30×48 is a standard catalog footprint class (30′-wide gothic tunnels from Rimol, ShelterTech, GrowSpan and others); gothic profile approximated as a half-ellipse, 30′ span × 12′ ridge × 48′ long, matching the catalog-standard 12′ peak; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; film carries a 4-year UV warranty and replacement cost is not modeled — both favor the tunnel. Corrections welcome.

Glazing solar transmittance 0.77 (decimal, normal incidence) — two 6-mil film layers at the single-film figure Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing (85–90%, midpoint 0.88): 0.88 × 0.88 = 0.77, consistent with the 76–80% commonly cited for inflated double poly. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Single-layer 6-mil greenhouse film; U-1.15, Bartok's single-layer value (any single glazing — Greenhouse Management engineering tables), zero frame penalty. Airtightness baseline 1.0 ACH — the identical design baseline the methodology assigns the dome, generous to a film house. Half-circle hoop geometry, 12′ span × 6′ ridge × 16′ long; full footprint counted as growing area (generous — no aisle deduction). Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; 6-mil film carries a 4-year UV warranty and its replacement cost is not modeled — both assumptions favor the hoop house. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence) — the midpoint of the 85–90% polyethylene-film range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. This is the highest transmittance of any published comparison preset, and the Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a film house is credited materially more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Single-layer 6-mil greenhouse film; U-1.15, Bartok's single-layer value (Greenhouse Management engineering tables), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. Half-circle hoop geometry, 20′ span × 10′ ridge × 24′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; 6-mil film carries a 4-year UV warranty and its replacement cost is not modeled — both favor the hoop house. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence) — the midpoint of the 85–90% polyethylene-film range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. This is the highest transmittance of any published comparison preset, and the Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a film house is credited materially more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Single-layer 6-mil greenhouse film; U-1.15, Bartok's single-layer value (Greenhouse Management engineering tables), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. Half-circle hoop geometry, 20′ span × 10′ ridge × 48′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; 6-mil film carries a 4-year UV warranty and its replacement cost is not modeled — both favor the hoop house. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence) — the midpoint of the 85–90% polyethylene-film range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. This is the highest transmittance of any published comparison preset, and the Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a film house is credited materially more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Single-layer 6-mil greenhouse film; U-1.15, Bartok's single-layer value (Greenhouse Management engineering tables), zero frame penalty. Airtightness baseline 1.0 ACH — the methodology's dome baseline, generous to a film house. 30′-wide round-profile houses are a standard farm catalog class; half-circle hoop geometry, 30′ span × 15′ ridge × 48′ long; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 15 years is the frame; 6-mil film carries a 4-year UV warranty and its replacement cost is not modeled — both favor the hoop house. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence) — the midpoint of the 85–90% polyethylene-film range Growing Spaces publishes in Glass vs. Polycarbonate Greenhouse Glazing. Transmittance is never derived from the U-value: the two measure different properties. This is the highest transmittance of any published comparison preset, and the Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so a film house is credited materially more solar gain per square foot of growing area than the dome. No angle-dependent optical adjustment is applied to either structure.

Single-wall rigid polycarbonate panels (big-box wood-frame kit class); U-1.15, Bartok's single-layer value for any single glazing (Greenhouse Management engineering tables), zero frame or joint penalty — generous to a panelized wood kit. Airtightness baseline 1.0 ACH, the methodology's dome baseline (panelized kits commonly run leakier). Gable geometry, 10′ × 12′, 5′ sidewalls, 2.5′ ridge rise; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, assumed parallel to the steel kit basis for an outdoor softwood frame. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence). Clear single-wall rigid polycarbonate is the one glazing class Growing Spaces' Glass vs. Polycarbonate Greenhouse Glazing comparison does not quantify directly; 0.88 sits inside that page's single-glazing bracket (film 85–90%, single glass 90–92%) and matches the 86–90% clear polycarbonate panel datasheets publish. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. Flagged for source review: this value rests on the panel-class bracket rather than a single published Growing Spaces figure. Corrections welcome.

Single-wall rigid polycarbonate panels (big-box wood-frame kit class); U-1.15, Bartok's single-layer value for any single glazing (Greenhouse Management engineering tables), zero frame or joint penalty — generous to a panelized wood kit. Airtightness baseline 1.0 ACH, the methodology's dome baseline (panelized kits commonly run leakier). Gable geometry, 12′ × 16′, 5′ sidewalls, 3′ ridge rise; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, assumed parallel to the steel kit basis for an outdoor softwood frame. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence). Clear single-wall rigid polycarbonate is the one glazing class Growing Spaces' Glass vs. Polycarbonate Greenhouse Glazing comparison does not quantify directly; 0.88 sits inside that page's single-glazing bracket (film 85–90%, single glass 90–92%) and matches the 86–90% clear polycarbonate panel datasheets publish. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. Flagged for source review: this value rests on the panel-class bracket rather than a single published Growing Spaces figure. Corrections welcome.

Single-wall rigid polycarbonate panels (big-box wood-frame kit class); U-1.15, Bartok's single-layer value for any single glazing (Greenhouse Management engineering tables), zero frame or joint penalty — generous to a panelized wood kit. Airtightness baseline 1.0 ACH, the methodology's dome baseline (panelized kits commonly run leakier). Gable geometry, 12′ × 24′, 5′ sidewalls, 3′ ridge rise; full footprint counted as growing area. Thermal capacitance scaled from the seeded kit's declared 420 BTU/°F by interior volume. Service life 12 years, assumed parallel to the steel kit basis for an outdoor softwood frame. Corrections welcome.

Glazing solar transmittance 0.88 (decimal, normal incidence). Clear single-wall rigid polycarbonate is the one glazing class Growing Spaces' Glass vs. Polycarbonate Greenhouse Glazing comparison does not quantify directly; 0.88 sits inside that page's single-glazing bracket (film 85–90%, single glass 90–92%) and matches the 86–90% clear polycarbonate panel datasheets publish. Transmittance is never derived from the U-value: the two measure different properties. The Growing Dome's 16 mm multi-wall glazing is published at approximately 65% on the same page, so this structure is credited more solar gain per square foot of growing area than the dome. Flagged for source review: this value rests on the panel-class bracket rather than a single published Growing Spaces figure. Corrections welcome.