How much does a passive solar greenhouse cost on Vancouver Island?

Swell's shell builds range from approximately $8,000–$15,000 for the starter (8×12ft), $18,000–$35,000 for the family size (12×24ft), and $45,000–$75,000 for the production size (16×40ft), installed. Free quotes across Vancouver Island.

Can I grow year-round in Campbell River in a passive solar greenhouse?

Yes. Cold-hardy crops — kale, spinach, lettuce, carrots, herbs — grow year-round in a well-designed passive solar greenhouse on Vancouver Island. Frost-sensitive crops get 6–8 extra weeks each end of the season. Key requirements: 16mm+ polycarbonate glazing and adequate thermal mass (water barrels).

What glazing do you recommend for a BC greenhouse?

We use 16mm triple-wall polycarbonate as our minimum and 25mm five-cell as our preferred spec. Polycarbonate diffuses light better than glass — important on Vancouver Island's overcast days — and handles hail and snow without cracking. We don't use single glass as primary glazing.

What's the best roof pitch for a greenhouse on Vancouver Island?

We build at 50–60°. This sheds rain and snow, and captures both direct winter sun and diffuse light on cloudy days. The theoretical optimum for clear climates at our latitude is about 65°, but our overcast coast benefits from a slightly shallower pitch that catches more diffuse light.

Do I need a permit for a greenhouse in BC?

Structures over 10 m² (about 107 sqft) generally require a building permit. Our starter size (8.9 m²) may be exempt. Family and production sizes typically need permits. We handle permit research as part of the quoting process.

Passive Solar Greenhouse Planner — Year-Round Growing on Vancouver Island

Greenhouse Planner

Size Selector

Choose from three standard shell sizes with proven cut lists. Dimensions are internal. All sizes use a 55° south-facing glazed slope, optimised for Vancouver Island's overcast climate.

Starter

8 × 12 ft

96 sqft / 8.9 m²

Glazing area: 4.5 m² south face
Peak height: 10 ft (3.0 m)
Knee wall: 3 ft
Rafter length: 13.9 ft
Aspect ratio: 1.5:1
Thermal mass: 450 L (3 barrels)
Vent count: 1 roof vent
For: 1–2 people, herbs + greens

Family

12 × 24 ft

288 sqft / 26.8 m²

Glazing area: 11.1 m² south face
Peak height: 12 ft (3.7 m)
Knee wall: 4 ft
Rafter length: 20.9 ft
Aspect ratio: 2:1 ✓
Thermal mass: 1,110 L (6 barrels)
Vent count: 3 roof vents
For: Family of 4, year-round salad

Production

16 × 40 ft

640 sqft / 59.5 m²

Glazing area: 23.8 m² south face
Peak height: 14 ft (4.3 m)
Knee wall: 4 ft
Rafter length: 27.9 ft
Aspect ratio: 2.5:1 ✓
Thermal mass: 2,380 L (12 barrels)
Vent count: 6 roof vents
For: Market garden, small CSA

Swell passive solar greenhouse — shed roof, polycarbonate south wall, metal-clad insulated north wall, green wood frame, Vancouver Island setting

Select a size above to see full calculated specs. All sizes can be quoted with custom dimensions — contact us for custom sizing.

Solar Gain Calculator

Compare monthly solar gain against heat loss to find which months need supplemental heat. All calculations use real Vancouver Island solar data and the Rob Avis passive solar formulas.

Location

Glazing type

Glazing area (m²)

Auto-filled from Size Selector. Starter: 4.5 m² | Family: 11.1 m² | Production: 23.8 m²

Target inside temp (°C)

Mode 1 (no freeze): 15°C. Mode 2 (season extension): 10°C. Drives heat loss calculation.

Monthly solar gain vs. heat loss (kWh/day)

Month	Sun hrs/day	Avg low °C	Solar gain kWh/day	Heat loss kWh/day	Net balance kWh/day

Glazing Comparison

All five glazing types compared side by side. Data from Rob Avis / Verge Permaculture and 2025 Vancouver Island pricing. Swell builds with 16mm triple-wall polycarbonate minimum and 25mm five-cell as our preferred spec.

Property	8mm Twin-wall Poly Budget	16mm Triple-wall Poly Recommended	25mm Five-cell Poly Preferred	Double Low-E Glass	Single Glass Not Recommended	PE Film Double Inflated
R-value	R-1.8	R-2.6	R-3.2	R-4.0	R-1.0	R-2.0
U-value (W/m²K)	3.6	2.5	2.1	1.8	5.8	3.5
SHGC	0.58	0.48	0.45	0.40	0.86	0.70
Light transmission	90%	72%	79%	72%	90%	84%
Light quality	Diffused	Diffused (better for plants)	Diffused (better for plants)	Clear + low-E coating	Direct — hot spots	Diffused
Cost/m² installed (CAD 2025)	$45–$75	$97–$151	$130–$185	$215–$430	$80–$140	$5–$11 + fan $200–$400
Lifespan	15 yr (warranty)	15–20 yr	20–25 yr	25–40 yr	20–30 yr (with maintenance)	3–5 yr (film only)
Hail resistance	Good	Excellent	Excellent	Good (tempered)	Poor — shatters	Good (film, repairable)
Snow load performance	Good — 25 lbs/sqft rated	Excellent — sheds well	Excellent — sheds well	Good	Risk of cracking under load	Good (flexible)
Condensation drip	Moderate (channels to edge)	Minimal (channels to perimeter)	Minimal (channels to perimeter)	Moderate	High — drips on plants	Low (anti-drip coating available)
Best for	Budget Mode 2 — mild coastal VI	Mode 2 standard — most VI builds	Mode 1 preferred — year-round	Premium permanent builds	Do not use as primary glazing	Temporary or production hoophouse

Local VI supplier: 8mm twin-wall polycarbonate is available from GreenhousePlastics.ca with free delivery Victoria to Nanaimo. 4×8 sheets from $96 ($86.40 in 10-packs). This is the most affordable polycarbonate option on Vancouver Island — good for Mode 2 / 3-season builds. For year-round (Mode 1), upgrade to 16mm or 25mm for the higher R-value.

Why polycarbonate outperforms glass on Vancouver Island: Our coast is overcast 60–70% of winter days. Polycarbonate diffuses light, spreading it evenly across all leaf surfaces — critical for photosynthesis in low-light conditions. Glass creates direct-beam hot spots and cold gaps. Polycarbonate also withstands hail and snow impact without shattering, handles thermal expansion across large panels, and weighs significantly less, reducing rafter loads.

Minimum transmissivity rule: Do not use any glazing below 70% light transmission as primary greenhouse glazing. Below this threshold, plants become leggy, photosynthesis slows, and yields drop significantly. Both 16mm and 25mm polycarbonate meet this threshold. Single glass at 90% transmits too much direct heat in summer, causing overheating and blossom end rot.

Cost Estimator

Shell build cost estimates for three standard sizes. Costs are in CAD at 2025 Vancouver Island market rates. Interior fit-out (soil, beds, irrigation) is listed separately as add-ons below.

Greenhouse size

Auto-filled from Size Selector if you selected a size there.

Foundation type (Budget tier)

Estimates include 12% contingency. Permit fees ($500–$2,000), design fees if applicable, and BC PST/GST are additional. Contact us for a site-specific quote — Swell builds across Vancouver Island.

Popular interior add-ons

Not included in shell scope — select to calculate your add-on total.

Selected add-ons total $0

Season Extension Calendar

Select your location and crops to see a colour-coded 12-month growing calendar. Mode 1 gives year-round production for cold-hardy crops. Mode 2 adds approximately 6 weeks each end of the outdoor season.

Location

Select crops to display

Prime growing (outdoor + greenhouse)

Greenhouse only (extended season)

Marginal / cold frame

Not growing

Passive Solar Greenhouse Planner

Start here — what's your goal?

Greenhouse Planner

Size Selector

Calculated specifications

Solar Gain Calculator

Monthly solar gain vs. heat loss (kWh/day)

Glazing Comparison

Cost Estimator

Popular interior add-ons

Season Extension Calendar

Get a Free Greenhouse Quote