Reference Charts

The trade every glazing choice makes, stated as numbers rather than adjectives, plus what a kit is rated to survive.

• Greenhouse glazing R-value and light transmission chart R-value, U-factor, PAR light transmission and service life for twelve greenhouse glazing types, from 6 mil film to five-wall polycarbonate and insulated glass.
• Greenhouse snow and wind load ratings Snow load in pounds per square foot and wind speed ratings for common greenhouse types, what a rating does and does not promise, and the anchoring each one requires.

Output and airflow figures for a given greenhouse volume and temperature target.

• Greenhouse heater BTU chart Required heater output in BTU per hour for twelve greenhouse sizes at four temperature differentials, with the 1500 W electric limit marked and the sizing formula shown.
• Greenhouse exhaust fan CFM chart Required exhaust fan airflow in CFM for twelve greenhouse sizes using the NGMA method, with elevation and shade corrections and the passive vent area each house needs.
• Shade cloth percentage chart by crop Recommended shade cloth percentage and daily light integral target for eleven greenhouse crop groups, plus the seasonal schedule and how shade factor is actually measured.

What each crop needs, and what it will tolerate before it stops growing or bolts.

• Daily light integral targets by crop Daily light integral targets for 30 greenhouse crops in mol/m2/day, with the PPFD each one needs at 12, 16 and 18 hour photoperiods and the winter light shortfall explained.
• Germination soil temperature chart Minimum, optimum and maximum soil temperature for germinating 26 vegetables, herbs and flowers, with days to emergence at each temperature and the dormancy traps.
• Greenhouse temperature tolerance chart Survival minimum, growth minimum, optimum day and night temperature and heat ceiling for 24 greenhouse crops, with the failure each crop shows outside its range.

Dates and dimensions for laying out a season and a bench.

• Frost dates and frost-free days by USDA zone Average annual minimum temperature, typical frost windows and frost-free day counts for USDA zones 3a through 10b, plus how much a greenhouse or cold frame shifts each one.
• Greenhouse plant spacing chart Spacing, plants per square foot and plants per 4 by 8 ft bed for 26 greenhouse crops, with the reason under-cover spacing is wider than outdoor spacing.

More tables worth keeping to hand.

• Greenhouse humidity and VPD chart Vapor pressure deficit in kPa across greenhouse temperatures and humidities, with target ranges by growth stage and the dew point table that predicts condensation.