An attached greenhouse is a great feature in any permaculture design because it serves so many functions. Your greenhouse can become not only a growing space but also a living space.
An attached greenhouse:
- provides a protected environment for growing seedlings
- extends the growing season into cooler months
- provides shade through hot months and shelter from extreme weather events (e.g. frost, hail, wind)
- controls the growing environment (e.g. irrigation, beneficial insects, nuisance animals).
To begin, work out how you will use your attached greenhouse – is it mostly for gardening or is it to warm or extend domestic space?
Design considerations for your attached greenhouse
Slope; orientation; location of services (power, water, drainage); altitude and latitude; climate and weather (e.g. prevailing winds); space available; access to garden and relevant features (e.g. location of compost); potential for shading (of and by it); and fire risk.
This will limit size possible and choice of materials; using standard dimensions is economical; attached greenhouses can be cheaper than freestanding ones.
Influenced by the architectural character of the house or other buildings (e.g. overall shape, proportions).
Active and passive features required (to store heat, screen, ventilate and circulate air); choice and availability of materials (including recycling/reuse of timber, windows and doors, paving); hygiene (how will you clean it?).
Personal and practical
A layout to fit your gardening style, tool use, physical circulation (e.g. to move a wheelbarrow) and storage needs; the sorts and size of plants you want to grow; time of day/year you will be active there – do you need supplementary lighting?; your interests – do you want somewhere to eat breakfast, read a book or entertain?
Construction and materials
When constructing a greenhouse there are a few essentials to consider:
Temperature control is critical as plants will suffer from extremes. Thermal mass stores heat from the sun during the day and radiates it out to warm the space overnight. It can be included in floors and walls with either concrete, bricks, mudbrick or similar blockwork, or movable, this might be black water-filled plastic containers or ponds.
Most glazed surfaces will allow heat to leak out of the greenhouse in cold weather unless you insulate them with blinds, shutters or foam panels.
Ventilation is also critical and requires intelligent placement of openings. Air rises when it’s hot, so include openings high up to suck hot air out of the space, and low to suck cooler air from outside. Air circulation within the space also matters, to even out temperatures and manage moisture and moulds.
You will be able to pick up most things you need second-hand. Using old windows and glass doors is probably the most economical way to build. When designing your attached greenhouse and choosing materials be sure to consider the extent of warming or cooling required; the likelihood of strong winds or storm events; and budget.
Foundations and flooring will vary with style, and may be integrated with a slab floor or you could choose a surface of pavers, gravel or earth or even coverings (e.g. matting).
Walls and roof
When choosing roof and wall materials you need to consider:
- glass (types and thicknesses) or synthetics (e.g. macrolon, fibreglass, acrylic, polycarbonate, polyethylene), reflection/ transmission/diffusion
- framing – structural, functional (e.g. light blocking?), character
- access doors to the house (optional), and to outside
thermal mass and insulation
- drainage within and around the structure.
Extract from, Marshall, R (2006), How to build your own greenhouse: designs and plans to meet your growing needs, Storey Publishing.