How to design a greenhouse

Types of greenhouses; choosing a site; installation. First decide on the type and size of structure you want and how much money you’re willing to spend. To provide for expansion, plan for more space than you anticipate using at first. Check with your local building department about permits and other regulations (see Building perm its).

Ready-to-assemble kits come in a variety of styles from window greenhouses to fully equipped, freestanding structures. Examine as many dealers’ catalogs as possible. If you want a nonstandard size or if your property has special problems, you may need a custom-built greenhouse. Or consider building it yourself. Types and materials

The two basic types of greenhouses are the lean-to, erected on a balcony or against a house wall, and the freestanding. The latter gives you more growing space and is more easily located to take advantage of sunlight. A

Lean-to is usually cheaper, can be hooked into existing house utilities, and is less exposed to wind and weather. It can also provide additional household heat and living space (see Solar greenhouses).

Aluminum and wood are the most common framing materials. Aluminum is lightweight, durable, and maintenance free. Wood is cheaper and retains heat better but requires
maintenance. The most popular glazing material is still glass. Sheet plastics are cheaper, but short-lived. If you don’t mind a translucent surface, consider rigid fiberglass. It’s expensive but very strong and weather resistant and retains heat better than glass. Abed of gravel over an earthen floor provides good drainage; add slate, tile, or wood-slat walkways. Choosing a site

A greenhouse should get as much light as possible, especially in the winter. Attach a lean-to to a south-facing wall; orient the long axis of a freestanding greenhouse east to west. Pick a site for the greenhouse that’s protected from winter winds by trees, a fence, or buildings. A nearby deciduous tree will provide shade in the summer; avoid obstructions that can block light in winter. The site should be level, well drained, and convenient to a source of water and electricity. Run utility lines to the site before putting up the greenhouse. Installation

Kit manufacturers usually provide foundation plans and installation instructions. In a mild climate, a small, lightweight greenhouse can rest on a sill secured to the ground with tie rods. In colder climates, foundation footings of poured concrete must extend below the frost line (see Footings and foundations).

Greenhouse furnishings

A freestanding greenhouse requires its own thermostat-controlled heating system; ask the company that sold you the greenhouse to recommend a unit of the right size and type. If your home has unused heating capacity and if you can set up a separate heating zone, you may be able to warm an attached greenhouse by extending the home system to it.

One or more roof vents, preferably with an automatic opener, is essential for maintaining proper temperature. Other vents may be located on the side walls. In some automatic systems, a thermostat-controlled fan circulates air. In case there is a power or equipment failure, install a battery
powered alarm to warn of sudden changes in greenhouse temperature.

Roller blinds on the outside of the roof are an efficient way to shade a greenhouse. Rain-resistant shading paint applied to the outside of the glass is also effective and cheap; wipe it off when it is no longer needed.