Earthbags are ideal for building greenhouses due to their resistance to moisture damage. Most anyone can build with earthbags, which can cut construction costs. When filled with insulation such as perlite or scoria, earthbag walls and foundations enable you to grow plants year-round.
Excess heat from a greenhouse attached to your home, like the one pictured below, can be vented into the main living space to reduce energy costs. In the summer the excess heat can be vented outdoors. This plan uses standard patio door replacement glass to reduce costs and is easy to extend lengthwise.
Plans for this earthbag greenhouse can be purchased from Dream Green Homes.