[spasticgoat]

I've been doing research on greenhouse building methods, especially methods for heating a greenhouse. I found some of these great tips...

MATERIALS
Finding materials is not usually a difficult process. Keep an eye on your local classifieds for windows and doors, stop in at an auction, or check in with suppliers of recycled building materials. Maybe you know someone who is ripping down an old building and has leftover materials, or you could spend the year hitting up recycling bins for bottles (invite the friends over for a few BYOB parties and collect!).

HEATING METHODS
Another consideration for greenhouses is heating. People have used a variety of methods for heating their greenhouses. You can purchase a small fan/heater combo for less than $30, but one of the most popular heating methods for a greenhouse is the “passive” approach, using materials that absorb heat during the day and omit the stored heat during cooler hours.

One of these passive methods involves the use of water. Storing 2 gallons of water in darkly painted containers (dark colors absorb more heat) for each square foot of greenhouse, collects heat during the daylight hours and then omits that heat throughout the night (just be sure you keep them away from the cold walls of the house). Water is also a great way to help add humidity.

Another method involves using rocks. Rocks are great heat absorbers (just observe a reptile sunbathing to see the warming benefits of rocks!). Bricks are also a great heat absorber, and can be painted black to absorb even more of the sun. You could try using bricks as wall dividers or even to build surfaces within the house to sit plants on.

Most importantly, you want to keep track of the temperature in the house to see how your methods are working. Don’t be afraid to experiment with a combination of methods. As long as the house is well put together and insulated, passive methods have proved successful for most homemade greenhouses.

To insulate the greenhouse floor, use a layer of pumice stone (you can dig a trench around the outside of the house and fill with stone to help insulate even further). This stone will keep frozen ground from cooling off all that stored heat you worked to create, and will also absorb and release its own heat! Be sure you seal all the cracks and divisions in the house as well.

see the full article: Building Your Own Greenhouse

Let me know if you have other suggestions or methods that have worked for you. I'm planning on trying this soon.