Well I like the idea of the natural way to heat a greenhouse:
it best utilizes what the greenhouse offers
not to mention it the cheapest rout to go :).
Here's a video that illustrates how solar rays are naturally trapped in the greenhouse.
And I promise you that you won't forget it. The song will be playing in your head for sometime to come:).
The basic concept, of how the suns rays naturally produce greenhouse solar heat, is illustrated pretty wellin that video.
In a nutshell:
the sun's rays are able to enter into the greenhouse throughthe glazing.
The heat from the solar rays will get trapped in any Thermal Masses that arein the greenhouse (eg. water barrels, and large stones or cocrete ), and radiat the heat when it gets colder out, like at night time.
Being able to take advantage of the natural ability of the greenhouse, greatly cuts downon heat loss as well as any heating expenses.
There are a few things that can be done to maximize the natural ways to heat a greenhouse:
Make sure that the Greenhouse is air tight, no drafts.
Create Thermal Mass
Put the greenhouse in the right location
Short and Long wavelength Rays?:
Short Wave rays from the sun are transmitted through the glazing.
Long wavelength rays are not able to escape the glazing, so theybounce back and stay trapped inthe greenhouse, bouncing back and forth untillthe heat is lost from the colder temperatures.
That's why having the most thermal mass built into the design of the greenhousewill help with keeping the temperature up.
Including the other points like sealing up the greenhouse to prevent drafts, willgreatly increase the natural way to heat a greenhouse that is true solar heating.
Pit Greenhouses, they make great solar greenhouse, and are a great way to store thermal heat. They are built rightinto the ground so there is lots of thermal mass to store the heat energy.
So What are some of the other things that are important to Greehouse gardening?