Are you looking for an even more environmental way to stay eco-friendly?  Perhaps your best bet would be to invest time and money in an earth-sheltered greenhouse.  They're relatively simple to construct and are especially useful for those seeking an almost all natural option for their year-round plants.

These greenhouses are so named because of their position underneath the earth.  They're the direct descendant of "grow holes", three foot ditches filled with a layer of fresh manure, a layer of topsoil, and a layer for the comfortable growth of vegetables.  These greenhouses have gone through a couple permutations in order to get the perfect combination of sun, soil, and energy.  The latest is the earth-sheltered solar greenhouse.

These houses use a simple glass or wooden framed pane set at an angle to allow the ideal amount of sun during the day for plants --that means as the sun sets, the plant is still able to get the most out of the sun because the angle of the glass provides a great refraction from the sun's rays to the plants.

These solar greenhouses are also ideal for keeping plants safe in inclement weather.  As they get their nutrients from the earth, their roots are never fully in danger of being deprived their necessary food.  With the glass covering the plants are equally able to be shielded from heavy rains, heavy winds, and frost.  Because these greenhouses are basically solar powered, the amount of energy necessary to keep plants alive is drastically minimized, thus preserving the goal to remain green while never sacrificing the quality of life your plants will receive.

The brilliance of the earth-sheltered solar greenhouse is its ability to remain motionless throughout the year and still provide your plants the ideal weather they need all year long.  One can't disregard the environmental advantages to using the earth as the ultimate greenhouse.  Plants that are grown in the ground without the interference of pottery or cramped shelving are more likely to bear incredible fruit (or vegetables) and flowers.  

Their roots are allowed to grow outwards as much as they need to absorb the nutrients in the soil and there is less competition between plants to get the amount of food they need to thrive.  Perhaps the most noticeable advantage is the fact that there isn't a polyethylene or aluminum piece in sight.  Wood, being the most versatile building media, allows breath-ability and provides the perfect shelter for your plants.  

Fiberglass is an economically feasible expense that will ensure that your plants are given the amount of sun they need to thrive.  This lowers the cost of supplies, the amount of foreign objects exposed to the soil, and the aches of building a house that may or may not withstand the trials of inclement weather.