(This is the ninth in a 10-part series. The previous post is here, or you can start at the beginning.)
I will spare you the entire thought and building processes and show you what we finally decided on.
Since this is southwest orientation, my main concern was getting extra light and heat, since the winter sun does not come around to that side until late morning. I put three fixed skylights along the lowest part of the ceiling, which has worked well. The sun comes through them a few hours before it gets to the front.
In the New Hampshire house, the south facing windows were floor-to-ceiling. I wanted as much sun coming in as possible for daytime heating. Here in Taos, I wanted a planting bed close to the windows for maximum light, so the windows are in the 5′ space above the 3′ deep planting bed. In both instances there is a 1′ spacer between them for support.
Ventilation is as important as heating. Plants and people don’t like temperatures that are too hot, as much as they don’t like them cold. To keep everyone and everything comfortable, I installed:
> A glass door flanked by two double-hung windows. This allows more sun in winter and serves double duty to ventilate in summer.
> Two double-hung windows in the end wall
> Two Velux® operable skylights in the upper part of the ceiling. This is where heat will rise, which made it the most logical place for a moveable vent. Air moves in through the windows carrying the heat out of the top vents. Moving air is cool air, so opening the windows and the vents cools off the greenhouse, even if it is hot outside.
The soil in the bed is to be part of the thermal mass. It will absorb the sun’s heat to keep the temperature levels even and keep the plants warm. The concrete floor and an adobe-lined wall on the northern side are also mass that will absorb sun and ambient heat to radiate back out at night.
The ceiling is super insulated, and exterior doors lead into the four rooms of the house. There is no supplemental heat in the greenhouse. In the event there are many cloudy days in a row or old-timey winter temperatures of 40 below, I will sacrifice the plants as the greenhouse gets cold, but the heat in the other rooms will not be lost. The girls have small gas heaters in their rooms for the coldest days and nights.
The work was done enough by Thanksgiving to start seeing the benefits. My fuel bills that following winter were half of what I’d been used to paying. I cut my wood consumption by half with the new ceiling insulation and double pane windows, and my natural gas bill was about $40 a month at it’s peak with the girls using their heaters.
Come spring, I got an energy audit and a surprisingly good HERS (Home Energy Rating System) score.
(Originally published at www.greenbuyguide.com.)
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March 25 – Broccoli, kale and lettuces have sprouted! It took four days. I love those 
April 10 – The greenhouse was 53 degrees this morning. That is wonderful! Warm weather seedlings, like tomatoes (right), do not like temps below 50, so they are happy. The cool weather plants like greens and broccoli don’t mind. They are actually the plants that grow all winter long – slowly, due to short days and the cold, but they grow. You need to plan ahead for winter harvest, more plants to get enough food, since they produce so slowly.
The beet greens (left) took off with a bit of organic nitrogen fertilizer a while back, so I chopped them down for breakfast this morning. Always harvest in the morning when the plants are fresh. During the day, they are working hard sucking up water and putting out new growth. They can be wilted to save water. They are tired by the end of the day, just like you, so plan for morning harvest and storage.
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