The “Green House” of the Past- and the Future

Posted by at 4:17PM

I came across this graph showing where energy is used in an average American home:

The Heating and Cooling costs (and CO2 emissions) are clearly the most substantial portion of household energy use. Homeowners who wish to reduce their emissions, therefore, should start here. Fortunately, a fairly easy solution exists for individuals who are designing and building their own home: Passive Solar Design
Passive solar design is based on two main principles: the tilting of the earth on its axis, and utilizing thermal mass to maintain an ideal temperature in the house.

Tilting of the Earth:
A passive solar house is built with its longest side facing directly (or as close as possible) south, and is covered in windows. During the summer, the sun is high in the sky over the house, and so direct sunlight does not shine through these windows, which would quickly over-heat the house. However, in the winter time, the sun is low in the sky and does shine through the windows, adding much needed heat.
Thermal Mass:
When the sunlight shines through the southern windows in the winter, it heats up the house. This heat would quickly escape, however, without some sort of substance to “trap” it: thermal mass. This thermal mass can be cement, tile, brick, water, etc. and should be placed close to the southern windows, so the direct sunlight heats it up efficiently. The thermal mass will then slowly release the heat after the sun goes down, keeping the house closer to an optimum temperature. During the summer, the thermal mass acts in the opposite direction- it cools off during the night (especially if you remember to open the windows) and slowly lets of the cool during the day.
I grew up in a passive solar house that my father designed- when my friends came to visit, they would always look in amazement at the rows of glass bottles filled with colorful water lining my living room, and at the long row of windows that cover almost the entire south wall of my house. I loved all the natural light that we got from the windows, and my mom grew an astonishing number of houseplants that thrived even in the winter. The most impressive part, however, I did not realize until I was in a high-school class comparing energy bills with my classmates. It only cost between $200-$300 a year to heat and cool my home, much lower than anyone else’s.
I should clarify- I’m from Montana, where temperatures in the single digits and below zero are fairly common on winter nights, and the summers are generally in the mid-to-upper 80s, with several weeks in the upper 90s. Despite these temperatures, it only cost $200-$300 a year to heat my home, and we never needed an AC.
According to one site, homeowners can cut their energy bills by up to 25% simply by placing the majority of their windows on the south side of their house. Homes that are designed to be passive solar can reduce heating costs by up to 70%.
This design is so simple, and so easy to implement, that every new home that will get any southern sunlight should be build using these guidelines. Except perhaps in CA, where the tilting of the earth seems to make no difference- how can we call it winter without any snow?



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