Ultra-efficient building - Using the Sun

The most efficient use of energy is to use no energy at all! With energy efficiency, you make the best of what you have by building a tight, well insulated home that utilizes natural heating, cooling and lighting as much as possible.

The use of passive solar design has been around as long as people have sought out shelter. The Anastasi cliff dwellings are classic examples of good design - they face south to take advantage of the sun for light and heat in the winter. The have large overhangs, to block the high summer sun, reducing unwanted heat in the summer. And, being built into cliffs, they are surrounded by a mass of earth, keeping the living space at a relatively constant temperature year-round.

You can take advantage of these same principles in your home to reduce your energy use. Minimize wasteful north facing windows which are cold and energy wasting in the winter. Put the majority of your windows on the south side of the house, where they can collect light and heat during the day and use ample overhangs to shade the windows during the summer.

Block unwanted heating even more by placing large deciduous trees to the south of the house to shade the windows and roof from the summer sun. This reduces the need for air conditioning by shading the home during the summer while allowing solar heating in the winter. Likewise, avoid sun-rooms or other large expanses of glass on the west side of the house where the hot afternoon sun is difficult to block and leads to excessive heating. Or, if you do have western windows, plant large shade trees to minimize the unwanted heating.


If you do take advantage of passive solar design and have good overhangs and shading to keep out the summer sun, remember that you want to let the sun's heat in during the winter. In order to do this, you do not want heat reflecting glass on the south side of your home. Most energy efficient windows today (i.e. low-e, thermal pane) are designed to reject much of the heat from the sun, defeating the purpose of passive solar design. The SHGC (solar heat gain coefficient) on the window tag is a value from 0 to 1 that indicates the fraction of the solar heat that gets through the window. For solar heating, higher SHGC is better for south facing windows.

Remember that glass is the worst building material with regards to insulation. Windows loses three to five times as much energy as the corresponding area of insulated wall. So, while beautiful, they can sap your home of energy. Careful consideration of the number and placement of windows is very important to the comfort and efficiency of your home.

Good passive solar design helps you create a much more comfortable and energy efficient home. Work with your natural resources and you'll experience reduced energy bills and a more pleasant home year round.

This article was written by Ted Inoue of Energy Testing & Consulting LLC.

Ted Inoue
Energy Testing & Consulting llc.
New Hope, PA 18938
215-760-0211
www.etccreations.com

Source:
Superior Woodcraft, Inc. Custom Cabinetry Blog
Superior Woodcraft, Inc. Website

References:
The Efficient Windows Collaborative - windows and ratings

Southern Windows: High solar gain, low-e, Argon/Krypton window specifications

Western Windows: Low solar gain, low-e window specifications