If you're designing a direct gain passive solar home, you will need to maintain a careful balance between two vital parts: the amount of glazing on each side of the house and the amount of thermal mass available inside to store and later release heat. Getting the glass-to-mass ratio wrong will result in too much or too little heating.
Windows & Doors
You are here
One of the aspects of passive solar house design that surprises many people is the need for shade. If your heating depends on sunlight, why would you block it? Because not all sunlight is beneficial to a passive solar home – the high summer sun, in particular, can produce far too much heat, requiring some kind of shade to stop your home turning into an oven.
One of the aspects of passive solar house design that surprised many people is the need for shade. If your heating depends on sunlight, why would you block it? Because not all sunlight is beneficial to a passive solar home – the high summer sun, in particular, can produce far too much heat, requiring some kind of shade to stop your home turning into an oven.
Windows have undergone a huge number of advances over the last few decades. While most construction methods and materials have remained the same, windows have changed from heat-sucking drafty holes to efficient light-capturing devices which help improve energy efficiency.
All parts of a window are important when you consider energy efficiency, but the glazing comes first. About 75% of a window's surface area is glazed, with the sash and frame making up the other 25%, so it is important to make the right choices for the glazing.
The glazing isn't the only part of a window that transfers heat: the sash and frame make up about 25% of an average window's surface area, so choosing energy-efficient materials and designs is important.
Traditionally, wooden sashes and frames are the most common, and this still holds true today. In fact, wooden windows are the number-one selling item in construction in the US.
When you go shopping for windows, it's easy to get confused by all the ratings and figures. Until recently, window manufacturers could rate their products almost any way they wished, which made comparisons a nightmare. Thankfully, they realized this and, in 1989, formed the non-profit National Fenestration Rating Council (NFRC) to standardize testing and rating for windows, doors and skylights.
Window technology has advanced a great deal in recent years, compared to traditional standards. Low-e coatings, double- and triple-glazing and noble gases in air space all help improve energy efficiency.
There are two parts to maximizing solar gain through windows: direct gain and indirect gain. The more obvious and common of the two is direct gain – using the sunlight that comes through the windows and heats the air and thermal mass in the home by falling directly on objects and walls.
Two alternatives to standard windows are clerestory windows – those high-up windows that sit between two levels of external roofing – and skylights. They both have their uses in passive solar design, though you have to be careful with their effects on light and heating.