Passive solar design is nothing new--vernacular builders have known its principles for millenia. From the Middle East to China, both rich and poor alike have traditionally used the sun’s free energy for comfort.
Western architects, on the other hand, often seem to have considered themselves above designing with the sun in mind. American colonial houses, with their foursquare symmetrical facades, already hint at the New World’s general unconcern for solar orientation. Perhaps this is because many of our forebears from England, Holland, and other sun-challenged Northern European countries seldom found sunlight worth bothering about.
Ironically, though, it was modernist architects, who claimed to put rational design above all else, who set a low point in concern for solar orientation. Aside from Frank Lloyd Wright and a handful of others who were uncommonly attuned to nature, modernist architects seemed barely to acknowledge that the sun existed except as a means of casting dramatic shadows. In their determination to discard all vestiges of the architectural past, it seems, the modernists also discarded traditional building wisdom gleaned over millenia.
Hence, modernist icons such as Mies van der Rohe’s famed Farnsworth House featured exterior walls entirely of glass, pointedly flouting millenia of common sense for the sake of aesthetic purity. In such houses, the unfortunate owners roasted in summer, and in winter sent countless BTUs fruitlessly to their doom. This same sense of aloofness from nature produced modernist apartment buildings with whole facades of balconies facing north, all predictably dark and uninhabited except by stored bicycles.
As thousands of years of vernacular building are once again confirming to our newly-green generation of architects, nothing is more necessary to a home’s livability than careful solar orientation. For buildings designed from scratch, this demands an awareness of exactly where and when sun will enter during the course of the day, taking into account not only theoretical sun positions but also man-made barriers such as neighboring buildings.
Some rooms, such as breakfast rooms (and for the hard-to-rouse, bedrooms) should receive sun during the morning hours, and therefore require an easterly exposure. Rooms that are used throughout the day, such as living rooms and kitchens, are best given southerly exposures. Rooms with afternoon usage, such as dining rooms, should ideally face west. Rooms that are only briefly occupied, such as bathrooms, laundry rooms, and garages should bring up the rear, receiving the least desirable northern exposures.
Beyond these basics, it’s important to acknowledge the seasonal changes in the sun’s altitude as well as the significant variations in where it rises and sets. Overlook these fine points, and you may find that a breakfast room that’s awash with light on a June morning will be sunless in the depths of December, just when you need old Sol the most.
This isn’t to say that every house should be ablaze with sunshine, though--in some climates, more sun is the last thing you want. Good solar orientation also demands an awareness of when and where you don’t want direct sun. Always bear in mind, though, that a house that gets too much sun can be easily fixed, while a house that gets too little often can't.