Passive Houses: A New Solution to an Old Problem
A recent article in the New York times highlighted an interesting trend in green building. Passive houses, which have been gaining popularity in Europe for years, are beginning to come to the United States. These homes, built for extreme energy efficiency, utilize no more than a quarter of the heating energy required in older structures. In some cases, such as the house described in the article above, the power required is as little as one twentieth of the norm, or about the amount required to run a hairdryer. In addition, when energy needs are this low, it's relatively easy to go a step further and supply them with solar or other green power sources. Of course, the idea of using passive heating isn't new, and many of the features of passive houses would be familiar to green builders. These homes tend to have large south-facing windows to take advantage of sunlight, and extremely efficient insulation to keep heat generated by occupants and their appliances inside. There is an important new twist, however: a heat exchange system ventilates the house with fresh air, while transferring 80% of the heat from the exhaust air to the intake. This allows every other area of the building to be built tighter than ever before without becoming stuffy. In Germany, where this technology was pioneered, passive houses (and other buildings, including schools), are becoming quite popular, and they now cost only about five percent more to build. In the United States the movement is still in its infancy, but some designers, such as Nabih Tahan in the Bay Area, are already helping it to gain a foothold. Hopefully we will see many future developments in this field!