天窗有多种形式，从廉价的塑料圆顶到可操作的屋顶窗户(可兼作屋顶紧急出口)。即使是最基本的天窗也允许日光进入室内空间，否则就必须用电照明。开和关的天窗还有一个额外的好处，那就是可以把上层房间的不透气空气排出去。根据它们的放置方式，天窗也可以提供很棒的户外视野。天窗玻璃有塑料和各种玻璃两种。塑料，通常是丙烯酸或聚碳酸酯，比玻璃便宜，但它不像玻璃那样抗划痕，长时间暴露在阳光下后，它可能会变得脆弱和褪色。聚碳酸酯具有更高的抗冲击性能，比丙烯酸贵。塑料天窗被制造成各种各样的形状——圆顶、矩形、圆形、椭圆形和三角形——这些都是很难用玻璃复制的。更昂贵的天窗是用玻璃制造的，制造商现在提供了各种各样的玻璃选择。这在为特定的屋顶位置或特定气候区选择天窗时很有用。 Skylights are manufactured by many companies, although there are only a few national players. The residential market for off-the-shelf skylights is dominated by Velux, a Danish company. Maine-based Wasco claims a distant second place. Other manufacturers, such as Tam, Columbia,and Sun-Tek, are stronger regional forces. Fakro, is a major European manufacturer but it hasn’t made serious inroads in the U.S. to date. Three major window manufacturers ( Andersen, Marvin and Pella) have dropped out of the skylight business in recent years as the industry consolidated. In addition to mass-marketed residential skylights, there’s also a booming trade in high-end custom skylights for residential as well as commercial buildings. Wasco considers itself the leader in that field. Matching…