When building green and healthful places, small skirmishes sometimes occur over those glassy things we call windows. For example, daylighting is known to improve occupant moods and increase worker productivity. But solar gain in summer or heat loss in winter force energy-conscious designers to wrestle with building fenestrations. Add to this the extraordinary demands of Passive House and net-zero standards. Such stringent construction standards influenced REHAU’s System 4500, an architectural window and door line that achieved a CW rating, which places the highest requirements on windows for performance factors relating to wind and water penetration. These windows can be used in high-rises and have a wide scope of commercial-building applications, but the system is equally at home in single-family construction.
In a Passive House, the 4500’s durability also translates into versatility. Defined by the tightest of envelopes, Passive Houses perform best when windows are operable. During warmer months, open windows provide cross ventilation that is less resource-intensive than mechanically forced air. (Standard air exchanges in most temperate-climate Passive House projects are designed for colder months.) The 4500 series windows have a tilt-and-turn design that conveniently allows
occupants the option of a tip-in or gate-style opening.
Condensation, another problem in tightly enclosed environments, is less an issue with the new 4500 series. The condensation resistance factor (CRF) is 70 or higher, surpassing standard aluminum commercial windows that generally score in the 50s. Other performance features include a compression seal sash, multipoint locking hardware that ensures safety and insulation, and sound-abatement properties, earning it an enviable 43 sound transmissions class (STC) score.