After covering thermal transmittance U and resistance R of opaque assemblies, and insulated glass, we now cover one of the most critical areas of the thermal envelope: window frames. Good windows are the cornerstone of a performing building for both comfort and energy efficiency, specially if it is a passive house.
Insulated glass units, IGU for short, have been around for a long time. These elements are of primary importance for the energy balance of highly performing buildings and passive houses: that is why we dedicate this article to the thermal transmittance of insulated glass.
To achieve thermal comfort and energy efficiency in buildings, a primary role is played by the thermal envelope: this is required to thermally decouple the indoor environment from the ever-changing external conditions, both in summer and in winter. The structures of the thermal envelope need to be able to control the amount of heat migrating through them: the thermal resistance and the thermal transmittance are two ways to describe this phenomenon.
The lambda value of a material indicates its ability to transfer heat: this property is therefore very important in the design of highly performing buildings and passive houses. The information commonly available is unfortunately quite confusing: with this article, we'll try and shed some light on the topic.
For new builds as well as energy retrofits, worldwide the construction industry is shifting more and more towards zero energy buildings and Passive Houses. With the thermal envelope becoming more and more advanced, the correct evaluation of thermal bridges becomes critical: with this article, we explain the PSI value.
Among the many parameters than play a role in the thermal behavior of a building, whether or not it is built to be a Passive House, the time constant is one of the least known ones. Nontheless, this parameter influences the way a building responses to changes in internal and external conditions, and therefore it is has a very important role in the correct operation of the building and its heating/cooling system.