Passive House Design centres its philosophy on a number of key principles. These are: ensure high air tightness, provide high levels of thermal insulation and optimise internal gains by providing large high performance solar collectors (windows) in the optimal solar orientation (i.e. towards the equator).
There are often issues of summer overheating and glare for consideration in the design as a result and this is often overcome by providing shading in some for or other that does not compromise solar gain in colder periods when it is most needed.
There are often issues of summer overheating and glare for consideration in the design as a result and this is often overcome by providing shading in some for or other that does not compromise solar gain in colder periods when it is most needed.
Large windows provide extra solar heat gains but they also have a much poorer thermal performance than other building elements which is a challenge for designers looking to achieve maximum solar gains without compromising thermal comfort.
This often means that walls that are not facing the sun typically have very small windows or none at all resulting in a lack of daylight and outside perspective for the rooms on these sides.
A study was carried out in Gothenburg, Sweden in 2001 of 20 terraced houses built to passive standards built with large south facing windows and small north facing windows to maximise solar gain and minimise thermal loss (see below). The total floor area is 120 m², and the original window area is about 16% of this, which is more than what is recommended in the Swedish building regulations for sufficient lighting conditions.
The study ran simulations on how varying the window sizes (south reduced north increased) would affect the energy consumption and maximum power load to maintain an indoor temperature of between 23 and 26 °C. They used a simulation tool DEROB-LTH (Dynamic Energy Response of Buildings LTH) which was capable of modeling both the diffuse and direct sunlight effects on these buildings for the various window sizes as well as orientation and window type.
The simulations showed that neither the size nor the orientation had a significant influence on the heating demand in the winter, but is relevant for the cooling need in summer (see results below).
Therefore it is possible to enlarge the window area facing north and get better lighting conditions, provide more aspects for the user to view and to provide extra cooling in the summer to reduce the cooling load on the HVAC system. This means that it is possible to have greater flexibility when planning window areas and glazing layouts in low energy buildings and passive house designs.
While the results of the study are particular to more northerly situated countries (approximately 60 degrees latitude) the principal findings of the study remain applicable to passive house design where heating demand is expected to exceed cooling demand.
In conclusion over glazing can lead to increased energy demand for cooling and poor internal lighting and aspects for the user. Reducing the window area for solar collection slightly can be beneficial to summer cooling energy costs, lighting and views without compromising on winter head demand.
In conclusion over glazing can lead to increased energy demand for cooling and poor internal lighting and aspects for the user. Reducing the window area for solar collection slightly can be beneficial to summer cooling energy costs, lighting and views without compromising on winter head demand.
