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EXTERNAL ENVELOPE
temperature within 4.2ºC of that of the surrounding space, preventing cold draughts and minimising ‘temperature asymmetry.’ This design approach not only enhances comfort, but also allows for the creation of architectural features like window seats – popular in Passivhaus properties – where occupants can enjoy views even on cold days without experiencing radiant cold or draughts.
Standard high performing triple glazed units with argon gas infill and low emissivity coating (Low-E) are ideal for Passivhaus and EnerPHit projects
Passivhaus – hygiene & health Conventional windows, apart from the discomfort they create, can also impact health. The colder surface temperature means that the relative humidity on the window surfaces can be high enough for mould growth or condensation to occur. Windows with exterior insulation properties keep the surface temperature above the mould growth threshold and dew point. Notably, even timber-aluminium windows – timber is more susceptible to mould growth problems, incorporating insulation between the aluminium cladding and the timber frame. This ensures that even the timber layer is kept comfortably above the mould growth temperature threshold; Mould develops
when the relative humidity of the surface exceeds 80%.
Longevity & airtightness The high energy efficiency of modern glazing units results in warm surface temperatures, low relative humidity levels of the surface, and absence of mould. These are prerequisites for the component’s longevity.
There are no required airtightness performance criterion stipulated by the Passivhaus standard for windows, as it focuses on the airtightness of the whole building. However, Passivhaus windows need to be as airtight as possible, minimising the infiltration heat losses. Additionally, when we consider a window’s airtightness, in windy conditions, if the most deformed part of the window not able to cope with the prevailing wind load, the airtightness no longer exists. Glazing units that are manufactured using glass bonding technology can withstand wind pressure up to 2000 Pa, which is equivalent to a wind speed of 205 Km/h.
Vasilis Giannopoulos is specifications manager at Internorm
WWW.ARCHITECTSDATAFILE.CO.UK
ADF MARCH 2024
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