Low-E Principles: The importance of Solar Heat Gain Control

Once your building is insulated and air-tight to Passivhaus standard, you will barely loose heat. While true in general, solar heat gain control of windows in summer is paramount.

To keep the unwanted sun out, fixed or passive shading as part of the building design and/or orientation such as very deep eaves and vertical shades, or else active external shading devices such as blinds, screens or shutters are required.

Mechanised external solar control comes in the form of textile screens (eg. zipScreens), insulated shutters or blinds, all of which have to be tracked at full height to survive high-wind situations. Operation of external devices is done by remote control, manually or via Building Management System (BMS).

Regularly, we’re offered from owners the request for high solar heat gain, as mentioned on shows such as Grand Designs. For the simple reason that Australia has a hugely hotter, sunnier and overall extreme climate, where England promotes SHG, Australia promotes controlling and curbing it, only when needed.

The misconception of solar-control glazing 
(AKA tinted glazing)

Despite popular belief, tinted glazing is omitted within Passivhaus construction as invariable, too costly and overall superfluous, as sufficient solar heat gain control is unable to be achieved using tinted glazing, while also limiting much wanted winter sun.

Relevant definition:

SHGC (Solar Heat Gain Coefficient)
The measure of how much thermal energy from the sun solar passes through a window.Efficacy: In Australia’s hot climate regions, lower SHGC values are preferred when no external shading is available. However, this also reduces the amount of visual light passing through the window.In cooler climates, windows which have a high SHGC allow a greater amount of solar radiation to pass through, offering much appreciated solar heating for the home. Low-E coatings are very important to keep the warmth indoors.