Building Fabric
Glazing and shading can strongly influence how an existing home feels throughout the year.
Windows bring light, outlook, ventilation and winter solar warmth into a home. But they can also create summer overheating, winter heat loss, glare and rooms that are difficult to heat or cool.
For existing homes, the question is not only whether the windows are single or double glazed. It is also whether the glass is facing the right direction, whether it is shaded at the right time, and how the window system works with insulation, ventilation and heating or cooling.
Quick Answer
In an existing home, glazing and shading can affect heat gain, heat loss, glare, daylight, ventilation and comfort. Poorly performing windows may lose heat in winter or allow too much summer sun into the home.
Shading can reduce unwanted solar heat before it reaches the glass. This is especially important for rooms with large, exposed or poorly oriented windows.
A home energy rating may consider window size, orientation, glazing type, frame type, shading and how these elements influence the home’s overall performance.
Windows are often one of the weakest parts of the building fabric. They usually perform differently from insulated walls, roofs and floors because glass allows light, heat and solar radiation to pass through in ways opaque building elements do not.
In winter, windows can lose heat and make nearby rooms feel cold. In summer, windows can admit unwanted solar heat and create overheating. If shading is poor, the room may become uncomfortable before the air conditioner is even switched on.
This is why glazing and shading should be reviewed together rather than treated as separate issues.
Glazing refers to the glass in windows, doors and skylights, as well as the wider window system that affects performance. In practical assessment, window performance is influenced by the glass, frame, seals, orientation, size and exposure.
Common glazing types include single glazing, double glazing, low-e glass, tinted glass and other performance glass products. The right choice depends on the home, climate, orientation and whether the main problem is summer heat gain, winter heat loss, glare or comfort near the glass.
For a home energy rating, glazing is not only a product choice. It is part of how the building performs as a whole.
Shading refers to anything that controls direct sun on windows, glazing and sometimes walls or outdoor areas. It can be fixed, adjustable, external, internal or created by nearby structures.
Common shading elements include:
External shading is often especially effective because it reduces direct sun before it passes through the glass.
Window performance is often described through two important concepts: U-value and Solar Heat Gain Coefficient, or SHGC.
U-value relates to how readily heat conducts through the window system. A lower U-value generally means the window is better at resisting heat transfer. SHGC relates to how much solar heat the glazing allows into the home from direct sunlight.
This matters because a window that performs well for winter heat loss may not automatically solve summer heat gain. The best window strategy depends on orientation, climate and shading.
The same window can behave differently depending on which direction it faces. In Australia, north, east, west and south-facing glazing can create very different comfort outcomes.
North-facing windows can often be shaded more predictably with well-designed horizontal shading. East and west-facing windows can be more difficult because low-angle morning and afternoon sun can penetrate deeply and create heat gain. South-facing windows may receive less direct sun in many locations but can still contribute to heat loss.
This is why a window upgrade should not simply use the same glazing and shading approach on every elevation.
Summer overheating is often driven by direct sun on glass. Once solar heat enters a room, it can be difficult to remove without mechanical cooling, especially if the room has poor ventilation or the home stores heat into the evening.
Good shading can reduce unwanted sun before it reaches the glass. In many existing homes, shading can be a more practical first step than replacing every window, especially where the main issue is exposed summer sun.
However, the right solution depends on which windows are causing the problem, how the home is ventilated and what other building fabric issues are present.
Windows can also be a major source of winter heat loss. Rooms near poorly performing windows may feel cold, even when the heating system is running.
Double glazing or other higher-performing glazing systems can help reduce heat loss, but the benefit depends on the whole window system, frame type, installation quality, air leakage and how the room is used.
Window upgrades should therefore be assessed alongside draught sealing, insulation and heating system strategy.
External shading is often powerful because it blocks or reduces direct sun before it passes through the glass. Examples include eaves, awnings, external blinds, screens, shutters and verandahs.
Internal blinds and curtains can improve comfort and privacy, and some products can help reduce heat movement. However, once sunlight has already passed through the glass, much of the heat is already inside the room.
For overheating problems, external shading is often worth reviewing before assuming the only answer is air conditioning or full window replacement.
Fixed shading includes elements such as eaves, roof overhangs, awnings, pergolas and verandahs. These can be durable and low-maintenance, but they need to be designed carefully for orientation and season.
Adjustable shading includes external blinds, shutters, operable louvres and some screen systems. These can provide more flexibility because they can respond to season, weather, time of day and occupant preference.
In existing homes, adjustable shading can sometimes be a practical retrofit option where fixed shading is difficult to add or where different seasons require different levels of solar access.
A home energy rating may consider glazing and shading because they influence heating and cooling demand. Window size, location, orientation, glass type, frame type and external shading can all affect the result.
In an existing home, some window information may be easy to identify. Other details may require documentation, product labels, site observations or reasonable assumptions under the relevant assessment pathway.
For more detail on what assessors review, see What Does a Home Energy Rating Assessor Look For?
Window upgrades can be valuable, but they should not be treated as the only performance measure. A home with better glazing may still perform poorly if insulation is missing, air leakage is high or shading is inadequate.
Likewise, shading can reduce summer heat gain but may not solve winter heat loss, draughts, poor ventilation or inefficient heating and cooling systems.
For that reason, glazing and shading should be assessed as part of the whole-home performance pathway.
Window and shading decisions can be difficult to change later. If a renovation involves new openings, replacement windows, facade changes, decks, pergolas or external works, glazing and shading should be considered early.
This can help avoid situations where a room is newly renovated but still overheats, loses heat or needs more mechanical cooling than expected.
For renovation context, see Existing Home Energy Rating vs Renovation Energy Assessment.
Common glazing and shading issues include:
A good assessment can help separate the visible symptom from the underlying performance issue.
Before requesting a home energy rating or upgrade review, it can help to prepare simple information about the windows and shading conditions.
Useful information may include:
For a full preparation checklist, see What Information Do You Need for a Home Energy Rating?
Glazing and shading matter because windows can drive heat gain, heat loss, glare and comfort problems. In existing homes, poor glazing or inadequate shading can increase heating and cooling demand.
Yes. A home energy rating may consider window size, location, orientation, glazing type, frame type and related window performance information where it can be identified or assessed under the relevant pathway.
Yes. Shading may be considered because it affects how much direct sun reaches windows and other glazed areas. The exact shading inputs depend on the assessment pathway and available information.
Glazing refers to the glass and window system itself. Shading refers to elements that reduce or control direct sun on the glass, such as eaves, awnings, external blinds, verandahs or nearby built form.
Yes. Appropriate external shading can help reduce unwanted summer sun on windows, which can reduce overheating and cooling demand. The best shading strategy depends on orientation, climate and window design.
Glazing and insulation should be reviewed together. The best upgrade sequence depends on the home, climate, comfort problems, budget, renovation timing and whether windows, shading or building fabric are the main performance issues.
Home Energy Rating Review
A home energy rating can help identify whether glazing, shading or other building fabric issues should be part of your upgrade pathway.