How to Specify Window Shrouds for BASIX Compliance

If you’re working on a residential project in NSW, chances are BASIX is already part of your workflow. The Building Sustainability Index sets minimum standards for water and energy efficiency, and solar control is one of the areas where window shrouds can genuinely contribute.

BASIX is a tool, not a prescriptive standard. Architects and designers input project data into the BASIX online tool, and the tool assesses whether the proposed design meets the thermal comfort targets set for that climate zone.

Shading is one of the inputs. When you add an external shading device to a glazed opening in the BASIX tool, it changes the solar heat gain calculation for that window. A window shroud or sun hood on a north-facing window in summer reduces the amount of direct solar radiation entering the space, which helps reduce cooling loads and improves the thermal score.

Done well, this can help a project meet BASIX without requiring smaller windows, more insulation, or a higher-spec glazing specification. In some cases, window shrouds are the most cost-effective path to compliance.

The Key Variable: Projection Depth

Projection depth is the distance the shroud extends outward from the facade. It’s the single most important specification variable when it comes to shading performance.

A deeper projection shades more of the glass during high sun angles, particularly in summer when the sun is high in the sky. A shallower projection lets more light through, which can be desirable in winter when passive solar gain is an asset, but less useful if your main goal is reducing summer heat load.

The right projection depth depends on three things:

Orientation. North-facing windows in NSW receive direct sun for much of the day. East and west elevations receive low-angle morning and afternoon sun that horizontal shading elements are less effective at blocking. South-facing elevations receive very little direct sun and typically don’t require shading for BASIX purposes.

Climate zone. NSW spans multiple climate zones. A project in Broken Hill has very different thermal requirements to one in Sydney or the Southern Highlands. The appropriate projection depth varies accordingly.

Window height and reveal. How much of the glazed area the shroud actually shades depends on the window height and how far the glass sits back from the facade. These measurements matter when calculating the solar angle cut-off.

What the BASIX Tool Accepts

The BASIX tool accepts external shading inputs as a fraction of the window protected by the shade element. This is expressed as a percentage of the window area shaded at a nominated solar angle.

To use a window shroud as a compliant shading input, you need to be able to confirm:

• The projection depth
• The window dimensions (height and width)
• The facade reveal depth (how far the window sits back from the face of the wall)
• The orientation of the window

With these four inputs, a qualified assessor or designer can calculate the effective shading fraction for each window and enter it into the BASIX tool accurately.

This is important. Incorrectly specifying a shading fraction, by overstating the protection a shroud provides, results in a BASIX certificate that doesn’t reflect the actual design. That creates problems at certification and, potentially, at occupation.

What Window Shrouds Can’t Do

It’s worth being direct about the limits.

Window shrouds work best on north-facing windows where summer sun angles are high. On east and west elevations, the sun is low in the morning and afternoon, and a horizontal element doesn’t intercept that low-angle radiation effectively. For those elevations, louvres, fins or internal screening are typically more effective.

A window shroud also doesn’t compensate for poor glazing specification or inadequate insulation. It’s one element in a thermal performance strategy, not a catch-all solution.

And a shroud that isn’t sized correctly for the window and orientation provides minimal thermal benefit, regardless of how good it looks on the facade.

Specifying Window Shrouds for BASIX: A Practical Checklist

Before you finalise your window shroud specification on a BASIX project, confirm the following:

• Orientation of each window. Identify which elevations will benefit from shading elements. Focus on north-facing glazing first.
• Required shading fraction. Work with your BASIX assessor to determine the shading fraction needed for each window to achieve the thermal target.
• Projection depth. Calculate the projection depth required to achieve that shading fraction, accounting for window height, reveal depth and latitude.
• Facade substrate. Confirm the fixing method is appropriate for your facade build-up. Brickwork, cladding and rendered surfaces each require different fixing details.
• Shroud profile. Select a product range that can achieve the required projection depth and suits the architectural intent. At Alumac, our Trendline, Modline and Centurion ranges cover a broad span of depth and profile requirements.
• Documentation. Ensure the shroud dimensions and specifications are clearly noted on drawings and in your BASIX certificate. An assessor who can’t verify the shading element from the documentation can’t give credit for it.

Oran Park Window Shroud ProjectArchitectural Window Shroud Custom made in SydneyWindow Shroud on brickwork

Working With Alumac on BASIX Projects

We regularly work with architects and certifiers on projects where window shrouds form part of the passive solar or BASIX¹ strategy. We can provide product specifications, projection depth data and profile drawings to support your documentation.

We manufacture in Sydney, which means shorter lead times and the flexibility to customise dimensions if a standard depth isn’t quite right for your shading calculation.

If you’re working on a project where BASIX solar control is a consideration, get in touch with the Alumac team. We’re happy to talk through the specification before anything is locked in.