Tips From Our Experts

Anne asks: Can you tell me what measurement an eave needs to be to block the summer sun coming into my house with the house facing north? We are in Victoria.

Orientation and Eave Sizes

Anne asks

Can you tell me what measurement an eave needs to be to block the summer sun coming into my house with the house facing north? We are in Victoria.

Our expert’s answer

Ideally, the top of the window should be at least 30% of the height (from underside of eaves to sill) below the eaves otherwise that window area will be permanently in shade i.e. receives no solar gain in winter. NB. This is not always possible.

image001Generally speaking we say between 450 – 600 mm.

To be a little more specific please see the following –

“Eaves width should be 45% of the height from the window sill to the bottom of the eaves. Aim for consistent sill heights where possible and consider extending the eaves overhang over full height doors or windows. This allows the 45% rule to be simply met with the following standard eaves overhangs:

Height of window, door or main glazed areaWidth of eave
900-1200mm450mm
1200–1350mm600mm
1350–2100mm900mm
2100–2700mm (floor to ceiling height window or glass doors)1200mm

Where sill heights vary on a single north façade, set your eaves overhang to the average sill height of larger glass areas. In warmer climates go up to the nearest size and in cooler climates go down to the nearest size. Think about how climate change and warming might affect the heating requirements of the home.”

See diagram from the shading section of Your Home.

(Remember it’s north facing living rooms which really give you the potential for reduced running costs and increased comfort as these are the room you normally heat or cool the most.)

John Knox

John Knox

The technical advice provided by the Alternative Technology Association as part of the ‘Ask an Expert’ forum/website, in relation to home and building sustainability improvements, is general in nature only. The impacts of specific energy or water saving or sustainability products will depend on how and where the are used and located, and particularly for larger investments, we would always suggest users seek a specific assessment from an appropriately qualified building designer or service / product supplier.

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