Window Orientation

With normal windows, the sun's rays can easily penetrate and heat your house. This can provide welcome warmth in the cooler months but can lead to overheating in summer, as the heating power of sunlight shining directly on east- and west-facing windows is around 1000 watts per square metre, equivalent to the heat generated by a one-bar heater. Double-glazed windows, while good at reducing conducted heat transfer, need to be used with effective external shading in summer.

Ideally, all north-facing windows should be full length so when the winter sun is low in the sky, the heat will penetrate well into your home. Use minimum or zero glass on the east and west sides, and small glass areas on the south side of the house. The total window area should be less than 30 percent of the total floor area of the house (these proportions are a guide only, as new energy-rating software for houses considers this and a range of design features when assessing the overall rating of the house). If windows are made too large, they can make the house uncomfortably hot in summer and hard to keep warm on cloudy winter days and nights.