Window Orientations

window orientations

North Facing Windows receive winter sun which allows light and warmth into the house.
These windows can be easily shaded in summer to help keep the house cool.
The size of these windows will depend on the structure being built and where.
But if the windows are too large then there could be major heat losses in winter as well as major heat gains in summer.

East/West Facing Windows receive little autumn and spring sunlight with winter sunlight being even less.
The west facing windows also receive excessive summer sunlight and should be shaded to help keep the house cool.
These windows should be kept smaller than North Facing Windows.

South Facing Windows receive no winter, autumn or spring sunlight but only receive early morning and late afternoon summer sunlight.
These windows should be kept even smaller than East/West facing windows but not completely deleted.
The reason for this is because of cross ventilation.
In summer a cool change generally comes from the south which helps cool the house down.

Glass Houses

It is rule of thumb, depending on the design and orientation, that if the total window area (frame & glass) is 20% or more than the total floor area (not include external or garage floor areas); then the windows start to move into double glazing territory.

So remember, if you are going to design/build whole walls out of windows then be prepared to pay for the glazing that will be required to get the project to the minimum Star Rating required.

Contact us here to get your project/assessment underway.


Windows are a very important part of any construction because they let in natural light, fresh air and allow us to view the outside from within.

But once all the floors, walls and roofs have been insulated windows become the weakest link the the chain of materials as far as energy efficiency is concerned.

Windows don't have any thermal mass and the glazing allows heat to travel in and out of the house freely.

When windows are used in an Energy Rating Report (Thermal Performance Assessment) they are entered in as U Values and SHGC Values of the Total Window's System which includes the frame and the glazing.

It is important that the window manufacturer, which is quoting and/or supplying the windows, follow the values and information that is contained within the Energy Rating Reports.

U Values, SHGC Values

U Values (Windows)

Put simply, the U Value of a Total Windows System is the measure of heat flow through the window frame and glazing at different temperatures either side of the materials.

The higher the U Value the greater the Heat Flow and the lower the U Value the lower the Heat Flow. In summer we referred to it as Heat Gain into the house and in winter we referred to it as Heat loss.

SHGC (Windows)

SHGC is the amount solar radiation that will pass through the glazing as well as the amount that will be deflected. In winter this can help heat up the house naturally but in summer it could over heat the house, that is why reasonable sized eaves are helpful.

The higher the SHGC Value the higher the solar radiation that pass through the window while a lower SHGC Value means less solar radiation will pass through.