Eaves or No Eaves ?

You need either eves or some form of external shading for northern windows. These should allow low winter sun to come in and block the higher summer sun. This is the first principle of passive solar design. Without this measure you'll be using extra heating and cooling than you need to.

With regard to the south side, if you have windows (say to enjoy a view), you need deeper external shading to block the summer sun in the early and, more importantly, latter part of the day.

You don't necessarily need eaves. You can get external shading that fits above windows, but it's probably cheaper (and it fits with more design styles) to go for eaves.

North facing windows
It is recommended that around a third to a half of the north face of your home be glass, as it is very effective at trapping winter warmth and can be easily shaded from summer sun with correctly designed eaves.

To calculate the overhang needed, multiply the distance from the eaves-line down to the bottom of the window by 0.7. This will ensure the glass is adequately shaded from September until March. For cooler regions, multiplying by 0.4 will provide suitable shade from October until February.

Eaves on the east and west side of the house are not required. The sun is too low in the sky when in the east (morning) and the west (afternoon) for eaves to be effective.


From the following website - http://www1.sedo.energy.wa.gov.au/pages/windows.asp
East and west facing windows
While east and west facing windows provide warmth in winter from the early morning and afternoon sun, they are difficult to protect from the sun in summer. This makes rooms on the east and west of your home uncomfortably warm, particularly west facing rooms which receive the hot afternoon sun. To keep cool in summer, it is recommended that the total area of east and west facing windows be kept to a minimum.

External shading devices provide some protection from the summer sun, with complete protection achieved only with full vertical screening, such as outside blinds or shutters. This is because the angle of sun will be close to horizontal early in the morning (east) and in the late afternoon (west), and only vertical screening can block the sun at these angles. Deciduous trees or vines growing on a trellis can also provide shading during summer.

From the same website..

Double glazing
Two panes of glass separated by at least 10 mm can reduce winter heat loss but is generally only cost effective in situations with high heating requirements. Double glazing can also reduce conductive summer heat gain. However, when exposed to sun double glazed windows will still allow significant heat transfer, which means that full shading is still required.

Eaves will also help shelter the windows and reduce the summer rain coming from in when you have the windows open - on any side of the building
And by stopping the rain actually hitting the windows - via eaves - the windows don't get as dirty - or at least the don't look like dusty rain spalttered windows everytime it rains.
I'm all for eaves - others are not.