In most designs, the size and location of windows are usually dictated either by their appearance from the outside or the views obtained from the inside. However, investing a little thought in how one locates their windows can have a significant influence on the overall comfort of their house,
Unfortunately, the majority of existing houses (and probably most new constructions) do not give sufficient attention to this detail and are destined to become uncomfortably cold in winter and/or over-heated in summer. Consequently they will require a strong dependence on supplemental heating or cooling that then result in excessive energy bills.
Unlike any other building material, windows are transparent to electromagnetic radiation. They allow visible light to enter (to provide views) but also allow infra-red heat radiation to penetrate the building envelope.
This is both the strength and Achilles heel of (what those in the industry call) fenestrations (Latin: window).
The impact of sunlight entering the building interior can significantly affect the internal comfort of the house. The heating potential of direct sunlight is equivalent to one bar radiator per square metre. If one is doubtful of this effect place a thermometer in direct light next to a window compared to placing it in a shaded area of the house.
A worthwhile exercise to try on your existing house is to take a look around the house during the hot and cold seasons. Which rooms get the most sunlight? What impact does this have on the comfort of that room? Where is the room situated in relationship to where the sun rises and sets? How are those rooms used in the daytime and evening?
Ideally one wants lots of warm sunlight to enter during cold winter days. On the other hand, it is equally important to block out direct sun during the summer. Blinds and shutters are one solution method of controlling this throughout the year.
If one has the luxury of building a new home, an even better one is to situate most of your windows and living areas on the north side of the building. With a modest sized eave you can simultaneously let in the low winter sun whilst blocking out the hot summer sun. A deep verandah on that side is unnecessary and in fact it will completely block out the useful winter sun.
It is also helpful to consider that the most vulnerable side of the house during the cold season is on the south side where there is no direct sunshine. Large windows on that side will also let a lot of heat to escape. In summer, western windows will admit the hot, low setting sun and can quickly result in unbearable conditions. Ideally one should try to avoid wide expanses of either unless additional measures are taken to prevent either excessive heat gain or heat loss.
Of course there are a number of other new innovations in window technology that have contributed significantly to the armamentarium of the energy-efficient house designer. These include double glazing, reflective tints and low-e windows. However, to gain maximum thermal benefit from these systems one should get all the other design issues ironed out.
We have applied all these principles in our new house design. Apart for the first couple hours in the morning we do not require additional heating throughout the day despite it being 10 degrees outside. On clear cold days the interior temperature easily climbs to 21 degrees or higher and our living areas are bathed in sunlight. On the other hand, when the temperature reaches the high 30s during summer, the inside gets no warmer than 28 degrees and no direct sunlight can enter the house during the middle of the day.
Currently our projected winter bill is probably going to be around one sixth of our previous residence. I will keep others posted of what our cooling bill in summer ends up being.