Are you using windows to heat your house?
I commonly ask my clients the following questions.
- Are you planning a passive solar design?
- If not, to what degree are you relying on the windows to heat your home in the cooler months? And,
- Are the windows going to cause an overheating problem?
What I find is,
- The vast majority of people are not planning a passive solar design.
- Windows have not been considered as part of the heating equation.
- Their design is pretty-well decided upon.
- They have not thought about heating or cooling.
In order to achieve a high-performance outcome, it is important to ask the questions as mentioned above. The tools we use, and the methods we employ to deliver a result vary greatly based on the design philosophy.
A passive solar design must adhere to strict design parameters to achieve an optimal result. A passive solar design delivers large temperature swings, and therefore requires an active occupant to ‘drive’ the home. A poor passive solar design, or a design wishfully applying pseudo-passive solar principles can lead to massive discomfort in the way of summer overheating and winter heat loss.
In the case of ‘most people’ who have a non-passive solar design, an energy conservation approach to reduce heating and cooling loads is more appropriate.
An energy conservation method deals with the building envelope under the Water-Air-Vapour-Thermal approach with an emphasis on the integrity these control layers. The windows in an ‘energy conservation’ design are not relied upon for heating. Windows are carefully considered for their insulation value for both winter and summer performance. Windows are also carefully considered for shading to prevent overheating. A fully developed energy conservation method leads to a good performance outcome. Passivhaus uses this approach.
So, when thinking about windows for your home, first pay attention to the underlying design philosophy. Then ask yourself, “To what degree am I relying on the windows to heat my home, and are the windows going to cause an overheating problem?”
Lastly, remember that building performance is to be treated as a system. Dealing with any component part in isolation with no regard for the rest of the system leads to trouble. Windows are just one part of the system.