We have only just taken off the winter duvet and turned off our heating and people are complaining that they are too hot. I have to say that it is no wonder that some houses are overheating when you look at how much south facing glass, rooflights and conservatories people have installed. We always remind our clients of this potential problem when we see the design developing but I guess for some clients it is hard to take this seriously in the depths of winter when we have not seen the sun for months. Sadly some clients think that air conditioning is the answer and do not want to consider other measures. These other measures do not have to be only reducing the glazing area, although this is the most effective. Other measures include the “brise soleil” which is a fixed sunshade fixed externally above the window so that when the sun is high (as it is in summer) a large part of the window is shaded or external blinds that can be drawn across when needed. It is worth pointing out here that external shading is much much more effective than inside shading because once the sunlight has passed through the glass the heat that is dissipated by the sunlight as it is interrupted by the blind is now trapped in the building. Internal blinds help reduce the glare of the sun but that is about it. If you want to stop the heat build up through sunlight coming through your windows, external blinds are really effective. Sadly, few companies make them although Velux do but do not push them which is bizarre.
Other measures include “stack effect” ventilation which can be a chimney not used for a fire but opened up to allow heat to rise up when desired to create air movement. This works well when cooler air can be drawn in from a shady part of the garden to replace the warm air being expelled. In new buildings, this can be a design feature such as the tower we designed into the Greenleys Familly Centre. Last we heard it was functioning perfectly doing its job in the summer completely passively and in the winter it allowed light into the centre of the building reducing the lighting bill.
Heat reflecting glass and the use of building mass to soak up the heat are other more expensive measures but have their place but for me just a good sensible balance of glass facing East, West and South is best as it is cheaper and has no running cost ( except window cleaning perhaps).
Written by Tony Keller – Building Tectonics Ltd.