Although not exhaustive this design guide conveys the essentials that make a solar passive building. We use it to make sure we don’t forget any of the essentials, though it is by now pretty well ingrained in everything we do.
It isn’t exhaustive – it doesn’t touch on the various ventilation methods that can be used for natural cooling, for example – it just says ‘enhanced natural ventilation’. There are a number of different ways of naturally cooling a solar passive building without using machinery. As mentioned elsewhere in this site natural cooling methods were well known to ancient peoples – particularly those of the hotter climes – the Middle East, for example. Similarly to solar passive heating, natural cooling has been forgotten to the extent that many buildings in hot climes are hardly habitable without relying on air conditioning. So, just as solar heating was lost to time because of carbon forms of heating, the same is true of natural cooling.
Ways that cooling can be achieved naturally, which can be used in any new building are:
- high thermal mass inside
- solar shading
- cross ventilation
- stack ventilation
- cross ventilation over water
- courtyards with shaded pools
- shade plants
- light colours inside and out
- ground cooling through buried earthen pipes.
- evaporative cooling through water walls
The Lightning Design Guide illustrates something else rather well also. That solar passive design is relatively simple. It has been practiced by humans since prehistoric times, with the most basic rule being – face the sun!
There is something else interesting in the checklist. Thermal mass is mentioned both in terms of receiving and storing the heat of the sun and also in respect of aiding passive cooling. So which is it to be? Both. This is because high thermal mass has a useful characteristic. When it is exposed to solar radiation is concerts the shortwave solar energy into longwave heat energy and stores it for a period of time dependent on the thickness and specific heat capacity of the thermal mass material. Thermal mass in shade, however, tends to cool the air around it. Think of a historic cottage or church with thick stone walls on a hot summer day – it is cool inside because ot the thermal mass in shade. Thermal mass is an essential ingredient of any solar passive design.