Design your home for the Sun
by Editorial Team - Build Your Dream
Our healthiest energy source is free
NZ may face energy crises
We have heard lately that future power crises are likely on the basis of an assumed doubling in electricity demand over the next 20 years. Given the environmental costs of damming rivers, the difficulty in finding new gas fields, and the fact that oil prices are expected to increase dramatically, some in the energy field are starting a new discussion questioning the wisdom of New Zealand’s nuclear free stance. They suggest nuclear power as an environmentally friendly power source that does not contribute to global warming, particularly when compared to the abundantly available coal resource.
There is no need for us, as individuals, to accept the role of victim. In all of the discussions there is a conspicuous lack of alternatives presented. The possibilities of saving power through efficiency measures are barely considered, while wind and solar power generation often only get a token and dismissive mention as minor energy contributors. However, these areas are precisely where we, as consumers, can act to get out of the victim’s trap and at the same time contribute to our own and the planet’s health.
What is Passive Solar Design?
In a nutshell, this design approach provides for a maximum of the low winter sun to enter the house (through large northerly windows), for it to warm thermal mass (like concrete, bricks, earth or tiles) which will store the sun’s heat, releasing it after the sun has set. This way the thermal mass acts as a radiator providing heat and contributing to a dry, comfortable and healthy indoor climate. The best part is that it is free while simultaneously reducing our energy needs.
Housing in New ZealandLooking at New Zealand as a whole there is enormous scope for energy saving using this method. A closer look at the existing housing stock from a perspective of passive use of solar energy gives a clear indication.
In the suburbs and towns of New Zealand during the first half of the last century, when bay villas and bungalows were being built en masse, very little consideration, if any, was given to the orientation of houses in order to make the most of the varying seasonal angles of the sun. Floor layouts were almost identical and the master bedroom and parlour were at the front and the kitchen and bathroom at the rear, regardless of sun orientation. Street appeal was everything and only in the country were houses placed on more practical orientations. Surprisingly, many homes today are still designed and built with a similar lack of consideration.
How does Passive Solar Design work?
Passive solar design is not just about letting the sun in during winter, but also about keeping it out during summer. It utilises the varying positions of the sun at different times of the day and year to control indoor temperature, thus reducing or even eliminating the need for additional heating or cooling. An advantage of New Zealand’s climate is the relatively high number of winter sunshine hours, throughout the country. One of the most efficient forms of thermal mass is a concrete floor slab, providing it is not covered with low-density coverings such as carpet or wood in the area where the sun will strike it. Tiles or slate are ideal floor coverings.
A thermal mass wall can also be used and variations range from direct gain, as described above, to isolated gain, where the storage is completely out of the occupied space such as in a conservatory.
Deciding on glass area along the northern side of the house becomes a balancing act between letting in as much natural light as possible and maintaining temperature control. For this reason there should be no obstruction to light directly outside the window, and in general tinting should be avoided - also because it disrupts the natural light spectrum. It is recommended that the glassed area be kept to a minimum necessary on south and west walls, south in particular to prevent heat loss during winter and west to avoid over-heating during summer afternoons.
Fortunately street appeal is no longer the only consideration for people building or renovating a house. Northerly aspect, making the most of sunny private spaces and a good indoor–outdoor flow are now of primary concern to most of us. This is the perfect precondition for incorporating passive solar design, at no extra cost but resulting in a considerable drop in the individual heating bill. And the accumulated nationwide reduction of greenhouse gases, and the end to any suggestion of the need for nuclear power, come as a spin off – just to make us feel even better.