allan . curran . architects

Energy Watch 2 – Site Selection

In the forthcoming articles for Energy Watch we will divide our comments into “New Build” and “Existing” but we hope that existing and prospective house owners will find time to read both sections as there are many ideas and philosophies that apply across the board. The big idea is that we do our bit for the world by reducing our carbon emissions (caused by burning fossil fuels), and the bonus is that in doing so we reduce the running costs of our homes. This week we are going to concentrate on site selection for a new build, as the obvious starting point.

Some people have the luxury, and indeed the excitement, of searching for the site for their new home, while many others obtain their sites from family lands. In this article we are going to concentrate on the two main elements of site selection that affect the future energy use of your house: its orientation and the shelter.

The orientation: where the sun rises and sets in relation to your site

In recent times, the way you face your house has usually depended on where the public road is. Most people place their house parallel to the road or facing where any views might be. As a result, the roof and windows usually face the road or the views, and the position of the sun is not so much taken into account. However, the amount of glass and the positioning of windows in your house are major factors in terms of your future heat loss and gain, so the position of the house in relation to the sun is vitally important. The roof is important as it is where solar panels and photovoltaic panels are most likely to be located, and they need to face the sun.

When sunlight comes through a window your building experiences solar gain i.e. you get heat from the sun. Just step into a green house on a sunny day for a quick demonstration.  The first rule in positioning windows is to put the absolute minimum amount of glazing on your north facing elevation where there is little solar gain, and put the maximum amount on your south facing elevation to take advantage of the sun’s heat and light.

For site selection the ideal site is one that has the access road on the north side, where you can put small windows to protect your privacy, and on the south side expansive views which you can make the most of with large windows to obtain maximum daylighting and solar gain.  If only life were that easy! It’s worth remembering that the windows are among the weakest points in your house as far as heat loss is concerned, so careful consideration is needed to balance the exploitation of views and solar gain against the heat losses that go with large windows that are inappropriately positioned.

It makes sense therefore to organise the house layout so that the main living accommodation is to the southern side of the house and the utility and service rooms are on the northern side. Following this logic, bedrooms might be on the east to catch the sunrise and dining/patio areas might be on the west for maximum appreciation of the sunset.

Shelter

In years gone by houses were generally placed in more sheltered spots as there was an inherent understanding of the effects of weather on the use of a dwelling.  The front door rarely faced into the prevailing south-west wind and of course windows were small. This had the effect of reducing draughts caused by wind pressure, because the old houses were quite leaky in that regard. Nowadays, we try to make houses very airtight to avoid draughts (and thus reduce heat loss), but the old principles are still relevant and worth considering at an early stage, when you are deciding where to position your house on the site. In spite of our modern building technologies, it’s still better to avoid building on exposed sites.

On the vast majority of sites compromises have to be made and each site will have its own unique solution.  As an example we show above an existing site where we are constructing a passive house close to a lake.  As you will see the access road is on the east, the views are to the south and west and the shelter is provided to the northwest. Clearly this is not the perfect site so a) we took the access from the road around to the back of the house so that parked cars would not sit between the house and the view and b) we angled the windows to pick up the sun and the views.