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If you are at all worried about keeping construction costs down and
lengthening the useable lifespan of your building, it’s critical that
energy performance is considered from the earliest stages of planning
and design. John Hearne spoke to a number of leading Irish
experts in sustainable design about following simple principles of
orientation, form and layout to achieve substantial energy improvements
for free
Whether it’s one-off housing, housing estates or commercial buildings, getting orientation, form and layout right won’t generate any additional capital costs, but it will deliver huge energy savings.
Jay Stuart, managing director of sustainable design consultants DW EcoCo, cites Paul Littlefair’s 1991 book, Site layout planning for daylight and sunlight: a guide to good practice, as the key reference work for the industry on this subject. The book’s basic proposition runs as follows: If at design stage, consideration is given to the orientation of the houses, the layout of the rooms and the distribution of the windows, you can reduce energy consumption by 10 per cent to 15 per cent at no extra cost to the developer. “Just by doing really, really simple, basic things.” says Stuart.
First, orientation and layout. “Say a house is a rectangle, built along an east/west axis. On the north side of the house you want to minimise the amount of glazing purely because there’s no solar gain on that side of the house. Conversely, you want the larger proportion of your glazing on the south side to let the sun in to warm the house. Then you want to organise the rooms so you’re sitting where the sun is, because people naturally gravitate to natural daylight. So you might consider, though this isn’t an absolute rule, the kitchen on the east side of the house and the living room on the west side of the house. You might have your staircase, storage and utility rooms on the north side of the house because you’re only there for a short while and they don’t have the same heating requirements. You might put the entrance with a draft lobby on the north side of the house.”
Now he introduces recent changes to Part L of the building regulations, which mandate the use of renewable energy – either 10kWh/m2/yr of thermal renewable energy from a heat pump, solar thermal system or biomass boiler, or 4kWh/m2/yr from micro-wind or solar electric. “The most cost-effective way to meet the building standards for renewable energy in low density housing is with a solar collector system, which is most cost-effective if it’s small, and it can be small if it’s at its optimum angle, and that’s at 40 degrees facing due south.”
Next he brings in building form. “In the Dwelling Energy Assessment Programme (DEAP), and in the Passive House Planning Package (PHPP), the ratio of the external envelope surface area to volume has the biggest single impact on a building’s energy performance. A long, thin building is going to have a very large external envelope area compared to a cube. The ideal would be a sphere, so the next thing that’s practical to build, unless you want to live in a geodesic dome, is a cube.”
So, to sum up: “The concept of the house you want to build is a cube facing south with a 40 degree pitch with solar collectors on it.”
Building with reference to site and sun is not a new idea. You only have to look at vernacular architecture. Architect Sinead Cullen, also of DW EcoCo, says that in cottage clusters all over Ireland, you’ll find the same recurring patterns. The main house, together with a series of outhouses form a square, with the main house and the larger windows facing south, with the outhouses providing shelter from prevailing winds and concentrating passive solar gain into the dwelling. Smaller windows are found on north elevations, larger ones on the south. “Responding to site and climatic conditions is something we've been doing for thousands of years.” says Cullen. “It’s just with cheap energy we no longer found it necessary to look to building form and orientation to help heat and protect our buildings. Looking to site conditions therefore is something that we just need to re-learn rather than learn from the beginning.”
Against that backdrop of cheap energy, and driven too by increased population densities and the housing boom, the disconnect between buildings and their environment intensified. When considering orientation, designers, suddenly blind to the sun, looked at planning controls, views, alignment with roads...“The typical case,” says leading sustainable architect John Goulding, “is where you’ve an east/west running street and the houses on the north side are exactly the same as the houses on the south side, with no rearrangement of internal planning to account for that.” The failure to set glazing ratios with regard to that orientation compounds the problem. Goulding, like everyone else interviewed for this article, uses one word repeatedly. Simple. “In one sense it’s very very simple. Once you know the constraints of the site that you have...it’s a question of coming up with a building form and glazing ratios and facade design that allow the building to do most of the work itself, leaving only a relatively minor, residual amount of energy to be provided by other means.”
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