A VERY BRIEF INTRODUCTION TO THE DESIGN OF SUSTAINABLE BUILDINGS
Older houses consume large quantities of energy for heating and power, most of which is generated from non-renewable sources involving the emission of carbons into the atmosphere. This is unsustainable, causes ecological damage and is resulting in the rising cost of power.
From the 1 January 2009, Regulations now require new houses and extensions to achieve certain levels of insulation and air tightness in the building fabric, and the reduction of CO2 emissions through the use of efficient building services, incorporating a certain amount of renewable energy technology. All buildings to be sold or rented now require a Building Energy Rating certificate, which may affect the value of the property. The BER certificate confirms a buildings performance on a scale of A1 (most efficient) down to G (least efficient). Compliance with Regulations in 2009 requires a new house to have a minimum BER rating of B1, and a BER Rating of A3 in 2010.
We are morally and legally obliged to ensure that house design is sustainable - that energy consumption is minimised. Individuals’ lifestyles differ, and change during a lifetime. To use energy lightly, to make use of passive energy sources, a close understanding of a client’s lifestyle is essential. Having done this, the building is designed from two aspects.
The shape and fabric of the building, and the services installed to provide power, heat and control water usage. Few advisors are expert on all these areas. They should be discussed in broad terms with your architect at the initial design stage, and outline proposals discussed with specialists who can compare the viability of alternatives.
The shape and fabric of the building.
Sustainable design starts through fundamental design issues such as ensuring there is no wastage of space, that the layout provides for generous southern lighting, protection from prevailing winds and so on.
Several aspects of the design will have a significant influence on environmental performance of the building.
- There is more heat loss on the sunless north side of the building, so increasing the insulation here and reducing the amount of windows will increase performance.
- The south side offers more solar gain and opportunities for heat collection by thermal stores (solid walls, structural elements etc). Atria allow warm air convection through the house.
- The reduction of pipe runs will significantly reduce heat loss, so it is helpful to centralize water heaters.
- Building Regulations require similar insulation and ventilation standards to those that apply in Northern Canada, where temperatures drop to -40C every winter. These levels of insulation create humidity problems in the Irish climate, and so if the inner face of the external walls is not completely moisture sealed, condensation will saturate insulation and render it useless. Timber frame construction is quick, uses renewable material, but requires great attention on site to ensure the ‘sealing membrane’ is flawless. Masonry construction provides a good seal, is slower to construct and discharges considerable C02 in the production of the blocks.
- Building Regulations require all houses to have concrete foundation and a concrete ground slab. Concrete involves the production of CO2 in its manufacture, but low carbon concretes are available.
- Windows – triple glazing offers more heat retention than double glazing, but tends to be less flexible in terms of glazing arrangements, and is much more expensive. Low emissivity glass retains heat gain whilst reducing heat loss. Timber window frames are renewable and can be treated against rot. PVC and aluminium are environmentally expensive but slightly cheaper.
- Certain building components are available from organic sources, such as wool insulation, timber particle boards and so on, which tend to be more expensive than the manufactured equivalents, but evidence suggests these may create a more benign internal environment.
Quality of Life.
Environmental targets can be achieved without compromising quality of life. Whilst it is of benefit to reduce the external envelope to reduce heat loss, large sunny spaces and extensions into the garden (for instance) can be introduced and be beneficial to the environmental performance of the building. Two examples follow:
House enlargement in Leopardstown.
The rear of this house faced south onto an angled garden, and this southern aspect offered great environmental opportunities. A double height glazed element ensured that the sunlight penetrated deep into the room and provided an airy dining area. The space is warmed by solar gain, the heat is stored by the insulated high-mass floor, and warm air is convected through the open landing to the rooms above. Heating costs have fallen since the work was done. A floor level eaves window in the converted loft space gives the impression of a floating roof, and dispels the cramped feeling so often experienced with loft conversions. Simple roof-lights give the surprise bonus of a previously hidden view of the Sugarloaf.
Garden extension in Sandyford.
The northerly aspect presented the risk of the extension darkening the dining area. Afternoon and evening light is drawn through a roof-light and reflected into the interior by a faceted wall. The ceiling is modelled to modulate the light and create an interesting space within. The dining area is lighter than it was previously. An octagon fulfilled the requirement to address the large garden which ran to the north east, and a short returning wall avoided ‘the view down the boundary fence’. The garage space provides for a shower / utility room and study.
The Services Installation.
The initial design should include a rough services proposal, which can be forwarded to experts who can draw up appropriate specifications and enable client and architect to compare the viability of alternatives. This initial design will take the following into account.
Compliance with Building Regulations.
The bottom line - in 2009 an entirely traditional installation with a condensing boiler and say 3 sqM of solar panels will achieve an adequate BER rating, subject to adequate insulation and draft sealing.
Power for appliances and cooking.
Whilst electricity can be produced through solar panels, wind generators and so on, the capital outlay is high and will not provide adequate or sufficiently reliable electricity to avoid an ESB electrical mains connection. Electricity can be supplied from a wind generated source.
Reduced dependency on mains power.
This can be achieved through the installation of a variety of systems:
- A geothermal heat pump extracts heat from the ground – the performance varies with the seasons, the amount of land available and the nature of the ground. This may avoid dependency on a boiler and fuel costs, but is relatively expensive to install.
- Air / water heat pumps can provide part of the energy required for heating or hot water, but another heat source will still be required. In certain circumstances, these may be preferable to solar panels.
- Heat pumps require electricity to run, (in the order of €500 per annum) and so they are most effective during night-rate periods. Their viability depends on the life style of the occupants. They produce a consistent flow of water warmed to a low level, so they work well in conjunction with under-floor heating. Continual day-time occupancy and extensive hot water usage reduce their effectiveness.
- Under-floor heating offers a payback period of 5-7 years.
- Wind turbines can be installed in houses, but are generally more efficient in large, carefully located centralized locations. They can reduce dependency on mains electricity.
- Photo-voltaic solar panels can reduce dependency on mains electricity.
- Heat exchanging air extractors can reduce the amount of space heating required.
- A central monitoring and control system can produce significant reductions in energy usage. An integrated moisture level controlled ventilation system can further reduce the amount of space heating required.
- ‘Real flame’ stoves can now be sealed units, maximizing the energy extracted from the fuel. They can be insulated, extending the heat output beyond the extinguishing of the fire. They can be connected to the heating system to reduce the dependency on the boiler or heat pump.
Reducing Water Usage.
Rainwater harvesting can provide water for WC flushing hot water, washing machines, garden irrigation and car washing. Methods can be simple - a rainwater butt - or more complex – an underground tank with pumps and filters. Porous pavings can provide comfortable walkways and driveways and reduce the surface water entering the drainage system.
Great savings in energy consumption can be achieved with centralized heating systems, or with centralized energy extraction systems feeding individual heat supply units.
This is only a very brief summary of the issues which will be taken into account during the design process. It is worth bearing in mind that simple steps can be very effective – wearing a woolly can reduce the burden on whatever heating system is employed. All energy comes from the sun, but each installation will be best suited if it is tailored to the clients needs, financial limitations and the opportunities offered by the site.
The performance and BER Rating of older houses can be effectively improved through increased loft insulation and pumped cavity insulation. Although more disruptive, effective improvements will be also be made by supporting insulation boards between ground floor joists. It is questionable whether it is cost effective to upgrade a house to sell. However, if a new house or adaptations to an existing one are under consideration, it is of huge benefit ( both in ecological terms and with a view to the anticipated escalation of fuel costs) to establish a high target BER Rating and develop the design towards this with a clear understanding of the clients lifestyle.