Sustainable Designs Reduces Running Costs

Sustainable Designs Reduces Running Costs

How can you use sustainable design in your home to reduce energy costs Architect, Simon Hoe RIBA explains how.

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). To use energy lightly, to make use of passive energy sources, should lead to savings in running costs which should offset the capital outlay. To decide on the right approach, a close understanding of a family's lifestyle is essential and then the building can be designed from two aspects: The shape and fabric of the building, and the services installed to provide power, heat and control water usage.

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.

The shape and fabric 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. Internal utility rooms can provide cost effective drying areas.
  • Comparing timber frame with masonry - timber frame is quicker and renewable. Masonry discharges considerable C02 in the production of the blocks, but the mass can be used to store heat to save running costs. Masonry is more easily "sealed" than timber frame, which is important due to the potential humidity problems created by the high levels of insulation demanded by the Building Regulations. (similar to those that apply in Northern Canada, where temperatures drop to -40C every winter!).
  • Windows - Double glazed windows can satisfy Building Regulations. Triple glazing offers more heat retention than double glazing, but is much more expensive. Minimizing the size of north facing windows reduces heat loss and capital outlay. 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 paints. They tend to be more expensive, but generally 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 minimise 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.

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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.

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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 modeled to modulate the light and create an interesting space within. The dining area is lighter than it was previously. Low emission double glazing provides sufficiently insulation to keep the room warm. The garage space provides for a shower / utility room and study.

The Services Installation.

The choice of power and heat producing equipment must take into account the family's lifestyle.

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. This will reduce running costs, but further improvements can be made.

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.

Reduced dependency on mains power is the realistic and achievable target, and this can be achieved through the installation of a variety of systems:

  • Geothermal and air to water heat pumps consistently provide low temperature warm water, but cost approx €500 per year to run. They would not be cost effective for the heavy demand for showers at peak periods such as a large family would make. However, they should successfully provide low cost heating 24 hours a day - ideal for a home in continuous occupation, possibly the elderly.
  • Under-floor heating stores heat in the concrete floor slab, so there is no sudden temperature drop when the heating goes off, and night time low cost electricity can be made use of. Manufacturers claim a pay back period of 5-7 years. Again, most suited to continuous occupation.
  • Wind turbines can be installed in houses, but are generally more efficient in large, carefully located centralized locations. They can be noisy.
  • Photo-voltaic solar panels produce electricity rather than hot water, and it is anticipated that excess can be sold to the grid in the foreseeable future.
  • 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.

Reduced Running Costs.
For new houses and house adaptations, 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.

For older buildings, it is questionable whether it is cost effective to upgrade a house to sell. However, the BER Rating and running costs can be effectively improved through increased loft insulation and pumped cavity insulation. Although more disruptive, further improvements will be made by supporting insulation boards between ground floor joists. A new high efficiency condensing boiler and a double skinned hot water tank should make valuable savings. would like to thank Simon Hoe Architect, for their helpful advice and tips for this article.

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