RETROFIT YOUR HOUSE FOR ENERGY EFFICIENCY

A guide for temperate climate regions in the southern hemisphere

Adapted from a report by Alison Bigg, "Retrofit your house for Energy Efficiency: A guideline to low—medium cost methods for the Perth region".

Introduction

The world currently relies predominantly on fossil fuels for most of its energy, and a large portion of this energy is wasted through inefficient use (New Internationalist, 1996). By reducing energy wastage, and increasing our use of renewable energy sources we are making an important step towards Ecologically Sustainable Development. Two major areas that can and need to be addressed are; existing, poorly designed housing (the topic of this paper) and the continuation of ‘off the rack’ housing development that has no regard for the importance of energy efficient designs (Okraglik, 1999).

The generation and distribution of electricity is only 25% efficient. This means that by saving one unit (kWh) of energy, you are effectively contributing a fourfold saving in environmental damage done during the production of that energy (Campbell, 1984). It has been estimated that 8.5% of Australia’s greenhouse gas emissions are from household energy use (Mullaly, 1998). If existing house owners were to become aware of the energy reductions they can make by some simple changes, the savings would be significant both environmentally and individually (Campbell, 1984).

 

Principles of climate sensible/energy efficient house design for temperate climates

There are five major areas to consider when determining the energy efficiency of a planned or existing house. These are:

• Orientation and layout.
• Correct use of windows and shading
• Correct and sufficient use of thermal mass
• Correct and sufficient use of insulating materials
• Ability to utilize ventilation
  

  (Busselton-Dunsborough Environment Centre Inc., 1995).

All of these except altering the orientation are applicable for retrofitting existing houses within a low to medium budget. Also important are patterns of consumption and energy preservation techniques.

 

Thermal Mass:

High thermal mass materials such as brick and concrete absorb heat from the sun during the day, and re-radiate it at night, (Okraglik, 1995) with the reverse occurring in summer (Busselton-Dunsborough Environment Centre Inc., 1995). As can be seen in Fig. 1, tiles can be used to good effect in conjunction with a concrete slab in order to increase the thermal mass. If the tiles were of a dark colour, the absorption of heat would be even greater (ibid).

FIGURE 1: Thermal mass created by tiling a concrete slab

 

With regard to space heating, the most cost effective method of reducing heat loss is through sealing of cracks and draughts which account for 15-20% of heat loss from most homes (Colesby & Townsend , 1975). These can be addressed using various forms of sealing, shown in Table 1. It must be remembered that some ventilation is necessary in the house, particularly if there is use of heating appliances such as gas where fumes may be problematic.

 

TABLE 1: Cost and Supplier of Various forms of draught-proofing

*Schlegel are wholesalers of these materials, retail prices would be in the range from 20-100% markup.

 

Use of vegetation and other shading devices:

Much can be done to improve the energy efficiency of a house by the appropriate use of shading in various forms. It is important in a temperate climate to block out the summer sun where possible, and allow it to penetrate in winter. Deciduous trees are particularly good in a Mediterranean climate for achieving passive solar gains, as they allow sun in during winter, but block it during summer. In the southern hemisphere, ideally, one would position deciduous trees on the northern face of the building, as shown in Figure 2. Shade trees (evergreen) are necessary on the south, east and west of the house to provide shade for when the sun angle is low, as in Figure 3. If shrubs are also located close to the house on these faces, the effect is enhanced (Campbell, 1984). With the added evaporative cooling function of vegetation, it has been shown that they are able to provide reductions in temperature of 10-15ūC (ibid).

FIGURE 2: Deciduous trees planted on the northern aspect of the house, to allow penetration of sun in winter, but restrict it during the hotter months.

FIGURE 3: Evergreen trees planted on the western side of the house for shade and wind protection.

 

Other methods of temperature moderation include the addition of a shadehouse on the western aspect, as shown in Figure 4. This structure was built 5 years ago, out of recycled timber, and cost under $1000. An even cheaper version of the same idea is shown in Figure 5, where shadecloth has been erected to the west of the dwelling. A pond has been added (using a second hand bathtub), and helps to cool the air that flows over it before it reaches the house.

FIGURE 4: Shadehouse erected on the Western side of the house for its cooling effect.

FIGURE 5: Shadecloth and bathtub to aid in reduction of heat on a western aspect

Movement of air within a house is an important aspect of design, allowing hot and cold air to be directed to where it is needed. A commercially available product to achieve the removal of hot air from the ceiling cavity of a house is the ’whirly bird’ ventilator. These are available from a variety of retailers at approximately $85. Installed they range from $150-170. It is claimed that they make a 5-10 degree C difference in the temperature of the house in summer by removing hot air from the ceiling cavity and drawing up cooler air from below. Vents can be created from below the house on the shady southern side to enhance this effect (Busselton-Dunsborough Environment Centre Inc., 1995).

In Perth the most significant winds are: hot summer winds from the east, cool summer breezes from the south-west and cold winter winds from the west and southwest (Campbell, 1984). Figure 6 shows a method of hindering the hot easterlies using bamboo blinds. The cool south westerly in summer can be channelled into the house via the judicious use of windows and doors, making a significant difference in the temperature.

FIGURE 6: Bamboo blinds used to hinder the hot summer easterly winds

Conclusion

Fossil fuel use has many associated environmental externalities, and when these are considered, it becomes not quite the cheap fuel it is considered today. Despite the fact that there are many alternatives available and many means of reducing our use of them, governments in Australia seem to have some reluctance (although this is changing slowly), to encouraging energy efficiency in both domestic and industrial areas. By incorporating some lifestyle changes, it is possible to prevent much of the current wastage of energy related to domestic use. One significant way to do this is by improving the energy efficiency of existing houses. There are many low to medium cost ways of retrofitting houses to this end e.g. landscaping, insulating and filling cracks and gaps.

 

References

Barker, J., (1991) ‘Energy in Buildings (1)- Insulation’, REAC Factsheet #3, Murdoch University, Murdoch, rpt in N210:Environmental Technology for Sustainable Development: Reader 1999, Murdoch University, Murdoch, WA, p29-31

Busselton-Dunsborough Environment Centre Inc. (1995). Energy Efficient Housing in South West WA. A Guide for Homebuyers and Builders, rpt in N210:Environmental Technology for Sustainable Development: Reader 1999, Murdoch University, Murdoch, WA, p33-37

Campbell, R., (1984) Modifying your home for energy efficiency, Appropriate Technology Development Group, North Fremantle, WA,

Colesby, J.A., Townsend, P. J., (1975) Keeping warm for half the cost, Prism Press, Dorset, UK

Mullaly, C., (1998) ‘Home energy use behaviour: a necessary component of successful local government home energy conservation (LGHEC) programs’, Energy Policy, Vol. 26, No.24, pp. 1041-1052

Okraglik, H., (1995) ‘The Challenge of Environmentally Sustainable Housing’ Green Heating Quest:First National Workshop, (Online), Available World Wide Web: URL: http://www.cfd.rmit.edu.au/gtq/GHQ/okraglik.htm (Accessed 21 August, 1999)