Energy efficiency is the buzzword of our times and increasingly gaining popularity in the building and construction industry. As catchy as it sounds, it is all about having low running costs which essentially means using less energy to achieve the same outcomes. This has several benefits like low energy bills, decreased personal carbon footprint and improved demand for energy efficient products in the market.
Having a passive building design should be the first step before you start building or renovating your house. A house with a good passive design maintains a comfortable temperature with the help of natural elements such as sunlight and air, thereby minimising its reliance on artificial sources of energy, ultimately reducing our energy bills. It is called passive because we do not have to make special efforts to have an energy efficient house.
An effective passive building design can be divided into seven elements: orientation, insulation, external shading, spatial zoning, ventilation, thermal mass and glazing. A successful combination of these can result in creating an energy efficient home.
Orientation plays a crucial part, especially in the southerly parts of Australia with temperate and cool climates. Orientation is the direction towards which the house faces. A house with correct orientation receives a minimum of five hours of sunlight per day. Harnessing this sunlight to increase heat retention in winters and heat deflection during summer time is the simplest way to achieve a high energy efficiency.
Simple things like living rooms facing north, windows with extended access to sunlight during winters and having operable windows can lower the energy requirements of your home.
Insulation acts as barrier between the internal and external elements of a house. It is mostly installed in the roof, wall cavities, above ceilings and below suspended floors.
Your insulation needs may vary based on your location and the building materials used to build your home. The purpose for which insulation is being used determines which type of insulation will be used. Well ventilated homes in the tropical regions use reflective insulation to restrict the amount of heat captured without restricting the amount of hot air escaping. To prevent heat from flowing out in winters and flowing in during summers, a combination of reflective insulation in he walls and bulk insulation in the ceiling is used.
Several other ways to insulate your home include adding weather seals to make your windows and doors draught proof, double glazing your glass units and covering your boiler to prevent heat loss.
Shading devices help keep up to 90% of unwanted sunlight from overheating a home, especially during summers. Various fixed and adjustable shading devices can be used to prevent direct sunlight from entering the house.
Traditionally, deep verandas, pergolas or eaves have been used to shade homes, but increasingly landscaping, plants, rollers shutters, external blinds and window awnings are being used. Ideally 30% of the windows and doors (height) should be shaded to ensure they work more efficiently with the sunlight. Seasonal shading like awning blinds or shutters can be pulled down as needed giving you the control over the amount of sunlight entering your house.
Thermal mass is the ability of a material to absorb and release heat. An efficient passive design utilises building materials like brick and concrete in a way that helps absorb excess heat from the inside of the house during summers and radiates the heats inwards during winters. If efficiently insulated from outside, these materials play a crucial role in regulating the internal temperature of the house due their ability to absorb, store and release energy as needed.
It is essential that thermal materials are insulated externally to make the most use out of them. These days brick is mainly used to veneer the exterior of the houses, which limits their thermal capabilities.
Ventilation plays a crucial role in ascertaining the energy efficiency of a home by keeping the internal temperature regulated.
A cross ventilation happens when air naturally breezes in from one end of the house and goes out from the other, without relying on artificial methods of circulation. Besides cooling, it also freshens up the entire house, thereby eliminating the threat of mould and infection.
Floor plans that allow natural air breeze to flow through the house augment natural cooling to provide efficiency and possible health benefits. The floor plans must be designed such that the windows and doors assist free circulation of air throughout the building.
Most Australian homes have central heating or cooling ducting systems, which lead to immense wastage and loss of energy. Zoning helps to curb this wastage by cordoning off unoccupied parts or creating zones to separately heat or cool occupied areas as required. This concentrates temperature requirements and reduces running costs.
Partitioning stairs, shutting off heating or cooling to unoccupied areas are some ways you can achieve effective zoning in your home. You can also create temporary zones to suit your changing needs with the changing weather by adding sliding or bifold doors or a porta door. All these ideal solutions to your partitioning needs.
Last but not the least is the impact glass glazing can have on the energy performance of your home. Vast amounts of heat can escape through thin sheets of glass. Before finalising on a window supplier, ensure that your windows have a high WERS (Windows Energy Rating Scheme) rating. WERS allows you to compare different window designs to suit the energy requirements of your building. Also, a WERS certified supplier will provide you with a glazing certificate that confirms the quality and performance level of the windows and doors.
Single glazed glass is usually not very efficient with heat retention, simply because it is not thick enough. Advanced double-glazed units and WERS rated windows have been developed over time to prevent dissipation of energy. Most houses these days are being designed with double glazed glass windows and doors to reduce energy bills, increase natural light and ensure energy efficiency. Standard double-glazed units these days have a sealed, argon filled spacer bar between two sheets of glass (standard thickness is 16 mm), which acts as an insulation to inhibit heat loss or gain as per seasonal requirements.
Window tinting (similar to car window tinting) can be another cost-effective option to limit solar heat absorption through your glazed doors or windows, especially when you want to improve the performance of your existing windows. A tinting film consists of a polymer layer with a reflective metal layer or a coloured dye with an adhesive at the back. Some films can reduce the heat absorption by up to 50%. Decorative films can also be used to increase the aesthetics of your house. A word of caution though, applying a coloured tint may reduce your visibility and this point should be carefully considered before you choose to go this route.
Another alternative is using a Low E glass, which has a special low emissivity coating on the top layer to reduce heat absorption without blocking light transmission. Therefore, Low E glass ensures that neither your view nor your light transmission is compromised. But be informed, choosing a Low E glass can add thousands of extras dollars since Low E glass tends to be quite expensive. For longevity and cost savings, Low E glass is used on the internal layer of a double-glazed unit. Most houses can achieve the required U-value and SHGC ratings with standard double-glazed glass units in thermally improved aluminium frames.
Aluminium frames are quite popular across Australia. Standard thermally improved aluminium frames are strong, durable and light weight. An initial investment in energy efficient glazed units can substantially lower your energy bills.
Thus, we see that the energy performance of our homes is a sum of averages where individual elements have minimal or no bearing. A successful marriage of several components is required to make our homes efficient to operate and comfortable to live in. Architects or building designers possess specialist knowledge in passive designing of a building. Approach them first to know special tricks and techniques to find the potential in your home. A building with good structural strength, layout and floor plan can be conveniently converted to optimise energy efficiency.