Any building (whether it be a house, a school, a supermarket or other structure altogether) that is truly energy efficient, comfortable, (relatively) affordable and ecological at the same time can be classified as passive construction. Keep in mind that ‘Passive House’ is not a brand name, but rather a construction concept that can be applied by any builder or supplier focusing on energy-efficient designs.
Eco buildings are not a new concept to South Africans, and passive houses (also called green buildings and eco homes) have taken this quite a few steps further, depending on which region of the country it is required. For example, a certain passive structure in an arid region (like Kimberley or Upington) was designed with operable screens surrounding the home's courtyard, allowing summer winds to ventilate the house when opened. On the same property, a conservatory with glazed stacking doors acts as a thermal heat collector during winter days. At night, blinds or curtains are closed to make any heat that has been collected in the concrete floors during the day radiate into the living areas and bedrooms.
In short, passive houses require a fraction of the energy used by traditional designs to heat and cool, which makes them a most welcome addition in South Africa, where electricity is among the most expensive in the world.
Passive Solar: Overhangs and screens can be used to block direct sun in summer. Deciduous vegetation can also be used to shade parts of the building and lower the temperature of the micro-climate in summer and allow light through in winter.
Passive Wind: When windows are placed at opposite ends of a room at different heights and sizes to create a draft, cross-ventilation is achieved. Windows can also be placed in relation to prevailing winds, which will cool a building down in summer and ensure a well-sealed structure in winter.
Passive Materials: It’s important to choose materials that have a high insulation value and can also absorb and release heat when necessary.
Passive Lighting: As South Africa enjoys lots of sunshine and clear skies during the day, this presents the ideal opportunity to use natural light through well-placed windows to light up indoor spaces during the day without having to use electricity.
Eco homes are definitely improving the quality of life for homeowners almost everywhere, but what advantages (and perhaps more importantly, disadvantages) do they pose?
· Green building construction offers a healthy and comfortable living environment without higher heating or cooling bills.
· Thicker walls that offer more heat retention.
· Insulation creates a sound barrier for more quiet indoor spaces.
· It can be beautifully integrated with hot-water heating systems.
· Due to the controlled ventilation, there is no condensation or mould.
· Low-temperature fluctuations.
· Lower operating costs.
· Independence from fossil fuels.
· It’s a sure investment in the future.
· It can be an expensive initial investment.
· The initial costs can be even higher (between 10% and 30%) for new or renovated constructions.
· Some locations require more insulation than others for ample heating and cooling, which means there's no ’one price/system fits all’.
· Additional heating and/or cooling systems may be needed as backup in case of extreme seasonal conditions.
· Occupants need to learn how to operate controls.
Passive houses or other structures can be seen as the next step in green building due to their environmentally friendly criteria, such as:
· Passive house buildings allow for heating and cooling-related energy savings of up to 90% compared to other building types. When it comes to heating oil, green buildings use less than 1.5 litres per square metre of living space per year, which is considerably less than for your average low-energy structure. Similar energy savings have been demonstrated in countries with warmer climates, like South Africa, where the buildings require more energy for cooling than for heating.
· Windows with excellent insulation properties, as well as a building shell consisting of good insulated exterior walls, roofs and floor slabs, help to keep the heat out during summer – and in during winter.
· A ventilation system is also put in place to consistently provide fresh air for enhanced quality without causing unpleasant draughts.
Searching for a “one price fits all” when it comes to eco houses, both in South Africa and abroad, is like asking how long is a piece of string: there are multiple answers as costs are all project-specific dependant on the process, size and complexity/simplicity of the brief and design, self involvement or not, etc. However, what we can do is study examples, such as the passive energy-efficient house in Pretoria that, thanks to its insulation properties, has an annual heating cost of approximately R567 (working at a kWh rate of R1,20).
Compare this to a standard, low-income house that doesn’t present all the energy-efficient properties as the previous one and has an annual heating cost of R4,082.
Our recommendation? Scope out builders and eco-friendly suppliers focused on environmentally friendly structures and passive houses in South Africa to find out what your required ‘green’ house will cost.
Don’t forget that homify has an ever-growing list of housing examples that not only includes passive homes, but also prefabricated structures, modular buildings, single-family residences, log cabins, wooden houses and many more. We also provide a list of professionals such as architects, interior designers and builders working throughout South Africa to help make your search for the best expert so much easier.