Pay attention to orientation & position of internal spaces (spatial zoning), Building materials (thermal mass), Breeze paths (ventilation), wall & roof insulation, summer & winter sun positions providing shading to match the season.
Orientation is fundamental to energy requirements. Good orientation is when a building lets the sun in during the cold season and prevents solar gain when it’s hot.
The objective is to stabilize internal house temperatures from one season to the next and reduce heating and cooling costs without increasing the cost to build.
The time to address these issues is at the concept design process. Whilst budget is important it should have no part in the passive design process considerations whilst the concept is maturing.
Heat, cool, breeze, lifestyle, natural light and living spaces. These are the main function at this stage.
We live in a temperate zone. Perth is zone 5. Our roof should reflect Australian temperate zones not colder North American or European zones.
The type of Insulation is always an important consideration. A renewable or recycled materials appeal to the mind. Whatever type of material you use it measures thermal resistance (or R-value). The higher the R-value, the more heat transfer is prevented. Minimum requirements are 6 stars. A higher star rating = more energy efficiency = less $$$ to buy energy for a comfortable home.
Ventilated Roof Space
Hot air in your roof space minimises affects the heat energy transmitted through the ceiling into living spaces. By venting the roof space ceiling insulation will be more efficient. Natural convection or mechanical extraction will include ‘whirlybirds’, solar extraction fans, roof ridge vents, gable vents and eave soffit vents allowing air into the enter the roof space from the underside of the eave. Roof venting is relatively low cost and on any cost benefits analysis it is value for money.
Common sense applies here. If the roof space is affected adversely by solar absorption a lighter colour is more effective. In Alpine areas a dark colour will absorb heat and will benefit those areas. For a temperate climate with a ventilated roof lighter seems better.
Perth Metropolitan is climate zone 5. Temperate.
The sun can be tracked on any day, any season and at any time of the day.
By understanding the sun's movements and angle in the sky a passive solar design can maximise sun penetration into the home for winter and exclusion in summer.
In some places around Perth prevailing winds and cooling breezes are a major consideration in a passive design.
Sunlight and breeze path through the home when properly designed will add comfort to home with reduced power consumption.
Significantly when designing or thinking about your home thinking ahead will pay dividends.
i. Is your family growing, or is it shrinking, will it stay constant?
ii. Families grow; children leave home and return with grandchildren.
iii. Planning for health or age in the future is important. Having an accessible bathroom is not a real cost at the design stage but to modify at a later time is expensive.
iv. Mindful of these things you can design a house that not only meets your current needs, but can meet your changing needs without you later incurring the cost of an extension or renovation. By future proofing your home you are adding value if you choose to sell your home.
v. With thoughtful design and sustainable building principles to guide the process many decisions are made simple as inefficient building practice is rejected earlier rather than later.
It is claimed that Australians have some of the biggest houses in the world. It is also claimed that smaller homes achieve higher energy efficiency standards with lower upfront and ongoing costs. There is merit to the argument for smaller homes are easier to keep warm equally there is a sustainable argument that larger houses are easier to keep cool in summer. Budget, lifestyle and personal taste are the real drivers in design.
This is probably the difficult part in this process of design. Many factors play into the equation.
Researching architectural trends, environmental issues, your needs for a satisfactory lifestyle experience and the resale of your home.
Complicated? Yes indeed. Whilst your home is probably your major investment in life the time you spend now researching what you want from your home will pay a huge dividend a long time after your project is built.
So invest your time now and invest it wisely.
a. Active heating / cooling may be essential in many Australian homes for extremely hot or cold days. Our temperate climate zone (zone 5) employing efficient and effective passive design principles a heater or air conditioner will be used only when needed. Providing comfort when needed but saving you money when it is not needed.
b. A major consideration is preventing leaks. Many older style Australian homes are traditionally ‘leaky’ and draughts can be responsible for up to 25 per cent of your heating costs – a similar amount if you air condition.
c. The Building Code of Australia requires all new homes to be fitted with air infiltration seals (draft excluders).
Lighting makes up about 11 per cent of the energy consumed in a typical home, about the same as refrigeration. Households can reduce energy use for lighting by 50 per cent or more by making smart lighting choices and using more efficient technology. Spending a little time and effort to get the lighting right in your house can save you money on energy bills and make rooms more comfortable and enjoyable.
It is important when considering the energy consumption of lighting to look at wattage, not voltage. Wattage measures electrical power, while voltage measures the electrical pressure or force a device runs at. Some bulbs, especially halogen down lights, are sold as ‘low voltage’, with many people thinking this equates to low energy consumption. This is not the case. The important factor is the power rating – 50 watts, for instance, is exactly that regardless of the voltage at which it is supplied and used.
Understanding your lighting requirement and matching that to you budget and lifestyle can be a bit tricky. Either get advice or do some research. Incandescent, fluorescent, halogen and led (light emitting diode) are the common technologies.
You may consider some lighting at the concept stage but it is later in the process that lighting should be considered in detail.
With the understanding of available technologies and a comprehensive lighting plan you will be able to have bright reading lights that transform to mood lighting for dining or home theatre viewing.
This part of the design process is often just left to the builder with sometimes disappointing results.
Being involved - asking questions and owning the final design considerations will help you achieve your lifestyle and home satisfaction.
A comprehensive lighting plan may look daunting and should only be viewed by experts. Not so. A comprehensive practical and even sophisticated lighting plan is easy to read and understand. The only thing you really need to do is give some quality time and own the results.
Of course you can just assign this to the designer and your lifestyle and expectations will be attempted. You will achieve a better outcome if you use the designer as a guide to achieving your expectations. By owning the outcome you will understand your new home better.
Solar hot water is a very mature technology and is a must for a passive solar design. Yes more expensive up front but the payback will make you smile.
PV panels have become a mature technology in recent years with the potential to add batteries to the system. What is not to like.
With these two rooftop technologies the time for consideration is at the concept stage. Your roof and orientation plays a major part in the efficiency of these technologies get it right in the planning and it will payback a large dividend.
Currently there are many homes being retro fitted with PV panels. The visual difficulties are very public. With a little forward planning your home could be designed for an expanded system with room for battery storage.
Your choice of building materials is about sustainable materials. All materials have an embodied energy, which is the energy used over their lifecycle, from processing of raw materials, to manufacturing through to product delivery. Choice of materials does not necessarily affect the efficiency of the material but instead address the issue of sustainable materials.
Efficient building materials is a requirement of the BCA with a minimum of 6 stars energy rating.
Sustainable building materials are a consumer choice.
Generally, the more processed a material is, the higher its embodied energy. So choosing sustainably sourced timbers, recycled and locally sourced materials, and low volatile organic compounds (VOC) paints and finishes will produce a sustainable house but not necessarily a more efficient house and can add to the cost of an efficient house.
Using sustainable building materials is about our responsibility to the next generation as is the discussion about climate change and sharing the earth’s resources.
So while we are discussing passive design principles there are some that have and use an environmental conscience.
It's fair to say that when people are environmentally informed they can bring to the design process specific ideas and use of materials that can be very interesting but more importantly this specific element of sustainable materials selection will feed into lifestyle and home satisfaction.
The passive design with sustainable building materials is not driven by resale value but by the satisfaction of responsibly caring for the earth and our environment.
Maybe one day this type of construction will be mainstream and those that achieve it today will be thought of as pioneers and praised for their efforts and commitment.
Windows and glazed doors will let heat & light in and heat out. So even if you’ve installed insulation a poorly placed window or glazed door will cancel out some of the benefit of insulation. As a general guide, the total window area of your home or a room should be less than 25% of the floor area locating glazed element on the North side on a home where good solar access is easiest to manage.
Today we can enjoy the benefits of many types of glass designed to suit very specific uses. Glass to stop heat from escaping. Glass to prevent intruding into our homes. Even self cleaning glass. Some types of glass have the ability to be clear and with the push of a button can instantly be a black.
Glass can be expensive and certain types of glass may not be practical or even cost effective. However if wow factor is what you are after and the budget can come second - there is a world of glass to research and explore.
Use three or four WELS star-rated shower heads, toilets and water fixtures.
What is WELS? WELS is Australia's water efficiency labelling scheme that requires certain products to be registered and labelled with their water efficiency in accordance with the standard set under the national Water Efficiency Labelling and Standards Act 2005
Kitchen, bathroom & laundry
a. Attention to selecting efficient appliance can affect the energy usage and the heat build-up in your home that can be a problematic in summer months.
b. Good quality extraction fans that self-close and efficiently remove steam and humid air from bathrooms will prevent mould and contribute to a healthy home.
c. Grey water - whilst not a requirement for passive design it does have sustainable design consideration for anyone considering a sustainable home design.
d. Black water is not considered for suburban development an even where appropriate is an expensive solution with associated health risks.
e. Rainwater Tanks - are appealing for sustainable design for a small household. The rainfall in Perth is not high and makes the practical use of rainwater tanks difficult but not impossible.