Tag Archives: Energy Savings

BDAV 10 star design Challenge Finalist 2012


I still can’t believe that we made it under the 3 finalists of this years 10 star design challenge, this came really unexpected. Especially as I mainly participated to get a certificate that I can design and rate 10 star homes and only spent one Saturday on this. Unbelievable.

Thanks again to the BDAV:

“This contemporary design, with clean lines and clever cantilevers, creates architectural appeal and a well-proportioned building. Innovative non-toxic and renewable building materials were used in combination with triple glazed PVC windows. The building has a small footprint; however, generous room sizes and good use of multi purposes areas create a practical and visual appealing design solution.”



What is Thermal Mass and why do we need it?

Although the term ‘thermal mass’ is not commonly used, there are many examples where we experience it and appreciate its benefits. The most impressive is the ocean: in winter, when there is less sunshine and the average air temperature is low, the water is chilly and only the tough ones might enjoy a swim! In spring, the sun will slowly heat up the water so that finally in summer it will have a comfortable warm temperature. Water has a great capacity of storing heat – it will stay constantly warm during day and night, and even in winter, it can be significantly warmer than its surrounding air temperature due to its ability to absorb solar energy. Water demonstrates the principle of thermal mass. How does it apply to construction?

Thermal Mass, Why Is It So Important?

Thermal mass is the ability of storing and releasing heat to help retain a constant indoor temperature. It is an effective way to improve thermal comfort in a building and plays an essential role in saving energy. Thermal mass inside a building will absorb heat when the surroundings are warmer than the mass, will store the heat and radiate it slowly when the surroundings are cooler. It can actively be used to regulate temperature, therefore, reducing the need for mechanical heating and cooling. Heavy materials, such as concrete and brick have great thermal storage capacity, whereas lightweight construction materials, such as timber and insulation cannot store heat. Generally speaking, the heavier a material the better its ability to store heat.

Summer benefits
Materials such as concrete and brick are cooler in summer than the surrounding air temperature, so they are able to absorb heat,  which consequently lowers the room temperature and the need for additional cooling. At night the thermal mass will slowly release stored heat. Natural ventilation, via open windows, ceiling or exhaust fans, are an effective way to let cool air in and to let heat – collected during the day – out. In extreme hot periods, when it doesn’t cool down at night, air conditioning may be required to regulate the room temperature. The greater the difference between day and night temperature, the more beneficial the thermal mass.

Winter benefits
In winter, thermal mass works like a heater: it absorbs radiant heat from the sun through north, east and west-facing windows, and also stores heat from mechanical heating. The thermal mass will slowly release the heat which reduces the need for heating. Even when the heaters are turned off, the house will stay warmer for longer. Furthermore, the air and the exposed surfaces have the same temperature (Mean Radiant Temperature), which means there are no unwanted draughts, and the Relative Air Velocity is low; these will increase the thermal comfort of the occupants.

Optimal Use Of Thermal Mass

How to locate thermal mass
Thermal mass needs to be situated correctly and needs to work in combination with passive solar design and good performing insulation, otherwise it can have negative effects and even increase the need for heating and cooling. Thermal mass should be situated on the interior face of the building envelope and must be thermally separated from the outside via insulative materials.

Thermal mass should be located throughout the building to maintain comfort in summer, but the main focus should be on north-facing rooms. Good solar access is obligatory as the low winter sun needs to be able to enter the building and to strike the thermal mass. The more glass area, the more thermal mass is required.
Thermal mass is extremely important for multi-storey buildings, as warm air rises and therefore the rooms tend to overheat easily. Unfortunately most upper storeys are usually built in lightweight construction, as this is cheaper and easier to build. It is important, however, to incorporate as much thermal mass as possible, for example concrete floors or internal brick walls.

Material and colour selection
Generally speaking, the more thermal mass the better and the heavier a material, the better its ability to store heat. The optimum would be a masonry home with a reverse brick veneer construction and concrete floors. If this option is too expensive use as much thermal mass as possible, concrete slab is preferable. In warmer climates the ground is colder and can help to cool the concrete. Therefore the indoor air temperature will be reduced. In colder climates, however, the concrete slab needs to be insulated from the ground in order to minimise heat loss in winter.
If a timber subfloor is requested, the focus should be at least on internal brick walls to the north which need to be exposed to the winter sun and are therefore able to absorb and release heat. Other materials that have a good thermal conductivity are water, sandstone, rammed earth and earth blocks, mud brick etc.
Moreover, colours and coverings can influence the performance of thermal mass. For example carpets and timber floors will minimise the ability of thermal mass to absorb and release heat as they work as additional insulation. This can lower the required heating in winter, but it will increase the need of additional cooling in summer, as the thermal mass can absorb less heat. On the other hand, hard floor finishes such as tiles, stone or slate on concrete slab can increase the ability to store heat. Dark colours or dark materials also tend to absorb more heat, however, light-coloured walls are more desirable as they maximise natural daylight. Dark walls will increase the need of artificial lighting, as they absorb light and can make rooms appear smaller. In short, material and colour selection can promote or adversely affect the performance of thermal mass.

Examples for wrong location of thermal mass
Brick veneer wall construction has brick to the exterior, studs to the interior with insulation between the studs. In this scenario, brick can’t act as a thermal mass as it can’t store or release heat to the interior space.  Conversely, double brick walls can absorb heat, but due to the fact that there is no thermal separation to the outside, they act as a thermal bridge and release heat to the exterior which will increase the heating needs in winter.

Heating And Thermal Mass
Split systems and ducted heating are the most common heating systems in Australia – they function by pumping hot air into the room. When fan or ducted heaters are turned on, a room will be warm, however, immediately after they are switched off, it is cold again. This is because they use convective heat which warms the air, not the materials in the room. Open fire, gas or hydronic heaters eject radiant heat from their hot surfaces. It takes longer to warm a room as it also warms up the objects and materials, the occupants in turn feel more comfortable, as the Mean Radiant Temperature is well balanced. Even when the heaters are turned off, the thermal mass will release its stored heat slowly and therefore keep the room warm for a longer time, depending on the performance of the insulation.

How Thermal Mass is Used Overseas
In most European countries, thermal mass is used as a matter of course. Although it takes a longer to heat up a house which contains a lot of thermal mass, it also takes a long time to cool down again. The thermal mass releases constant heat to the rooms and therefore heaters only need to be on a low setting or turned off completely. Unlike in Australia, split systems and ducted heating are rarely used overseas as they use convective heat. The main focus lies on radiant heaters as they heat thermal mass.
If thermal mass is combined with effective insulation and has good solar access, the interior is perceived to be comfortable, without the need for additional heating, even if the external temperature is well below 20°C. The combination of thermal mass and well performing insulation is a condition of passive solar design, as well as low and zero-energy housing.

Thermal mass is an effective way to reduce the need for mechanical heating and cooling and to increase the comfort and well-being of the occupants. In order to perform at its best, it needs to be located appropriately and sized adequately, with a careful eye on insulation and thermal bridges.

Why Is Good Window Design So Important?

Is double glazing worth the money? The answer is YES, but ONLY if it is installed correctly without a cold bridge (thermal bridge). A window or a door is essentially a hole in the wall and responsible for most of the unwanted heat loss or gain.

Windows are essential for a house and the comfort and well-being of its habitants, as they let natural light and fresh air into the building and enable views. Appropriate window design, size, location and glazing treatment, combined with shading and internal covers, can significantly reduce the energy required for heating and cooling. Maximum solar access for north-facing windows can reduce winter heating bills up to 25%. External shading can block up to 80% of summer heat gain through windows. Double glazing and internal coverings can reduce heat loss in winter up to 40%.
Glass is the potential weak point of a building in terms of energy efficiency. A single glazed window can gain or lose up to ten times more heat than an insulated wall. The main heat gain through windows is due to thermal radiation. Windows receive direct solar radiation when the sun strikes the glass, but also diffuse radiation reflected from the sky and the ground. Between 30-40% of total radiation to north windows is diffuse, depending on the weather conditions. Radiation from the sun travels through glass to the inside of a house. This radiant heat is absorbed by thermal mass, building elements and furniture, which when warmed up, re-radiates heat to the room air. This re-radiated heat is trapped inside, resulting in convective heat build-up within the room. This process is called ‘glasshouse effect’. In order to hinder direct rays from the sun entering the building in summer, glass needs to be shaded appropriately. On the other hand it is also important to ensure valuable winter sun can shine into the house, as heat gains in winter can reduce the requirements for mechanical heating.

Energy Efficient Window Design
The total radiation received per window varies according to the time of the year and the orientation. In summer, all windows receive heat gains, in particular those facing east and west. Whereas in winter, only windows facing north, north-west and north-east have a net heat gain, with heat gains outweighing heat losses. Windows facing all other directions will affectively lose more heat than they can gain. However, in the absence of northern solar access, windows to the east and west can provide some winter heat gains.
The most appropriate size of windows in terms of energy efficiency depends on many factors, such as glazing type, orientation of a building and thermal mass located inside the building materials. It is important to consider every room separately, as each room may have different acceptable limits and therefore may need different sized windows. Thinking about the windows early in the design process can save time and money otherwise needed later in the progress, to chase after the required stars to obtain a valid energy rating. We can help determine the effect of variations to window orientations, window sizes, internal glazing, double glazing versus single glazing, shading and internal coverings by using the FirstRate House Energy Rating software. Below are some clues on how and where to place windows.

How to orientate and size windows
Windows should be orientated to the north where possible. If solar access is good, north-facing windows should be large, but the size also depends on the amount of thermal mass in the building. South and east-facing windows should be kept pretty small, and windows to the south need to be positioned to enable cooling summer breezes to pass easily through the rooms. Whereas west-facing windows should be avoided where possible, if needed they should be relatively small and well shaded.
Appropriate window sizing, combined with double glazing, and/or close-fitting internal coverings such as drapes with pelmets, can minimise heat loss in winter. Furthermore, it is important not to overshadow windows in winter by the structure of the building itself, as it will reduce the solar access.

How to respond to poor solar access

Innovative design can overcome problems of poor solar access and overshadowing,  especially in renovations, infill developments, higher density or small allotments with bad orientation, which can cause problems. In these cases, it’s important to use better performing insulation, protect windows, minimise overshadowing and courtyards, and reduce air leakage as much as possible. To compensate for poor solar access, the total window area of a building should be reduced.
Where solar access to north-facing windows is obstructed, clearstory windows are a good option to get solar energy into the building. Another option in responding to bad solar access is raising the sill height, as it will minimise permanent shaded glass areas, as these aren’t able to gain heat in winter and will lose heat instead.
Skylights and roof lights are also a good way to bring light into rooms, if obstructions from other buildings and structures prevent good solar access. Furthermore it’s a great opportunity to overcome overlooking into neighbouring properties, as windows above 1.7m don’t need to be screened. However, it is vital to protect the windows against harsh summer sun. Double glazing is mandatory as well as shading (a combination of external as well as internal shading would be the ideal solution).

How To Reduce Unwanted Heat Transfer

Summer heat gain
It is important to protect windows with external shading devices, through appropriate window sizing and location, in order to minimise heat gain in summer.

Comparison of heat gains through different treatments for windows in summer
(According to Sustainable Energy Authority Victoria 2002)

  • Unshaded single-glazed window: 100%
  • Standard double glazing as available in Australia: 90%
  • Vertical blinds/open weave drapes: 76%
  • Internal venetian blinds: 55-85% (Effectiveness is reduced as the colour darkens)
  • Internal drapes or Holland blinds: 55-65%
  • Tinted glass: 46-65%
  • Solar control film/reflective glass: 20-60% (Available in different kind of configuration with varying effectiveness)
  • Trees, full shade: 20-60%
  • 1 metre eave over north wall: 30%
  • Roller shutters: 30%
  • External awnings: 25-30%
  • 2m pergola over north wall covered with deciduous vines or shade cloth: 20%
  • Outside metal blind or miniature louvers, parallel and close to window: 15-20%

External shading devices are an effective way to minimise heat gain through glass in summer and keep a building cool. They provide far better protection from heat gain than internal window covering. However, if external shading is not possible, internal coverings can at least reduce the unwanted heat gains. Shading devices should always enable ventilation outside the window, as shading fitted too closely to a window can trap warm air which can be conducted into the house.
Eaves, verandas or pergolas are commonly a part of the building structure, they are durable and do not require ongoing adjustments. It is essential to have a certain distance between the underside of the shading devise and the top of the window. But these fixed shading devises should only be used over north-facing windows, as they lack flexibility and aren’t adjustable. East and west-facing windows need a flexible shading devise that can be completely retracted in order to let the valuable sun through in winter, but to protect from the harsh summer sun. Adjustable shading includes amongst other things canvas blinds, different types of shutters, angled metal slats, louvers or shadecloth over pergolas. Adjustable shading requires action from the occupants, as they have to respond to climatic conditions.

Winter heat loss
Unprotected  glazing  and single glazing in particular means the surface of the glass is noticeable colder than the warm air in the room. This lowers the room temperature and produces draughts. The Relative Air Velocity ends up too high and occupants will feel winter discomfort. For this reason, all windows require protection from heat loss in winter. To minimise winter heat loss, it is important to trap a layer of insulation still air between the window and the room. This can be achieved for instance by using internal coverings, such as drapes, Holland blinds, Roman blinds or Australian blinds, and thin or lace curtains combined with pelmets.

Effect of window treatments on winter heat loss
(According to Sustainable Energy Authority Victoria 2002)

  • Unprotected single glazing: 100%
  • Vertical or venetian blinds: 100%
  • Unlined drapes or Holland blinds, no pelmet: 92%
  • Heavy, lined drapes, no pelmet: 87%
  • Unlined drapes or Holland blinds, pelmet: 79%
  • Standard double glazing: 67% (the higher the U-value the less the heat loss can be)
  • Heavy, lined drapes, pelmet: 63%
  • Double glazing with Low-E coating: 57%
  • Double glazing, heavy drapes, pelmet: 46%

Double glazing
The most effective way to protect windows against heat loss in winter is a combination of double glazing and internal window coverings. However, if internal coverings are inappropriate or not desired, for instance in highlight or clerestory windows, in kitchens or simply where unobstructed views are wanted, double glazing is an indispensable measurement in order to prevent heat loss in winter. Yet double glazing won’t prevent sun coming into the building, which means that the windows need to be protected from harsh summer sun by means of external shading.

Window frames
Another, often underestimated roll in the energy efficiency of a window, is the frame itself, as it can effect negatively on the overall performance. As we talked about in the blog “Adequate Insulation”, some materials, such as metal, glass or aluminium, allow heat to pass through them more easily, therefore they shouldn’t be used for windows frames if at all possible. If metal frames are used, such as aluminium, they should have thermal breaks to reduce the heat transfer. Generally speaking, PVC and timber frames perform better than metal frames.

Comparison of heat loss through different window frames
(According to Sustainable Energy Authority Victoria 2002)

  • Single-glazed industry typical aluminium: 100%
  • Single-glazed thermally improved aluminium: 87%
  • Single-glazed timber or PVC: 82%
  • Double-glazed industry typical aluminium: 72%
  • Double-glazed thermally improved aluminium: 60%
  • Double-glazed timber or PVC: 54%

Sealing and weather-stripping
A good U-value is no guarantee for a well performing window. The installation of doors and windows needs to be done according to the manufactures guidelines. All gaps must be sealed and weather-stripped carefully in order to perform to the specified U-value. Unfortunately, the energy rating just states the material U-value of the window and not the end product and common practice often shows incorrect installation leading to thermal bridges around the windows.

Window Energy Rating Scheme
The Window Energy Rating Scheme (WERS) is a program implemented by the Australian Window Council Inc. (AWC) with the support of the Australian Greenhouse Office. The windows are evaluated with stars, the more stars, the better the performance. If buying windows, always check the label before making a decision.
A single-glazed window with a typical aluminium frame has U-values ranging from 7.9 W/m²K to 5.5 W/m²K (according to the indicative ranges of whole glazing element performance values in the BCA). These U-values will make it hard to reach a good energy rating for a building. Keep in mind, the lower the U-value the better performing a window. Double glazing windows with timber framing in Australia usually range between a U-value of 3.8 W/m²K and 2.5 W/m²K.

Windows And Double Glazing Overseas
Whereas most countries in Europe require double glazing and even recommend triple glazing, it is not standard in Australia yet. Unfortunately, double glazing is still more expensive than single glazing in Australia, in Europe it’s actually the other way around. Due to the fact that single glazing is not allowed any more, no one is producing it on a large scale making it quite expensive. Double-glazing on the other hand is a standard, and although better performing than common double-glazed windows in Australia, they are available for about a quarter of the price. For instance, the minimum required U-value for windows in Germany is currently 1.3 W/m²K. I trust that with time, double glazing will become more affordable and will become mandatory in Australia to achieve good passive solar design.

YES, double glazing is worth its money. It is the best method to reduce heat loss in winter, as long as it is applied, installed and used properly.  The window size should respond to the location and the climate, the insulation around the window needs to be snug fit, in order to prevent thermal bridges. Appropriate window frames need to be used and furthermore, adequate internal and or external covers needs to be applied. All these measurements need to work together, otherwise a window is nothing more than a hole in the wall and will be the major contributor for unwanted heat gain and loss, therefore preventing energy efficiency.

Adequate Insulation

Thermal insulation is a fundamental factor to achieve thermal comfort for occupants. Insulation reduces undesirable heat loss or gain and can lower the energy demand on heating and cooling systems.

The Victorian Government is planning to introduce new regulations for the existing housing market. Originally planned for 2011, then moved to 2012, we’re now in 2016 and it this initiative is still getting postponed further. However, eventually  hopefully it will be a requirement to provide information about energy, water and greenhouse performance to buyers and renters.

Assume two homes are for sale in the same street, both are three bedrooms single storey brick veneer buildings with a double garage on a block of approximately the same size. One has a 2-star energy rating and the other one has 5-stars. Which one is more likely to sell for more?




Insulation, Why Is It So Important?
Insulation is the most effective way to improve the energy efficiency of a building, as it acts as a barrier to heat transfer. It will keep the house warm in winter and will help to stay cool in summer, improves thermal comfort and well-being, and minimises condensation on walls and ceilings. Furthermore, insulation needs to be combined with appropriate shading devices to windows and adequate ventilation possibilities, otherwise heat entering a building through windows will be trapped inside by the insulation and lead to overheating.
Older houses in particular pose a problem: inadequate insulation, poor solar access and air leakages amongst other things lead to unwanted heat gain and loss, and consequently higher energy bills.
Adding insulation to a home can save 45-55% of mechanical heating and cooling needs and as a result, save non-renewable resources and reduce greenhouse gas emissions. With the current energy prices, additional insulation usually pays for itself in around five to six years. With the prospect of rising energy prices it’s more than likely that insulation retrofitting will pay off even quicker.

Different Types Of Insulation
The purpose of thermal insulation in a building is to regulate the internal temperature by minimising or stopping heat transfer through radiation, convection and conduction. Generally speaking, there are two different types of insulation that must work together to prevent heat transfer: Bulk insulation and reflective insulation.

Bulk insulation
Bulk insulation mostly resists the transfer of conducted and convected heat, using millions of tiny pockets filled with still air or other gases within its structure. This air provides the material’s insulating effect, therefore it’s essential not to compress bulk insulation. Bulk insulation is available in different shapes and materials.
-Batts and Blankets (Glasswool/Fibreglass, Rockwool, Natural Wool, Polyester)
-Loose-fill insulation (Cellulose Fibre, Natural Wool, Granulated Rockwool)
-Boards (Extruded Polystyrene, Foil-faced expanded polystyrene, Wood Fibre)

Reflective insulation
Reflective insulation mainly resists radiant heat flow. It is made of thin sheets of highly reflective aluminium foil, which reflects heat from its polished surfaces. The performance relies on the presence of an air layer of at least 25 mm next to the reflecting surface. Keep in mind that dust will greatly reduce the performance. Some examples include:
– Reflective Foil Laminate
– Multi-Cell Reflective Foil Products
– Expandable Concertina-Style Foil
– Foil Bonded to Bulk Insulation
For information about electrical safety checks for householders with foil insulation go to ‘Home Insulation Program’ webpage from the Australian Government.

Insulation needs to be installed with careful attention to detail, as inappropriate or incorrect application will crucially decrease performance. For instance, failure to butt all ends and edges of batts to give a snug fit could mean that about 5% of the ceiling area is not being covered. This could result in losing up to 50% of the potential insulation benefits.

  • Avoid thermal bridges
  • Eliminate gaps in insulation
  • Do not compress bulk insulation
  • Protect insulation from contact with moisture, provide vapour and moisture barriers to prevent condensation
  • Provide a sealed air space of 25mm adjacent to reflective insulation
  • Allow clearance around appliances and fittings
  • All electrical wiring encased in insulation must conform to AS3000: Electrical installations-buildings, structures and premises. It’s best to keep wiring clear of insulation, e.g. to run wiring on top of ceiling joists.

How Much Insulation Is Needed?

The Building Code of Australia (BCA) identifies eight different climate zones for Australia, but within a zone, there are some locations with slightly different temperature ranges.  There can be significant differences between maximum and minimum temperatures in summer and winter and in length and intensity of heating and cooling periods. The house design, the insulation and construction must respond to these variations in order to be able to perform energy efficient. But keep in mind, the required R-values in the BCA are minimum requirements and NOT best practice!!!!

For simplicity, Victoria is divided in five climate zones, with winter heating as the predominant concern especially in the Temperate Coastal and Cool Inland Zones. Summer cooling is variable but generally less significant. House design in these zones requires attention to better performing insulation, draught proofing, window protection in winter and shading in summer. Likewise, in warmer cities and areas like Mildura supplementary heating is obligatory for thermal comfort.  In these regions, it’s advisable to include extra thermal mass, cross ventilation and summer shading, whereas alpine areas may require constant heating for most of the year and cooling requirements are negligible.  Consequently, a  5-star home inMildura wouldn’t comply with the minimum requirements for a  5-star home in Ballarat.

The higher the R-value the better the performance. Consider what insulation is needed in order to build an energy efficient home in a certain climate zone early in the design process. In particular, it’s important to think about the roof insulation. For example, it would be cheaper to use larger rafters in order to fit in sufficient glasswool to fulfil the desired R-value, instead of using thinner expensive extruded polystyrene. Larger rafters would mean that the overall height of the building rises slightly. This is no problem, if the amendments are done early in the design. However, if a town planning permit has already been granted, it’s not that easy any more. It’s necessary to go back to the council with the changes, which can cost a lot of time and money, therefore in most cases, people choose to use the thinner, more expensive insulation instead.
Adding R1.0 insulation can significantly improve the energy efficiency. For example in Melbourne, adding insulation with a R-value of R3.0 to the ceilings and R1.5 insulation to walls can save 12% on energy bills each year and can ensure a higher level of comfort.

Insulation Regulations Overseas

Thermal bridges
When I started working in Australia, I was puzzled how thin walls can be. For example, a typical timber wall measures 110mm, 90mm for the timber studs, 10mm plasterboard on each side and insulation just between the studs. This construction is not allowed in most European countries, as it creates a structural thermal bridge. The U-value of timber is much higher than the U-value of the insulation, which means that heat can escape through the timber and consequently increases unwanted heat gain or loss. In Europe, the main focus lies on avoiding thermal bridges. A timber construction is usually done as a double stud wall. In this case, there is also a timber stud to the interior, covered with plasterboard and insulation between the studs, but at the outside is another continuous layer of insulation, and then another timber stud, with external plasterboard and again insulation in between. (see diagram below)
In Australia, there are no strict regulations about thermal bridges and also no minimum insulation regulations for concrete slab-on-ground construction, roof or internal walls.


Example for an insulation for a typical Australian home compared to a German home

External Wall R-value: 1.3 R-value: 5.0
Roof Not required R-value: 6.6
Ceiling R-value: 2.2 R-value: 3.3
Internal Walls (to garage, bathroom, staircase etc.) Not required R-value: 3.3
Floor R-value: 1.0 R-value: 3.3

Obviously, the average temperature in Germany is much lower than in Australia, therefore it is natural, that the R-values of the insulation need to be higher, but there are also some differences in where the insulation needs to be installed. In Australia, usually just the ceiling gets insulated, although the roof space is ventilated, heat can be trapped inside in summer which can transfer through the ceiling and heat up the rooms below. In Germany, the main focus lies on the roof itself, the whole outside of the building is treated as a continuous shell. Ideally, no heat should be able to transfer into the building at all. There are no wall or roof vents, most of the buildings are even air-tight.
For instance, in winter you can easily distinguish between a good and a bad insulated home in Germany. In a good insulated home snow won’t melt on the roof tiles, as no internal heat can escape the through the insulation which reduces the energy required for heating enormously. Furthermore, it is also a requirement to insulate the ceiling to a roof space and to floors/ceilings between different levels, as well as to place insulation on some internal walls, for instance walls between rooms with different heating requirements, to unheated corridors, garages etc. This is to stop heat ‘traveling’ through a house from room to room.
Furthermore, typical brick veneer constructions, as shown above, are not advisable, as the thermal mass is located on the outside of the building and therefore can’t be used to actively contribute to heating and cooling needs. Brick should be located on the inside. Therefore a better opting would be to use a reverse-brick construction, where the brick is inside the building envelope and consequently is able to store heat and to regulate the indoor temperature.

What can we learn from overseas?
Minimising thermal bridges and heat transfer is mandatory in order to create energy efficient and environmentally friendly buildings. All insulation must be installed snug-fit, there should be no gaps and also thermal bridges should be avoided where possible in order to minimise greenhouse gas emission and to protect the environment.

Neither a 6 or 7-star energy rating nor high R-values are a guarantee for energy efficiency. The building envelope needs to be treated as a delicate continuous shell. Each small gap and leakage will impair the performance of the insulation. It is essential to consider the end product in order to determine how energy efficient a building really is. Even small gaps in the insulation such as around windows or other wall penetrations can halve the potential insulation benefits.  Adding good performing and appropriately installed insulation can save a lot on your energy bill and minimise the greenhouse gas emission.

Thermal Comfort

Nowadays, you can see sustainable buildings and green design solutions everywhere. But what does it actually mean?  Is a so called sustainable home automatically environmentally friendly?  How to distinguish between real sustainable design and one that claims to be?


What IsThermal Comfort And Why Is It So Important For The Well-Being?

What is thermal comfort?

Human thermal comfort describes the state of mind that expresses satisfaction with the surrounding environment and refers to several conditions in which the majority of people feel comfortable. The human body produces heat depending on the level of activity, and expels heat according to the surrounding environmental conditions.

The body loses heat in three main ways:  radiation, convection and evaporation. An unpleasant sensation of being too hot or too cold (thermal discomfort) can distract people from their activities and disturb their well being. This may reduce the ability to concentrate and decrease motivation to work. Thermal comfort is affected by six variable factors which are needed to maintain a healthy balance in order to sustain satisfaction with the surrounding environment.

1) Air Temperature is the most common measure of thermal comfort and can easily be influenced with passive and mechanical heating and cooling.

2) Mean Radiant Temperature is the weighted average temperature of all exposed surfaces in a room. The greater the difference between air temperature and exposed surfaces, the greater the Relative Air Velocity.

3) Relative Air Velocity (‘wind chill factor’) is the apparent temperature felt on exposed skin due to wind.  For example, if cold air is leaking in from a window, the air temperature feels lower than the actual air temperature, hence the increased likelihood of feeling cold, even when the heater is on.

4) Humidity or relative humidity is the moisture content of the air. If the humidity is above 70% or below 30% it may cause discomfort.

5) Activity Levels can reduce the heating needs, as lower air temperature is acceptable when occupants have higher activity levels.

6) Thermal Resistance of clothing or warm blankets in a bedroom can reduce the need of heating.

Building design is affected by the first four of these thermal comfort variables. The last two depend on the action and behaviour of the occupants.

What factors are influencing  thermal comfort ?
If the insulation applied is faulty or insufficient, the exposed surfaces in a room will stay significantly colder in winter or hotter in summer than the room temperature. Although the heater pumps hot air into a room, or the air-conditioning blows cool air, the thermal radiation will affect the equilibrium. The Mean Radiant Temperature is affected negatively and the occupants won’t feel comfortable.

  • The ceiling isn’t insulated or the insulation is penetrated for example because of the installation of down light. As warm air is always moving upwards, heat is lost to the cooler air in the roof space.
  • Air leakage around doors, windows, down lights, pipes, and other wall penetrations are exceeding the acceptable Relative Air Velocity.
  • Wrong application of thermal mass can influence the Mean Radiant Temperature and can therefore increase the need of mechanic heating and cooling.
  • Under- performing windows and doors (when air is able to leak in/out of poor fitting doors and windows) are also influencing the Mean Radiant Temperature and the Relative Air Velocity.

When it comes to comfort, the perception of temperature is more important than the temperature itself. For a person to feel comfortable, the difference of temperature between the head and the feet should not exceed 2.5 degrees. This demonstrates the importance of floor insulation and this explains why we usually feel more comfortable standing barefoot on carpet than on tiles.

Energy Ratings In Australia And Overseas
In Australia, energy rating assessments are done pre-construction, assuming competent application of all insulation and building materials. However, common construction practices often demonstrate misapplications and air leakages. In Europe, energy efficiency is most often assessed or checked post construction, with special attention to the prevention of thermal bridges. Some countries require airtight buildings, and amongst other things, double glazing, solar energy for hot water and heating systems, the usage of storm water, greywater recycling, recycled materials and product life cycle considerations to minimise energy demand and carbon footprint.

Well performing insulation and building materials is not a guarantee for well performing homes. The building envelope needs to be treated as a delicate continuous shell. Each small gap and leakage will impair the energy efficiency and the well being of the occupants. It is essential to consider the end product in order to determine how energy efficient a building really is.

House Siting & Solar Access

The siting and orientation of a building is essential in achieving good solar access and hence good energy efficiency. The house needs to be designed according to the site and must respond to site-specific conditions to maximise free solar energy. Moreover, it’s important how the rooms are arranged; the right zoning can significantly help save energy otherwise needed for heating and cooling.

Energy use, occupant thermal and visual comfort are influenced by decisions taken in the first steps of a project, usually by choices made even before the actual design begins. The selection of the site and early decisions regarding site layout, room orientation and building form can determine sunshine conditions in and around a building.

How To Optimise Solar Access
Solar access refers to the amount of direct and diffuse solar energy a building receives. Optimal solar access can improve the thermal comfort, decrease energy requirements, reducing greenhouse emission and therefore, benefiting our environment. It’s important to design your building location in order to achieve a good level of unobstructed winter sun. North-facing windows are no guarantee of good solar access. Obstructions in the form of other buildings or trees to the north, northeast or northwest can block free solar heating. The Australian Bureau of Meteorology (BOM) generally recommends that the sun should shine six hours during winter into the windows. Especially in cooler areas, the BOM also recommends solar access to east-facing windows.
New houses or renovations should always try to maximise the site’s potential free solar energy. Good orientation is a condition for energy efficiency. It is easier and more economical to consider this early in the design rather than upgrading a building once its been built. Correct siting and good solar access is relatively easy to achieve for lower density housing, whereas medium and higher density housing sometimes presents a challenge. Smart subdivisions are a requirement for adequate solar orientation and distances between buildings need to be greater to enable unobstructed sunshine into the windows.

Surface-Area-To-Volume Ratio / Building Shape
The surface area to volume ratio (S/V) is an important factor for the performance of a building. The greater the surface area, the greater the potential heat gain or loss through it. Consequently, a small S/V ratio implies minimum heat gain and heat loss. In order to minimise unwanted losses and gains through the fabric of a building, it’s desirable to design a compact shape, without articulation. In theory, the most compact building would be a cube. This configuration may not be acceptable for many reasons, such as restrictions to daylight access, site and neighbouring character, planning regulations or simply personal preferences. However, to minimise heat transfer through the building envelope, the building shape and accordingly the floor plan itself, should be as compact as possible. When designing your home consider thoughtfully what rooms are really needed. Instead of adding rooms you might need. Create multifunctional rooms, spaces that can be used for more than one function and that can easily adapt to a changing lifestyle.

House Siting
In order for a building to be energy efficient and environmentally friendly in any way, there are many things to consider when searching for a site or placing a house on a site.

Analysing needs and lifestyle – current and future

  • What type of home is needed?
    (house, apartment, villa; is a large garden required, lifestyle options and access to facilities)
  • Does the location suit your lifestyle and can it accommodate potential changes in the future?
    (family addition, retirement, old age, health and so on)
  • Is the site close to public transport, work, school, family members or other social activities?
    (Proximity may reduce the need of a second car. It will reduce car trips, travel time and carbon footprint, consequently protecting the environment, and saving money).
  • Determine the true cost of the location.
    (A site/ home in the outer suburbs may be cheaper, but will this compensate the higher transport cost and the additional times spend on the road or on public transport?)

Study the site and the local climate

  • Seasonal and diurnal temperature ranges
  • Direction of hot, cold and wet winds and cooling breezes
  • Humidity range
  • Effect of local geographic features or climate conditions, like the fall of a site, vegetation or neighbouring properties that might modify air movement and solar access.
  • Seasonal characteristics
  • Orientation of the site, determine where north is. Will the configuration of the site allow for good solar access, and the positioning of private open space and garden areas facing north?
  • Are existing or proposed buildings or trees overshadowing the site?

How to place a building
In hot climates with negligible heating needs, the building should be orientated to maximise exposure to cool breezes. The construction should aim to exclude harsh sun all year around, by minimising window sizes and/ or providing large overhangs or other effective shading devices.
All other climate zones, as well as alpine zones, need to incorporate passive solar heating and cooling. The extent of heating and cooling requirements depends on the climate. To determine if you need mostly passive heating, passive cooling, or a combination of both, you can compare summer and winter energy bills, consult a designer or an architect, or check meteorological records on the Australian Bureau of Meteorology website.
In the southern hemisphere, living areas should be ideally orientated within the range of 15°W-20°E of true or ‘solar’ north (20°W-30°E of true north is considered acceptable).  Accurate location and direction will enable standard overhangs to prevent overheating in summer and allow lower winter sun to heat the building with no extra costs or effort from the occupants.  On the other hand, a poor orientation will result in heat loss in winter and will lead to overheating in summer, by allowing low angled west or east sun to strike glass surfaces. North facing walls and windows should be set back significantly from large obstructions to the north, like trees, fences and other buildings. Keep in mind that they cast shadows two to three times their height in mid-winter. The distance to a single storey building to the north should be minimum 5.5 metres, to a double storey at least 10 metres.

  • If possible, garages, carports and other buildings or structures shouldn’t be placed on the northern side of the site.
  • Consider sharing walls with neighbours, especially on the east or west boundary as it will minimise unwanted heat loss or gain through these walls.

How to organise a floor plan
Rooms are utilised for distinct purposes at different times of the day and their placement will influence energy efficiency as well as comfort levels. Zoning means the creation of zones by grouping rooms with similar uses, and closing off unheated rooms, such as laundries or guest bedrooms, to reduce heating and cooling needs. It is important to separate heated and unheated areas with doors, such as glass or bi-fold doors to help retain the open-plan aesthetic if required.

  • Daytime living areas such as family rooms, kitchen and rumpus rooms should be north facing.
  • Avoid orientation and windows to the harsh west sun, especially for living rooms and bedrooms.
  • Locating the garages or carports to the west, east or south can protect the building from summer sun and winter wind.
  • Areas that use water (hot water in particular) should be grouped together to minimise heat loss from pipes, plumbing costs and water wastage.
  • Create buffer zones to the west and south, as this is where most of the unwanted heat gain or loss will occur, such as bathrooms, laundry or storage rooms.
  • Avoid self-shading; deep north facing courtyards, garages or other deep articulations should not overshadow north-facing windows.
  • Air-locks to external doors are essential to reduce the loss of heated air when the external doors are opened.
  • Allow for cross-ventilation. Openable windows and external doors should be located on       different      sides of the home, with less than 8 metres distance between them to create air flow.

If medium and high density housing is designed with careful attention to good solar access and other passive design solutions, it will use less energy compared to single storey or detached houses. The reasons for this are due to the shared walls and floors, but also the lower percentage of building envelope per dwelling, and each dwelling may have less area of external wall or roof surface. The less the outer shell is in contact with outdoor air, the less the potential thermal radiation, and therefore unwanted heat gain or loss is reduced. Moreover, a free standing home needs more construction material than high density housing and this starts an endless cycle of additional production, waste, labour and travel time.

The dream of a freestanding home is quickly becoming a distant thought; one dwelling on a block seems like an extravagance as land gets more and more precious closer to the city, forcing people to move further out into the suburbs. This leads to longer travel times, increases the dependency of cars, and consequently increases the greenhouse gas emissions through vehicles. As the population of our cities continues to grow rapidly, we have to think about alternative ways of living and have to restructure and improve our public transport system. We have to create new dreams for our sustainable future and find new ways to make medium and higher density living more desirable.
This cultural shift in how we choose to live may seem insignificant to the individual or single family, but imagine where we would end up if the majority of the population understood the positive effect of a sustainable housing model?

5.6 Stars: It’s not that hard

Now, after we have retrofitted the insulation and sealed all the gaps,  it’s time to look into other options on how to improve the energy efficiency. But also we want to optimise the floor plan.
We think there is potential to utilise the floor area more efficient. We decided to reorganise the kitchen/living/dining area and also that an European laundry would be enough for us. That means we will be able to transform the 2 bedroom unit into a 3 bedroom unit. But that’s not all, we will even manage to fit in an extra ensuite for the new master bedroom.

But what are we planning to do to that will improve the energy efficiency?



One of the first things you should do is to put in an air-lock. With the extra door you can close of the entry area. This is especially important in Winter, then
the moment you open the front door the warm air gets sucked out and you have to start afresh. In summer it can be open all the time, but there should be a way in winter to close it off.

Replace Windows/Doors

Many might think, there is no point replacing one or 2 windows, it won’t make a difference. But you would be surprised what you can achieve. Especially big windows lead to unwanted heat gains or losses. Even just replacing some windows can make a massive difference.
We want to put in a new french door towards the new deck, also we will put in a new door and new windows in the new master bedroom. So altogether we will put in 2 new windows and 2 new doors. Keep in mind, the lower the U-value the better performing the window. In our case, we will try to get the best windows/doors we can get; double glazed, uPVC or timber windows, with a  U-value of 1.99 or lower.

Energy Savings

Just putting in the air-lock and a few new windows/doors increases our energy rating to 5.6 Stars. This means the renovated house will need 81% less energy, meaning instead of $4,300, we will just pay $829 per year.

Imagine how much energy you could save!!!

3.6 Stars: How to make an existing home more energy efficient without spending a lot of money

There are a few simple things you can do that will make a huge difference to your energy bill, without spending a lot of money.
In our case, it brings us already up to 3.6 stars. This means that we will need 62% less energy than before the renovation. Instead of paying more than $4,300 per year, we can reduce our energy bill to approximately $1,600.

So what did we do?

Seal your house

Every little gap causes unwanted heat losses and heat gains, therefore, one of the first things you can do to make your house more energy efficient are:

– Close off wall and ceiling vents

– Replace existing exhaust fans with self-closing ones

– Weather-stripe existing windows and doors

– Don’t use standard down lights in the ceiling as they leave gaps/holes in the insulation

Insulate your home as much as possible

The more insulation the better. Put in as much insulation as you can
In our case, we’re going to install insulation to the ceiling and to the roof, with a combined overall R-value of  R6.0 and insulation to the timber sub-floor of R2.0.

– Insulate the sub floor using waterproof rigid insulation and ensure there are no gaps around the insulation – for example, use expandable foam.

– Update roof/ceiling insulation using both reflective and bulk insulation, the higher the R-value the better. Aim for a combined R-value for the roof and the ceiling insulation of min. R.5.0

Retrofitting an existing brick veneer wall is a bit more tricky.  It is a pretty time intense and messy job. Therefore we decided not to insulate the walls, at least not at this stage.
Taking off the plasterboard to install bulk insulation may be the most obvious way, but you can also bore holes in between studs and pump in cellulose fibre. But if you do this you have to ensure that the walls are closed at the bottom and that the insulation can’t fall though.

3.6 stars is a good start, but we can do better.