Tag Archives: Thermal Comfort

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.

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?

Sustainable Design Features 101


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

The following article is an introduction to a step-by-step series that brings together all the elements that make up sustainable design into one simple overview.


The word first appeared in the Brundland Report (1987). Sustainability is defined as “a concept which deals with mankind’s impact, through development, on the environment. Sustainable Development is “development which meets the needs of the present without compromising the ability of future generations to meet their own needs.” Today’s environmental problems, like air pollution, are largely a consequence of the unsustainable consumption of natural resources and the mismanagement of waste products. Sustainability is about environmental protection, sustained economic growth and social equity”.

Sustainability and Gruen Eco Design

We at Gruen Eco Design are passionate about sustainable design and committed to finding the best solutions for our clients and the environment. We believe sustainable design can and must be affordable and as a matter of course should be integrated naturally throughout the whole design process, rather than designing something and trying to make it sustainable later.  My name is Simone Schenkel and I’m a designer and sustainability consultant at Gruen Eco Design. Thanks to my architectural studies in Germany, an essential part of my education was based on sustainability as well as passive house design. Due to its strict regulations and building requirements, Germany was able to achieve its Kyoto targets three years early and is currently the “world’s leader in climate protection”. I trust that, as Australians we will adopt stricter requirements, as we all play our part in saving energy and protecting our environment. In the meantime I see it as my mission to talk about sustainability and how to save energy passively as well as actively.

The basics of sustainable design

Passive Solar Design aims to maintain interior thermal comfort and to reduce the need of mechanical heating or cooling by allowing the structure of the home itself to collect, store and redistribute heat.

It’s important to note that all sites are different and that there will never be a final or the best design solution. However, there are common features and approaches that need to be applied to every job and it doesn’t matter if you build a townhouse in Melbourne or an apartment block in Alaska. Things like:

  • Optimal House Siting
  • Good Solar Access
  • Thermal Comfort
  • Adequate Insulation
  • Good Windows
  • Thermal Mass
  • Minimising Thermal Bridges + Air Leakage
  • Specifying Sustainable Materials

Each of the above points is important for the energy efficiency of a building. Yet they all need to work together, if one of the elements is misapplied it can jeopardize the performance of a building.

Here is a brief description of the most important things you have to consider when thinking about sustainable architecture.

House Siting  and Solar Access

The siting and orientation of a building is essential to achieve good solar access and hence good energy efficiency. The house needs to be designed according to the site and must respond to specific site conditions to maximize 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.

More details about how to locate a house on the site and solar access are coming soon.

Thermal Comfort

Why are some houses always uncomfortable and freezing even when the heater is on? 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. Thermal comfort is affected by a range of factors such as convection, conduction, radiation and evaporative heat loss, so even if a heater is on, cold air coming from the window will leave an uncomfortable sensation.

More details about thermal comfort and why it is so important are coming soon.


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 of heating and cooling systems. The ability of insulation is evaluated by its R-value. Nevertheless, an R-value does not consider the quality of the construction, the application of the insulation or local environmental factors for a building. The building codes specify requirements for every climate zone, but keep in mind these are bare minimums only and not best practice.

More details about insulation and which insulation you should chose for your project are coming soon.

Good Windows

Is double glazing worth its 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.

More details about windows and what makes windows energy efficient is coming soon.

Thermal Mass

Thermal mass is the capacity of an object to store heat. It is an effective way to improve thermal comfort in a building, since it will absorb heat when the surroundings are hotter than the mass, and give heat back when the surroundings are cooler. When situated well and in combination with passive solar design, thermal mass can play an essential role in saving energy and be used actively for heating and cooling.

More details about thermal mass and how you should install it are coming soon.

Minimising Thermal Bridges and Air Leakage

Ventilation is the process of “changing” or replacing air to regulate temperature and moisture control amongst other things. By applying the right design features, natural ventilation and cross ventilation can be used to control indoor temperature and therefore reduce the energy bill significantly. For these reasons, controlling the air movement is essential. Thermal bridges and air leakages will increase the need of supplementary mechanical cooling and heating.

More on how to avoid thermal bridges and air leakage are coming soon.

Specifying Sustainable Materials

What makes a material environmentally friendly and what makes it green? Choosing materials for a building requires careful consideration of products and materials that have a reduced impact not just on the environment but also on the health of the occupants.  Origin, manufacturing process and the life cycle of a product are just some of the properties that play a decisive role in the selection of materials.

More details about which materials you should use for your building are coming soon.

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!!!