Tag Archives: Sustainable Design

Optimal House Siting

Optimal House Siting

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?

If you do want to know more about how to place a building on your site and how to arrange your floor plan for optimal solar access please check our other articles.

 

How to Place a Building

How to Place a Building

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.

If you do want to know more about optimal house siting and how to arrange your floor plan for optimal solar access please check out our other articles.

How Much Insulation Is Needed?

climate zones

In short: the more the better:

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.
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 6-star home in Mildura wouldn’t comply with the minimum requirements for a 6-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.

One important thing to consider is that the energy requirements as listed in the BCA are minimum requirements only, not best practice. So if someone is telling you to not put any more insulation in as the regulations call for: don’t listen to them. They don’t have a clue.

If you put in anything less, your building would not comply, so if you are after an energy efficient home, why would you be happy to only have the legally required minimum? Rather put in as much insulation as fits into the wall/roof/ or wall and as much as your budget allows.

Keep in mind, while it is quite easy and common to upgrade bathrooms and kitchens every 10-20 years, you will typically not touch the insulation again. So make sure you make your home future proof!

Thermal Bridges And Ventilation Overseas

thermal bridges
In Europe, strict regulations are in place to control thermal bridges and air-leakages to minimise the energy needed for heating and cooling. Furthermore, due to the colder climate, a lot of structural damage can occur if heat and vapour is able to ‘travel’ through building materials.

Unlike in Europe, the significance of avoiding gaps and thermal bridges is commonly unknown and not a regulatory requirement in Australia. Common practice often shows that there is barely attention paid to minimising gaps and thermal bridges, leading to unwanted thermal bridges and air-leakages and therefore increases the need for cooling and heating.

Requirements to minimise thermal bridges
Maximum values of heat transfer through thermal bridges are specified and need to get incorporated into the energy ratings. Windows and doors as well as junctions of different building parts and materials require much detailing during the working drawing stage, as well as on the building site. It’s the architect’s/designer’s responsibility to find and draw solutions to overcome thermal bridges, and the builder’s to build accordingly.

Conclusion
Although air-leakages and thermal bridges are not accounted for in energy ratings, they can majorly limit the ability and the potential benefits of insulation and other passive solar design solution. Consequently even a house with a 6, 7 or 8 star-energy rating could be draughty in winter. Avoiding air-leakages and thermal bridges means minimising unwanted heat gain or loss and therefore reduces the energy needed to cool or heat a building.

The Role of Ceiling Fans & Exhaust Fans

 

ceiling fans

Ventilation is the active process of “changing” or replacing air to regulate temperature and moisture. It should always occur under controlled conditions, by opening windows or with ceiling or exhaust fans, NOT through gaps and air-leakage.

Exhaust fans

Exhaust fans should always be self-closing, so that the replacement of air is controlled and not accidental. With out a self closing mechanism they are one of the main contributor of air leakage.

However, if they are self-closing they are an effective way to replace air, especially in rooms where no natural ventilation is available, or where natural ventilation might not be sufficient, such as kitchens or bathrooms.

Ceiling fans
Ceiling fans are an easy and cost effective way to improve the indoor air quality in summer and also to gain points towards the desired energy rating stars.

Ceiling fans provide additional air movement/wind, increasing the Relative Air Velocity (‘wind chill factor’) resulting in the apparent temperature felt on exposed skin to be 3 °C colder than the actual air temperature, thereby reducing the need for additional cooling.

Nowadays there are so many efficient fans available on the market.
If choosing a ceiling fan make sure you get one with at least 3 speeds, with the lowest speed being slow enough to still move air, but not to create a cool feeling draught, so that you can use them in winter mode)

 

The Difference between Air-Leakage & Ventilation

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Ventilation
Ventilation is the active process of “changing” or replacing air to regulate temperature and moisture. It should always occur under controlled conditions, by opening windows or with ceiling or exhaust fans, NOT through gaps and air-leakage. Ventilation is important to support the ability of thermal mass to absorb and release heat in order to regulate the indoor temperature.

It is necessary to ascertain where natural breezes are to locate the windows accordingly. Landscaping and other buildings can influence and obstruct air flow; therefore it is necessary to visit and check the site before locating windows. Cool summer breezes in and around Melbourne usually come from south; detailed information can be found from the Bureau of Meteorology (BOM) web site.
The less gaps and air-leakage occur the air-tighter a building gets. Therefore regular ventilation is mandatory to renew oxygen and discharge odours, water vapour, carbon dioxide and other contaminations.

For instance, in Germany it’s recommended to cross-ventilate every day for a few minutes, even in winter. If the occupants forget to ventilate regularly, water vapour will be trapped inside and will lead to mildew and mould on the walls and the ceilings.

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 allow for adequate and effective air flow. Cooler air enters the building where the breeze is loctated, passes through the building and exits on the other side. The warm air inside gets replaced by fresh and cooler air.

How to locate air-leakage and thermal bridges

hp photosmart 720
hp photosmart 720

Draughts + air-leakage
Older style buildings commonly have draughts and air-leakages due to unsealed windows and doors, and unsealed vents and exhausted fans, therefore, heat and air can escape. It is difficult to control the air movement. Other sources for draughts are gaps within or around insulation, vented skylights, gaps between floorboards, open fire places, around air conditioners and heaters, gaps around other wall penetrations, such as down lights, pipes, cables etc. .

Thermal bridges
A thermal bridge is an element or part of a building, which allows heat to travel through it more quickly than through other parts and is therefore responsible for unwanted heat loss or gain. A thermal bridge arises for instance when poor insulative materials touch each other, when gaps occur between insulative materials and structural surfaces, and when materials with different R-values/U-values come in contact with each other. These thermal bridges allow heat transfer from a warmer to a cooler material. The main thermal bridges in a building are located at the junctions of floor to the wall, wall to the roof, balconies and window and door frames.

How to locate draughts?

– Are there any visible gaps? For example is light coming through gaps around windows and doors?
– Are blinds or curtains moving when the windows are closed?
A lit candle can be used to check air movement, such as around windows and doors, vents, floorboards, junctions of floor to wall and wall to roof connections

Air Leakage + Thermal Bridges explained

Capture3Imagine it is winter. You wake up in the morning, put on your favourite hand-knitted wool socks and walk to the kitchen to have breakfast. But something is different today, your left toes are cold, you start to shiver and feel uncomfortable. What happened? The fabric on the toes has worn-out, there is even a little gap. The socks that used to keep your feet warm and cosy have a leakage and they are not able to keep you warm any more.

The same principle applies to a house. The building envelope’s task is to protect its occupants from the environment and to keep them warm. The building envelope needs to be a continuous shell, each little breach will negatively influence the overall performance and reduce the insulation’s potential benefits.

The following will explain where air-leakages in a building usually occur and how to prevent them.

Air-Leakage And Thermal Bridges

Thermal bridges and air leakages will increase the need of supplementary mechanical cooling and heating, but they will also increase the Relative Air Velocity and the Mean Radiant Temperature which will negatively influence the well-being and the comfort of the residents. By applying the right design features, natural ventilation and cross ventilation can be used to control indoor temperature and therefore reduce energy bills significantly. For these reasons, controlling the air movement is essential.

Read our next article if you want to know more about where air-leakage and thermal bridges typically can occur.

 

Thermal Mass and Heating Choices

thermal massIn most European countries, thermal mass is used as a matter of course. Although it takes  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 only convective heat. The main focus lies on radiant heaters as they heat thermal mass. The main form of heating in Europe is hydronic heating, mostly in form of hydronic heating panels, but also as in slab heating. Other sources of radiant heat are wood or gas fire places. Hydronic heating is also way more allergy friendly than ducted heating or split systems. But this is more the subject for a separate blog post.

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.

Conclusion
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.