Tag Archives: Sustainable House 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!

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

Thermal Mass: material and colour selection

Material and colour selection

FullSizeRender-3
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. Or using something like concrete block walls and insulate at the outside, with isolation boards.

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.  When looking a the energy start rating,  insulating the slab on ground can add up to 1 star to your star rating.

If a timber subfloor is requested or required, 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.

One alternative to adding thermal mass as a actual building material is to add something that acts as thermal mass, but is light weight. There is one product on the Australian market, calle BioPCM. This phase change material acts as thermal mass, without the weight actual thermal mass has, and hence standard light weight construction and footings are sufficient, which are usually significantly cheaper than if you are building with brick and or block work.

“BioPCM™ is a lightweight smart thermal mass, providing design flexibility and easy installation for a cost effective and simple approach to integrating sustainable technology into buildings.
BioPCM™ absorbs excess heat during the day and releases this energy back in the evening as buildings cool.”

 

We have used the BioPCM to line the walls of a pantry, to keep it cooler and create some sort of cool – room. And the result was really great. The room always stays much colder then the rest of the well insulated weatherboard home.

 

 

Optimal Use Of Thermal Mass

How to locate thermal mass

optimal 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.

When using thermal mass in upper storey buildings careful attention has to be paid on the details. For instance that there are no structural thermal bridges, which can lead to unwanted heat transfer between the outside and the upper level concrete floors. But also the floors itself need to be insulated, to avoid heat rising up and heating up the upper levels. Insulating concrete floors isn’t a legal requirements, but highly recommended, if you do want to enjoy the thermal benefits and not the negative side effects of thermal mass.

In our next article we will speak about material and colour selections.

How can thermal mass help in Winter or Summer to regulate room temperature?

summer and winter

 

When deciding on what materials to use for your house many only think about factors such as cost and aesthetics. But when it comes to creating an energy efficient home the performance of a material and its ability to store heat needs to be taken into consideration. Thermal mass will help regulate the indoor temperature in summer as well as in winter and will reduce the need of mechanical heating and cooling.

 

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.

 

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.

 

Please be aware, that a standard brick veneer home will not give you any benefits for your indoor temperature, as the thermal mass is located externally, and separated from the indoor climate via insulation

What is Thermal Mass and why should we use it in construction?

thermal mass

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 for Construction?
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.

If you want to know more about thermal mass please also read our further articles about this subject.

Window Energy Rating Scheme

 

Untitled1The 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/ built an energy efficient home.

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.

Sealing and weather-stripping
However, 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.

 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 1.1 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.

Up until then, you, as the client, has to make informed decisions about what glazing you are buying. You can’t just trust a manufacturer stating their glazing is energy efficient. They have to prove the performance to you by showing you the actual u-value of the window system.

What to look for when buying windows?
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.