Things to consider when choosing the best building products for building your new home, renovation or house extension.

Firstly, what does sustainable energy efficiency mean and why do we need it?

Anything that is sustainable is also efficient.
We need efficient building materials because they save us money and make a home more pleasant to live in, as they combine to help regulate internal temperatures.
This makes the efficient home not only cheaper to build but cheaper to run.

Interesting fact: Buildings account for 60 % of greenhouse emissions.

Embodied energy: is the amount of effort/energy which goes into producing building materials.
Bricks, heavy steel and concrete for instance contain lots of embodied energy due to their weight which requires energy used by plant and equipment to produce and transport them.

This also makes such materials expensive and more difficult to handle and less relevant in hot climates, earthquake prone regions, difficult access areas.

Generally the lighter the material the less embodied energy it contains and the easier it is to work with and transport.

Advantages of heavy building products /materials:

  • Thermal mass, durability and strength if correctly utilised.
  • Can be recycled. Good fire rating for boundary and tenancy walls.

Disadvantages of heavy building materials:

  • More prone to cracking in reactive soils.
  • External thermal masses, ie external brick walls, are hot in summer and take a long time to cool down and display the opposite response in cold climates.
  • So the traditional brick home is less than ideal for building an energy-efficient building envelope.
  • Bricks are not as suitable in earthquake regions, labour intensive particularly in remote areas or difficult access and small sites.
  • Mortars must be specially formulated for corrosive environments such as in coastal areas.
  • Special coatings are required on steel for corrosive environments and exhibit thermal bridging if not installed correctly.
  • They are not as suitable for prefabricated homes, which are gaining increasing market share.

1. Efficient/sustainable floor structure materials
for building a new home, renovation or extension in Melbourne.

The two systems most used are the concrete slab and the more traditional timber platform floor.
Both have their advantages and disadvantages.

  • Timber floors are more compatible when extending and renovating period style or older style
    homes that already have timber floor structures.  Extending same-with-same helps maintain similar structural movement, ventilation and floor levels.
  • For sloping sites the platform floor is generally easier and more cost-effective as it can circumvent or reduce the necessity for excavation.
  • Domestic second-story and upper-level extensions and renovations almost exclusively use timber floor structures with the occasional steel beam included for large spans.
  • Timber floors need to be well insulated and sealed and require correct underfloor ventilation.
  • They can provide additional storage space.
  • The big advantage with concrete floors is their thermal mass, which helps maintain and regulate the inside temperature of the house. To perform at their best they still need to be insulated underneath prior to pouring.
  • Because slabs are generally closer to the ground surface they are sometimes used to achieve higher ceilings close to boundaries, where there are regulations limiting wall heights near boundaries.
  • Slabs are naturally way more durable and always used in garages and heavy traffic or work areas.

2. Efficient/sustainable Wall structural systems (wall frames)
for building a new home, renovation or extension in Melbourne.

  • Nearly all residential new home, extension and renovation builds in Melbourne use timber frames.
  • Timber frames are sustainable because new trees can be regrown and their growth removes carbon dioxide from the atmosphere. Timber is easy to use and transport and there are only rare examples when other materials such as lightweight steel may prove advantageous.
  • Timber frames can be prefabricated, saving time.
  • Timber frames are at the forefront of the most recent technological development in building known as prefabricated housing.
  • Timber is light and easy to use and is now being used on some very large housing developments up to 6 storeys high.

3. Efficient/sustainable Wall claddings (wallboards)
for building a new Home, renovation or extension in Melbourne.

Pound-for-pound modern Fibre cement sheeting and weatherboard products, such as produced in Australia by James Hardie and CSR, are increasingly becoming the go-to material for the professional Builder and Developer. They combine the durability of masonry with the lightness and ease of use required for cost effective, fast and energy-efficient building.

The large range of these products also means designers have plenty of scope for the individuality of designs.

4. Efficient/sustainable Roof claddings (tiles or steel)
for building a new Home, renovation or extension in Melbourne.

Once again the two main systems have their advantages and disadvantages.  From a cost perspective, both are similar.

  • Tiles tend to be more durable but may not perform so well in high wind areas.
  • Tiles take longer to heat and cool and not as easy to insulate well.
  • Once again steel roofing is light weight so it requires less structure and can be used for all pitches of roofs. Tiles don’t work on roofs flatter than 22 degrees.
  • Cold climates need a dark colour roof to attract the heat.  Hot climates require light colour roofs, be it steel or tiles, to reflect the heat.
  • All roofing materials should have a layer of sealed insulation under them as well as above the ceiling.
  • Two such sealed layers form a cavity which is an air layer regulating temperature differentials between outside and inside.

5. Efficient/sustainable windows and doors
for building a new home, renovation or extension in Melbourne.

With the advent of 5-star building regulations (2005) and the reduction in double glazing costs, Double glazed windows are now almost always being used, instead of single glazed units. Windows are the weakest point of a house when it comes to energy loss (heat transfer). Triple glazing is even better but probably not worth the extra expense in most Australian situations.  Exterior awnings provide better protection from the sun than any extra layer of glass and pelmets with drapes or blinds do a great job reducing heat loss in the cooler months.

The frame can also be a factor in the heat transfer equation.

Timber framed windows perform well and are less conductive than aluminium.

Some manufacturers of aluminium windows have found a way of reducing this heat transfer by inserting a nonconductive layer between the outside frame and the inside frame. This is great if you want a low maintenance window but adds considerably to the cost compared with timber.

So timber is probably still the most efficient choice having the advantages of being nonconductive, sustainable material, and low embodied energy to produce.

If well painted and protected by eaves timber framed windows should not have to be repainted for up to 10 years.

As a rule, the number of Windows and their opening sizes should be kept to a minimum particularly on East, South and particularly West facing walls.

North windows are the most effective but need an eave to protect them from summer sun. North eaves are usually somewhere between 600mm and 1000mm wide, still allowing the sun to heat the windows in winter when the sun angle is lower.

6. Efficient/sustainable insulation and uses
for building a new home, renovation or extension in Melbourne.

  • All domestic walls now contain R2 wall bats or equivalent insulation and external reflective foil sheeting prior to being clad. Some claddings such as rendered foam board have their own R rating, subject to size and correct installation.
  • Ceiling cavities should contain R 5 Batts and roof cover should be reflective foil covered prior to installation of the Roof Tiles or Metal roofing.
  • With all this insulation and modern sealed doors and windows buildings are becoming more airtight.
  • Some designer/builders are now also using membranes to virtually draft proof their houses.
  • The downside of well-sealed homes is their requirement to be constantly well ventilated, to prevent moisture from condensation and stale air.
  • Without a quality Heat Recovery Ventilation system (HRV) it is a lot of effort for home owners to regularly and correctly ventilate their home and ventilating on very hot or cold days negates all the heating and cooling effort expended on the building.
  • There are numerous types of insulation materials all of which serve a slightly different criteria be it sound, temperature, fire, nonconductive, environmental sustainability to mention a few.  To make an educated choice requires a great deal of research or advice from a green living builder or sustainability professional, many of which can be found through Passive House Association or Green Living Master Builders.

Active efficiency versus Passive efficiency

So far this article has been concerned about the passive ability of the building envelope to regulate inside temperature without any mechanical systems (active systems).

Sustainable home building materials part 2 will examine sustainable active systems designed to reduce energy consumption of the typical new, efficient home.