5 Star lightweight home solutions

smart design –
a philosophy of 'less is more'

Existing energy approaches follow the traditional 'solar efficient house' concept of construction using massive materials to absorb and store heat from sunshine falling on them.

Lightweight design, with timber frame construction and a timber-sub-floor, allows for a range of design solutions to achieve environmentally friendly housing in all climatic zones. Timber-framed houses can be found in very cold climates such as Scandinavia and Canada through to the very hot tropical climates of South East Asia; each will have a different approach to cope with the climate challenges.

Lightweight design principles:  Light on the environment, strong on environmental and energy benefits.

building materials – thermal mass

• Massive, heavy-weight construction materials generally have a high embodied energy component in their manufacture and correspondingly high CO2 emissions when compared to lightweight low embodied energy timber construction.

• With lightweight buildings little energy is wasted simply warming up or cooling down the structure.

• If needed, thermal mass can be built into lightweight constructions through the use of masonry features or water tanks integrated into the walls or floors.

orientation

Lightweight design, being less reliant on solar access and absorption, provides much greater flexibility in a range of areas:

• No restriction is placed on siting, design, layout and zoning as northern orientation of living areas or feature windows is not critical

• Solar absorption parameters need not restrict landscape designs, tree choice or placement

• Street appeal is enhanced when a home is built up off the ground

• Homes can be economically elevated to capture views

• Curtains and blinds can be kept closed during the day, providing privacy and security from prying eyes.

insulation designed to score

Insulation of the building envelope is critical in lightweight design to achieve constant, comfortable indoor conditions in cool and temperate climates – in summer to keep heat out and in winter to keep the heat in.

As a general rule, maximise insulation:

• Reflective roof foil: Install above rafters.

• Ceiling insulation: Maximise bulk insulation (R3.5 or greater), utilising reflective foil over the bulk insulation can also enhance thermal resistance.

double glazing and high performance glass

To maximise window performance consider thermally improved glass or smart use of double glazing. Simple alternatives which save on heating and cooling costs, glazing solutions are much-favoured in second and third homes.

window positioning

Same shape, different place – orientation and siting of rooms.

• Bring the magic of lightening eastern skies to the kitchen and bedrooms, making mornings special.

• Restrict a west-facing window to standing height to take advantage of the setting sun's beauty, without needing to cover up a large window expanse to protect furniture and fabrics from summer afternoon glare.

• Block out neighbours and let in light with mixed materials in window areas.

• Frame any views and be strategic letting in light rather than using windows as an alternative wall material.

• Minimise south facing windows to cut heat loss through glazing areas.

timber window frames

Use timber window frames as they have far better thermal properties than most alternatives – the conductivity of aluminium for instance is typically about 1700 times greater than timber.

To minimise ongoing maintenance consider combining attributes in a timber frame with an aluminium skin.

creative window design

Window design and selection is enormously important to all 5 Star houses, particularly those with timber sub-floors. Optimise window shape and size – big is not always best.

• Why full length windows if the view is better framed at sitting height?

• New furnishing options abound when items can be placed under a window, rather than in front of one.

• Different window shapes give a building a different look – imagine a diamond, for instance, capturing the view of a tree and introducing a new shape to the walls.

• Reflect or complement an unusual window shape with the roofline or in detailing.

insulation

Insulation of the building envelope is critical in lightweight design to achieve constant, comfortable indoor conditions in cool and temperate climates – in summer to keep heat out and in winter to keep the heat in.

As a general rule, maximise insulation:

• Wall insulation: Bulk wall insulation is critical – use the highest R value available (R2.0 minimum).

• Inter-zonal insulation: There are two aspects:

1. inter-zonal walls – between conditioned and non-conditioned zones (e.g. living room and bedrooms)

2. between storeys in two-storey homes where the inter-zonal insulation could be of the ceiling/first floor cavity.

insulation

Insulation of the building envelope is critical in lightweight design to achieve constant, comfortable indoor conditions in cool and temperate climates – in summer to keep heat out and in winter to keep the heat in.

• Floor insulation: Provides significant improvement in cool climates. FirstRate5 provides for both bulk and foil sub-floor insulation options.

• Sub-floor wall insulation: can also improve the 5 Star House Energy Rating. Ventilation still needs to be adequate, of course.

• Choice of floor system: new products include a foil-backed particleboard which delivers an improved rating with no extra work.

By cutting down on air movement in the sub-floor space one can easily achieve the required 5 Star House Energy Rating and gain these advantages. Options have been developed for brick veneer and lightweight cladding.

cavity flashing

The thermal performance of timber floors in brick veneer construction can be readily improved by eliminating the cavity airflow path.

A 'flashing' across the wall cavity controls the airflow through the sub-floor, disconnecting the roof space from the sub-floor space. This change will directly improve the House Energy Rating of a design with an enclosed sub-floor.

Make the change in either the roof or sub-floor area by taking the flashing from the top or bottom plate to the brickwork. With the bottom plate option you will need weep holes for removing condensation.

Another way is to fold over and secure foil across the cavity gap in the roof.

enclosing timber sub-floors

There are alternative methods for enclosing timber sub-floors to improve the house energy rating for lightweight cladding systems.

You can do it simply by closing the gaps between timber base boards, or use fibre-cement sheeting instead, with a small gap between the sub-floor sheeting and the wall cladding.

Another method is to totally enclose the sub-floor and insert wall vents at the correct spacings.

sub-floor space advantages

• Space to use for storage (including rainwater).

• With room to move under the house, it is easy to alter and repair services, and check for pests.

• Heating systems are installed more efficiently from below, because hot air rises.