Insulation is the most effective way to improve the energy efficiency of a home. Insulation of the building envelope helps keep heat in during the winter, but keep heat out during summer to improve comfort and save energy. Insulating a home can save 45–55% of heating and cooling energy.
Insulation acts as a barrier to heat flow. It can make your home more comfortable by reducing the amount of heat escaping in winter and reducing the amount of heat entering in summer. By insulating you can significantly reduce your heating and cooling bills and help to reduce greenhouse gas emissions. The higher the R-value of insulation the more it slows heat flow and the better it works.
R-value determines the effectiveness of the insulation.
Although ceilings and walls may be insulated, heat loss will still occur in winter if there are large areas of unprotected glass or through fixed wall vents and gaps and cracks around external doors.
Therefore to effectively insulate a house you need to carry out the following :-
Generally 40% of the heat transfer in your home through the roof, up to 25% through walls and up to 15% through the floor.
Building Code of Australia recommends R 5 in the ceiling and R2.7 walls, R1.5 under floor in Canberra region.
There are two types of insulation
Works by trapping tiny pockets of still air within its structure. This air provides a barrier or resistance to heat flow. Resistance to heat flow (R value) is not seasonally dependent for bulk insulation.
Works by a combination of reflecting heat away from its polished metallic surface and/or by reducing the radiant heat being emitted from the surface. To be fully effective there needs to be an air gap of 25mm beside the reflective side of the insulation. Because reflective insulation works by reflecting radiant energy, it is more effective at higher temperatures and generally has a higher rating for summer R-values than for winter values. A layer of foil under roof tiles provides R0.0.23 in winter and R0.9 for summer.
Since Canberra has a climate that requires far more heating than cooling it is generally easier to get adequate levels of insulation using bulk insulation rather than foil insulation.
Composition: Melted glass spun into a mat of fibres. Batts with different R-values are available. Glasswool batts are flexible and easily cut and installed by a householder or a contractor. A dust mask, gloves and a long sleeved shirt should be worn during the installation process. Fibreglass blankets with foil backing are also available and are typically used under the roof as insulation and a moisture (condensation) barrier. Gaps around and between the edges of batts can impact on the overall effectiveness of insulation. If you choose batts make sure they are installed without gaps. Once installed, it does not release dust or fibres and is not known to have any ill effects on health.
Composition: Melted volcanic rock (basalt) spun into fibres. Available in loose fill form for vertical wall cavities and as batts and blankets for ceilings and frame walls. Rockwool is denser than fibreglass and possesses superior thermal and acoustic insulation properties, but is usually more expensive. The same precautions should be taken when installing rockwool as when installing fibreglass.
Composition: Finely shredded waste paper. Borax and boracic acid are added as fire retardants and to deter insects and rodents. Cellulose fibre is pumped or blown into ceilings by contractors to the required depth for the R-value purchased. Depending on the installation method, this material may settle over time with an associated reduction in performance. There are instances where houses with cellulose fibre has caught fire.
Please see sections under cavity wall insulation, double glazing and draught sealing for complete insulation of a home.