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Insulation
Why install insulation? Insulation acts as a barrier to heat flow. It can make your home more comfortable by reducing the amount of warmth 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. In an uninsulated house most heat is lost or gained through the ceiling and roof - this is the most important part of the home to insulate. Insulating external walls can bring further benefits. Sealing air gaps also helps. Opening and closing windows and window coverings at appropriate times to control air flows and heat transfer will also increase your comfort levels. This is particularly important in summer to prevent your house overheating. If you allow too much direct summer sun into your home through windows then insulation may act to keep the home warmer for a longer period of time.
Typical areas of heat transfer
How insulation works The two main types of insulation are bulk insulation and reflective insulation. Bulk insulation works by trapping small cells or layers of air within the insulating material. Many pockets of still air are very effective at retarding heat transfer. Reflective insulation works by reflecting significant proportions of light and heat. Some reflective foils can be used both as a vapour barrier and to reduce heat transfer. The R value is a measure of resistance to heat flow - the
Insulation.
higher the R value the greater the resistance and the better the product is at insulating.
E n e r g y S m a r t i s a W es t e r n A u s t r a l i a n G o v e r n m e n t i n i t i a t i v e
Bulk insulation Cellulose fibre Composition: Finely shredded recycled paper.
Wool Composition: Wool. Wool is a natural material with good
frames. Perforated expandable foil batts that allow the free passage of moisture can be used under timber floors.
insulation properties. Only fully scoured
Multiple foil batts
Borax and boracic acid are added as fire
wool that has been treated with a vermin
Composition: Several layers of double-
retardants and to deter insects and rodents.
and rot-proofing agent should be used - for
sided foil held apart by separating strips to
Cellulose fibre is pumped or blown into
fire safety and to prevent infestation by
form a layered cell structure.
ceilings by contractors to the required depth
insects.
for the R value purchased. Depending on the
The R value of wool is dependent upon the
joists or between wall studs. They must be
density at which it is installed. It is therefore
butted firmly against each other and
important to ensure that it is installed at the
against building frames to prevent airflow.
required density by an experienced
In ceilings the batts may sag over time and
contractor. The density of wool insulation
become slightly less effective. Covering
can be quite low, which means that a
ceiling joists can also create a safety
If your roof space is prone to air movement,
greater thickness of insulation is required to
hazard by obscuring safe footing positions.
ask your supplier if they provide a seal over
achieve the same R value as other more
the top of the cellulose fibre to minimise
dense products.
installation method, this material may settle over time with an associated reduction in performance. It is recommended that your contract guarantees the compacted depth and R value.
movement of the product.
Glasswool (fibreglass) batts
Reflective Insulation
These batts can be installed over ceiling
Other insulation products The range of products listed in this
Composition: Melted glass spun into a mat of
Reflective foil laminate
fibres.
Composition: Usually metallic foils,
with other products available on the market
Batts with different R values are available.
laminated to paper and reinforced with
at any time. When choosing any insulation
Fibreglass batts are flexible and easily cut and
glass fibres.
product, remember to ask about the R
installed by a householder or a contractor. A
This is supplied in rolls and often used as
values for both summer and winter
dust mask, gloves and a long sleeved shirt
both a vapour barrier and insulation. Double
should be worn during the installation
sided and single sided foils are available. To
process. Fibreglass blankets with foil backing
optimise their effect, the shiny metallic
are also available and are typically used under
surfaces must be adjacent to a still air gap
the roof as insulation and a moisture barrier. If
of 25 mm or more.
you choose batts make sure they are installed without gaps and the manufacturer’s instructions are followed.
Some types of double sided reflective foil have an anti-glare coating (often blue) on one side to make installation safer in sunny
Polyester batts
conditions.
Composition: Polyester fibres spun into a mat.
Any holes or joins in the foil or any gaps
These are similar to fibreglass batts, except that polyester is not known to cause irritation during installation. Foil-backed polyester blankets are also available.
Polystyrene foam boards Composition: Polystyrene shaped into boards. These can be used in double brick and brick veneer walls and against solid concrete and rammed earth walls.
Rockwool Composition: Melted volcanic rock (basalt) spun into fibres.
around the edges will affect insulation performance and should be taped up. Dust build up on shiny surfaces will also affect performance.
performance relevant to your requirements and if any performance guarantees or test certificates are available from reputable authorities. It is also important to consider other properties such as durability, fire safety, installation safety and pest resistance.
Building materials Building materials have varying insulating properties. Aerated concrete bricks and panels, some wood fibre boards and prefabricated wall panels comprising of a sheet of polystyrene foam sandwiched between two lining boards, such as
Reflective foil with bulk insulation blankets
plasterboard, are all good insulating
Composition: Usually reflective foil laminate
Paints and materials that are white or light
bonded to glasswool.
coloured can help keep houses cooler in
These are typically used under the roof as a
summer by reflecting the hot sun. Special
condensation barrier and insulation. As with
insulating paints are marketed but presently
normal reflective foil, the insulation
there is no conclusive proof that their
performance will be highest if the foil faces
reflectivity is significantly better than a high
a still air gap.
quality white paint. Paint does not have any
Available in loose fill form for vertical wall
Expandable foil batts
cavities and as batts and blankets for ceilings
Composition: Double-sided reflective foil
and frame walls. Rockwool is denser than
laminates folded into an expandable
fibreglass and possesses superior thermal
concertina form.
and acoustic insulation properties.
brochure is not necessarily comprehensive,
These can be cut to fit between wall studs and floor joists and are stapled into place where they must fit tightly against building
building materials.
insulating properties itself and should not be used as a substitute for appropriate insulation.
Selecting insulation for your zone When selecting the type of insulation best suited to your needs remember that, while each of the different types has a varying physical look and size, you can compare the insulating abilities by comparing the R value. For bulk insulation, R values are related to thickness, density and nature of the insulating material. Increasing the depth of the bulk
How thick (in mm) does the insulation have to be? Common bulk insulation materials
R1.0
R1.5
R2.0
R2.5
R3.0
R3.5
Cellulose fibre loose fill
40
60
80
100
120
140
Glass fibre batt
44
66
88
110
132
154
Polyester or wool blanket
45
68
90
113
135
158
Polystyrene expanded
39
59
78
98
117
137
Polystyrene extruded
28
42
56
70
84
98
Rockwool batt
28
42
56
83
99
116
Wool (20%) Polyester (80%) batt
45
68
90
113
135
158
insulation will increase its R value. Reflective insulation does not have insulation properties by itself. Instead the insulation
These values are indicative only. R value is reduced if the material is compressed to a lesser thickness that
value depends on the particular installation
affects the density. Refer to manufacturer’s catalogue for values at various densities.
details, including the presence of still air gaps next to the shiny surfaces, as well as the properties of the reflective material itself. Reflective insulation has different R values depending on how it is installed and can have different R values in summer and winter (with the winter R value being less). Settled dust will reduce the effectiveness of reflective insulation products where the dust covers any upward facing shiny surfaces. It is important to ensure that the R value used for reflective insulation is the correct one for the particular circumstances in which it is to be used, with allowances made for dust settling on surfaces over time.
Recommended levels The level of insulation required for your home depends upon two things: the climate and the type of construction used. The map (right) gives a general indication of the climate zones that dictate the level of ceiling, wall and under floor insulation required. Using the map, determine which zone your house is in. Then select the “Easy Guide to Insulation” attachment for your zone and select the type of construction used for your home. The guide will give you the level of ceiling and wall insulation required for a house that is built on a concrete slab on ground in your zone. For other types of floor construction, refer to the Building Code of Australia (BCA). Also refer to the BCA for installation requirements for reflective foil laminates, and combination foil and bulk insulation. Insulation in new homes and renovations must adhere to the requirements for the BCA. The ‘Easy Guide to Insulation’ may be used to select insulation levels for existing houses, however, retrofitting insulation in existing walls and in some ceilings may be difficult.
Using the map determine your zone to identify which 'Easy Guide to Insulation' attachment is applicable to you. The map is available to download on the Sustainable Energy Devleopment Office website.
General installation and safety tips
Ceiling vents
Whether installing the insulation yourself or
cardboard, thin plywood or a similar product
having a professional do it, ensure the
so that insulation material does not fall into
manufacturer’s instructions concerning
rooms below and to prevent unnecessary
installation, safety and care of the product are
air and heat flow into the roof space.
correctly followed.
However, ceiling vents above unflued gas
Installation tips Bulk insulation Loose fill insulation is often installed to the
including fire retardants, in accordance with
In older homes with ceiling vents, the vents should be covered from above with
heaters should not be covered to allow adequate ventilation. Instead a barrier as described previously should be built around the vent to stop insulation falling through.
the appropriate standard.
Electrical safety When installing your own insulation, extreme care must be taken when inside the roof cavity. Because of electrical wiring, the roof cavity is a very dangerous place. If you have any concerns check with the supplier before attempting to do any of the work yourself. You should seek advice from an electrical contractor if you have any queries or concerns about the wiring itself, such as
Moisture
loose wiring that is not fixed to the brackets.
insulation and allow access to the roof cavity.
Allowing your insulation to become wet will
Reflective foils generally have metallic
However, this limits the R value of the
decrease its effectiveness and may damage
coatings that will conduct electricity. These
insulation. Insulation can be installed to a
your ceiling.
materials should be prevented from touching
height of ceiling joists in order to contain the
greater thickness provided suitable mechanisms are in place for restraining the insulation and allowing safe roof access. Some types of loose fill insulation may blow around in the roof space if the roof space is ventilated. Loose fill insulation can be sprayed with a coating to prevent this and the installation of baffles can also assist. Batts should be firmly butted against each other and against ceiling joists, wall frames, etc. Batts can easily be installed to a thickness greater than the ceiling joists. This need not restrict roof access as ceiling joists are usually still visible.
any electrical fittings and contacts.
Safety tips
Wiring should be kept clear of insulation in general, avoid placing insulation over wiring
Health issues
and/or install a spacer to keep the insulation
The insulation industry abounds with claims and counter-claims about the health and safety risks of competitor products. Fibreglass and rockwool can cause short term irritation to the skin, eyes, nose and
All gaps, tears or holes in reflective foil should be minimised or taped up except when using some products in wall cavities or under timber
In all cases, the manufacturer’s safety advice and installation instructions should be followed.
throat. A good dust mask, goggles, gloves and a long sleeved shirt should be worn when handling these materials. Breathing in any insulation fibres should be avoided and care should be taken when handling any insulation material.
Reflective insulation
clear of wiring.
Fire safety All insulation products should have flammability test certificates. Cellulose fibre
floors to prevent condensation.
insulation is treated with a fire retardant by
Hot flues, exhaust fans and downlights
resistant, although greasy wool is potentially
There should be a gap of at least 90mm
flammable, due to lanolin coating the wool.
between any insulation and hot flues or
Polyester does not burn but will melt if
exhaust fans, a 200mm gap between halogen
exposed to a flame. Polystyrene is
downlights recessed into the ceiling and a
combustible and should only be installed
50mm gap between incandescent downlights
between fire resistant materials. Fire
recessed into the ceiling and insulation. A
retardant polystyrene is also available and
sheet of metal or a similar fire-resistant barrier
may be suitable for exposed situations.
should be used to maintain this gap. It is also
Fibreglass and rockwool products are non-
possible to purchase downlight guards, which
combustible.
are placed over each downlight in the ceiling
It is recommended that your contract
and insulation can be placed up to the edge of
guarantees that the insulation is
the guard.
manufactured with the correct chemicals,
the manufacturers. Wool is naturally fire
More Information
Use the information in this brochure to assist you to decide which insulating products are suitable for your particular application and estimate the R value you require. Look up the Energy Smart Directory or local newspapers and contact a few insulation suppliers. Check the price per square metre, the R value of the material, whether it is installed professionally or DIY, and any other advantages or disadvantages of their particular products. Based on all of these factors choose which insulation is best for you. As in any purchase, check to make sure you get what you pay for, especially the thickness of the insulation and the absence of gaps in the installation.
The information and advice contained in this brochure is provided in good faith. However the accuracy and appropriateness of that information and advice is not guaranteed. The Sustainable Energy Development Office, its employees and agents disclaim all liability in respect of any act or omission occurring in reliance on the contents of this brochure. This document can be made available in alternative formats to meet the needs of people with disabilities.
Published in May 2009 by the Sustainable Energy Development Office. Level 9, 197 St Georges Terrace, PERTH WA 6000. Printed on 100% recycled paper
SEDO100/003/001
If you want to know more about insulating your home, keeping it cool in summer and warm in winter, simply phone the Sustainable Energy Development Office’s Energy Smart Line on 1300 658 158 or visit the Sustainable Energy Development Office’s web site at www.sedo.energy.wa.gov.au
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