Eco Priority Guide: Insulation
Overview
Provided the building is designed in accordance with the
principles of passive solar design, insulation of some form is
definitely desirable in every roof and most walls.
The Building Code of Australia (BCA 2005-2006) gives detailed
prescriptions about the differing insulation levels that relate to
the 8 climates zones across Australia in the 'Deemed to Satisfy'
criteria. Obviously these levels can change when the design is
undertaken on a performance basis.
If a building is improperly designed in the first place,
insulation can make performance worse, particularly in summer e.g.:
...if you insulate an oven, it stays hotter, longer.
The moral of the story? Insulation is an integral part of
overall thermal design.
Overall, insulation in the right place, of an appropriate
R-value, installed correctly, contributes a net-benefit to the
performance of building. Many insulation products will save more
energy than it takes to make them in just weeks or months, as well
as delivering higher levels of comfort (Wooley, Kimmins et al. 1997
p.44).
Eco-Priorities
The following issues relate to both potential positive and
negative issues associated with each product class:
Priority Order
|
Glasswool, Rockwool
|
Cellulose
|
Polyester
|
EPS & Foiled EPS
|
XPS
|
Wool
|
Reflective
Alumin Foils
|
Hybrid Polythene
Cell + Foil
|
Silicon Aerogel Blanket
|
1
|
GHG
|
Life Cycle issues
|
GHG
|
GHG
|
GHG
|
GHG +
|
Life-cycle issues
|
GHG
|
GHG
|
2
|
Health
|
Resources +
|
Resources
|
Resources
|
Resources
|
Resources +
|
Resources
|
Resources
|
Resources
|
3
|
Resources
|
Toxicity +
|
Toxicity +
|
Toxicity
|
Toxicity
|
Life-cycle issues
|
|
Life-cycle issues +
|
Life-cycle issues +
|
Issues of concern?*
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
Table Key
GHG - Production of greenhouse gases, ozone-depleting
chemicals
Life-Cycle Issues - Durability and
maintenanceBiodiversity - Destruction or an erosion of
habitat and/or biodiversity values, e.g. threatened species
or species loss.
Toxics - Toxic and/or persistent and/or bio-accumulative
emissions to the environment
Health - Products or emissions during production or use that
directly impact on human health
Resources - The use of raw resources, e.g. oil, metal
ores.
+ Indicates an overall positive outcome.
* Issues that are of high concern and are a potential
eco-design basis for not using the product.
Making a Decision
Commentary
- Insulation is designed to resist the passage of heat in various
forms from one side of the material to the other. There are 3
effective kinds of insulation:
- Resistive insulations that resist conducted heat flow;
- Reflective insulations that resist radiant energy flows,
and
- Insulations that combine the benefits of both types - these are
usually the most effective overall insulations thermally.
Resistive or Bulk Insulation works as a result
of the efficiency of the encompassing material at enclosing and
stilling trapped air within the material. The actual thermal
qualities of the enclosing materials have some impact on the
overall efficiency but with most common insulation materials the
benefits (or otherwise) of the encompassing materials usually
relate to other matters. Examples of bulk insulations include
cellulose, fibreglass, polyester, wool, jute and loose fill.
The performance of resistive insulation depends on the ability
of the insulation to retain its 'loft' or air content. Any process
that reduces this will reduce its efficiency. Problematic issues
include:
- any tendency of the material to compress or compact under its
own weight, for example by slumping in walls;
- physical compaction by loading, being walked on etc;
- degradation by water, or
- insect and/or rodent attack.
Reflective insulation works predominantly as a
result of the reflectivity of the surface of the material, with the
higher the reflectivity the better the insulation. To work most
effectively, reflective insulations need to be used in conjunction
with still air spaces on either side of their reflective faces. A
significant portion of the thermal effect of reflective insulations
relates to the thermal effect of the still air boundary film
immediately adjacent. Detailing that does not provide still
air films in this way either by allowing large air movement or by
eliminating the air space reduces the effectiveness of reflective
insulations. Examples include concertina foil batts, reflective
sarking and reflective window films.
The factors that impact on the quality of reflective insulations
are:
- They are highly susceptible to the quality of installation and
detailing that does not provide still air films adjoining the
reflective faces either by allowing large air movement (bad
installation, torn fabric or poor detailing) or by eliminating the
air space (or making it too small - best is over 20mm).
- There is also a potential long-term reduction in effectiveness
by being coated in dust over time, although initial performance
figures usually allow for this anyway.
Resistive/Reflective insulation combines the
benefits of both types of insulations and typically as a result
they are able to deliver higher overall performance. They require
the same installation criteria as reflective insulations to deliver
the rated performance. Examples include Air-cell, Silver Batts, and
fibreglass/mineral wool, polyester and woolen blankets with foil
facings.
Decision-Making Checklist
- Does a thing have to be made or used? If so, does it create a
net benefit?
- Fate: Start with the end in mind. If the product is not
reusable, fully biodegradable or highly recyclable at the end of
life, or facilitating these activities, its not sustainable.
- Energy: What will the product's likely net energy balance be
over its life? Will it save more energy than it uses?
- Durability: Does the product embody an appropriate level of
durability for its accessibility, criticality and maintenance
profile?
- Biodiversity: Is there a chance that the product has had a
negative impact on biodiversity? Erosion of biodiversity is a
one-way street.
- Toxicity: Is the product toxic and or persistent in the
environment at any stage in its life cycle? If so, don't use
it.
- Resources: Does the product use rare resources/ create a net
negative flow of resources (e.g. poor maintainability/ high
maintenance requirements)
- Is the product socially sustainable?
- Does the product, or its use, contribute to delivering synergy
benefits in other building systems?
Source: Adapted from Andrew Walker Morison
Quick Guide
Mineral wool
|
For
- Proven tested technology
- Resistant to settlement
- Resistant to rot, decay, pests
- Re-classified in 2001 as 'Non-Classifiable' by the IARC (i.e.
not a suspected carcinogen)
- Mineral wool Batts content is 100% recycled blast furnace
slag
- Modern fibres bio-soluble
|
Against
- High embodied energy
- Use of compounds such as phenol, which may account for 5%
weight. Phenol approx 3% used in mineral wool (Berge 2000).
- Product may offgas in-use as well as in manufacture &
curing
- Production emissions include fluoride, chloride and
particulates
- Mineral wool significantly heavier than glasswool
- Material is a skin irritant. Contact with bare skin may cause
irritations lasting day/s
|
Fibreglass
|
For
- Proven tested technology
- Resistant to settlement
- Resistant to rot, decay, pests
- Re-classified in 2001 as 'Non-Classifiable' by the IARC (i.e.
not a suspected carcinogen)
- Fibreglass content is approximately 30% recycled glass
- Modern fibres bio-soluble
|
Against
- Moderate energy embodied energy
- Use of compounds such as phenol, which may account for up to
3%)
- Product may offgas in-use as well as in manufacture &
curing
- Production emissions include fluoride, chloride and
particulates
- Material is a skin irritant. Contact with bare skin may cause
irritations lasting day/s
|
Cellulose
|
For
- Lowest embodied energy relative to comparable products when
loose filled without stabilising skins
- Still low embodied energy when sprayed as finish on walls,
ceilings or sprayed with PVA skin in ceiling
- Largely natural, non-persistent 100% post consumer waste
product
- Anti-flammability and insecticide compound is considered low
toxicity
|
Against
- Un-skinned can move if roof space not sealed properly
- Some concern that (like wood dust) respirable particles could
lead to nasal disease
- Borax, and Boracic Acid mix used to, provide fire resistance
and as a pesticide. Scarce resource with two global deposits and
estimated 50yr resource (EBN Vol. 2 (5) p.13)
|
Expanded Polystyrene (EPS)
|
For
- Can be formed in a board - improved potential for reuse
- At higher densities, can be adhesive/mesh/rendered to form
actual external wall skins
- Vapour permeable without render skins
- Can be used in cavity
High moisture resistance can be used under structural slabs
|
Against
- GHG intensive, depending on blowing agent - usually HCFC, but
can be CO2
- High embodied energy
- Poor to very poor potential for reuse or recycling if used in
loose form
- Without skins easily broken
|
Polyester Batts and Blankets (PET)
|
For
- Can contain high levels of post-consumer recycled content
- Ultra low/Zero VOC product
- Not associated with health concerns
- Recyclable and some manufacturers will recover and recycle
- NOTE: recycled PET/polyester insulation has significantly lower
embodied energy and is up to 88% recycled
|
Against
- High energy requirement for virgin manufacture
- Recycled PET/polyester insulation has significantly lower
embodied energy but still contains approx 12% virgin melt
fibre)
|
Extruded Polystyrene (XPS) Board -
Styrofoam
|
For
- Rigid self-supporting board -
- Can be adhesive/mesh/rendered to form actual external wall
skins
- High moisture resistance can be used under structural
slabs
- XPS guaranteed NOT to contain CFCs is readily available - but
obtain certification from supplier
|
Against
- GHG intensive - uses HCFC as blowing agent
- Some product may have effective ozone depleting potential (ODP)
equivalent up to 10% CFC of blowing agents - check with supplier
for certification of CFC free
- Very high energy embodied energy
- Not-easily recycled
|
Wools
|
For
- All insulation wool surveyed contained post industrial cycle
waste or recovered agricultural by-product wool
- Natural low embodied energy product
- Low Toxicity quaternary ammonium compounds (QACs) as
flammability and insecticide agents
- Suitable for 'breathing' walls and ceilings
- Loose fill wool very low embodied energy
|
Against
- Production of wool associated with significant environmental
toxins e.g. in sheep dip or soil degradation. However, as
insulation wool is wool waste-based wool, insulation is not
considered to contribute to this degradation in other than a minor
economic way.
- Care needed to select respected quality-controlled manufacturer
to ensure proper dosing of QACs to control insects.
- Wool batts contain various levels of virgin polyester as binder
and lofting agent. 'Wool Rich' brandings usually mean high embodied
energy as polyester can be 10-90% content.
|
Single and Multilayer Silver Batts and Concertina
Reflective Foils
|
For
- Low embodied energy
- Usually have recycled or plantation softwood Kraft-paper core
with extremely thin aluminium foil facings
- Can double as vapour barrier
- Multi-layer reflective foil batts give high effective R-values
and present high value for money (R-value/$)
- Concertina batts easy to install and fix in walls
- Different manufacturers can have very different Emissivity
values - check 'E' value before buying - a 'Low-E' foil face is
approx 0.03-0.01 - Mid Range is 0.05 (Anti-glare side is approx
0.5)
|
Against
- Single layer sarking easily torn and usually not properly
installed
- Susceptible to water damage over time if in cavity or under
leak
- Efficacy reduced slightly with dust cover
- Needs still air space against reflective faces for
efficiency
- Multi-layer batts need careful fixing to ensure long-term
lofting.
- Concertina batts need careful fixing to ensure long-term
integrity.
|
Bubble Foil Reflective Wrap
|
For
- Moderate embodied energy
- Very durable
- Waterproof
- Flexible
- Ultra low VOC - healthy
- Different manufacturers have different 'E' values - check
emissivity of specific manufacturer foils
- Dust layers already included in stated R-values
|
Against
- Damage to bubble layer will reduce efficiency of
insulation
- R-value dependant on construction final and 'layering' of
materials properly installed
|
Silicon Aerogel Blanket
|
For
- High thermal efficiency
- Recycled content
- Small volume, flexible blanket form
- Radiant hybrid form also
- Zero ODP
- GGE <5
- Moisture resistant
- Long life
- Recyclable (but no process identified)
|
Against
- Minimal but potential impacts from dust of when cutting
- Moderate embodied energy
|
Further Information
For more detailed information on this topic admin@ecospecifier.org.
References
Ambrose, M. (1996), Embodied Energy Calculations for a
Typical House, CSIRO, Melbourne.
Baggs, D.W. (1999), A Designers Guide to the Eco-Rating Of
Building Materials: Conference Proceedings, ANZSES Passive and
Low Energy Architecture Conference, Brisbane.
Berge, B. (2000). Ecology of Building Materials.
Butterworth Heinemann, Oxford.
Insulation Council of Australia and New Zealand
(ICANZ), Accessed 27/03/13, http://www.icanz.org.au
Lawson, W.R., and Rudder, D., (1996), Building Materials,
Energy and the Environment - Towards Ecologically Sustainable
Development, Royal Australian Institute of Architects,
Canberra.
Schwartz, A., "Simplified Physics of Vapour and Thermal
Insulation", USA.
Treloar, G.J. (1996), Embodied Energy- The Current State of
Play, Proceedings of Conf. Deakin University, Geelong.
Treloar, G.J. (1998), A Comprehensive Embodied Energy
Analysis Framework, Unpublished PhD. Faculty of Science and
Technology, Deakin University, Geelong.
Wooley, T., A. Kimmins, et al. (1997). Green Building
Handbook. E & FN Spon, London.