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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

  1. 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:
  2. Resistive insulations that resist conducted heat flow;
  3. Reflective insulations that resist radiant energy flows, and
  4. 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:

  1. any tendency of the material to compress or compact under its own weight, for example by slumping in walls;
  2. physical compaction by loading, being walked on etc;
  3. degradation by water, or
  4. 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:

  1. 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).
  2. 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

  1. Does a thing have to be made or used? If so, does it create a net benefit?
  2. 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.
  3. Energy: What will the product's likely net energy balance be over its life? Will it save more energy than it uses?
  4. Durability: Does the product embody an appropriate level of durability for its accessibility, criticality and maintenance profile?
  5. Biodiversity: Is there a chance that the product has had a negative impact on biodiversity? Erosion of biodiversity is a one-way street.
  6. Toxicity: Is the product toxic and or persistent in the environment at any stage in its life cycle? If so, don't use it.
  7. Resources: Does the product use rare resources/ create a net negative flow of resources (e.g. poor maintainability/ high maintenance requirements)
  8. Is the product socially sustainable?
  9. 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.