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:

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

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.