Eco Priority Guide: Windows (frames)

Overview

Windows are one of the most exposed elements in a building, therefore the main eco-priority is their energy efficiency. However, once this is established, e.g. by referring to a widow performance assessment system such as (the Australian) Window Energy Rating Scheme (WERS) or Commercial Frame Rating system, the next most important issues are biodiversity and life-cycle costs, i.e. maintenance and durability.

Depending on what type of framing material is used, an additional finish may be required (e.g. timber windows), potentially resulting in high overall maintenance requirements. The long term durability of a window will depend on a number of issues such as; exposure, frame material, finish, maintenance regime and environmental conditions.

Depending on which frame type is used, there are a range of important issues that require consideration. Whether it is aluminium, timber or PVCu, each can have its own problematic and sometimes controversial environmental impacts. However, some of these can be mitigated by changing material content. Examples include; using more ecologically benign timber selection (FSC) and harvesting processes, introducing or increasing recycled content, or introducing thermal breaks into conductive aluminium frames. Aluminium and PVCu consistently have the highest negative environmental and health impacts according to life cycle assessment techniques (Source: USGBC). However, these techniques do not include species and biodiversity impacts, e.g. relating to forestry or mining practices.

Eco-Priorities

The following issues relate to both potential positive and negative issues associated with each product class:

Priority Order

PVCu

Timber - Non FSC

Timber - FSC, recycled or equivalent

Aluminium

1

GHG + / Health

GHG+

GHG +

GHG / Health

2

Life-Cycle + (Durability)

Biodiversity +

Biodiversity +

Durability +

3

Recyclability +

Life-Cycle (Maintenance)

Life-Cycle (Maintenance)

Recyclability +

4

Resources  (Finite)

Resources  (Renewable)

Resources  (Renewable)

Resources (Abundant)

Issues of concern/Red Lights?*

Yes - Health

Yes - Biodiversity

No

Yes - GHG

Table Key

GHG - Production of greenhouse gases, ozone-depleting chemicals.
Life-Cycle Issues
- Durability and maintenance.
Biodiversity
- 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

Thermal considerations for window frames include;

  • A significant part of the thermal energy transmission can be through the frames. Another significant energy pathway is the porosity of the construction including sealing.
  • Timber and PVCu are approximately thermally equivalent and provide high level of energy efficiency compared to a Standard aluminium frame.
  • Standard aluminium frames can have a poor energy performance. To become more energy efficient aluminium frames need to be improved through performance enhancing design features or through the use of thermal breaks.
  • US Green Building Council research has shown that the majority of even Thermally Broken Aluminium frames are relatively poor compared to timber or PVC and all aluminium consistently shows greater environmental and human health impacts than other frames types.

The use of aluminium framing includes the following considerations;

  • Standard Aluminium Frames refer to all aluminium frames unless the manufacturer provides a Windows Energy Rating (WERS) which demonstrates a lower U-value. The generic U-value for Standard frames is 12.7W/m2K.
  • Thermally Broken Aluminium Frames refer to a frame that has a gap of less than 5.30mm between the segments of Aluminium (in line with the U.S National Fenestration Rating Council NFRC 100-2001). The generic U-value for Broken frames is 3.8W/m2K.
  • Thermally Improved Aluminium Frames refer to a frame that incorporates design improvements that enhance performance (e.g. exterior/interior trim made of wood or plastic). The generic U-value for Improved Aluminium frames is 8.0W/m2K, and generally has a lower U value than standard frames.
  • It is important to note that in some instances Standard Aluminium Frames can offer better thermal efficiency than either Broken or Thermally Improved frames due to their specific design features. Therefore, it is important to identify the U-value for the frame you are considering. Note: the lower the U-value the better a product prevents heat from escaping.

A specific consideration for timber framing includes the use of wood preservatives. Windows are typically treated with a H3 application (outside but not in-ground) and include the following options;

  • LOSP (Light Organic Solvent Preservative): A preservative, fungicide and insecticide with low-toxicity.
  • LOSP (using linseed oil carrier): Also low toxic, but avoids the use of a greenhouse gas intensive white-spirit solvent as found in standard LOSP. Commonly available with a synthetic pyrethroid insecticide (Permethrin) which also has low toxicity.

The use of timber framing also includes the following considerations;

  • Use reused and recycled timbers where possible.
  • Preference third-party certified products with chain of custody, e.g. Forest Stewardship Council (FSC), whether local or imported in preference to AFS, PEFC or non-certified products.
  • 'Certification' or other market claims without Chain of Custody (CoC) offer limited scope for independent auditing and should be treated with caution.
  • Use local timbers in preference to imported timbers, except where imported timbers have superior certification.
  • Specify smaller section timbers and sizes to optimise for plantation and regrowth timbers.
  • Minimise toxicity. Not all glues and preservatives are created equal. Use lowest impact option for the application.
  • Be aware of differing meanings in specification. Terms like 'plantation' may be used in instances that do not strictly fit, e.g. the Federal definition is 'intensively managed stands of trees of either native or exotic species, created by the regular placement of seedlings or seed' (Source: Walker-Morison, 2003).
  • In 2005, the Department of Agriculture, Fisheries and Forestry commissioned an overview of the impact of illegal logging on Australian imports of forest products to help develop the Government's policy options. The report estimated that in 2003-04, up to nine per cent of Australia's forest product imports, or approximately AUD $400 million in value, was from potentially illegal or suspected illegal sources. The key product lines affected were furniture, paper and paperboard, plywood, sawn wood and miscellaneous items such as doors and mouldings (Source: Commonwealth of Australia, 2007).

Specific considerations for PVCu framing include;

  • PVC is a controversial material. In March 2007 the US Green Building Council (USGBC) published a report that concludes there are strong environmental and human health concerns associated with the use of PVC materials in buildings. The report clearly indicates that from a cradle-to-grave perspective, PVC is consistently viewed as one of the worst materials for cancer-related impacts overall. Howerver, recent changes to PVC formulations in Europe and Australia have had an impact in reducing these whole of life impacts to some extent.

Decision-Making Checklist

  1. Does a product 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, it's 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

PVCu

For

  • Inherent thermal characteristics -insulation
  • High Durability & stability
  • Recyclable
  • Paintable

Against

  • Moderate embodied energy
  • Moderate (compared to Aluminium) toxic and carcinogenic health impacts
    • Fossil fuel based

Timber - run-of-mill e.g. Western Red Cedar - Victorian Ash

For

  • Renewable resource
  • High thermal performance

Against

  • High potential biodiversity impacts
  • High maintenance
  • Potentially needs preserving

Timber - Finger Jointed LOSP plantation source

For

  • Finger jointing provides highly stable, maximum resource use product
  • Eco-friendly LOSP treatment
  • Available Australia wide

Against

  • Single supply only
  • No Australian sawlog sources FSC certified
  • Must be painted - potential for film build up over time compared to oil finish
  • High maintenance

Timber - Araucaria plantation source - Finlaysons

For

  • The most sustainable non-FSC certified plantation timber in Australia
  • Eco-friendly LOSP treatment
  • Available in QLD, NSW & Vic
    • Suitable for oil finish - no film build up over time

Against

  • Single supplier only
  • No sawlog sources FSC certified
  • Merbau Asian rainforest species trafficable sills unless specifically ordered otherwise
  • Not suitable for double glazing due to frame thicknesses
  • Seals must be ordered separately
  • High maintenance

Timber - Sustainable - FSC recycled or equivalent

For

  • The most sustainable renewable window frame type subject to suitable durability class selection

Against

  • Poor supply
  • Until local FSC sources available - products expensive
  • High maintenance

Aluminium - single frame and thermally broken

For

  • High durability & stability
  • Lightweight
  • 100% Recyclable
  • Minimum maintenance

Against

  • High embodied energy
  • High toxic and carcinogenic health impacts
  • High thermal conductivity unless thermally broken or enhanced design features
  • Thermal break performance needs to be properly considered

 

Further Information

For more detailed information on this topic contact admin@ecospecifier.org.

References

Australian Window Association, 2011, at http://www.awa.org.au/

US Green Building Council, 2007, Assessment of the Technical Basis of a PVC related Credit for LEED  http://www.usgbc.org

Walker-Morison, A. (2003). TIMBER & WOOD PRODUCTS: APPLICATIONS AND ESD DECISION MAKING. Environment Design Guide. Melbourne, Building Design Professionals Association.

Commonwealth of Australia, October 2007, Bringing Down the Axe on Illegal Logging, http://www.daff.gov.au/__data/assets/pdf_file/0018/408501/DAFF-Illegal-Logging-Policy.pdf

 

All internet references last accessed on 27/03/13.