Further to this, a strong correlation between visual impairment and age is evident with more than 13% of the total population aged 75 years or older affected by some form of visual impairment which cannot be corrected by glasses alone. Coupled with the now established understanding that we are a society that is aging quickly, designing with this population in mind is increasingly important.
The type of lighting provided, its location and application within a particular building, as well as the importance of factors such as selecting materials which reduce glare are all important factors to be considered. However changes to the relevant Australian Standards (AS 1428 parts 1 and 4.1 2009) have raised very specific requirements with regard to the concept of ‘luminance contrast’ and its application in the selection and placement of materials within particular situations.
Luminance contrast as it applies to these Standards, is defined as the difference in the amount of light reflected from two adjacent building elements. According to the Standards, a suitable ratio in the Luminance Reflectance Value (LRV) of the two materials to be considered is 30% or greater. For materials that are to be used outdoors the need to test them in both wet and dry conditions is also raised as values can vary significantly.
The building elements identified include tactile ground surface indicators and the surfaces they are installed on; visual indication of glazing (decals) and the floor or wall finishes they will be viewed against through the glass; door finishes and their surrounding wall, frame, jams or architraves; and the nosings of treads at steps and stairs.
An appendix to these Standards outlines a very prescriptive method of assessment as well as instrumentation to be used. Even though the instrumentation identified is relatively accessible in industry, the viewing geometry specified is far less so. A limited amount of instruments meet the specifications documented. These instruments also tend to be significantly more expensive than other instruments without the capability of providing the required viewing geometry.
In many instances building certifiers are requesting certificates confirming compliance to the relevant standard during their assessments. Designers, developers, building owners and managers should therefore exercise some diligence in selecting suitable assessors of luminance contrast and the instruments they are using. It has been reported that some assessors are using instruments which do not meet the specific requirements of the Standards. Even though some important information can be gained from alternative instruments, they do not accurately meet the requirements of the Standards and therefore present some risk to all parties.
The relevance and value of applying the principle of luminance contrast in the selection of materials of course goes well beyond that of the elements indicated above. Paths of travel can clearly be indicated by selecting finishes to walls and floors which provide effective contrast. Furniture and movable items which contrast to the finishes they are viewed against reduce the hazard associated with collisions, trips and falls. Bench tops and work surfaces in joinery can be better identified and more usable to people with low vision.
The implications for a broader group of people are also obvious. Steps and stairs are possibly the largest source of falls and fall related injuries in the built environment. A study from the Monash University Accident Research Centre found that in excess of 19,000 such injuries were reported between 2002 and 2005. It may also be reasonable to suggest that the incidence of falls resulting in minor injuries which weren’t reported and therefore not identified in studies such as this may be far higher. Providing appropriately contrasting nosings, as well as handrails present important strategies in mitigating this risk.
People colliding with large format glazing is another common source of injuries within buildings regardless of ability and vision impairment. Applying suitably contrasting adhesive treatments as well as careful consideration of the finishes surrounding the glazing can contribute to reducing the associated rate of incidence.
It’s important to also note that testing is not always necessary when attempting to assess and apply luminance contrast effectively. Several paint manufacturers for example now publish LRVs for their products which allows designers to perform the calculations themselves. Greater awareness of this area over time will hopefully also see manufacturers of other building materials routinely publish these values for generic use and application.
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