By Ryan Danks, Senior Engineer | Research & Development Specialist
I previously wrote a post highlighting the issue of regulating urban shadows. In this post I’ll be talking about the opposite problem, the issue of solar reflections and glare.
A Glaring Problem
In recent years there have been numerous cases where uncontrolled reflections from the built environment had severe impacts on their surroundings. The Shard in London was blamed for dazzling the view of train drivers. Rooftop photovoltaic solar panels blinded air traffic controllers at an airport in New Hampshire. Both the Vdara hotel in Las Vegas and 20 Fenchurch in London reportedly focused enough reflected sunlight to injure people and damage property. However, it's not just large buildings with extensive curtain walls causing problems; residential windows and even an art installation have been blamed for similar impacts. Given the risks, you would think that cities would have regulations in place to prevent these issues right?
Most city regulations around glare are vague and qualitative; they don’t provide guidance on what needs to be studied, how it should be studied or what’s considered “acceptable”. Some cities do have more prescriptive rules, usually taking the form of limits on how reflective facade components can be. Unfortunately, this sort of rule misses key aspects of the science and doesn't necessarily prevent glare in all cases.
One of the likely reasons for this lack of regulation is that there are no widely accepted metrics for defining the visual and thermal impact of a building's reflections on its neighbours. This leaves those of us in industry in the unenviable position of being asked to answer our clients’ questions about glare impacts, but with limited guidance from regulators and the scientific community on what would be “acceptable”.
The First Step
To better address our clients’ concerns about glare in urban environments, I and my RWDI colleagues, Joel Good and Ray Sinclair have created pragmatic criteria to assess the visual and thermal impacts of reflected light from the built environment. An extensive review of literature and our experience gained from our study of reflections from buildings around the world has lead us to proposing what we believe, are pragmatic criteria to assess risks of visual and thermal impacts of glare.
We are pleased to announce that the results of our efforts will be published in the July issue of the peer-reviewed journal, Building and Environment. Our hope with this paper is to spark conversation and encourage further research to better understand this phenomenon and determine the best way to predict and prevent dangerous impacts from reflections. In the meantime, we hope it will provide guidance to assist designers and regulators in understanding how a building’s reflections impact its neighbours.