Lesson's Learned? - Curtain Glazed Walling in the Residential Environment - does it need more thought?

8 August 2018

Over countless years we have lobbied hard for fire loss in the commercial sector to be recognised more in our building regulations but without life-loss we experience little interest. Read Dr Jim Glocking's article on whether we should have allowed GCW in to the residential sector.

It might be said that one the 'Grenfell Issues' is that a building method was taken from the Commercial environment and applied with little thought to the Residential environment where the controls, risks, and interest levels in problems relating to fire, are very different. Fire is obviously of great interest to the insurance community because a single event can cause total loss of property and cause such business interruption that the company becomes unviable and never recovers - seldom is this true of other perils, such as security. Over countless years we have lobbied hard for fire loss in the commercial sector to be recognised more in our building regulations but without life-loss we experience little interest. It could be argued that this flippancy leads to one great failing - no-one in authority is considering what happens when the building methods cross over from the Commercial sector (which let's not forget is very heavily regulated for safety, and most likely to have other protection systems in place, such as sprinklers - yet even then has fire issues), to the Residential sector, where:

  • Very different risks exist (Sleeping Risks)
  • Occupancies can be less fit to cope in fire
  • There is little or no control over contents and activities
  • Investment in protection systems over and above the minimum is scarce
  • There is less regulation and system testing than the workplace

In the same way that rain-screen cladding systems have made their way in to the residential sector, so too is Glazed Curtain Walling (GCW). Has anyone considered whether this is an OK thing to do? Clearly GCW is entirely appropriate for the commercial environment, but consideration must be given to whether it is appropriate in its own right (on a stand-alone material basis), or ONLY in association with the other controls which may or may not be present, in the Residential environment.

We can ask this question with some authority. In 1999, when the Loss Prevention Council, we conducted on behalf of UK insurers one of the largest studies of Fire Spread in Glazed Curtain Walling Systems ever undertaken. The remit of this work was to establish whether the Estimated Maximum Loss (EML) calculations used by insurers had merit.

EML - competitive insuring seldom assumes that every multi-storey building fire will result in a total loss. Instead, assumptions are made on the building's ability of resist fire spread - a typical crude assumption of a well designed and built building might be that you lose the fire floor to fire, the 2 floors above to smoke damage, and the floor below to water damage - i.e. insurance is for the loss of 4 floors, not every floor.

Across 24 full-scale tests we isolated the failure times of each key component in turn, the brackets, the aluminium grid, and the glazing. Failure times of the system were startlingly short with glazing failing in 13 minutes and considerably shorter times when combustible material was placed on window sills, and even the major components (transoms and mullions) 'consumed' in 24 minutes. However, the work also demonstrated quite clearly the effectiveness of sprinkler systems at maintaining fire conditions to a level that meant the CGW system was not threatened (and how good fire resisting systems can be). The work was presented to NFPA in 1999, South African FPA in 2008, and at the Tall Buildings Seminar in 2014 - a brief paper can be found here:

Paper on Fire Spread in Glazed Curtail Walled Buildings

The overarching conclusions at the time was that without the provision of sprinklers it was difficult to envisage how uncontrolled vertical fire spread could be avoided. But .... at this same time, through the fact that we were talking about a Commercial building system, and we had those spendid things called Local Acts in place (now repealed by the former DCLG), CGW probably would be accompanied by a sprinkler system.

So, what about now? This is not a question on the combustibility of facades, CGW does not burn, but it is incredibly structurally weak to fire ........... from what we understand from the research done, its application in the Residential environment, without a sprinkler system in support might be foolhardy at best and life-threatening at worst. There seems to be no impact analysis made on this - do we have to await the problem to manifest before action is taken again?
 

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Lesson's Learned? - Curtain Glazed Walling in the Residential Environment - does it need more thought?