GGF addresses reduced sightline IGU issue

  • 25 Oct 2017

Recent news coverage concerning the manufacture and compliance of some reduced sightline insulating glass units has led The Glass and Glazing Federation (GGF) to address the issue from a technical and GGF policy perspective.

On the compliance with Building regulations, Steve Rice (above picture), GGF Director of Technical Affairs explained: ““Initially we need to clarify the issue as to whether or not narrow cavity IGUs comply with Building Regulations.

“In all countries within the UK there are provisions for non-compliance with the general thermal requirements in properties that are classed as heritage assets (listed buildings) and conservation areas where the use of compliant products would significantly change the fenestration of the building.”

Russell Day, GGF Director of Home Improvement added, “In terms of the demand for the IGUs in question, it is not the narrowness of the cavity but the reduced sightlines of the spacer bar, some being as low as 5mm from edge of glass to top of spacer bar.

“This market demand is generated in the main, by local authority planning officers, in particular conservation officers, who demand that replacement glazing or windows into listed properties must be glazed into glazing rebates, either in the frame or sash that limits the dimension between edge of glass and top of spacer bar.

“This is of particular relevance where the sash is sub-divided into small panes such as is seen in Georgian style properties.

“Planners commonly restrict the width of glazing bars which sub-divide sashes into small panes, it is common to see these restricted to between 18 and 22mm, which in turn results in glazing rebate upstands in the range of 6 to 8mm, leaving a feather of 6mm to support and provide a level of strength to the window sash.”

At Glaziers Hall in London, in front of over 100 GGF Members, GGF Group Chief Executive announced its position on the compliance of reduced sightline units.

“If a member chooses for their own advantage to breach the GGF rules or indeed the law, it is the GGF’s duty to inform them and to guide and support them to return within the boundaries of the GGF rules and the law.

“If they choose to ignore that guidance then upon a finding of guilt they will be expelled. We have evidence that that course of action has worked in the past. But we are not a policing authority.

“However, if we find that a member is operating outside of the GGF Rules because of other authorities’ failings then it is the GGF’s duty to both guide that member and address the root cause that is putting that member under pressure to act in a way that takes them outside of the GGF Rules.”

The GGF has worked mainly in Scotland on this issue, having many meetings with Historic Environment Scotland, Building Control, MSPs and Scottish ministers, Trading Standards and local authority planning departments.

One manufacturer has been referred to Trading Standards – it has not been confirmed whether or not they have been investigated but given they are still trading the same products, it is assumed that Trading Standards have not yet dealt with the case.

Phil Pluck concluded, “The GGF remains committed to addressing the root causes of this issue but in order to do so, other stakeholders such as policing and planning authorities must accept that an issue exists, and that a joint approach is required to resolve it.

“GGF, on behalf of the industry and its members remains open to such discussions.”

The GGF has recently published a new guidance document, entitled Insulating Glass Units (IGUs) – Conforming to the Construction Products Regulation (CPR).

This is available as a free download to all in the industry. at



Glass and Glazing Federation
40 Rushworth Street

t: 0207 939 9101

Visit the Glass and Glazing Federation (GGF) website

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