December 19, 2012

Want to Extend or Renovate a Historic or Listed Building?

Written by Rebecca Clayton

frameless structural glass link between a home and newly renovated barn house

The Link Between New and Old

Renovating a historic or listed building to incorporate new, modern elements is a popular trend within the architectural landscape. Whether replacing original windows or extending, the integrity of the original building must be carefully considered in order to modernise the property whilst creating a contrast to the original structure.

renovation on a listed townhouse

Window glazing

IQ Glass can offer slim double glazed units which serve as brilliant replacement units for historic and conservation properties, greatly increasing their thermal and efficiency performance.

Our slim glazing units are double glazed units with a unit thickness of just 10-12mm. Using this system we are able to effectively and invisibly upgrade thermally inefficient, old and cracked single glazed units with a double glazed system, achieving u-values that surpass the Building Regulations thermal efficiency targets.

The glass panels consist of two panes of 4mm glass, the inner pane applied with low-e coatings to increase thermal efficiency, an inert gas filling and warm edge spacer technology.

The gas used in these units is generally a mixture of Krypton and Xenon. These gases are heavier than the standard Argon gas filling which is used in most double glazed units and are perfect for this small cavity opening. The heavier gas along with the small cavity spacer means that no convection currents can form in the internal gas filling and cavity, resulting in less heat loss to the external faces.

frameless up and over glazing in a listed home renovationThe glass units look like single glazing from any distance, thus not changing the outward appearance of an old or listed property.

However, using this glazing solution gives you U Values from as little as 1.2 W/m2K compared with the typical 5.4 W/m2K in a single glass panel, ensuring a comfortable living temperature all year round. 

These slim units are extremely suitable for replacing glass in traditional Georgian sash windows, able to fit into a rebate of only 7mm, and have been acclaimed by Kevin McCloud for their ability to both thermally enhance historic buildings whilst keeping the design integrity of the original structure in place.


Structural glazing
Glass can be engineered to have many enhanced properties but is naturally transparent. This is the reason it is used to great extent as a bridge between what was and what will be.

It is often a requirement of the planning permission that any structure linking from a listed building to a new structure be transparent and frameless, but even if it is not, that clear definition in the structure and design of the building can allow you to do something different, new and contrasting without impeding on the classic architecture of the existing building.

IQ have designed a thermally broken structural glazing system, Invisio, that is the UK's first fully tested thermally broken structural glass system. With few limitations on size, shape or structure, structural glazing is perfect for creating a clear differentiation between old and new. All fixing details would be concealed within the building finishes for the most subtle design, preserving the original character of the building whilst adding modern elements.


listed building connected to modern extension with a structural glass link


IQ Glass, as specialist glaziers in frameless structural assemblies, have been called upon to provide just that many times over the years. One of the most notable would be the RIBA award-winning property by Found Associates. The country cottage based in the rolling greenery of the Cotswolds in a picturesque lakeside setting was given a complete re-haul and extension. IQ’s minimal windows were used throughout but the connection between the old and the new was a frameless, colourless, almost invisible glass link. Supported by the stonework of the new and original buildings, the glass link space provides a clear break in materials making the extension seem almost as if they were freestanding, individual buildings.


Unique frameless glass link between two parts of a grade 2 listed building

Edge House

Another example of this invisible glasswork would be at this large residence, the link here was to connect the main house with the games and entertainment space. The invisibility of the frameless glass construction was made possible with the use of low iron glass, keeping the visual feel of the original structure and design.

The structural glass link has a modular look, giving the illusion of having been manufactured off-site and simply put in place. This was achieved by highly technical installation work which creates an effortless finish.


Yew Tree House

grade 2 listed home with glass box extension to create a new modern living spaceThis cottage was both listed and in a conservation area, making the design and approval process incredibly technical. IQ utilised the vast knowledge and experience working on heritage buildings to gain approval for a ‘transparent’ structure. The minimal windows have a frame of 21mm, perfectly in keeping with the frames of the structural glass walls surrounding them.

In keeping with the transparent structure and sleek design, where an inward-facing aluminium casement door was installed, the glass within the door was stepped over the framing profile. The result was a completely glazed, sleek exterior.


Contact IQ Glass today at to discuss your listed or heritage project.