Amazing new glazing technology allows period homes and buildings to become more energy-efficient without changing the window frames.

One of the biggest challenges facing architects, heritage officers and homeowners today is improving the energy performance of listed and period homes and buildings. While the energy-saving, comfort and environmental factors are obvious, making changes to a building’s façade without compromising its aesthetics or historic integrity is a difficult balance to strike. Fortunately, there is new glass technology readily available to help achieve this balance.

How can the thermal performance of single-glazed sash windows be improved without changing the window frames?

 Until now, to achieve a thermal improvement comparable to today’s double or triple glazing required the complete removal and replacement of the window frames. The reason for this is that a good double-glazed unit needs to be at least 24mm thick and a good triple-glazed unit at least 36mm thick. Quite simply, there is not enough room for sash windows to accommodate these thicknesses and so the windows are often replaced where permission is granted – and in some cases without permission – or more often the case nothing is done.

Energlaze, one of Ireland’s most successful retrofitting companies, has just introduced an amazing product. Fineo is a Vacuum Insulated Glass Unit manufactured in Belgium in a joint venture between AGC Glass Europe and Panasonic. The system takes two highly insulated glass panes and seals them airtight. A vacuum is created in the space between the two glass panes, which are held apart by microscopic pillars of just 0.1mm. 

The astonishing result of this latest technology is a slim double-glazed unit with an overall thickness of 6.1mm, allowing it to be retrofitted into all timber single-glazed sash windows. An amazing U-value of 0.7 W/m² K makes it 8 times more efficient than single glazing, 42% more efficient than modern double glazing and, most impressively, 12.5% more efficient than a modern 36mm triple-glazed unit.

This is not the first Vacuum Insulated Glass unit to come to market, but it is the first to be manufactured in Europe and has the best thermal performance when compared to others. A further environmental benefit is that Fineo does not use inert gases such as argon or krypton to achieve thermal performance, unlike current double and triple glazing.

Other notable positives are that it comes with a market-leading guarantee of 15 years, it has no visible extraction cap like some of its predecessors and it has excellent light transmission. It also has very impressive noise reduction characteristics, with a perceived noise reduction of 34% compared to single glazing and an 18% reduction compared to double and triple glazing.

Peter Campbell, managing director of Energlaze Home Energy Upgrades believes “this technology is ground-breaking in that it is the first slim double-glazed unit to achieve a thermal performance better than a 36mm triple-glazed unit. This is where the glass industry is heading. We need new technologies to improve thermal performance but not by increasing the size and weight of our windows and glass: thinner and lighter is where it needs to go. Period homes and buildings must not be left behind in our drive towards lower CO2 emissions and I believe this product can help solve an age-old problem.”

Further information is available at or by calling Energlaze Home Energy Upgrades on 01 9011635.

Energlaze AGC Fineo