The Problem with Conservation Double Glazing

The Problem with Conservation Double Glazing

Slim Double Glazing in Heritage Windows

Conservation area double glazing has always been a sensitive area in the restoration of Listed Buildings and those in Conservation Areas.

The owners of the building want to install windows with modern performance to make their rooms more comfortable, and their heating bills more manageable!

However local planning officers and organisations such as English Heritage put conservation first. They much prefer to restore original windows that to replace them.

In this post we discuss the dilemma facing home owners and conservation officers when upgrading listed building to slim double glazing.

The Background:

Slim double glazing came into use about 50 years ago and comprised of 2 panes of glass separated by air. Whilst this was a major step forward from single glazing it was soon found that the insulating value was poor. As technology advanced, the space between the glass panes was increased which improved it’s thermal performance. Also the edge spacer technology improved to ensure there was sufficient secondary sealant to maintain the integrity of the air space and enough dessicant to control any moisture within. So the now standard 28mm Double Glazed Unit was evolved and has been a reliable addition to almost every home.

Conservation Area Double Glazing

People who live in period homes, Victorian and Georgian properties, could not benefit from this technology . The original timber frames in Conservation and Listed buildings simply could not accept such a wide unit.

Slim Double Glazing was not the solution it was supposed to be

So the glass industry created the first slim double glazed units that could fit into such frames. The reduction of air space between the glass panes was compensated for by injecting noble gases such as Argon and Krypton. This slowed down heat transfer between the panes. The desire to fit them into the small glazing rebates led to very low sightline edge spacers, sometimes as low as 5mm.

Why Slim Double Glazing Units Fail

Whilst this achieved the desired aesthetics, and good performance, the fact is the reduction in secondary sealant and desiccant has led to these units failing at an alarming rate. Not helped by contractors attempting to squeeze a ‘quart into a pint pot’ by reducing the bedding compounds etc. 5 years of service life seems quite common before the units ‘mist-up’. I recently heard of an installation that failed after 1 year.

Role of Conservation Officers:

Conservation Officers are currently stuck between a rock and a hard place. On the one hand they are doing their job by protecting and preserving the built environment and the country’s heritage. On the other hand they are under pressure from all sides by Climate Change targets, energy saving and performance targets, as well as the demand from listed building occupants who claim the right to the comfort and energy savings than others enjoy.

It’s also an unfortunate by-product that a great deal of rot on existing single glazed timber windows is caused by the constant running and pooling of water caused by internal condensation.

Some Conservation Officers will allow retro-glazing with slim double glazed units so long as the existing profiles and glazing bars remain. In-advertently they may be driving the demand for such units that fail far too early.

The environmental story is poor. Retain single glazing and have poor energy performance and possible timber rot. Insist on slim units and the regular renewal will fill landfill sites.

The solution: Vacuum Insulated Glazing

One solution for conservation double glazing is to look to the new technology Vacuum Insulated Glazing. Ultra -thin by design and not reliant on dessicant or gas. Design based on the principle of the vacuum flask, two panes of glass separated by a vacuum space of 0.3mm. These units allow for retro-glazing of existing windows with single large panes of glass and with glazing bars bonded on to achieve the multi-pane effect if needed.

Vacuum Glass is a solution for Conservation Double Glazing

Whilst I can almost hear Conservation Officers and English Heritage screaming, think about the benefits. Glazing bars as fine as the originals, some as slim as 16mm wide and profiles as ornate as the original. More efficient windows, as the glass has a higher thermal efficient than timber glazing bar and putty. Conservation area double glazing that is 10 times more efficient than single glazing. No funny reflections as the panes are so close, and a service life in excess of 25 years, so less landfill and customer frustration.


Some close up shots of Heritage Windows with Vacuum Insulated Glazing

Vacuum Insulated Glass | The scope of VIG in the United Kingdom

Vacuum Insulated Glass | The scope of VIG in the United Kingdom

In 1913, the inception of Vacuum insulated glass raised on a very high level in front of people. The vacuum simply has a double glazed unit and not gas in the cavity. For refitting the heritage windows, from single glazing to double glazing and vacuum insulated glass is used for high performances and appearance to single glazing. With an ultra slim profile of just 10.3mm VIG can offer you a U value of 0.4W m2.K. Further, you find it helping in saving the lost energy in every window system of 8mm glass.

The scope of vacuum insulated glass

As it becomes more and more important every year to make every effort to protect our planets environment, VIG can help. People in the UK have been using Vacuum insulated glass (VIG) to help reduce energy usage (and bills!).

The basic purposes and uses of VIG

Here are some great applications for vacuum insulated glass:

High rise structures

VIG was developed in Japan’s earthquake zones to make buildings that are mostly class – i.e. skyscrapers, office buildings etc, stronger. The design enables engineers to make stronger, lighter buildings that are more resilient to earthquakes.

Passive House Systems

VIG is perfect for the Passive Houses where energy efficient windows that are tightly sealed integrate with the system. Passive Houses work by restricting air flow in and out of the building and being incredibly well insulated. This means that rooms can easily maintain regular temperatures, so it takes a lot less energy to keep them warm or cool.

Heritage Windows

The slim profile of vacuum insulated glass makes it popular with heritage renovation projects where the main objective for the local planning authority is to have an appearance of single glazed windows. Of course, using archaic and inefficient building materials is not what any home owner would want, so VIG fits the bill perfectly.

In Conclusion

So, it totally depends upon us to take care of the future and think outside of the box while using VIG for windows. To assist you completely in the selection of the right product, Grosvenor Restoration plays a very important role. For the renovation and new projects, we will provide you with VIG that will be of high quality and fulfil your needs perfectly. We are one of only a handful of LandVac distributors and installers in the UK. Our knowledge and expertise will ensure you get the right product for your needs.

Read More: Vacuum Double Glazing in Listed Buildings, What is Vacuum glazing? New effective technology for efficient buildings, Condensation problems with Glass | Vacuum insulated glass, Thin double glazing listed buildings | Grosvenor Restoration, Why choose Slimline double glazed units? Any Advantage?

What is Vacuum glazing? New effective technology for efficient buildings

What is Vacuum glazing? New effective technology for efficient buildings

Vacuum glazing as a highly efficient window technology that helps insulate and soundproof buildings. More efficient and with much slimmer profiles than standard or thin double glazing, vacuum glazing will help improve the efficiency of standard and special structures such as.

How Does Vacuum Glazing Work?

The concept behind vacuum glazing is simple. Standard double glazing has 2 panes of glass separated by a cavity filled with a noble gas, such as argon. The purpose of the denser gas is to make it harder for heat to pass through.

Rather than using air or other mixtures of gas between the panes of glass, vacuum glazing instead employs a layer of nothing. With there being nothing between the glasses, there is nothing to transfer the heat between the panes, and so it can’t go anywhere. 

In order to prevent further heat loss, the other elements of the window can also be improved to make them more efficient. All the different parts of the window, from the frames down to the minute pieces such as micro spacers and bars can be made more efficient.

There are improvements that can be made to the glass itself – such as a low emissivity coating, and specialist sealants to verify optimal efficiency for the long term.

The major advantage of vacuum glazing

The major advantage of vacuum glazing is the greatly improved efficiency. It also has superb soundproofing qualities.

Another advantage of this technology is how thin the units can be. The gap between standard or even slimline double glazing can be from 10 – 25mm. With vacuum glazing, the gap is reduced to a mere 0.6mm. This means that the windows can appear to be single glazed units with none of the unsightly inner cavity showing.

the major advantage of vacuum glazing

What are the applications of Vacuum Glazing?

Vacuum insulated glass is suitable for any property and will improve its efficiency. However, as it is somewhat more expensive than other units, it’s used in more specialised applications where either the slimmer profile or the improved heat insulating properties are more important than cost.

An example of a situation where energy efficiency is needed is the passive house system. 

For applications where the ultra thin profile is needed is for heritage windows in listed buildings. This is where an older property would have been originally fitted with single glazed windows. When replacing the windows, the planning authority requires the new units to be single glazed as per the original installation. This is not always acceptable to home owners who want lower heating bills and warmer rooms. In this case, the ultra thin profile of vacuum glazing is an excellent solution that keeps both parties happy.

Final verdict to take home on vacuum glazing

To conclude, for warmer, quieter and more relaxing rooms, choose vacuum glazing. They will improve the appearance of your home, make it more efficient and lower your contribution to global warming.

Read More: Condensation problems with Glass | Vacuum insulated glass , What is Vacuum Double Glazing? ,
Vacuum Double Glazing in Listed Buildings