How does double glazing work?

In this post MPS explain how double glazing works so if you are in the process of planning your own home renovation this post will provide you with the information to make an informed decision.

What is double glazing?

Double glazing has become ubiquitous throughout modern homes and for good reason. It reduces energy bills, noise and pollution whilst improving security and making your home more comfortable to live in. 

The history of double glazing.

The concept of double glazing is thought to have been developed in Scotland in the 1870’s, but it wasn’t until the 1930 that modern double glazing was invented and popularised by Haven in the USA. This new product did not catch on in the U.K until the 1970’s for two reasons.

Relaxed building regulations

  1. Relaxed building codes and a lack of incentive to improve the energy efficiency of their homes meant window technology did not change.

An energy crisis

The oil crisis of the 1970’s caused a sharp rise in energy prices and made the U.K rethink its approach to home energy use. As a result a maximum value of 1.8 for windows was introduced.

Is double glazing a legal requirement?

Since April 2002 all homes have a mandatory requirement to comply with Building Regulations ensuring adequate thermal, ventilation and safety standards. 

From 2007 it was mandatory for all properties to have an Energy Performance Certificate rating A-G. This does not necessarily mean you must use double glazing, only that the window must hold a minimum rating. 

As of April 2018 all private rental properties have been required to hold a minimum rating of E. All of MPS windows hold a rating of A and we can provide ratings up to A++.

Double glazing for listed buildings

If your property is listed and you wanted to replace the existing sliding casement window for a uPVC double glazed unit, this unlikely to satisfy conservation officers. Our customers living in listed buildings will often opt for secondary glazing and/or thicker curtains to minimise heat loss. MPS do offer market leading timber and steel alternative windows, which we often replace in conservation areas.

How does double glazing work?

Double glazing works by trapping gas within two panes of glass. The gas void is made airtight and this facilitates reduced heat transfer – in layman’s terms it reduces heat escaping from your home and cold air entering your home. 

This design is an evolution from storm windows which would see two separate panes of glass to separate interior and exterior openings during summer and winter. The double layer would provide a degree of insulation but this was very simplistic in comparison to modern glazing technology.

What is low-emissivity glass?

Our most efficient double glazing has gas between the panes, but also uses low-emissivity glass (Low-E). This works reflecting sunlight back into a home through a  reflective coating set within the glass. This is applied to all MPS glazing units as standard.

Double glazing heat loss

To understand how double glazing helps reduce heat then the simple answer is argon. Apart from being the third most abundant gas in the Earth’s atmosphere, argon is also a key element in the manufacture of double glazing. A layer of argon is trapped between the two panes of glass and it uses 65% of the thermal conductivity of air, meaning it is particularly ineffective at conducting heat. In this scenario ineffectiveness is desirable as it means cold air outside cannot transfer as easily to the interior, or that warm air inside does not escape outside.

Each double glazing unit also contains a spacer bar, this is located where the glass meets the frame and plays an important role for insulation. A spacer bar prevents heat loss and aided energy efficiency.

Double glazing payback time

The graph below shows the potential savings between house type by replacing your single glazing with double glazing during the course of one year in the U.K. 

From this graph we can also create an estimate for your payback time by using the following equation:

Obviously the payback time is only focused on energy savings and does not take into consideration energy price shocks or subjective topics, like a warmer, more aesthetically pleasing home with less condensation. From our experience the value can differ dramatically between homeowners.

What types of double glazing frames are available?

The most common type of double glazed window frame MPS install is uPVC, with white the most popular colour – although other colours are available. Other window frame options include aluminum and composite both of which come in a variety of colours but are more expensive versus uPVC.

Types of glass for double glazing?

MPS offer a variety of different glass types for double glazing, this will typically apply to commercial buildings such as schools or restaurants and on residential buildings glass roofing or low level glazing.

Annealed / Float Glass:

The least expensive of the three options, annealed glass is typically used for residential glazing. If broken annealed glass will break into shards however when installed as double glazing the panes give it shock absorbing properties. It is also surprisingly hard to break.

Toughened / Tempered Glass:

Toughened glass refers to panes that have gone through an additional heating process to increase its strength. Were the glass to break it shatters into small pieces, rather than sharp shards. This type of glass is ideal to use from showerscreens and balustrading to low level windows 800mm or less from the floor.

Laminated / Safety Glass:

Laminated glass is stronger again. Within the two panes of glass are thin interlayers of plastic which if broken prevent the glass from falling out of the pane and onto the floor. These characteristics also mean it provides excellent security as no opening is made when broken.

Still have some unanswered questions? MPS are on hand to help you make an informed decision from the years of experience in installing double glazing across Devon and the South West. Please feel free to give us a call on 01395 268712.

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