Double Glazing

So you've decided to replace your old windows with uPVC double glazing. You've started to research the market, then BANG your suddenly hit with a million different requirements, options and brands.

So where do you start? The best way is to look at your home and then your budget as many of the optional extras that can be added to double glazing can have a drastic effect on the price.

Understanding these options and requirements will allow you to assess any quote you have, as you will be able to understand exactly what is going on. Essentially no one will be able to pull the wool over your eyes.

In the England and Wales replacement double glazing needs to meet a number of building regulations. If you are planning to install the windows yourself you will need to contact building regulations to obtain the necessary documentation, alternatively you can have the windows installed by a FENSA registered company. The regulations are:

Thermal insulation:

Replacement windows must comply with minimum standards of thermal insulation. For uPVC frames the glazing needs to achieve a maximum U-value of 2.0W / m2K Make sure when ordering your new windows that your supplier can provide evidence that the glazing units meet these requirements, as a building control surveyor will need to see proof of this before issuing a completion certificate.

Structural Safety

If the replacement windows are wider than those they replace, or involve the replacement of bay windows, then the Building Control Surveyor will need to be satisfied that proper structural support is provided above the window and in the bays that support corner posts are adequate.

Safety Glazing

Low level glazing areas within 800mm of the floor, glazing in doors and within 300mm of door edges less than 1500mm above floor level should generally be of the type so that if broken, it will break safely. This means the glass should be toughened or laminated.


Building regulations require that adequate ventilation should be provided for people in buildings, so you must not worsen the existing rooms ventilation provisions. If your original windows have background trickle ventilation, then the replacements should also have them fitted. In addition all habitable rooms and rooms containing a wc should have opening lights of at least 1 / 20th of the floor area of ​​the room they serve. Kitchens and bathrooms also normally require an extractor fan, so if you are removing window fans these must also be reinstated.

Combustion air to fires and heating appliances

In some cases the existing windows may contain a permanent vent to supply combustion air to heating appliances, also you may find the removal of ill fitting windows which previously let air filter into the room could cause problems to your appliances. If this is the case you should ensure that either the replacement window contains a similar permanent vent, or that some other means of providing the required ventilation is installed at the same time. It is advisable to have your appliances checked out by registered installer eg corgi for gas appliances.

Retention of disabled thresholds

Many newer properties are now provided with level access thresholds and your new doors must not worsen this access, nor reduce the doors clear opening width.

Means of escape

All first floor windows in dwellings should ideally have opening lights large enough to allow you to escape through them if you were trapped in the room by a fire. This also applies to ground rooms where they do not open directly into a hall leading to an external door through which you can escape. To meet this requirement all such windows should have an unobstructed open area of ​​at least 0.33m2 and be not less than 450mm high and 450mm wide (the route through the window may be at an angle rather than straight through).

So once you've come to grips with the requirements your windows need to meet, then you need to look at the myriad of glass options available, some of the options will be mandatory due to building regulations ie low E glass to meet Thermal insulation etc . Some of the options available are:

Toughened glass: is a type of glass that has increased strength and will usually shatter into small fragments when broken.

Laminated glass: is a type of glass that holds together when shattered. When it is broken, it is held in place by an interlayer, typically of polyvinyl butyral (PVB). between its two more layers of glass. This interlayer keeps the layers of glass bonded even when broken. This produces a spider web cracking pattern when the impact is not sufficient to pierce the glass.

Low E glass. Transparent coating applied to glass surface to separate heat energy (long wave) and light energy (short wave) – long wave is reflected back to the heat source and the short wave can pass through the coating. Brands of low E glass include.

Gas filled: Argon is a colourless, odorless, non-flammable, non-reactive, inert gas. Argon gas filled glazed windows are used to reduce heat loss in sealed units by slowing down convection inside the air space between to the two panels of glass.

Low maintenance glass. Is an ordinary glass with a special photocatalytic coating. It is made by chemically bonding and integrating a microscopically-thin surface layer to the exterior surface of clear glass. Use of this glass in hard to clean areas can be especially useful.

Hopefully this information will arm you with enough knowledge to decipher any quote that may come your way. If you need any information on any glazing product, stop by at Conservatory TV [] they have a wealth of articles and videos and an honest opinion.