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Double Glazing FAQ

This is a primer all about the basics of double glazing – how it works, why to install it, how to buy it and the latest advances.


What is double glazing, exactly?

Cold winter scene viewed through large double glazed windows

Up to 20% of a home's heat is lost through the windows

Double glazing refers to a type of window or door that contains two sheets of glass sealed together, with a gap between them.

The gap is filled with inert gas or air, providing effective insulation for your home.


Why should I consider having double glazed windows or doors installed?

Double glazed windows or doors are much more energy-efficient than single glazing.  Double glazed windows will keep your home cooler in summer and warmer in winter.

Not only will you and your family be more comfortable throughout the year, but you will also conserve significant amounts of energy, and that means saving money off your energy bills.


Can double glazing help me save money on my energy bills?

Yes.  Because double glazing is a very effective way to insulate your home, you’ll find that you save quite a bit on your energy bills.  The average home loses up to 20% of its heat through the windows, so it is often well worth the money to replace your old windows and stop the heat escaping.

The exact amount of money you’ll save on your energy bills depends, of course, on the size of your home, your region’s climate and energy costs, and your in-home temperature preference.


Will a double glazing company give me a no-obligation quote?

Yes.  All professional companies should give you no-obligation quotes for the cost of having replacement windows installed in your home.  Before you contact a company for a quote, it helps to know the dimensions of the windows and doors that you’d like to replace.


I hear that double glazing can be quite expensive.  Will most companies allow me to pay by installment?

The cost of double glazing can be high.  Double glazed doors and windows cost more to manufacture and are generally of very high quality.  Installing the windows and doors requires professional skill and, of course, time.

Some companies will offer installment payment plans.  Some may not offer this option, but if financing is difficult for you contact your local council, building society, or bank.  There may be loan programs available to homeowners who wish to make their homes more energy-efficient.


I’d like to look at some samples of the double glazed windows or doors I can choose to have installed in my home.  Where can I inspect some sample options?

Having double glazing installed in your home is a major investment.  Before you decide on a manufacturer or model of double glazed windows and doors for your home, it’s a very good idea to inspect some samples in person.

You can do this at home improvement showrooms, or you can ask a glazier if he or she has samples available for you to look at.  You can also do basic research on the internet.


I’ve heard that double glazed windows are more secure than single-pane ones.  Is this true?  If so, why?

Yes.  Double glazed windows and doors are more secure than single-pane windows and doors.  This is because the two sheets of glass in double glazed windows and doors make them stronger and therefore more difficult for a burglar to shatter.


Must I pay a deposit to the company to have them install my windows, or can I pay the entire invoice when they complete the installation?

Most companies will require you to pay an initial deposit before they start work on your home.  This deposit amount is not standardized and it depends on the policies of a particular company.

However, the usual amount of a deposit is from 10 to 30 percent of the total cost of your installation.  Generally, it’s in your best interest to pay a small deposit rather than a larger one.

If the installation doesn’t proceed in the way you want it to, you are in a better negotiating position if you haven’t already paid a large deposit.


How can I tell if a double glazing service is reputable?

The vast majority of companies in the UK are reputable, professional businesses.  However, before you hire any contractors to work on your home, there are a few things you should consider.

Any reputable company should be easily contactable.  Smaller companies may not always have someone in the office to answer the phone, but they should reply to voicemail promptly.

Also, a reputable company should posses a business license and proper insurance.  Its workmen should be polite and well-trained, and the company should clearly explain what guarantees or warrantees are included in the installation service it provides.


Radiator and blue sky in home interior

Double Glazing helps to keep the heat inside your home

What about pushy salesmen?

The best way to deal with double glazing salesmen is to not feel pressured by them. A salesman is trying to persuade you to buy his product, and some may resort to unscrupulous tactics to do that.

Do not feel that you have to buy on the spot – a deal which is “now or never” is likely to be there tomorrow (unless it is for ex-display stock).

It is advisable to get a quote from at least three different companies, then you can spot if any of them are offering deals which are “too good to be true”.

Our article about pushy salesmen highlights the most common tactics.


Why do I need ventilation? I’ve just double-glazed my home!

Ventilation is necessary in all homes to prevent damage from damp and moisture. The ventilation of your house must be carefully considered when you install replacement windows.

In single-glazed houses (with poorly insulated frames), there is usually enough natural ventilation to combat these problems. However, when you install new windows (with tightly sealed frames), moisture in the air cannot leave the house, and problems with damp can arise.

You could just open them every day, but this is not very practical, especially in the winter! The answer is to buy windows which have integral vents in the window frames, or to retro-fit vents or fans to your double glazing.


What is Low-E glass?

Low-E (or Low Emissivity) glass is glass which has been treated with a thin invisible metallic coating. This is also called energy efficient glass.

The metallic coating increases the efficiency of the glass – it reflects the heat back inside the house (rather than letting it through the glass), and allows the sun’s heat and light into the room.  The coating is usually applied to one of the internal surfaces of a sealed unit.

There are two types of coating – soft coating, and hard coating. Soft coating is more effective, but also more expensive than hard coating, as the coating is not as durable, and so needs special handling.

When used in conjunction with argon gas in the gap between the panes of glass, low-E glass is one of best ways to achieve low U-rating.

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