Double Glazing: Is it Worth it?

Getting double glazing installed is extremely expensive on even a modest-sized house, so the potential benefits and drawbacks must be understood before you decide what course to take.

The instant gain from double glazing is the reduction in draughts and your ability to determine when fresh air can enter the house. It is good to have a reasonably frequent change of air, but on cold days it is highly wasteful to do this through draughty windows. You are better off keeping draught-proof windows shut most of the time, and open them for a minute or two when a change of air is needed.

What kind of double glazing should I get?

If you're just wondering which company you should go with, it's fairly hard for us lay people to judge. The salesmen will come to your house and show you bits and pieces of the types of windows they offer. Whether it's really quality is hard to say. There's nothing to beat personal recommendation, but without that consider how long has the company been in business. If it's over ten years, they probably take more pride in their product and will do lots to encourage recommendations by word of mouth -- you're more likely to get quality.

Other things to consider:

Real wood or Plastic

Plastic windows (PVC) are virtually zero maintenance, the lowest cost option, and last about 20 years (typically) before they will need replacement. Depending on quality of installation, they may separate from their frames, they can get condensation inside, or crack to bits. Condensation inside the units can be fixed relatively easily, but cracked frames means whole new windows. PVC windows come in white or wood effect. Recycling any part of these windows is difficult. Some people consider them fundamentally ugly, and in bad taste on older character-full buildings.

Hardwood double glazed windows are the most expensive (although not by a huge margin). Potentially they last the longest, if properly maintained (50 years or more). Like softwood windows, they can become completely ruined within just a few years without proper maintence. They are a specialist item and in a way that guarantees quality (the few manufacturers have to produce quality to stay in business at all). These can be the most beautiful double glazed windows, and in many ways can make a house very appealing.

Softwood DG was popular for a while, but is harder and harder to find. They are cheaper than hardwood DG, more expensive than PVC, but require as much maintenance as hardwood DG. Still, a good compromise in some ways, and required in some listed buildings.

Parts of wooden windows can be recycled.


Don't go for false economy if you don't have to; the cheapest quote may not be best. Try to find a firm that has been in business at least ten years so you know it's likely the windows you buy will last at least that long.


All DG window installations nowadays must meet certain low emission standards. Basically, to conserve heat inside the building, the glass is coated with some kind of reflective material (metal-based) to reflect heat back into rooms (cut heat emissions). There are two options:
  • Hardcoat -- this is the most common "Low-E" glass in new windows. The hard-coat has to do with how the metallic particles are fixed onto the glass. Hardcoat is cheaper than soft-coat (see below), but also conserves heat less well, and is more likely to make rooms dark -- it literally reflects more light back to the outdoors.
  • Softcoat -- trickier to apply on the glass, and for the installers to handle -- hence more expensive. But it insulates better, and doesn't have problems of dimming the outside light.
Most of the major glass manufacturers do both hard- and soft-coat glass, anybody quoting you for new windows should be able to get you soft-coat glass if you prefer (if the salesperson is clueless what you're talking about, they probably aren't the company you want to go with!).

A lot of other features that sales-people will tell you about are actually pretty standard: night openings, choice of handle cover, noise reduction potential, easy cleaning of upstairs windows, etc. It's worthwhile, too, to simply ask "Why should I choose your product over any other?"


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