Double glazing is one of those things you only notice when it is not working properly. Misted panes, cold spots by the window, a constant draught or the sound of every bus going past are all signs your glazing is no longer doing its job. Modern double glazing is far better than the units many Newcastle homes had fitted twenty or thirty years ago, and replacing tired windows can make a real difference to how warm and quiet your home feels.
Here we explain how double glazing works, what the ratings mean, how it helps with condensation and noise, and how to tell when it is time to replace what you have.
How double glazing works
A double-glazed unit is two panes of glass held apart by a spacer bar around the edge, with the gap between them sealed. Several parts work together to slow down heat loss.
The cavity and gas fill
The sealed gap between the panes is usually filled with argon gas. Argon is denser than air and conducts heat less readily, so it slows heat moving from the warm inner pane to the cold outer one.
Low-E coatings
A low-emissivity coating is a microscopically thin layer on one of the panes. You cannot see it, but it reflects heat back into the room while still letting daylight through. It is one of the biggest reasons modern units outperform older ones.
Warm-edge spacers
Older units used aluminium spacer bars, which conduct heat and create a cold strip around the edge of the glass. Warm-edge spacers are made from less conductive materials, which keeps the edge of the glass warmer and reduces condensation there.
U-values, WER and Building Regulations
You will see two ways of describing how well a window keeps heat in.
- U-value: measures how much heat passes through the whole window, in W/m²K. The lower the number, the better the window insulates.
- Window Energy Rating (WER): a band from A++ downwards, a bit like the labels on fridges. It takes into account heat loss, solar gain from sunshine and air leakage.
In England, replacement windows must achieve a U-value of 1.4 W/m²K or better, or a WER of band B or better, under Part L of the Building Regulations. The work must be carried out by an installer registered with a Competent Person Scheme or signed off by your council's building control. We provide a compliance certificate with every installation.
Some rooms also have escape requirements. Where a window serves as a fire escape route, for example in some upstairs bedrooms, the replacement must provide an opening at least as good for escape as the one it replaces.
Will double glazing stop condensation?
It helps a great deal, but it is worth understanding where condensation comes from. Warm, moist air from cooking, showers, drying clothes and breathing condenses when it meets a cold surface. Single glazing and old double glazing have cold inner panes, so that is where the water collects.
Modern double glazing keeps the inner pane much warmer, so far less condensation forms on it. Warm-edge spacers help at the bottom of the glass, where water often gathers. However, if a house has high humidity and little ventilation, condensation can still appear in the coldest spot, which may then be a wall or a corner. New windows include trickle vents where needed, and using them along with extractor fans makes a big difference.
Condensation on the inside of your windows is a ventilation issue. Moisture trapped between the two panes is different. That means the seal on the unit has failed and the unit needs replacing.
Reducing noise with double glazing
Any modern double glazing will quieten a room compared with single glazing, mainly because it seals the gaps around the window. For homes near busy roads such as the Coast Road, the Central Motorway or under the flight path to Newcastle Airport, acoustic glass gives a further improvement.
Acoustic units use laminated glass with a special interlayer that dampens sound, and often use panes of different thicknesses so that each pane blocks a different range of frequencies. The frame and how well the window is sealed into the wall matter just as much as the glass, so a careful installation is important.
Signs your double glazing needs replacing
Not every problem means new windows. Here is a rough guide.
| Problem | Usual fix |
|---|---|
| Misting between the panes | Replace the sealed unit only, if the frame is sound |
| Draughts around the opening sash | New seals or hinge adjustment |
| Handle or lock not working | Replace the handle or locking mechanism |
| Warped, cracked or discoloured frames | Replace the window |
| Old units with no Low-E coating | Replacement windows for a real improvement |
If the frames are in good order, our repairs service can replace individual misted units. If several windows are failing, or the frames are old and inefficient, full replacement is usually the better long-term choice.
Double glazing for period homes and conservation areas
Older homes can have double glazing without losing their character. Slimline units fit into replacement sash windows, and flush casements suit cottages and 1930s houses. The key is matching the proportions and glazing bars of the originals as closely as possible.
If your home is in a conservation area, an Article 4 direction may mean you need planning permission to change windows on certain elevations. Listed buildings need listed building consent. Always check with Newcastle City Council or your local council first. Our guide to replacing windows in a conservation area explains what to ask.
What affects the cost of double glazing?
We give a fixed, itemised quote after surveying your home, and the main factors are the number and size of windows, the frame material, the style of window, the colour and finish, and any upgraded glass such as acoustic, solar-control or obscure glass. Access also plays a part, for example on upper floors of Tyneside flats or houses with no rear access.
For most homes in Newcastle, good double glazing gives the best balance of cost and performance. If your home is very exposed, you might also look at triple glazing. You can request a free survey through the quote form whenever suits you.
