Windows

Upgrading your windows lets you keep the heat in for longer. This makes your home warmer whilst saving you money on your energy bills.  

Energy efficient windows also have the added bonus of reducing condensation and insulating against noise from the outdoors. 

In this article we’ll go through what you need to look out for when upgrading your windows. 

U-values for windows 

When choosing new windows, one of the things to consider is the window’s u-value.  

The u-value for windows measures how easily heat moves through the window. The lower the u-value, the less easily heat passes through the window.

Whilst u-values are helpful, they don’t give a full picture of the window’s energy efficiency. As with appliances like TVs and freezers, windows should come with an energy efficiency rating. The energy efficiency rating considers the u-value, but also looks at other factors which affect the window’s overall performance.  

The energy efficient rating runs from A++ (most energy efficient) to E (least energy efficient).

Double glazing vs triple glazing 

Double glazed windows have two panes of glass separated by a gap. Triple glazed windows have three panes and two gaps.  

As a general rule, triple glazing will be more energy efficient than double-glazing, but this will depend on: 

• The materials used 
• The size of the gaps between the panes 
• What kind of gas (if any) the gaps are filled with  

Comparing the energy efficiency ratings for double and triple glazed windows should give you a good indication of the difference in effectiveness.  

Although triple glazing is generally more energy efficient than double glazing, it’s not simply a case of automatically choosing triple glazing. This is because: 

Triple glazing is more expensive than double glazing 

Depending on your budget, it might not be feasible to upgrade all your windows to triple glazing. There are currently no window grants in Scotland for upgrading to triple glazing, which may further impact affordability. 

If your budget allows, you might consider installing a mix of double and triple glazed windows. You could choose triple glazed windows for the coldest rooms in your home, and double glazed for the rest. 

Triple glazed windows have deeper frames than double glazed windows 

When replacing your windows, you’ll need to make sure the new window frames aren’t too deep for the existing window space. 

Standard double glazed windows have a depth of 28mm. Standard triple glazed windows have a depth of 36mm. The greater depth of triple glazed windows means they might not fit correctly in an existing property.  

New windows and planning permission 

When thinking about replacing your windows it’s good to check if there are any restrictions on the changes you can make to your property. A good starting point is your local authority’s office for building standards.  

There are also likely to be limits on what you can do with your windows if you live in a conservation area or a listed building. In conservation areas, any changes to your windows might need to be in keeping with the look of the building or the locality. In listed buildings, you may not be allowed to replace the windows. In cases like these, secondary glazing is often an option. 

The mygov.scot website has a helpful tool which can help you work out whether you live in a conservation area or listed building. It also tells you who you’ll need to contact for different types of planning permission.

Secondary glazing 

Secondary glazing can be an option if your budget or building restrictions mean you can’t install double or triple glazing.  

Secondary glazing adds an extra layer of glass inside your property, directly behind the existing window.  

It’s possible to put in secondary glazing yourself with a DIY kit, or you might opt for a professional to install a more energy efficient and bespoke system. 

Budget options are also available for secondary glazing. You may have seen cling-film like material being applied to the inside of windows to create an extra layer of insulation. This type of secondary glazing has some impact on energy efficiency, but the material doesn’t tend to last very long.

Window grants in Scotland 

Whilst there are currently no window grants in Scotland for double or triple glazing, you can still take advantage of other funding options.  

Home Energy Scotland offer an interest-free loan of up to £4,500 to upgrade single glazing to double glazing. To find out more about the Home Energy Scotland Loan, simply call their freephone number on 0808 808 2282. An advisor will be able to talk you through the process. 

Scottish grant funding for secondary glazing may be available through the Warmer Homes Scotland scheme. Information about the Warmer Homes Scotland scheme – including the eligibility criteria – is available on Home Energy Scotland’s website. Alternatively, you can call Home Energy Scotland on 0808 808 2282 and an advisor can let you know whether you qualify.