Quotatis | Double Glazing Advice

Five ways to keep heat in with sash windows


Sash windows look great and are a prominent feature on period properties. But one of their problems is they’re notoriously draughty. This isn’t good news when you consider how expensive it now is to keep your home warm.

Essentially, the more heat that’s allowed to escape the more you’ll be spending on your bills.

With a rough calculation there are 43 million sash windows still in Britain. That’s fantastic for keeping an aesthetically pleasing appeal but isn’t helping anything when it comes to their expenses.

But fixing the problem isn’t exactly cheap. A complete replacement would see you spend a few thousand pounds. So we’ve listed below the six best ways of improving your energy efficiency, with appropriate costing included.

1. Don’t make any amendments to the window

First off, let’s take a look at the option of not making a physical change to the window itself. Historic Scotland found that heavy blinds or curtains can be a major factor in energy efficiency and account for a 14-50% reduction in heat loss.


  • You needn’t change the window
  • This can all be completed DIY
  • You’ll be keeping costs down


  • Will only work when curtains or blinds are closed
  • The glass itself will still collect condensation because it remains cold
  • You won’t benefit from noise reduction or extra security.

2. Draught-proofing

Draught-proofing the window is another solution. Try sticking masking tape over unused windows which is pretty effective, especially in winter. However, always be careful because if there isn’t adequate ventilation, especially in bathrooms or kitchens, then your home could suffer from high humidity.

We recommend you avoid surface mounted metal strips as they aren’t very effective and don’t look particularly appealing either.

3. Secondary glazing

Secondary glazing is fantastic for properties in Conservation Areas or listed buildings because nine time out of ten you’ll be granted permission. This is the complete opposite to proposing double or triple glazing. Secondary glazing is also cheaper.

Essentially, with secondary glazing a second pane is fitted on the inside of the original window.


  • Will help to slash your heat loss by a third
  • Can reduce draughts in your home
  • Is removable


  • Secondary glazing can be damaged
  • Once installed you can’t open the window.

4. Replacing the sash glazing

This is probably going to be your best option if finances permit. And the good news is you’ll probably be granted permission to do this, even by the most stringent of conservation officers. The frames will stay the same and the glass will simply be replaced by thin double glazing.


  • Huge reduction in heat loss
  • Virtually unnoticeable once installed
  • Retain appeal with the same frames and boxes

Of course, this isn’t work you’ll be able to carry out yourself. You’ll need to bring in an expert to replace the glass and prices will start from a few hundred pounds per window.

5. Replacing your sash windows

A more extreme way to go about suring up your home’s efficiency would be to replace the entire sash unit rather than just the glazing. You could choose to replace like-for-like or even have a full double glazed window put into your home.

Planning permission could be an issue here though so you should always speak to your local planning officer before going ahead with any work. Otherwise you could be asked to remove the new windows.

You’ll also want a FENSA or Certass registered installer to complete the work, because these companies comply with all regulations.

Also ensure your new windows have a low emissivity glass and the spacer is filled with a gas such as Argon or Xenon.


Facts & Figures You’ll Love To Share

  • Inefficient windows can lose 20% of the heat you produce in the home, seeing you with less disposable income.
  • Energy Performance Certificates range from A to G, and improving your windows will see your home’s rating boosted.
  • Always use a FENSA or Certass registered company to ensure your windows are fitted to the highest industry standards.
  • The annual household bill has doubled since 2004 and experts predict it’ll double again by 2020.

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