Probably the most common upgrade to any property is double glazing.  Insulating glass, more commonly known as double glazing (or double-pane, and increasingly triple glazing/pane), consists of two or three glass window panes separated by a vacuum or gas filled space to reduce heat transfer across a part of the building envelope.

Insulating glass units are manufactured with glass in range of thickness from 3 to 10 mm (1/8″ to 3/8″) or more in special applications. Laminated or tempered glass may also be used as part of the construction. Most units are produced with the same thickness of glass used on both panes but some special applications such as acoustic attenuation or security may require wide ranges of thicknesses to be incorporated in the same unit.

It can also be secondary double glazing.  Secondary glazing involves the installation of an additional pane of glass and frame to existing windows. This can be used as an alternative to double glazing which involves the removal and replacement of existing windows. It can be used to improve sound insulation and to reduce heat loss and draughts through windows.

Secondary glazing is considered most suitable for:

  • Listed buildings, period properties and heritage/conservation areas.
  • Areas where there is traffic noise (such as buildings on main roads).
  • Properties where it may be uneconomical to install double glazing.
  • Properties where it would be difficult to modify existing external windows (such as single glazed timber sash windows).
  • Windows that require noise reduction, draught reduction, and so on.

Why is it green?

It helps to cut heat loss and reduces drafts.

What’s involved?

For some double glazing, simply replacing single glazed with double glazed panels, but if the whole frame needs to be replaced, then it involves removing the old frames, and possibly adjusting the window surround including the sill, plastering and external render.  Secondary glazing can be much simpler.

Can you DIY?

No, this is another job for a professional, glass can be heavy and breaks easily so specialist handling is required.

How much does it cost?

An average double glazing system on a four bed house will cost between £6,000 and £10,000.  It depends on how many windows and the specification.

Does it save money?

It would save about £80 – £100 a year for the average house.

Can it be done in a church?

It can, but it is a more cost effective method for a church, where usually the windows are fixed and not opening, to install secondary glazing as opposed to changing the windows and installing double glazing.

Other Thoughts?

You may wonder why it is so popular to install double glazing when the ‘pay back’ period is so long.  Initial finance, heat insulation and thermal performance is not always the only consideration, new windows will reduce noise, make maintenance simpler and are usually longer lasting.  In areas where casual vandalism is a concern then an outer layer of safety glass or plexiglass could be used.