Secondary Windows, are they the Right Choice for Insulating Your Single Glazed Windows?

Single glazing insulation, to create energy efficient windows, is a “must do” these days for both Residential and Commercial properties - rising energy costs plus the comfort factor make it essential.

At around 30% of a property’s total poor insulation heat loss - insulating single glazed windows offers probably the biggest single saving and the fastest capital cost payback.

And in the summer, secondary windows help to keep the heat out and further reduce energy costs where air conditioning is in use.

Secondary Glazing Windows? How to Decide!

With over 30 years of dealing with these issues, we have found that these are the most important considerations when deciding if Secondary Windows are the best option:

• our standard range of Secondary Glazed Windows provide excellent Window Insulation, completely eliminate Draughts and will provide you with a quick, clean, low cost (compared to replacement double glazing) upgrade to Energy Efficient Windows. Adding Low E Glass will achieve Heat Insulation for Windows that is comparable to modern Replacement Double Glazing!
• because of the lower installation cost, the payback of Capital Investment via Reduced Energy Bills will always be much quicker with Secondary Glazing Windows
• when the Original Windows are still Basically Sound but in need of upgrading to provide a modern standard of Insulating Windows, then Secondary Windows will provide an effective and very economical solution
• for Leasehold and Joint Freehold properties and those subject to Conservation Area or Listed Building status, all very common in and around London, Secondary Window Glazing will often be the only allowable upgrade and certainly the quickest, least stressful and cheapest option

Secondary Glazed Energy Windows - Heat & Energy Insulation Values

To put this into perspective, heat insulation for windows is expressed as the U Value - the lower the U Value the better the window insulation.

For those of a technical nature, the U Value is the measure used for Thermal Transmittance, in this case Heat Loss, of the rate of transfer of heat (in watts) through one square metre of a window, divided by the difference in temperature across the whole window. It is expressed in watts per square metre kelvin, abbreviated to W/m²K.

A window with a U value of 4.0 (W/m²K) will lose twice as much heat as one with a U value of 2.0 (W/m²K)

Or, conversely, a window with a U value of 1.5 (W/m²K) will conserve twice as much heat as one with a U value of 3.0 (W/m²K)

Secondary Glazing Windows - How Much Money Will I Save?

There are so many variables - area and the quality of sealing of your windows, floor area, type of heating, type of property - that it is difficult to be exact, but based upon our many years of experience and taking average calculations, we can give you a pretty good idea.

The Government’s annual English Housing Survey gives us average sizes for different types of properties and the Statistical Office publishes Annual Domestic Energy Bills for both electricity and gas, used as fuel.

With the above information and using both tested and calculated reduction in heat loss for our secondary insulating windows, the following chart provides you with a very good guide:

Just look for your property type - or, if you want to be more accurate - use the floor area of your property and multiply by the m² or ft² factors at the end of the chart.

For further information about secondary windows:

• Soundproofing & Noise Reduction
• Heat & Energy Insulation Case Studies
• Product Range & Specifications

Download our Secondary Glazing Brochure