Double Glazing versus Secondary Glazing

Double Glazing versus Secondary Glazing – Which should you choose?

What is Double Glazing?

Double glazing is a window comprising two panes of glass. The space between the two panes of glass in double glazed windows can be filled simply with air, or argon gas can be injected into it to create an insulating barrier. This inert gas is a poor heat conductor and therefore keeps warm air trapped inside a building, helping to improve energy efficiency. The rest of this article intends to outline the key differences in the battle of double glazing versus secondary glazing.

The added insulation also acts as an extra barrier to external noise, contributing to a quieter environment. The extra pane of glass further improves security as a barrier to unwanted intrusion. Different material options for double glazing window frames include PVC-U, timber, aluminium or steel.

What is Secondary Glazing?

Secondary glazing involves adding an additional internal window in addition to an existing single, double or triple glazed window. This high-performance yet affordable solution provides greater thermal insulation, reduces noise intrusion and improves security as a deterrent to unwanted intrusion.

Secondary glazed windows use slimline aluminium frames that ensure they blend in with any interior décor and don’t change the appearance of a room. For Listed Buildings and those in Conservation areas, secondary glazing is often the preferred option where the original windows cannot be replaced due to planning restrictions.

Does Secondary Glazing cost less than Double Glazing?

Secondary glazing can be installed for around 25% of the cost for double glazing windows, depending on the size and style of the chosen system. This makes it a cost-effective alternative for window insulation.

For the best results, a secondary glazing system is made to your windows’ bespoke measurements and expertly fitted to ensure it works effectively over its lifetime. As secondary glazing is fitted to your existing windows, any disruption is minimal.

If you decide to install double glazing, your old windows need to be measured and entirely new units manufactured to specifically fit in your home. Fitting double glazed windows has to be done properly by professional installers; it’s definitely not a DIY job.

Double glazing is also more expensive due to the greater complexity of the window construction and components.

Which glazing should I choose to minimise heat loss?

Studies show that up to 10% of heat is lost through your windows. Given current high energy prices, investing in either double glazing or secondary glazing is worthwhile to keep your home warmer. Both glazing types will improve the thermal efficiency of your home and help to reduce energy bills.

Potential savings are, of course, influenced by various factors, such as the size of your home, size of the windows and any other insulation measures.

Double glazing is effective at minimising heat loss, and you could save between £50 to £175 on your energy bills per year.

Installing secondary glazing adds an extra barrier to prevent heat loss. As secondary glazing is often fitted with a 150mm – 200mm cavity from the primary window, the air-filled cavity acts as an insulator.

The creation of an insulating layer of air is as important to the retention of energy as the fitment and seals. With the right glass, the result can be a reduction in heat loss by as much as 65 percent.

Which type of glazing is better for acoustic insulation?

While both types of windows are effective at reducing external noise intrusion, secondary glazing is the clear winner here. This is because the larger air cavity between the primary window and the secondary glazing pane has a greater ‘dampening’ effect and prevents sound waves penetrating the room.

The triple barrier defence of primary window, air gap and secondary glazing pane creates a very effective noise reduction tool – eliminating noise intrusion by up to a considerable 80%.

Double glazed windows typically have a 14 to 20mm air gap between the two panes of glass. This much narrower means they are not as good as cutting out noise.