Discreet double glazing for timber sash windows

Upgrade your sash windows with slim double glazing for a warmer home

Sash windows are an integral part of a period property – but single glazed sash windows can compromise a home’s comfort levels. At Ventrolla, our double glazing solutions will help you keep the traditional charm of your wooden windows, while also benefiting from modern energy performance, sound insulation and security. We offer two double glazed options for sash windows. We can make slimline, double glazed sashes and install them into your existing sash box, and we can manufacture new hardwood double glazed sash windows.

Is your property listed, in a conservation area or protected? Our secondary glazing for sash windows could be a more suitable alternative to double glazing for your home.

Heritage style, modern energy-efficiency

Whether you choose replacement sashes or new double glazed windows, our highly-skilled craftsmen will tailor-make your units in our dedicated joinery workshop, to fit with the period style of your home. Every sash or window will also include our innovative Ventrolla Perimeter Sealing System (VPSS), which we have designed to virtually eliminate draughts, leaks and rattles. So you’ll enjoy energy efficiency, reduced noise from outside and a more secure home. In fact, our slim units perform just like those in uPVC windows, yet retain the elegant profile of an original timber sash. So you can enjoy the best of both worlds.

Find out more about our impressive draught-proofing system, the Ventrolla Perimeter Sealing System

Your questions answered

How does double glazing work?

Even though glass is classed as an insulator, with a single pane separating the outside and inside air, any warmth in your room is whipped away by a cold window. Double glazing works by adding a second pane of glass. The gap between the layers of glass is filled with an inert gas, like Krypton, which is an excellent insulator. This separates the warm air inside your home from the cold air outside of your home. 

Can I add double glazing to my original sash windows?

If you look at original windows, you’ll notice that the glazing bars – that the panes are positioned between – are relatively slim. They were designed to hold a single pane of delicate glass. The increased depth of a modern double glazed unit means that it’s larger and heavier, and simply wouldn’t fit in, or be supported by, the original timber glazing bars.

How do I install double glazed sash windows in my home?

We can craft made-to-measure double glazed sashes and fit them into your existing window box frame. We can also make completely new double glazed sash windows, bespoke to your property. Both options retain the integrity of your period windows, while making your home as comfortable as possible.

The latest double glazing technology, from Ventrolla

Double glazed sash units

Slim 14mm (4/6/4) double glazed units, Planitherm Total+ glass (outer pane) and krypton filled cavity. Centre Pane U-Value of 1.5 Wm²K and Total Window U-Value of 1.8 Wm²K

New double glazed windows

Slim 16mm (4/8/4) double glazed units, Planitherm Total+ glass (outer pane) and krypton filled cavity. Centre Pane U-Value of 1.2 Wm²K and Total Window U-Value of 1.5 Wm²K

Enhanced draught proofing technology

Our unique draught proofing system, the Ventrolla Perimeter Sealing System (VPSS), is fitted on all new joinery, as standard.

Cost-saving energy efficiency

Enjoy reduced energy costs and up to 30% improvement in energy efficiency thanks to the Ventrolla Perimeter Sealing System (VPSS), which is also used on our single glazed windows.


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From sash window repairs to bespoke replacement windows, we can help you:

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