Retrofitting Traditional Buildings: Windows

In our third blog in our TBHC Retrofit series, Callum, SCHT Heritage Trainee, takes a look at retrofit solutions for sash and case windows.
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In this blog post, we’re taking a look at how to retrofit your sash & case windows. But first, let’s have a brief introduction to the history of windows in traditional buildings in Scotland. The types of windows found within traditional buildings vary greatly. Originally, windows were simply openings formed within the wall structure, fitted with wooden shutters or boarding to enable them to be opened or closed. Cloth, paper, leather, and animal horn were also used in place of glass. However, advancements in glass production technology enabled the creation of glazed windows. Due to the quality and quantity of glass available, the first glazed windows used very small panes of glass.

In the late 1600s, pulleys and weights were introduced to windows and the sash & case window was created. They became very popular and were installed in buildings across Scotland in the 1680s-90s. A sash window consists of at least two panels which slide within a frame. The panels are connected by cords to weights which serve as a counterbalance to the weight of the window as it is opened or closed. They are now a familiar part of our historic environment.

Window Defects & Retrofit Solutions

We take a Fabric First approach to retrofit, which means that before any retrofit measures are installed, your windows should be well maintained and in good working order, or the retrofit measures may not work. You can find a great guide on how to properly repair and maintain your sash & case windows here: Short Guide: Sash and Case Windows | Historic Environment Scotland

It is also important to ensure that prior to carrying out any retrofit works, you obtain all necessary statutory consents required to make changes to your property. Always contact your local planning department for advice if you are unsure.

Draughts

Problem

These unwanted streams of cold air pass through gaps in the building’s fabric, causing heat to be lost. Draughts occur most commonly around the sashes.

Solutions

  • One way of solving this is to install draughtproofing. There are two main types of draughtproofing, brush seals and compression seals. Draughtproofing can be installed as part of a general window overhaul by competent joiners, but there are also a number of more temporary solutions which can be installed by homeowners on a DIY basis. Installing draughtproofing can even decrease noise pollution.
  • You should also ensure that the glazing putty around your window panes is well-maintained and not cracked or missing, providing a good seal between the glass and timber of your windows. Linseed oil putty protects your window timbers and prevents panes from being draughty and rattling.
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Heat Loss

Problem

As traditional windows are single-glazed, this can cause a property to lose heat.

Solutions

  •  A relatively simple method of improving window thermal efficiency is to install thick lined curtains or blinds. These will help to reduce heat loss and draughts and are also useful around your entrance doors.
  • Shutters can also be reinstated or repaired, which will help to reduce heat loss. Reinstatement/replacement will require a competent joiner, but small repairs such as freeing shutters which have been overpainted or nailed/screwed into their boxes, can be done by the homeowner.
  • Internal secondary glazing systems can be considered. There are various secondary glazing systems and they differ widely in their installation methods, materials, and costs. Some secondary glazing systems are hinged, others use a magnetic fixing system or are held in place via friction. When choosing a secondary glazing system, it’s important to consider not only how effective the system will be, but also if its installation will affect existing building fabric.

Case Study Involving Window Retrofit

To gain a better understanding of the methods which can be used to retrofit the windows of traditional buildings, it’s helpful to look at relevant case studies. An interesting example is the retrofit of several tenement flats in Edinburgh, which was performed by Castle Rock Edinvar Housing Association. The project involved works to 5 Category B Listed tenements with timber sash & case windows. The retrofit works focussed on making improvements to windows and the surrounding building fabric. Works performed included installing secondary glazing and insulating window reveals and shutters, and they significantly improved the thermal performance of the windows and the properties overall.

TBHC Retrofit Inspections

Stirling City Heritage Trust is now operating a Retrofit and Energy Efficiency service. The new service is open to existing members of the Traditional Buildings Health Check and will support owners of traditional buildings and aims to support traditional property owners to make their homes more energy efficient. Traditional building owners in Stirling, Bridge of Allan, Dunblane, and Blairlogie can start their Retrofit journey by signing up to join the Traditional Buildings Health Check scheme and booking a TBHC Inspection.

Further Information

More information about maintaining sash & case windows, possible retrofit solutions and relevant case studies is available online for free from Historic Environment Scotland:

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