Sash windows are not only beautiful architectural features but also essential for maintaining a comfortable and energy-efficient home. In this guide, we answer the most common questions about sash window performance, from double and triple glazing to insulation, airtightness, and costs. Whether you’re upgrading existing windows or exploring energy-saving options, this article offers practical tips and expert insights to help you make informed decisions.
Yes. Modern timber sash windows can be fitted with double glazing to improve energy efficiency and reduce noise. By retaining the charm and character of traditional designs while upgrading the glazing, you can create a warmer, quieter home with lower heating bills.
Yes, triple glazing is also possible for sash windows, especially with the LandVac Optimum triple glazing solution. Unlike traditional triple glazing, LandVac Optimum maintains the slim profile of double glazing while offering enhanced thermal performance.
Its advanced vacuum-insulated technology reduces heat loss without compromising on appearance, making it ideal for heritage-style windows.
Find out more about LandVac Optimum triple glazed windows here.
Timber sash windows can be highly energy efficient when paired with quality double or triple glazing. The thermal performance depends on both the glazing and the frame construction.
Choosing sustainable timber such as Accoya can further improve performance. Timber is a renewable material and, when responsibly sourced, offers excellent environmental benefits. On a cradle-to-grave assessment, timber windows are considered carbon negative.
By contrast, materials like uPVC and aluminium contribute more to greenhouse gas emissions and pollution.
Read more in our independent Sustainability in Windows Study.
Double glazed sash windows typically have a higher upfront cost than single glazed versions. uPVC options tend to be the most budget-friendly, while triple glazed windows can be around 35% more expensive than standard double glazing.
However, energy savings, reduced maintenance, and longer product lifespan can make higher-end options more cost-effective in the long term. Investing in better glazing and materials pays off with warmer rooms, quieter interiors, and lower energy bills.
No, high-quality modern sash windows are designed to minimise draughts. They include weather-stripping and sealing systems that prevent air leakage.
As with any product, performance depends on the quality of materials and the skill of the installer. To avoid draughts, choose a reputable manufacturer and ensure professional installation.
Modern sash windows can achieve a reasonably airtight seal. While their sliding mechanism means some small gaps are necessary, well-designed weather stripping helps prevent excessive air leakage.
They may not match the airtightness of fixed or casement windows, but they offer a strong balance between traditional design and modern performance. Regular maintenance, such as checking the seals, will help retain airtightness.
Yes, modern sash windows can be just as warm and insulating as any other window type. The key is to use the right glazing and materials.
Double and triple glazing options are available, including vacuum-insulated glass, which offers excellent thermal performance in a slim profile. These upgrades can dramatically improve heat retention and reduce energy loss.
With the right configuration, sash windows can help create a warm, energy-efficient home without sacrificing their classic appearance.
Gowercroft offers a wide range of energy-efficient sash windows in sustainably sourced timber. Our Frontier Range combines the elegance of traditional joinery with modern glazing technologies like LandVac vacuum glazing.
Whether you’re upgrading existing windows or starting from scratch, our products deliver outstanding insulation, long lifespan, and timeless design.
Ready to improve your home’s warmth and comfort?
Explore our Frontier Range of timber sash windows and experience the benefits of quality craftsmanship and modern performance.