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December 2024

Choosing energy-efficient windows for period properties

For energy efficiency, Fineo is an impressive option, offering a U-value of just 0.7 W/m²K. This ultra-low value signifies excellent thermal performance, surpassing standard double glazing and approaching triple-glazed efficiency but without the thickness and weight. Fineo uses vacuum technology within a slim 7.7mm profile, making it more suitable than double glazing for period properties.

CosyGlazing upgrades a period property's original windows, preserving their original joinery and craftsmanship, crucial for maintaining Britain's architectural heritage. It's also an environmentally friendly option, as it avoids full window replacement and keeps existing materials out of landfill.

Are you looking for energy-efficient windows that respect your period property's charm? Mitchell and Dickinson outlines two options that provide thermal efficiency while retaining your windows' historical significance.

Windows are one of the most scrutinised architectural elements in preserving the character of listed and period properties. While essential to a property's historical authenticity, they often lack the energy efficiency that modern homeowners desire.

Traditional single glazing, with a U-value of 5.8 W/m²K, allows significant heat loss, while modern building standards call for double-glazed panes with a U-value around 1.6 W/m²K. However, standard double glazing typically measures 28mm thick, making it incompatible with many period windows without significant modification.

For period homeowners hoping to improve their property's insulation, alternative glazing solutions like Fineo and CosyGlazing provide compelling options. Each has its own merits, as well as practical and aesthetic considerations.

A high-performance option

For energy efficiency, Fineo is an impressive option, offering a U-value of just 0.7 W/m²K. This ultra-low value signifies excellent thermal performance, surpassing standard double glazing and approaching triple-glazed efficiency but without the thickness and weight. Fineo uses vacuum technology within a slim 7.7mm profile, making it more suitable than double glazing for period properties.

"The appeal of Fineo," explains Tom Coles, Managing Director of Mitchell & Dickinson, "is that it achieves outstanding thermal efficiency and reasonable soundproofing, but within a thinner profile than modern double or triple glazing. It's a good solution if you're aiming for energy efficiency in a period property without compromising too much on thickness."

Property owners can replace poorly performing single-glazed windows with completely new replica units incorporating Fineo glazing. However, this can be a complicated and costly option as full replacements typically require using astragals or applied glazing bars to recreate the multi-pane appearance of period windows.

"Astragals are stuck onto the glass to mimic the original glazing bars," Tom explains, "but it's obviously not traditional joinery. Some conservation officers accept it, but others feel it compromises historical authenticity. It really depends on the officer's perspective and the property's conservation status."

Another factor with Fineo is "the dots"- tiny structural pillars separating the panes in Fineo's vacuum glass. While inconspicuous from a distance, they're visible upon close inspection. "Most people don't mind the dots, but it's something to be aware of," says Tom. "For some, it's a small aesthetic compromise, but for others, particularly conservation officers, it can detract from the authentic appearance."

Challenges of retrofitting period windows

Retrofitting Fineo glazing into existing windows is another option. However, some period windows, such as Georgian sashes with narrow glazing bars, may not support the added weight and thickness of the glazing. While modest by modern standards, this thickness can still be too much for original windows, which often have narrow rebates.

"The rebates in many period window frames just aren't wide enough to accommodate Fineo without a significant level of modification," explains Tom. "The windows would need to be re-engineered, and in some cases, reinforced to support the weight. That's not always feasible or desirable, especially if preservation is the primary goal.

"When you start altering the frame structure, it can quickly become an issue for heritage officers. They're understandably cautious about anything that alters the original materials or appearance of the windows."

CosyGlazing: a reversible solution

While Fineo's high thermal efficiency is hard to beat, Mitchell & Dickinson's CosyGlazing offers a more versatile option with fewer challenges.With a U-value of 1.7 W/m²K, CosyGlazing may not match Fineo's energy performance, but it offers a vast improvement on single glazing and is comparable with other forms of heritage double glazing. Moreover, its 4mm thickness and lightweight design make it ideal for most applications where Fineo's added thickness or weight would pose a problem.

CosyGlazing upgrades a period property's original windows, preserving their original joinery and craftsmanship, crucial for maintaining Britain's architectural heritage. It's also an environmentally friendly option, as it avoids full window replacement and keeps existing materials out of landfill.

One of CosyGlazing's primary advantages is its reversibility. Unlike Fineo, which requires a more permanent modification to the frame, CosyGlazing can be installed and removed without compromising the original structure. "CosyGlazing was created specifically to meet the demands of listed properties," Tom shares. "It's discreet, can be removed without damage, and is virtually invisible from the outside. Conservation officers like it because it doesn't alter the window's historic face."

Making the right choice for your property

Before choosing a glazing solution, Tom highlights the importance of considering the property's condition and specific requirements. "Every listed property is unique, and the solution depends on more than just the glass's U-value. We look at the window design, the joinery's condition, and conservation requirements. The last thing we want is to compromise the structure just to make it more efficient."

Conservation officers' opinions vary, especially regarding Fineo. While some accept the use of astragals as a close approximation of traditional joinery, others feel that glued-on bars fail to honour the property's original character. In contrast, CosyGlazing's removable, nearly invisible system tends to draw more consistent approval.

Ultimately, selecting the right glazing solution for a period property requires balancing energy efficiency with preservation goals. Mitchell & Dickinson specialise in period home energy upgrades, offering both Fineo and CosyGlazing to help homeowners achieve a balance between comfort and conservation. For owners considering full window replacement, Fineo offers top-tier insulation with some necessary compromises in aesthetics. For those who prefer to preserve the original glazing and joinery, CosyGlazing provides a flexible, minimally invasive option.

Keen to know more? Contact Mitchell & Dickinson today for expert guidance on the perfect glazing solution for your period property. Call 01237 871127 or email enquiries@mitchellanddickinson.co.uk

For further information, please visithttps://mitchellanddickinson.co.uk/

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With Compliments

Taylor Alden
Email:media@tayloralden.co.uk

Editor's note

Mitchell & Dickinson specialises in delivering bespoke insulation solutions for period homes and listed buildings in the UK. Products include a unique, advanced secondary glazing system known asCosyGlazinghigh-quality draught proofing for windows and doors, and specialist sheep's wool insulation for underfloor, sloping ceilings and lofts which will greatly improve the energy savings, soundproofing and ventilation. Mitchell & Dickinson's insulation solutions are installed on site, by expert craftsmen all of whom are direct employees and fully trained in house. The company also offer restoration services which often precede the installation of its products.

One of the founding principles of Mitchell & Dickinson is to cut carbon; the carbon savings that result from the work carried out are 50 times greater than the carbon footprint which ensures Mitchell & Dickinson is a carbon-negative company. So far, over 100,000 tonnes of CO2e have been saved since Mitchell & Dickinson started insulating homes in 2010, which equates to 800,000 flights to Paris, or 50,000 cars taken off the road for a year.