Reports suggest around 29 million UK homes require retrofitting to meet zero-carbon targets by 2050. Many developers and building designers are turning to windows and doors to drive thermal performance. Mike Stevenson, technical specification advisor at NorDan, identifies the retrofitting challenges and reveals the importance of a fabric-first approach and how aluminium-clad timber windows and doors’ natural low carbon and proven insulation properties offer a sustainable, aesthetically pleasing and affordable solution.
CLIMATE change is undeniably driving modern building design, with the government’s sustainability targets seeing energy efficiency becoming an increasingly important aspect of retrofitting projects. However, with the ongoing cost-of-living crisis impacting everyone, concerns around climate change can often be eclipsed by worries over budgets and financial viability.
With Scotland, particularly Glasgow and Edinburgh, seeing a housing emergency, clients and contractors are under increasing pressure to build fast and cheap. This risks long-term legacy problems, such as damp, poor quality, premature failure and/or maintenance burdens, and expensive-to-run homes that don’t have energy efficiency at the forefront of design; only adding to the number of projects requiring retrofitting by 2050.
Furthermore, while the UK Net Zero Carbon Building Standard defines net zero to include embodied carbon, it is entirely voluntary and uptake has been fairly limited so far. Concerningly, there is currently no requirement to measure, mitigate or reduce embodied carbon in Scotland. This elephant in the room cannot and must not be ignored.
Despite needing to overcome significant hurdles, retrofitting offers clients, developers, architects and specifiers an ideal opportunity to substantially optimise energy performance and truly transform Scotland’s built environment.
The importance of a fabric-first approach
Able to reduce carbon emissions and enhance energy performance, heat pumps are becoming increasingly popular with architects and specifiers. However, installing them in poorly insulated buildings can increase heating costs. Consequently, with windows and doors often acknowledged to be weak points in a building’s thermal envelope, these – along with walls, floors and roofs – must be thermally efficient and airtight before implementing low-carbon heating.
Correct specification and better understanding are vital
While energy efficient products, such as windows and doors, are often popular with environmentally-conscious clients, architects and specifiers, the ongoing cost-of-living crisis and rising material costs can see some contractors focusing on upfront costs – leading to them pushing for specification changes when the project goes to tender. As a result, plastic window frames can often be specified due to their perceived affordability. However, cheaper products with a shorter life expectancy can often require costly, frequent repairs and maintenance.
Many plastic windows typically have a lifespan of approximately 20 years, meaning up to three replacements for any building designed to last 60 years. Conversely, NorDan’s aluminium-clad timber windows have a lifecycle assessment-backed 60-year life expectancy, typically lasting up to three times longer. This means a plastic window’s cheaper upfront capital cost doesn’t mean lower whole-life cost.
A typical plastic window will achieve a U-value of around 1.3-1.4 W/m2K with double glazing. Meanwhile, a NorDan aluminium-clad timber double glazed window can attain a U-value of 1.2 W/m2K, resulting in a 17% reduction in energy use for a tenant or occupant over a year – based on 25m2 of glazing. This should be a huge consideration given increasing fuel poverty and the cost-of-living crisis.
From a whole life carbon perspective, plastic windows also have between two and three times more embodied carbon than their aluminium-clad timber equivalents.
Timber windows and doors offer a much-needed retrofitting solution
By utilising biophilic design principles, timber windows and doors offer an effective way of enhancing occupant productivity and wellbeing. Surrounding occupants with natural, wood-finished materials helps create a calming, warming and restorative environment, lowering blood pressure and reducing stress.
NorDan’s aluminium clad timber windows and doors are designed for the harsh climate and exposed coastline of Norway’s west coast, making them well-suited for the most extreme of Scottish and UK weather conditions. A future-proof solution given the changing climate and worsening weather extremes.
This, along with the energy-saving and aesthetic benefits of aluminium-clad timber windows and doors, is seeing them increasingly utilised across Scotland and the UK. In fact, NorDan StormGuard windows are specified for ad-hoc replacements across 44 tower blocks as part of a major City of Edinburgh Council retrofit project.
Retrofitting Scotland and the UK’s building stock to meet increasingly stringent sustainability and energy efficiency targets must remain a priority for those in the built environment. However, the net zero message must be reframed to focus on the immediate benefits to property owners, occupants and tenants, such as lower bills and warmer homes, rather than distant targets like 2045 or 2050.
Ultimately, enhancing understanding about the need to implement trusted and energy efficient materials early in the design process and changing people’s perceptions around specification must happen at client level.
