Whether you have designs on protecting the planet or just saving money on your energy bills, making environmentally-minded choices for windows and doors goes way beyond just double glazing.
Image: Aluminium fixed glazing, Kloeber
Climate change is a hot topic and more than ever, we are aware of the need to reduce our impact on the environment. Choosing your doors and windows for your self‐build project is no exception. By making the right choice, you can reduce your carbon footprint, save money on bills with the benefit of creating a well‐insulated, comfortable home.
Doors and windows are a critical component in ensuring the sustainability of your project. In an average home, up to 40% of its heat loss is through doors and windows so it’s important to understand the difference between the materials in order to make an informed, responsible choice.
Energy efficiency and sustainability go hand in hand. Therefore understanding if the timber in your doors and windows is sustainably sourced or FSC certified or whether they are made of a material that can be recycled is as important as their insulation properties (measured by R‐values) and energy efficiency (measured by U‐values).
The Grand Designs magazine teamed asked the bespoke glazing specialists at Kloeber to break down the eco-credentials of the varying styles of windows and doors available.
Image: Timber FunkyFront windows and fixed timber glazing, Kloeber
Timber is a naturally insulating material therefore energy efficient with a U‐value of around 1.2 W/m2 for a high quality timber window. When choosing a sustainable timber, make sure it has credentials such as FSC certification that assures you the timber is sourced from a responsibly managed forest where the highest environmental standards are met.
Modern microporous paints and stains have made maintenance easy therefore increasing the life of your timber doors or windows. These paints and stains are absorbed into the wood so they don’t blister or flake and depending on the environment around the property, a high quality paint finish should only require maintenance every 8‐10 years.
Image: Aluminium fixed glazing and French doors, Kloeber
Perhaps you prefer the aesthetics of aluminium but are concerned about its eco‐credentials? Aluminium is more environmentally friendly than you might think. Often called the ‘green’ metal, it is 100% recyclable and is the most recyclable industrial material available. Recycling aluminium saves 95% of the energy required to produce it from raw material.
There is a misconception that aluminium is not energy efficient. Thermally broken aluminium (where a polyamide plastic insert separates the internal and external aluminium profiles to prevent condensation and increase insulation) is extremely energy efficient with U‐values as low as 1.2 W/m2 for a window with triple glazing.
Aluminium is light but very strong so the perfect material choice for large apertures where vast expanses of glass are required. It is extremely durable and resistant to corrosion as a powder‐coated finish ensures little need for maintenance.
Image: Alu-clad windows, Kloeber
Alu‐clad or composite frames offer the best of both worlds. With great insulating values, they are extremely durable and energy efficient. Originally designed and produced in Scandinavia to be able to withstand the harsh winters, alu‐clad is a high‐performance material that offers a lowmaintenance thermally broken aluminium exterior along with the sustainable properties of a timber interior. Do make sure the timber is sustainably sourced, with FSC certification.
Understanding the impact of different material types on the environment is complex and different studies on the component parts of a window including it’s lifespan, thermal and acoustic properties of the frame and glass as well as it’s recyclability, have resulted in no definitive answer. FSC certified timber comes from managed forests where ecosystems are protected and certified frames are carbon‐negative over their life‐cycle. Whereas plastic and aluminium take more energy to produce but both can be recycled. The thermal and acoustic performance of a window or door has to be taken into account when establishing eco‐credentials and the glass spec has a huge impact on this performance.
Image: Aluminium bifold doors, Kloeber
When you think of energy efficient doors or windows you may immediately think double or triple glazing, however, there are many different types of glass with energy efficient properties that should be considered that will help you find the right balance between solar gain (the increase in solar radiation) and thermal efficiency.
Low E glass or low‐emissivity, glass slows the rate at which heat transfers through the glass and is great for all round performance and energy efficiency, helping to maintain the ideal temperature indoors, cool in the summer and warmer in the winter.
Low Iron glass increases solar gain, letting in more of the sun’s energy and heat into your home so is particularly good for north facing properties.
Solar control glass reflects or absorbs solar radiation and is the ideal choice for south facing properties where there are large expanses of glazing.
Consider a supplier that only uses FSC certified timber and is a carbon neutral organisation – these are basic indicators that the company is well place to ensure you make the sustainable choice for your project.