Triple glazing is a very popular choice in home improvement and is marketed as an environmental solution. But how can you be certain that it is a green investment?
A green product or environmentally friendly product has the following attributes:
It is energy efficient, durable and have low maintenance requirements;
is free of ozone-depleting chemicals, toxic compounds and that is manufactured without any toxic by-products;
is made from or contains recycled materials or is made from renewable or sustainable resources;
has been locally manufactured;
is biodegradable or can easily be recycled.
When you want to determine the green properties of a building material, it’s important to not only look at the direct impact it may have on the building and its inhabitants, but also the materials and processes involved in its manufacture.
Triple glazing frames can be made up of 4 different materials: wood, uPVC, aluminium, or wood clad with aluminium.
When looking at the environmental impact of wooden frames, you have to consider where the timber is being sourced from, the treatment of the wood, as wel as the maintenance. Wood should only be sourced from sustainable forests that have been certified by the Forest Stewardship Council. Typically, these will be temperate hardwoods known for their durability, like oak, larch and sweet chestnut. Sapwood is explicitly being excluded. Transportation of the wood from source to factory also has a big impact on its carbon footprint and it is therefore essential that only UK sourced wood is being used.
While painting frames may prolong their lifespan, the paint further adds to the frames’ environmental impact. For this reason, naturally durable species that do not require painting is the option with the highest environmental rating.
Aluminium frames combines the environmental sustainability of wood with the high longevity of aluminium. While the typical wooden window has a lifespan of 30 years, the aluminium cladding onto the outside of the frame prolongs its life by another 10 years. Both wood and aluminium are completely recyclable and requires little to no maintenance. Wood has very low thermal conductivity so aluminium-clad wooden frames are rated as very good thermal insulators. As with wood-only frames, it is important to verify the source of the timber as coming from a sustainable forest.
uPVC or unplasticized polyvinyl chloride is a very sought-after building material because it is lightweight, durable and requires little to no maintenance. And because its thermal conductivity is extremely low, it’s a great insulation material as well. uPVC is made from non-renewable petroleum, counting heavily against it when looking at its green rating. The frames can last from 25 – 40 years and although they cannot readily be repaired, uPVC can be down-cycled.
When looking at both materials and manufacturing processes of triple glazing frames, wood is certainly the most environmentally friendly choice.
Glass is an inherently environmentally friendly product. It is sustainable and fully recyclable while using little water and power in its manufacturing. Being made from an abundant natural resource sand, or from recycled glass, it can be recycled again and again without losing any of its properties. Recycled glass also melts at a lower temperature than silica or sand, making it an even more energy efficient option.
The glass that is being used in triple glazing also has significantly lower levels of iron, which results in a much clearer glass. This type of glass doesn’t have the blue-green tinge that standard glass has. Using this low-iron glass enables additional free solar heat gain, further adding to the reduced need for heating.
Low E-glass or low emissivity glass increases the efficiency of a triple glazed window unit by reflecting long wave infrared energy, or heat, back into the room. The coating consists of 2 or 3 layers of silver nitrate, a microscopic and undetectable layer. This coating deflects heat, preventing it from escaping, and thereby reduces radiant heat loss.
The spaces between the glass panes are filled with Krypton [Kr] gas. Krypton is a rare atmospheric gas which is non-toxic and chemically inert (source).
Krypton gas has a 34% lower conductivity than air which further aids in preventing heat loss through a triple glazed window. Where a double-glazed unit has only 1 gas pocket – usually filled with Argon gas – the 2 gas pockets of a triple glazed window make the unit so much more thermally efficient.
To understand the environmental impact of a window, you only have to look at the manufacturer’s Window Energy Rating. This rating is based on the manufacturing processes, and not the energy efficiency of the window as such.
When looking at the energy efficiency of a window, there are so many variables to consider: the location and orientation, the environment, the size of the window. So the WER is a rating on the manufacturing of the window unit only. Triple glazing windows have the highest ratings of domestic windows, with WER of A+ or A++ for some manufacturers.
Ensure that you triple glazing installer removes the old frames and disposes of them responsibly. This means recycling of wood, glass and aluminium as far as possible, and as little of the original windows ending up in a landfill.
Now that we have assessed the green credentials of a triple glazed window, let’s look at the impact it will have on your home. The first thing to look at would be the impact triple glazing has on your domestic Energy Performance Certificates (EPC).
EPC’s were introduced in England and Wales in 2007 to help prospective homeowners understand the running costs of a property. It was initially only required for homes with 4 bedrooms or more, but later the legislation was extended to include smaller homes and flats as well as rental properties.
An EPC measures and rates the overall energy efficiency of a home, its CO2 impact, and its current expenses in terms of lighting, heating and boilers. An EPC also makes recommendations of improvements.
Among these recommendations will be insulation of roof spaces, insulating and walls and floors, installation of triple glazing to improve the heat retention capabilities of windows, upgrading outdated and high energy heating systems and installation of energy efficient appliances. The assessment will also note the savings that can be made should these recommendations be implemented.
The certificate also includes an itemized summary of individual elements in your home that influence the given rating, and rates them Very Poor / Poor / Average / Good / Very Good. Elements that are rated are walls, the roof and floor, windows, the main heating source and controls as well as secondary heating, hot water and lighting.
The typical triple glazed window unit has 30 – 50% increased heat retention when compared with a double-glazed window of the same size and in the same location. Heat loss through windows is measured as a U-value. The lower the U-value, the better the ability of the window to resist heat transference and the higher its insulating properties. Standard single glass has a U-value of 5 while double glazing has a U-value of 1.4, already being a significant improvement in heat retention. Triple glazing has a U-value of less than 0.7 which makes it more than twice as efficient as double glazing.
Because of its extremely high resistance to heat loss, and the ability to retain heat and a consistent temperature inside a home, triple glazing is a home upgrade that makes complete environmental sense.
Published on : 1st March 2017
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