Energy Efficient Windows

“Energy efficient” is a term we hear used a lot at the moment. From architectural specifications to kitchen appliances, it’s a buzzword that elicits a vague kind of feeling that we’re ‘being green’ and ‘sustainable’. Unfortunately, the status of being ‘energy efficient’ is hard to quantify and is often another prime target of so-called greenwashing.

A BACKGROUND

There can be an overwhelming range of recommended design details when you start your research as a first-time builder – we highlighted this and dove deep into the Passive House Standard in this article, which we recommend for a general overview along with our ‘Why Triple Glazing?’ page. In the average home, 20-25% of heat is generally lost through windows and doors – a not insignificant amount. This still means, though, that somewhere around 75% of all heat loss comes through other elements of the structure – so, while opting for thermally efficient windows and doors can make a real difference to the comfort of your home, it is important to consider the thermal envelope of your entire home in a more holistic approach and design and build accordingly.

Norrsken are the leading supplier high-performance windows and doors. We’re not architects or designers – but we are about energy efficiency. Windows and doors are a major undertaking in any build – both stylistically and in their impact on the overall thermal envelope of the structure. Our products are designed, produced, and installed in line with our company ethos: to deliver outstanding thermal performance and excellent durability – and to help our customers build homes, offices and spaces that look superb and provide an excellent level of comfort in which to live and work.

ENERGY EFFICIENCY DEFINED

The concept centres around making the best use of technology and design to reduce the amount of energy required for the same output.

When we talk about ‘energy efficiency’ we are talking about reducing - or even eliminating - energy waste.

In the construction sector, increasing emphasis continues to be placed on minimising unnecessary energy waste. Despite huge setbacks in early 2020, the construction industry is pushing a 156% increase in new housing [ONS] in the period from April 2020, mid-pandemic, to February 2021 as the country emerges and steadily recovers from the effects of the coronavirus outbreak. With this boom, there is a very real opportunity to make a substantial impact on our approach to energy consumption as a country by adapting the energy efficiency of our building methods.

So what criteria should you take into account when searching for low-energy ways to build, heat and run your home?

Do ‘energy efficient’ windows really do what they say?

How do they work – and what benefits can you expect from choosing an energy efficient window system?

Building - A Background

In the average home, 20-25% of heat is generally lost through windows and doors – a not insignificant amount. This still means, though, that somewhere around 75% of all heat loss comes through other elements of the structure – so, while opting for thermally efficient windows and doors can make a real difference to the comfort of your home, it is important to consider the thermal envelope of your entire home in a more holistic approach and design and build accordingly.

Energy wasted: 20-25% of heat is lost through the windows and doors of an average UK home

HOW WINDOWS AND DOORS LET YOU DOWN

Typically, heat loss around thermally deficient or poorly fitted windows and doors can occur via:

Air leakage around opening sashes
Conduction through glazing spacer bars
Radiation through glazing
Conduction through the frame
Air leakage around the frame

By contrast, well-installed, high-performance windows and doors minimise this heat loss and augment the building’s overall thermal efficiency. For example, our beautiful oak-finished composite products work so effectively in this low-energy passive house that the home requires zero heating.

Norrsken are the leading supplier high-performance windows and doors. We’re not architects or designers – but we are about energy efficiency. Windows and doors are a major undertaking in any build – both stylistically and in their impact on the overall thermal envelope of the structure.

The impact of energy efficient building: This Passive House is entirely unheated

Our products are designed, produced, and installed in line with our company ethos: to deliver outstanding thermal performance and excellent durability – and to help our customers build homes, offices and spaces that look superb and provide an excellent level of comfort in which to live and work.

SO WHAT SHOULD YOU LOOK OUT FOR?

The components that make up a window all contribute to its functionality and insulating properties. Frame materials, glazing features, gas fills and spacer bars all play an important part in the performance of windows and doors.

Frame material – Consider the thermal conductivity of the frame material when choosing your windows. Comparing timber and aluminium frames, for example - as a raw material, timber is around 800 times more effective as an insulator than aluminium, and is similarly superior in this department to uPVC. Combined with the sleek, low-maintenance alu-cladding with which we encase our windows, Norrsken’s timber framed windows are, in our opinion, rather unbeatable.

Glazing – Single glazing no longer meets current (UK) legislation on thermal performance. (2.0 W/(m2K) is the limiting fabric requirement, 1.4 W/(m2K) recommended [Great Home]) Double glazing is now one of the most popular forms of glazing and comprises two panes separated by a spacer bar. Heat is trapped between these panes, which slows its escape from the building. Triple glazing follows the same concept but performs better again, as the additional space between the second and third panes of glass slows the heat loss further. In our systems, you can expect 40-50% better performance from a triple-glazed window over a double-glazed version.

Glass types – Double and triple-glazed windows in our systems have one or two panes of Low-Emissivity (Low-E) glass respectively. Heat-reflective coatings in this glass type reduce heat loss from the building by allowing warming infra-red rays into the building but preventing them from passing back out through the glass. Rays that would otherwise be lost to outside are reflected back into the room and disrupt heat loss.

Gas filling – Glazing units today are commonly filled with inert gas (such as argon or xenon) rather than air, which acts approximately 60% better as an insulator than air.

This gas filling minimises heat transfer between the interior and exterior of the window. All our units are argon-filled.

Spacer bars – Spacer bars keep the panes of glass apart in double and triple glazed units, maintaining the all-important ‘air gap’ between glass panes outlined above. There are various different spacer bars available, and the type used will affect the heat loss through your windows. Aluminium spacer bars, for example, facilitate heat loss, while alternatives such as warm edge spacer bars - made from a low conductivity plastic - provide better thermal performance.

Seals – Poor seals and gaskets on your windows and doors will affect air leakage rates and allow heat to escape from your home. Energy efficient windows and doors will often have multiple seals and gaskets, of differing types, which significantly contribute to the performance of the products.

Installation - Efficient windows and doors can be compromised, and their benefits wasted, if not installed correctly. Various measures can be taken throughout the installation to minimise air loss around the windows and doors. Examples include using airtight expanding foams between the units and the structural opening, and sealing the products with compriband tapes. Choosing a reputable and experienced installation company will allow you to explore your options and achieve your desired detail.

MEASURING THE ENERGY EFFICIENCY OF WINDOWS AND DOORS

When choosing new windows and doors, it might seem overwhelming to consider all of the components outlined above.

A simple way you might choose to compare products is by considering their U-values.

The calculation for this measurement is based on how effectively a material prevents heat transmission. The lower the U-value, the more energy efficient the product in question will be. Our full lowdown on U-values, how to calculate them, and what U-values to look for can be found here.

THE FINAL WORD

Windows and doors play a significant role in determining the energy efficiency of a building, but we also know quality and style are high on the agenda for our clients. Can you achieve superb comfort levels in your build without compromising a stunning aesthetic appeal?

Our superbly engineered all timber and timber alu-clad products deliver excellent energy efficiencies, have a superior life-span and enhance the look of any property. Browse our Gallery page for more inspiration and see the diverse range of projects to which our products will add value and appeal for many years to come.