Tell Me More About...Energy Efficient Windows

Published on Wednesday, 31st May 2017

Energy efficient windows installed in a Passivhaus installation

"Energy efficient" is becoming more of a buzz word in terms of construction and new build and with pressure being put on manufacturers to continually improve the energy performance of a window, consumers are looking past double glazing for better thermal performing windows.

Are they right to?

In this blog, we explain the pros and cons of the different glazings available on the roof window market.

Why is there a need for energy efficient windows?

The need for energy efficient windows has grown tenfold in recent years with many architects and homeowners developing greener, more sustainable properties which use less energy and reduce heat loss. Passivhaus projects are becoming more popular due to the desire to create a more sustainable way of living.

New builds have to meet certain requirements when it comes to saving energy and reducing heat loss. These requirements are set in accordance with Building Regulations & Associated Legislation, and developed by the Government and approved by Parliament. Building Regulations set national standards for all building work which covers all aspects of construction and building stability.

When the term "energy efficient" is mentioned, the immediate belief is to head towards triple glazed windows however with a number of improvements to the manufacturing of double glazed windows increasing their worth and ability, double glazed rooflights are able to offer an excellent level of energy efficiency.

Energy efficient roof windows from FAKRO

What glazings are available?

Double glazed

Double glazing is the industry standard when it comes to windows but roof windows, in particular, are now more affordable than ever before. With only two glazing panes in the sash, and the use of inert gas between these panes (instead of the previously preferred argon), double glazed windows let in more daylight than triple or multiple glazed windows.

Building Regulations state that any window you wish to install should have a U-value no worse than 1.6 W/m²K. Double glazed windows sit perfectly below the required U-value rating.

You may be asking yourself, "what is a U-value?" - you can read more about what they are in our dedicated blog.

Triple glazed

Triple glazed skylights are often assumed to be the better option when it comes to comparing them with double glazed ones. However, this isn't necessarily the case. Triple glazed windows are only as efficient as the way it's being installed. Use special accessories to insulate between the window and rafter is key to helping stop heat and energy from escaping.

Triple glazed windows are predominantly available for their ability to achieve U-values of 1.0 or better, however, these low U-values are only beneficial when they fit into a specified energy saving construction. Adding an extra glazing pane to a window sash will lose 10% daylight when compared to a double glazed window. This is because light has an extra layer to travel through to reach its intended destination.

Ideally, triple glazed windows should be installed on a north facing roof. With no direct sunlight or heat coming into the room through the window, this energy manifests in the room creating a comfortable living space. Installing a triple glazed window onto a south facing roof would make the room below too hot. Direct sunlight and heat would come into the room and wouldn't escape, thus causing an uncomfortable living space.

Legislation in Sweden & Norway is outlining that all new builds must consist of triple glazed windows as standard due to the harsher weather climates in these countries.

Quadruple glazed

Quadruple glazed windows are synonymous to FAKRO and are the only roof window company to offer quadruple glazing on their windows. Their highly energy efficient roof windows are suitable for passive buildings and energy efficient construction.

Offering a U-value of 0.58W/m²K, these windows have four glazing panes instead of the traditional two.

Quintuple glazed

Five glazing panes in one roof window - it does exist! It’s something of a secret in the UK but it is available at Sterlingbuild! VELUX offer a quintuple glazed, solar powered roof window suitable for a specialist Passive House installation.

Consisting of a U-value of 0.51 W/m²K, this roof window offers the lowest U-value on the market whilst meeting British Standard EN ISO 12567-2.

Passive House installation in Belgium

What is Passive House?

Passive House (or Passivhaus) is a construction concept where the aim is to reduce the ecological footprint of the building to as low a rating as possible. A building of PassivHaus specification is truly energy efficient, comfortable, affordable and ecological at the same time.

A Passive House has heating energy savings of over 75% when compared to a standard new build with inhabitants using solar heat or even body heat to warm the building.

Specialist energy efficient components are used in the building process and when combined with a quality ventilation system, potential savings of energy are considered to be vast.

Find out more about Passivhaus windows or triple glazed units.