Olav Skretteberg, energy enthusiast and Scottish-based timber windows and doors supplier, asks the question.

2016 is the Government target for all new build houses to be ‘Zero Carbon’ rated- just nine short years away. To date, however, a commercially viable “zero carbon” house is still a theoretical rather than a practical reality. But there is an established, tried-and-tested form of low energy housing– the Passive House – which the UK housing industry should consider.

One of the most important things about Passive Housing Technology is that it is nothing new – it has been around for over 100 years and is commonly used in Germany, Austria and Denmark.

Another is that Passive Housing is a construction standard rather than a single method or style of building. Passive Housing can therefore be created using a variety of technologies, designs and materials, and factors such as location, climate, materials, structure and ventilation all affect the Passive House you build.

Basically, Passive Houses are built to ensure a comfortable indoor climate in summer and winter, without using conventional heating systems. Passive solar design optimises the amount of energy derived directly from the sun, by careful planning of buildings to collect the sun’s heat. As a result a Passive House only uses 10% of the energy a ‘normal’ home uses and only requires 15kWh/ (m2a) annually for space heating. By contrast, a traditional home uses around 180kWh/ (m2a) and most ordinary Scottish homes get only about 15% of their space heating from solar energy.

Of course, there are questions about the quality and cost of Passive Houses. Can they really stay warm? Are they very much more expensive? Is the whole thing not too complicated?

The answer to the first question is 'yes'- they really do stay warm – and cool. As to cost, the answer is 'not much more' - around 8% - 10% more expensive to build, but delivering savings of up to 40% on running costs. As to complexity, the answer is a resounding 'no!' While there are strict criteria for creating a Passive House, Passive House Technology depends largely on good building practice – and on good, common sense.

For example, the Passive approach suggests that it is not sensible to ventilate our modern houses by cutting holes in high spec doors and windows, ruining U values and creating drafts. Common practice in the UK – but surely not common sense! The Passive approach also requires that windows and doors are fitted well, minimising heat loss from drafts, thermal bridges and air leakage – common sense, but not common practice.
 
Passive House Technology addresses such issues specifically, requiring that all houses should have:

• Excellent air-tightness
• Thermally efficient windows and doors
• An efficient heat recovery and ventilation system

Other key criteria for a Passive House include:

• Well insulated walls (U-value 0.1-0.15 W/(m2K)
• Compact building design (surface to area volume)
• Minimal thermal bridging
• Positioning of the house in relation to the sun and altitude

One of the most crucial factors in building a Passive House is the design and type of windows used. Glazed external surfaces have a major impact on the energy efficiency of a building envelope. Get the windows wrong- specification, location, design or fitting – and substantial unwanted heat transfer between the interior and exterior can follow. Get the windows right and they will help maintain the correct level of in-house comfort, winter and summer.

It is a fact that heat loss and gain in a well insulated home occurs mostly through the windows. In summer each square metre of glass in direct sun can allow as much heat in as would be produced by a single bar radiator. In the winter months losses from a window can be ten or more times the losses through the same area of insulated wall. With a good passive design – large, south facing windows are typical- windows can trap warmth in winter and repel summer heat; and admit cooling breezes for warmer days and exclude cold winter winds on others.

There are many choices of glazing for windows for a Passive House. Double or triple insulated glass is key to good thermal performance– for example my own company now supplies a window which can offer a U value as low as 0.6w/Mk2. Tinted or Toned Glass is an option; it has a 'sunglasses' effect that reduces the solar radiation entering the house thus keeping it cool in the summer months.

The spacing between the glass is also an important factor and the best thermal protection occurs when there is a 12mm to 15mm space. Solar control glass can also be used on the outer panel and a low emissivity panel for the inner, blocking radiation from getting in and heat loss from getting out.

So, we have the technology to create Passive Houses in the UK. And with the drive for sustainable construction, maybe we also now have the will.

To learn more about Broxwood windows and doors for Passive Houses view our new Alpine Range.