Can you give us an overview of Passive House?

Passive House is a global standard that was first developed in the early 1990s in Germany and can be awarded to a building or component that meets its stringent criteria. It aims to dramatically reduce energy use and carbon emissions from buildings to support the building’ s ongoing health, whilst also providing high standards of comfort by producing excellent indoor air quality.

traditional heating equipment is no longer considered as essential

The Passive House standard supports the construction of truly energy efficient buildings that minimise‘ heating demand’ by using energy sources from inside the property, such as the body heat from residents or solar heat that enters through windows. This means traditional heating equipment is no longer considered as essential, as thermal comfort can be achieved solely by post-heating or post-cooling the natural air mass found within the property.

Buildings that meet Passive House standards also have low heating demands of less than 15kWh per square metre per year, helping to reduce annual fuel costs and offer a more sustainable approach to heating.

Can you tell us more about the Passive House rooflight process?

To achieve the specific quality of glazing required by the Passive House Institute( PHI), the rooflight must restrict the thermal losses of the window frame and glass edge. PHI therefore developed a Uw( U-Value) exemplary testing certification, to ensure all criteria has been defined and subsequently met by the product. PHI’ s hygiene criterion must also be met, which limits the minimum individual temperature on window surfaces to prevent condensation and mould growth. Certified windows and rooflights are ranked by their thermal losses through the non transparent elements of the product( such as the frame and seal). The efficiency classes are based on the U-Value of the frame, the frame width, the Opaque-Value of the glass edge and the length of the glass edge. The simulation of the thermal values of the frame sections are based on the regulations of the standard ISO 10077-1:2010 and 10077-2:2012. The thermal conductivities of the materials refer to relevant standards, technical approvals or have been determined by measured values according to ISO 10077-2:2012, chapter 5.1.

Passive House will only test the thermal efficiency of the rooflight when it is horizontal, rather than when it is vertical, which is particularly important for our fixed flat rooflight as it is installed in the horizontal position. Because heat rises and falls, a vertical window

will have a greater thermal efficiency than a horizontal window as the air is able to travel up and down the panes of glass in a wider space than a horizontal window as there is less room for the air to move. With this in mind, the same window will have a greater U-Value when it is vertical, than when it is horizontal, making it potentially fall short of PHI’ s criteria. To ensure this doesn’ t happen, PHI only examines the U-Value of the window in a horizontal position.

We’ re delighted to have created a fixed flat rooflight that meets Passive House standards

Why did Roof Maker want to create a Passive House rooflight?

Since 2001 Roof Maker has been at the forefront of research and development for the manufacture of innovative rooflights in bespoke sizes, styles and designs that reflect the continued changes and advancements of the sector. As a top level supplier there was a key market opportunity for us to extend our range of premium products by bringing another Passive House component to the market, facilitating the superior quality of the standard. We’ re delighted to have created a fixed flat rooflight that meets Passive House standards, supporting architects and installers in constructing energy

efficient homes by specifying approved materials and products that are easily available.

Can you tell us more about the technical process?

We initially contacted the Passive House team in Germany regarding our interest in manufacturing a rooflight that would meet its stringent requirements. Over a four-month period we worked closely with Passive House’ s technical engineers to ensure our fixed flat rooflight met every single area of its criteria and helped to produce a fully sealed home.

The Passive House team fed back on aspects they felt we could technically improve on after

reviewing the rooflight via its software, which challenged the product through a range of tests including thermal imagery. The engineers then installed the rooflight on a Passive House system to measure whether it helped to achieve the greatest level of thermal efficiency.

What technical features did you change to achieve the Passive House standard?

Following the Passive House technical team’ s feedback, the fixed flat rooflight features a unique stepped frame that has been designed to accommodate a 30o difference between the outside and inside temperature. For example, if the external temperature was-10o, the interior