By Wojciech Brożyna – MD of Aluprof UK
Seen by some, Passivhaus construction offers the ‘gold standard’ when it comes to building high insulation homes for our low-carbon future. Earlier in the year Scotland took a bold first step to develop and legislate their own Passivhaus standard for all new homes built from December 2024, but the Passivhaus standard is already being widely specified across Scotland for commercial projects.
What the new standard will be in Scotland has not been revealed yet, all we know is that is will be Scotland’s own take on the highly respected Passivhaus standard, but, no doubt it will follow the core values of Passivhaus.
A staggering 35% of our total global energy consumption is used in buildings, so cutting this energy will help reduce our carbon emissions. A Passivhaus certified building is optimised for a decarbonised energy grid, something the UK is working towards. Passivhaus also offers living and working spaces designed for the best health and wellbeing. This high level of occupant comfort that comes with Passivhaus uses very little energy for heating and cooling. Insulation plays a major role but this is only one of the five principles of Passivhaus design.
Whilst ‘Passivhaus’ is commonly considered as a German innovation, in fact, it was an American physicist, William Shurcliff who in 1982 published a book “The Saunders-Shrewsbury House,” in which he describes the concepts of “super-insulation” and passive solar as “passive house.” In the late 1980s a passive house movement had emerged in North America, but, shortly after America lost its appetite for energy conservation, Germany picked up the reins. A German physicist Wolfgang Feist refined the passive house concept to further improve efficiency and proposed a passive house concept with an annual energy demand of just fifteen kilowatt-hours per square metre of floor area.
Window insulation and airtightness is a major requirement in Passivhaus design needing a minimum of requirement of triple glazing for doors, windows and curtain wall. Aluminium, you may be surprised to know, can perform exceptionally well at high insulation levels using wide thermal breaks, inserted insulation and wide window seals. Some aluminium window systems can get down to a Uw of 0.55 W/(m2K) and door systems down to a Uw of 0.65 W/(m2K). Whilst these high performance systems come at a premium, the principles of design are now well known and aluminium plus polyamide thermal breaks are relatively quick to design and cost effective to produce, unlike window systems in some alternative materials. With today’s advanced powder coatings, aluminium fenestration products can easily outperform other materials when it comes to life expectancy and low-maintenance.
Passivhaus principles and low-carbon construction take a ‘fabric first’ approach, basically there is no point in using alternative heating systems, such as heat pumps in old dwellings, until the whole building fabric is re-designed to offer minimal heat losses. There are five principles that need to be introduced into the building before minimal heat sources can be considered. We must also remember that at certain times of the year, even in the UK, we also need to ensure we can keep the heat out in the extremes of weather.
- Air tightness to reduce draughts through building structure interfaces and fenestration helps isolate the living/working space from the exterior.
- Good quality and effective insulation of walls, ceilings and floors, to ensure that the interior space remains isolated in extremes of temperature.
- Often between building interfaces, walls and windows for example, thermal ‘cold bridging’ can occur where insulation areas are interrupted, these areas need very careful design. Designs of window reveals are particularly relevant here, including the window cill and head to ensure that the window frames high thermal perimeter performance is not reduced by poor reveal design.
- The window and facade systems themselves need to be of high thermal performance and airtight. These systems are carefully located within the building to take advantage of solar gain but not to extremes.
- Once we have the building airtight and thermally efficient, air changes are crucial and these can be achieved by using MVHR (Mechanical Ventilation with Heat Recovery) which provides fresh filtered air into a building whilst retaining most of the heating energy that has already been used in the building. These systems can currently achieve an 85% efficiency.
These five principles are the cornerstones of all Passivhaus construction for new build accommodation, offices and public buildings. Importantly for the UK’s extensive old building stock, the principles can also be applied to the refurbishment of any existing building.
Depending on the building construction, a new build to current building regulations will increase in cost by approximately 10% when constructed to Passivhaus standard. This increase in cost will be recouped over a few years and will then continue to offer significant energy savings. This is ‘responsible’ construction at its best, designed to meet the demand for our low-carbon future. In addition, compared to other materials used in fenestration product production, aluminium stands out as the most environmentally friendly option, being both highly recyclable and carbon neutral. Not only is it right for our planet, in the long term energy savings are significant for developers and clients.
Aluprof, one of the leading aluminium systems suppliers in the UK, have been supplying Passivhaus certified windows, doors and facades to Passivhaus projects for a number of years and have gained a wealth of experience in facade design, the design of thermal interfaces and importantly, logistics. Project managers are available to explain the benefits of specifying Aluprof Passivhaus certified systems and can assist in the design of thermally efficient interfaces with the building fabric. Installation in the UK and Ireland is undertaken by national facade companies who are fully trained in Aluprof systems.
Further information on the Passivhaus systems available and their specification is available through the company’s website at aluprof.co.uk, directly from their UK head office in Altrincham or from their London office at the Building Design Centre by phoning +44 (0) 161 941 4005.