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Building performance is a crucial consideration of today’s Architecture. Owners and inhabitants of archaic buildings, like myself, often envy the breathable, low-carbon, and highly energy-efficient offerings of a Passivhaus construction where thermal bridges and accuracy are addressed at every stage and heating costs are little to nothing. In my own house, similar to many others of their age, even a 90-degree angle on wall corners often is too much to ask, a note to consider when fitting a new kitchen or fitted furniture. Passivhaus standards are progressively being materialised in many new constructions and large retrofitting projects across the globe. But until recently, I considered the old, sometimes wonky houses we cherish for character a little too obsolete for the ‘modern update’.
For those not in the know-how, Passivhaus or ‘Passive House’ is a voluntary building standard that prioritises human comfort, sustainability and energy efficiency. As we approach a state of ‘climate-crisis’ where 35% of global energy consumption is down to our constructions (Passivhaus Trust), the need to harness the power of environmental and efficiency focused design is becoming ever more relevant and urgent. Passivhaus is the resolution using 80-90% less energy for heating and cooling compared to a conventional home with lifetime savings on energy, offsetting the initial investment.
A Passivhaus standard is achieved mainly through these five main points:
- High quality and effectively used insulation.
- Heat Control, using high performance glazing (to reduce heat loss)
- Airtightness (a major weakness in period properties)
- Mechanical Heat Recovery Ventilation Systems (these allow for a constant influx of fresh air to be drawn in and warmed using existing heat)
- Elimination of all thermal bridges
Adopting a Passivhaus standard presents a wealth of benefits, not just to our environment and our pockets but also our overall health and wellbeing, defeating many of the associated health impacts of cold, unventilated, humid, mouldy air polluted dwellings.
As I write this, wrapped up in a jacket, a flow of air covers my legs and Passivhaus feels unfortunately closer to a dream rather than a reality for many archaic, period property homeowners – a pair of Victorian townhouses on Zetland Road, Manchester, prove otherwise.
The pair of semi-detached houses provide a valuable case-study to many homeowners who cherish the character of their property. Here, heritage and character no longer come at a cost of the thermal comfort, or sky-high energy bills, with much of the ‘street charm’ one has come to expect from a Victorian townhouse being retained, all whilst meeting the Passivhaus EnerPHit Plus Standard, the first of its type in Europe.
On the front façade, the building maintains its brickwork and decorative design with insulation placed on the interior. The building no longer requires central heating, maintaining thermal comfort and elevated levels of air quality throughout every season. The rear of the property is retrofitted more aggressively however, replacing the existing brickwork with a clad, highly insulated timber structure along the building’s original footprint allowing for glazing to be positioned for maximal solar gain and a higher level of breathability possible compared to if the rear brickwork was to be retained.
Whilst a Passivhaus standard has proved possible, it often proves unrealistic for existing buildings, an EnerPHit standard serves as the more accessible achievement albeit still a challenging route. EnerPHit instead uses Passivhaus components ‘for an economically and ecologically optimal energy retrofit, [in place for] for old buildings that cannot achieve Passive House Standard with reasonable effort’ (Passivhaus Trust).
To meet the EnerPHit Standard, the retrofit must include:
- A Mechanical Heat Recovery System (MVHR)
- High-Performance Triple-Glazing in all windows and external doors, with consideration given to the way they are installed to minimise thermal bridges.
- An airtightness of 1.0 air changes per hour
- High levels of insulation
When dealing with period properties, incorporating EnerPHit requirements can prove tricky. It seems to be a game of balancing internal insulation (external if you aren’t worried about your external façade) with tight spaces, the risk of interstitial condensation and existing structural junctions that prevent airtightness or create thermal bridges, hence the necessity for in-depth planning.
The case highlights how initiatives like Passivhaus and EnerPHit can offer tailored approaches to preserving the past while addressing modern climate and energy challenges. Although achieving these standards can be a complex and costly endeavour, the long-term environmental, financial, and health benefits make them a worthy pursuit. For homeowners of older buildings, this proves that embracing the future of sustainable design does not have to mean leaving the past behind – it means building a more sustainable, harmonious co-existence.
