There are many terms relating to sustainable buildings, and we find they are often used interchangeably, or incorrectly, to the confusion and detriment of a client’s ambition. For example, someone might want to build an ultra low energy, low carbon home, yet commission an ‘Eco House’ not realising that this is an umbrella term, and doesn’t have to meet any specific requirements regarding energy, materials or performance.
To help avoid these pitfalls we’ve assembled our simple ‘what’s what?’ guide to decipher what all the jargon actually means. These terms apply to all building types.
Passivhaus
Passivhaus is a Germany-originated energy standard dating back to the 1990s. Through thicker insulation, exceptionally high air tightness, minimising thermal bridges, triple glazing, mechanical ventilation with heat recovery and carefully considered construction, Passivhaus buildings will achieve an operational energy consumption for heating of less than 15kWh/m2/yr (around one tenth of a Building Regulation standard house) with a payback period of as little as eight years. Passivhaus buildings also provide its occupants with greater energy independence and a pollutant, pollen and mould-free internal environment.
Passivhaus Plus / Premium
Passivhaus Plus and Premium are superior grades of Passivhaus, with a focus on further reducing general energy consumption whilst generating renewable energy themselves. As a rough rule of thumb a Passivhaus Plus will generate as much energy as it needs to function (when considered across the year), while a Passivhaus Premium will vastly exceed this, developing a significant surplus which can be exported back to the grid or to other buildings.
Passivhaus Low Energy Building Standard
More accurately known as the PHI Low Energy Building Standard, is a standard similar to Passivhaus, but with slightly more relaxed criteria where Passivhaus cannot be achieved. This standard requires a heating energy consumption of under 30kWh/m2/yr, rather than 15.
Retrofit
Retrofit refers to the process of upgrading existing buildings to improve their energy efficiency. Retrofit will typically solve other problems such as ventilation, damp and mould at the same time if done correctly, and if carefully considered can result in a visual and performance transformation.
EnerPHit
The EnerPHit standard specifically relates to retrofit of existing buildings. The principles are the same as those of Passivhaus, but EnerPHit adopts more relaxed criteria for both air tightness and heating energy (25kWh/m2/yr), recognising limitations imposed by the existing building’s orientation and original construction. An EnerPHit building should also solve damp and mould problems. There is also EnerPHit Plus and Premium which reflect their Passivhaus counterparts.
Embodied carbon vs operational carbon
‘Embodied carbon’ refers to the carbon footprint of the materials and processes involved in the creation and maintenance of the fabric of the building. ‘Operational carbon’ refers to the carbon emitted through the continual, daily use of the building. Most standards generally refer to the operational (ongoing) carbon usage - Passivhaus being one such example.
Net zero
Net zero relates to all greenhouse gases including carbon emissions, specifically obtaining a neutral balance between emitted and captured gases for operational and embodied energy. The term is commonly used in relation to Net Zero 2050, which is the UKs net zero target by that year. An interesting side note is that the Building Regulation standards at present mean that we are still creating buildings which are insufficient to meet the UK’s 2050 net zero target and will require retrofit.
Building regulations
Building regulations are a government legislated minimum building standard relating to structure, fire, moisture, energy and safety, to name just a few. In this context ‘Part L’ or ‘ADL’ of the regulations defines a minimum energy standard by component, rather than a holistic approach. This standard is not enough to achieve net zero carbon by 2050, and is widely regarded to be antiquated and insufficient. For context a new home built to Building Regulations will likely have a real world energy consumption for heating of over 100kWh/m2/yr, 10 times that of the Passivhaus standard.
Future Homes Standard
The Future Homes Standard is an upgrade to Part L (energy consumption) of the building regulations which should be implemented in 2025. The exact criteria within are still being considered, but originally aimed to reduce building carbon emission by 75-80%.
Eco home
‘Eco home’ is a generic umbrella term often used to describe buildings that claim to minimise their environmental impact. However they do not have to meet specific criteria or guidelines. For example an Eco home could be an off-grid, carbon neutral Passivhaus Plus, or it could be a building which is made from locally coppiced trees using zero concrete but in fact have a relatively high energy consumption.
Carbon neutral
A carbon neutral building is one whereby the operational and embodied carbon is balanced. It is similar to net zero, other than that net zero refers to all greenhouse gases, not just carbon.
Low energy
A low energy building is a non-specific term for a building which has a significantly reduced energy consumption. Passivhaus, Passivhaus Plus, Passivhaus Premium and EnerPHit are all examples of this.
Off-grid
An off-grid building is one which does not rely on statuary (public) services and is completely independent. It will generate its own electricity, treat and dispose of its own drainage, and even harvest its own water from the ground and sky.
This guide aims to simplify complex concepts, helping you make informed decisions about your sustainable building project. We’d love to talk to you more about what this could mean for your project.