The international Passive House (Passivhaus) Standard
The world’s fastest growing energy efficiency standard for buildings. The standard is based on achieving the optimum indoor conditions for human comfort and well-being (based in part on BS EN ISO 7730), whilst only requiring a minimal amount of energy. It is a performance standard with clearly defined metrics and a rigorous design and performance modelling methodology. The standard is administered by the Passive House Institute in Germany. For more information, see: What is the Passive House Standard?

Passive House Classes
There are 4 levels of Passive House for new buildings:

  1. Low Energy House – as Passive House below but slightly relaxed targets
  2. Passive House ‘Classic’ – well insulated, draught-free, good solar design, ventilation system with heat recovery, high performance windows and doors. This is typically what is meant by “Passive House”.
  3. Passive House Plus – as ‘Classic’ above with renewable energy generation accounted for based on the building footprint
  4. Passive House Premium – as ‘Plus’ above with surplus energy generation

Passive House Retrofit: EnerPHit
As Passive House ‘Classic’ above but with slightly less stringent requirements due to the nature and complexity of retrofit. EnerPHit can be achieved by meeting energy demand requirements or alternatively by following the ‘component method’ using Passive House certified components.

Thermal Envelope
This refers to the parts of a building that thermally separate the inside from the outside. It includes walls, floors, roofs (or ceilings, depending on where the insulation is located), windows and doors. It must be continuous and unbroken for Passive House. For more information, see: What is the Passive House Building Envelope?

Heat Loss Area
The total surface area that forms the thermal envelope of a building and therefore may lose heat. It includes ground floor, walls, roof, soffits etc. Areas are measured in total without subtracting windows, doors, rooflights, etc.

Treated Floor Area
The convention for measuring usable floor area within the thermal envelope. Rooms are measured from the internal finish of the walls, ignoring fitted furniture etc. Stairs and lifts are excluded, full landings, store rooms, bathrooms etc are included.

Heat Loss Form Factor
The ratio of heat loss area to treated floor area. Generally, a ratio of 3 and below is efficient. For more information, see: What is the Heat Loss Form Factor?

Heating Demand
The total amount of annual heating energy required per square metre of treated floor area to maintain a Passive House building at the design temperature. The Passive House standard requirement: 15 kWh/(m2.a)

Heating Load
The maximum amount of power required per square metre of treated floor area to maintain aPassive House building at the design temperature.The Passive House standard requirement: 10 W/m2

Design temperature
The Passive House standard uses 20 °C (68 °F) as a design temperature by convention. This is within the healthy range of temperatures for human occupation at 50% Relative Humidity (RH). Occupants may, of course, choose what temperature to maintain their house at regardless of the design temperature. Energy consumption will vary accordingly.

Primary Energy (PE) or Primary Energy Renewable (PER)
The total amount of source energy used from fossil fuels (Primary Energy) or from a mixture of fossil fuel and renewable energy (Primary Energy Renewable) including on site renewable energy generation. The Passive House standard requirements are –

  1. Passive House Classic: 120 kWh/(m2.a) PE or 60 kWh/(m2.a) PER demand.
  2. Passive House Plus: 45 kWh/(m2.a) PER demand and 60 kWh/(m2.a) PER generation.
  3. Passive House Premium: 30 kWh/(m2.a) PER demand and 120 kWh/(m2.a) PER generation.

Thermal Bridge
A thermal bridge is where something that conducts heat passes through (‘bridges’) the insulation. For example, steel, concrete or timber. Heat transfer follows the path of least resistance therefore thermal bridges can contribute significate unwanted heat loss. Thermal bridges also increase the risk of localised condensation, mould and moisture related issues. For these reasons, Passive House aims to eliminate thermal bridges. For more information, see: What is Thermal Bridge Free Construction?

The Passive House Planning Package – the building performance modelling tool that must be used in Passive House design and certification. For more information, see: What is the Passive House Planning Package (PHPP)?

“Air changes per hour” the units used when measuring how airtight a Passive House building is. A blower door test (V50) is used to measure how often the enclosed visible air volume (ceiling voids, partition cavities etc are excluded) would be changed by infiltration through the building fabric at 50 pascals air pressure. That’s about the same as a 32 kilometre per hour wind (20mph) blowing against the building.

A Concise Passive House Glossary