Passivhaus or Passive House is a performance-based set of design criteria for very low energy buildings, which can help create buildings which use around 90% less energy than standard UK buildings. Developed in Germany at the beginning of the 1990s by Professor Wolfgang Feist with Professor Bo Adamson from Lund University, Sweden, Passivhaus design is based on well researched and proven building physics.
The Passive House Institute is constantly developing and improving upon algorithms and software tools for dynamic building simulations, the determination of energy balances and the planning of Passive House buildings (for example, through the Passive House Planning Package). The Institute acts as an independent testing and certification centre for buildings and building components such as wall and construction systems, windows, doors, connections, ventilation systems and compact systems. PHI research staff also provide manufacturers of energy efficient components with in-depth consultancy on product development and optimisation. PHI further facilitates the upholding of the strict quality requirements set by the Passive House Standard through the professional certifications it offers worldwide.
The house must be designed from the ground up as a Passivhaus. There is a complex spreadsheet known as the Passivhaus Planning Package (PHPP) into which you feed all the relevant construction details, including:
- the insulation depths
- the window sizes and orientations
- the junction details.
- This gives you a predicted space heating demand (expressed in kWh/m²/yr).
You keep adjusting the design until your outcome meets the standard. Passivhaus can be built using almost any construction method. However, there are some universal features, including:
- massive insulation (average depth 300mm)
- triple glazing with insulated frames
- fantastic airtightness levels (must score better than 0.6 air changes per hour)
- mechanical ventilation with heat recovery.
- Uses 90% less energy to heat than an average home. Heating costs around £75 a year
- Optimises heat from the sun
- Minimal micro-renewables
- Mechanical Ventilation with Heat Recovery (MVHR) provides constant fresh air and retain heat inside the house
- Triple glazing with insulated frame
- The Tea Cosy Effect (or ‘minimising thermal bridging’). Wrapping building in insulation minimises any breaks or cold spots
- House retains heat from sun and occupants’ activities
- First cavity wall Passivhaus in the UK
- 20 times more airtight than a standard build
Does it Work?
The first houses built to Passivhaus standard were completed in 1991, and since then over 50,000 houses, schools, offices etc have been constructed to the standard in Europe, USA and many other parts of the world. There has been extensive monitoring of Passivhaus buildings which has demonstrated conclusively that they deliver what they promise. The design specifies that heating load should be no more than 15 kWh/m2/year, and the data confirms this. Of course there is a range, depending on lifestyle, but studies have repeatedly shown that the median value is always at the design figure.
EnviroVent and Passivhaus
Four mechanical ventilation heat recovery (MVHR) units from EnviroVent, one of the UK’s leading ventilation manufacturers, have been approved by the Passive House Institute, for use in Passive House developments.
EnviroVent’s energiSava® 300 and 400 and Slimline 150 and 300 units have been awarded a PHI Component Certificate, after each one passed rigorous quality and energy performance tests set by the Passive House Institute.
The energiSava® models are high efficiency whole house heat recovery systems with maximum airflow capacities of 300 and 400 m3/h. The units are ideal for use within the home to provide a constant supply of clean air and reduce humidity levels, therefore preventing condensation and associated issues.
The Slimline 150 and 300 are high efficiency, compact mechanical ventilation heat recovery (MVHR) units with maximum airflow rates of 150 and 300 m3/h. With their low profile, compacted design, the systems are perfect for ceiling mounted applications and installation in smaller dwellings where space is restricted.