Tackling energy efficiency of offices and schools with Passivhaus building techniques

Tackling energy efficiency of offices and schools with Passivhaus building techniques

As global prices rise, reducing dependence on fossil fuels becomes ever more important. Our low-carbon, energy-efficient Passivhaus is one of the most innovative and exciting environmentally-friendly construction methods to come to the UK and is a solution many are considering.

Interserve has demonstrated its commitment to Passivhaus building techniques by commissioning and building the UK’s first Passivhaus office to be the home for its East Midlands office in Leicester. Since construction of the office, the company has built a further two Passivhaus schools which tell an interesting story.

What is Passivhaus?

Passivhaus logoDeveloped in Germany, Passivhaus is a method of construction that builds on energy efficiency. The core focus of Passivhaus design is to dramatically reduce the requirement for heating and cooling. Most of this is done using ‘passive’ sources that don’t require fossil fuels.

So, what are the benefits?

According to Passivhaus: The heating requirement in a Passivhaus is “reduced to the point where a traditional heating system is no longer considered essential. Cooling is also minimised by the same principles and through the use of shading and in some cases via the pre-cooling of the supply air.”

University Professor Dr Wolfgang Feist, Head of Energy Efficient Construction/Building Physics at the University of Innsbruch Austria, Darmstadt in Germany says: “The heat losses of the (Passivhaus) building are reduced so much that it hardly needs any heating at all. ‘Passive’ heat sources like the sun, human occupants, household appliances and the heat from the extract air cover a large part of heating demand.”

This means that by building to Passivhaus standards there are savings – up to 90% reduction in energy costs – as well as protecting and investing in future generations by reducing the burden on the environment.

So to sum up, the benefits are clear:

  • Financial savings: significantly lower energy costs in comparison to traditionally-built properties
  • Lower emissions: reduced carbon footprint throughout the entire lifecycle
  • Lower maintenance: simpler mechanical and electrical installation, easier operation, reduced maintenance costs
  • Improved comfort: a comfortable temperature, whatever the weather outside
  • Improved air quality: a continuous supply of clean, fresh air.

Passivhaus build for schools – the Leeds example

After building the UK’s first Passivhaus commercial office in Leicester, we extended the application of Passivhaus to schools.

Richmond Hill Primary School is the third non-domestic Passivhaus-certified building constructed by Interserve, and is thought to be the largest Passivhaus-certified building in the UK.

The school for 630 pupils completed in Leeds has not only achieved Passivhaus certification, but has smashed the air tightness target of the Passivhaus Institute. Richmond Hill Primary School, built on behalf of Leeds City Council, will use up to 80 per cent less energy than a conventionally-built equivalent facility, reducing carbon emissions by 60 per cent without the use of renewable energy.

The new school was given a Passivhaus air tightness target of 0.6 ACH (Air Changes Per Hour), which means the building must not leak more than 0.6 times its volume of air per hour at 50 pascals. This level of air tightness is well over ten times better than the current building regulations’ requirement of 10m3/m2/hour at 50 pascals. However, tests have revealed the school has achieved an enormously impressive 0.25 ACH, which is just 1/20 of the ACH level required by British Building Regulations.

Superb levels of insulation, coupled with a highly efficient mechanical ventilation heat recovery (MVHR) system have all contributed to the building achieving its Passivhaus certification.

Helping to achieve superior levels of thermal insulation is Interserve’s solution for the eradication of cold bridging between the building’s piled foundations and steelwork frame, using high-strength insulation normally used in industrial process plant installations.

The walls and roof of Richmond Hill School achieve excellent thermal insulation performance, with U-Values (a measure of heat loss in a building element such as a wall, floor or roof) far exceeding the requirements of the current building regulations. Structural Insulated Panels (SIPs) manufactured off-site featuring polyurethane insulation have been used to form the structural fabric of the walls, and further SIPs panels with extra mineral wool insulation form the roof of the new building. The materials enable an impressive U-Value of 0.1W/m2K to be achieved for the walls.

Triple glazed timber windows, certified by the Passivhaus Institute, facilitate excellent standards of thermal insulation, whilst also helping to keep air leakage to a minimum. The specific heat demand of the building is 11kWh/m2/year (well under the target of 15kWh/m2/year) and the Primary Energy Demand is 112kWh/m2/year (again, well below the target set of 120 kWh/m2/year); therefore the school will benefit from lower energy costs.

Swillington Primary School, one of these Passivhaus schemes, is also in Leeds, and has recently been completed in partnership with Leeds City Council. Richmond Hill Primary School also won the Yorkshire and Humberside Constructing Excellence Innovation Award.

Head teacher Sue Mudie talks about the positive impact the new Passivhaus school will have to the local community and pupils.

An interview with Interserve’s Jim Shaw as he walks around Richmond Hill School during its construction

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