When WSP was tasked with providing natural ventilation for a school underneath Heathrow Airport’s flight path, the company had to think differently to come up with an appropriate solution.
- Minimising aeroplane noise
- A natural solution
- Overcoming pipe challenges
- TSB’s Low Impact Building Innovation Platform
- Earth tube ventilation system provides natural ventilation
- Annual carbon saving of six tonnes by using earth tube pipes
- Solar PV on the roof
- Low air leakage with enhanced thermal performance
- U-values better than required by Building Regulations
The noise and sight of aeroplanes crisscrossing the sky is commonplace for many people living in the UK, but for those living underneath the flight path of any of the country’s main airports, the disruption can be considerable.
The new £8.9m Westbrook Primary School in the London Borough of Hounslow is located directly below the path of planes using Heathrow Airport, meaning designers had to come up with an alternative way of ventilating the school, as simply opening the windows would expose the school’s occupants to aircraft noise.
“The project has a number of interesting challenges and energy performance aspirations,” says WSP director Neville Rye.
Minimising aeroplane noise
WSP is the M&E engineer, BREEAM assessor, highways consultant and acoustic consultant on the project, working alongside Pollard Thomas Edwards architects, which is leading the design team.
“The school being located under the flight path into Heathrow makes natural ventilation using opening windows very difficult,” Mr Rye says.
Because of its location, the school requires significant acoustic protection, but sustainability objectives ruled out many conventional cooling and ventilation systems, notably mechanical cooling.
“The client was keen to use a conventional approach to space heating, with the emphasis on energy reduction through enhanced fabric efficiency”
Neville Rye, WSP
“Our clients’ aspiration for a BREEAM Very Good school together with A-rated energy performance required our engineers to explore more innovative passive approach to providing a low-energy ventilation system to the school.”
Westbrook Primary School is one of a number of school designs in Hounslow developing noise mitigation strategies to help tackle the roar of passing aircraft.
The project has also been awarded £100,000 by the Technology Strategy Board to carry out research, develop a strategy and implement proposals to futureproof the school against predicted climate changes over the next 100 years.
“The client was keen to avoid the use of low-carbon or sustainable technologies such as heat pumps and use a conventional approach to space heating, with the emphasis on energy reduction through enhanced fabric efficiency,” Mr Rye says.
A natural solution
The design team decided to install an earth tube system, which will draw fresh air remotely from the building and mean it’s not necessary to open windows.
“We needed a ventilation system that provided a low-energy solution to deliver fresh air to the learning spaces,” Mr Rye says.
Ventilation air is supplied to classrooms through a network of earth tubes – pipes buried in the ground. This system provides ‘free’ heating and cooling using stored thermal energy.
“During peak days the system has the capacity to heat and cool the air by up to 6 deg C – all from free renewable energy from the ground”
Neville Rye, WSP
“The ground coupled earth tubes provide free cooling and heating of fresh air being delivered to the learning spaces, while the mass of the ground provides a natural attenuation path to reduce the aircraft noise,” Mr Rye explains.
“Because the air travels underground, where the temperatures are more stable, the incoming air stream is heated in winter and cooled during the summer.
“Our calculations indicated that during peak days the system has the capacity to heat and cool the air by up to 6 deg C – all from free renewable energy from the ground.”
The system also eliminates the requirement for refrigeration plant, which enhances the green credentials of the school.
“The use of the earth tube will provide an annual carbon saving of six tonnes of CO2, which helps to deliver a 28 per cent reduction over 2010 Part L and an A-rated EPC rating,” he adds.
Overcoming pipe challenges
The ventilation system was developed by WSP’s sustainable building group, working with pipe manufacturer Polypipe.
It was tested with BSRIA, an independent laboratory for testing, validation and performance verification of HVAC products, systems and indoor climates, to evaluate the tube’s thermal conductivity.
Specialist software was used to optimise pipe size and layout, and the system was integrated with other mechanical and electrical elements. Filters and seals are included to keep the system clean.
The tubes will be lined with an antimicrobial layer, which will eliminate the risk of biological contaminants in the air being circulated in the school.
“The knowledge gained on the scheme has enabled us to consider this technology for other projects”
Neville Rye, WSP
“The greatest challenge we faced was finding an affordable, large-diameter earth tube with integrated anti-microbial lining,” Mr Rye explains.
“Our engineers collaborated with manufacturer Polypipe and BSRIA to develop a calculation tool to establish the thermal performance of the earth tube.”
Now that the team have developed the technology, it’s available for similar projects in the future.
“Thanks to the research and development implemented by WSP, Polypipe and BSRIA, we now have a much better understanding on the thermal performance of polymer earth tubes,” Mr Rye says.
“The knowledge gained on the scheme has enabled us to consider this technology for other projects.”
Aside from the natural ventilation system, the school will also have very low air leakage and enhanced thermal performance, with U-values that are better than the current Building Regulations. “A small area of solar PV was also requested by the local planning authority,” Mr Rye adds.
Works started on site in August 2013 and the school is due to be completed, including demolition of the old school, in April 2015.
TSB’s Low Impact Building Innovation Platform
The Technology Strategy Board established the Low Impact Building Innovation Platform in 2008 to support UK industry in supplying the growing demand for low-impact domestic and non-domestic new build and retrofit.
In consultation with the industry and the government, the Low Impact Building Innovation Platform has identified six challenges it can support with innovation:
- Design for future climate change
- Design and decision tools
- Build process
- Management and operation of buildings
- Materials and components for sustainable buildings
- Integrating with sustainable infrastructure
Projects so far include:
- Retrofit for the future – to catalyse the domestic retrofit sector.
- Building Performance Evaluation – to understand the performance gap.
- Design for future climate – to incorporate climate reliance within our buildings.
- A major collaboration between Barratt Homes, Crest Nicholson and Stewart Milne to share research in developing affordable low-energy homes for the mass market.