High-end Residential

Objectives

In Central London, keeping the poor-quality, polluted air out of your building can be tricky. It's no surprise that due to London's densely-crowded centre, levels of gases like Carbon Dioxide and Nitrogen Oxides and particulate matter (PM2.5, PM10) can be particularly high. Our client, nestled tightly between Euston train station, an active construction project, and where the A501 meets Tottenham Court Road, had to meet Building Regulations in order to open their newly-constructed mixed-use block. The problem, however, obviously lies in the heavy pollution in the area due to the combustion from cars and trains and the construction site beside Euston station. To meet Approved Document F of the Building Regulations 2010, this client would either need to prove the outdoor exposure levels are below minimum thresholds, or they would have to install some serious MVHR filters to keep the indoor air clean. 

We also had to be mindful that certain filters might obstruct the air path and lower airflow. Our client's Nuaire MVHR units were a major component in how they would keep the building at a stable temperature, and they had been carefully designed to supply around 55 litres per second (l/s) and extract 40l/s from the kitchen extractor and 15l/s from the toilet extractor. If we were to install new, more heavy-duty filters, we would need to be careful not to affect this airflow too much or risk destabilising the entire system.

Solutions

We modelled the outdoor air quality, and the results weren't particularly promising. We anticipated the level of Nitrogen Dioxide pollution (NO2) could be too high to pass Building Regulations at an estimation of just under 40µg/m³. Because this figure was so close to the limit stated within Part F, the council deemed the result invalid to proceed with opening the building for residential use. Instead, we installed diffuser tubes (passive sampling) across the exterior façade of the building, which took a total of 6 months for the data to be considered reliable. Unfortunately, this test also deemed the Nitrogen Dioxide levels to be too high.

Our client, understandably frustrated, asked for our advice. We could test over and over again, but they'd likely fail. Understanding that within Approved Document F it states that technologies may be used 'to minimise the intake of external air pollutants', we advised our client that the next best step would be to install sufficient filters to reduce the levels of pollutants within the indoor space. Effectively, the only option we had would be to take effective measures to cleanse the indoor air as the outdoor air quality was unlikely to improve any time soon.

Accordingly, we then installed ePM10 and Molecular Filters in their Nuaire MVHR units to ensure that they capture any pollutants circulating throughout the indoor space. These ePM10 filters are very effective at removing between 50-90% of all PM10 particles which was crucial in capturing the particles emitted from the local road, construction site, and train station. Molecular filters were also installed to capture the harmful gases like NO2. Testing the airflow (known as ventilation validation) from the MVHR units, we measured a supply of 58l/s (5l/s higher than the design volume), the kitchen extractor measured 40l/s and the toilet extractor measured 15l/s (both identical to their respective design volumes). This results in an overall efficiency increase as the unit runs at 118% of the design volume with these newly-installed filters. With the confidence that residents would be able to breathe safe, clean air, the residential building was finally approved to open.