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The natural way to adapt to climate change

Using smoke ventilation systems for natural ventilation has been highlighted as a key strategy for helping commercial sites adapt to climate change, explains Rob Davies
Many commercial buildings are obliged to install smoke ventilation systems to meet health and safety legislation. However, the industry has long argued for end users to extract greater benefit from these systems by also adapting them to provide low cost natural ventilation that improves indoor air quality, reduces the threat of overheating and cuts potential carbon emissions.

In this way life safety smoke ventilation can also play an important role in the day-to-day operation of commercial facilities as well as being ready to respond in the event of a fire and an in-depth study for improving the resilience of frame and lightweight clad buildings has now added weight to that argument.

The detailed climate adaptation study at a mixed used scheme in Ammanford, South Wales was project managed by consultants Kassanis+Thomas for the client Quadrant Estates and funded by the Technology Strategy Board.

The purpose of the study was to investigate a range of strategies that could be used by different types of building to mitigate the increasingly extreme weather conditions caused by climate change.

Ideal
The Betws Washery facility at Ammanford was seen as an ideal test case because it comprises a wide variety of facilities including a food store; petrol station; drive through restaurant; retail terrace; starter units; doctor's surgery; retirement complex; and a residential scheme.

Weather trends based on climate change scenarios were derived from the University of Exeter's PROMETHEUS 'weather generator'. Emerging patterns are likely to be increased average temperatures throughout the year; higher peak temperatures for part of the year; lower relative humidity during the summer; potentially less rainfall during the summer, but more in the winter; as well as increased frequency and intensity of storm events.

The effect these weather trends would have on the food store, retail units and the external areas (valued together at around £15m) was then examined. This revealed that the site would become increasingly vulnerable to problems with thermal comfort and energy use; water management; and green infrastructure.

The research team created a series of design models that assumed an overall increase in temperature throughout the year of between 2-3ºC by 2030 with exaggerated summer peak temperatures up to 7ºC higher than today's by 2050. In theory this would mean the buildings required lower levels of heating in the winter, but higher levels of cooling in the summer to maintain comfort conditions.

The design study showed that the current strategy for cooling would be unable to cope with the summer peaks to a point that some of the buildings could become unusable at certain times of year. It also revealed that the energy demand for additional cooling would outstrip the energy saved from the reduced winter heating bills - unless innovative solutions were considered.

'There may come a point when, combined with rising energy prices, the overall energy bill threatens the viability of the retailer's business,' the study said. It was important, therefore, to identify strategies for offsetting the most extreme climate conditions, but any adaptations of the existing buildings would have to be realistic in cost terms to maintain the viability of the retail premises, in particular.

It quickly became apparent that the smoke ventilation system could play a significant role. Most major retailers are legally required to use smoke ventilators as part of their fire safety strategy as detailed in the Building Regulations. As a general rule, smoke ventilation will be employed to improve the buildings life safety and means of escape if a building is more than 2,000m2 in overall floor area or has a 45 metres escape distance.

When a mezzanine floor is included the fire/smoke scenario is even more problematic, with escape routes and safe travel distances impeded. It is, therefore, not unusual for food stores and retail units to already have smoke ventilation systems installed in the roof.

Quality
The equipment should be tested and CE certified to EN12101-2 for smoke ventilation, but also for a secondary purpose as a natural ventilation system. Good quality smoke ventilation products, such as the Certilam Natural Smoke and Heat Exhaust Ventilator (NSHEV) from Adexsi UK, can be adapted to respond to given climatic conditions including temperature, light levels, wind, rain, and CO2.

A comparatively simple addition to the control strategy will instruct the system to purge the occupied areas of warm stale air under certain conditions. One major benefit of this approach is that the end user gains natural ventilation at no additional energy penalty and only a small extra capital cost.

This adaptation was simulated in the project team's climate model by setting the vents to open when the internal temperature reached 23°C with the aim of producing five air changes per hour.

Other ways of delivering the same air change rate were possible, but none at such a low capital and energy cost, the study concluded.

'Using the smoke vents for natural ventilation makes enough inroads into reducing overheating to warrant them having a role to play, especially as this can be achieved at a comparatively low cost,' the researchers concluded.

Rising summer temperatures and more extreme winter weather events are increasingly regular features of the UK climate so more innovative strategies for dealing with buildings overheating and air quality are clearly going to be needed, as this study shows.

As smoke ventilation systems are already a requirement for many facilities, it seems sensible to at least investigate their further use for this purpose before embarking on other potentially more costly solutions.

// The author is the director of Adexsi UK //
2 April 2014

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