Guidance & regulation Good guidanc P
Shockingly,we spend around 90%of our approach to HVAC is needed. architectural design, it’s clear that awhole-building the increasing requirements for air-tightness in healthcare sector £20bn annually. Combined with and 36,000 deaths a year, costing the pollution is responsible for between 28,000 ublic Health England estimates that air
time indoors.With this inmind, it’s crucial that building occupants have access to a healthy, clean and pleasant internal environment - free from pollutants, allergens, odours andwater vapour. There are numerous factors that contribute to the creation of a comfortable internal environment, including lighting, humidity, cleanliness,
temperature and fresh air. Ensuring that all these factors are consideredwithin the building design, with a suitable level of control also enabled, is key Inmanyways, effective ventilation is the
y.
cornerstone of achieving thiswell-balanced internal environment. Put simply, ventilation works by removing stale indoor air and replacing it with ‘fresh’ ’ outdoor air. It also helps to extractwater vapour, airborne pollutants and odours and control humidity. Although opening awindowmay, on the surface, appear to be an equivalent solution, it is not always possible – particularly inmodern high-rise buildings – and actually, it can domore harmthan good, allowing polluted air fromoutside to enter the internal space.
If a ventilation systemis to succeed in its role of improving indoor environment quality, itmust be designed to provide both sufficient fresh air supply and extraction. Only then can itminimisemoisture build-up, dealwith bio-effluents (body odour) and keep exposure to NO2, CO and VOCs to aminimum. When approaching a systemdesign that takes all of the above factors into account, it is important to refer to the relevant building regulations. In the UK, ventilation design is controlled by the Building Regulations Approved Document Part F,which sets out the criteria for both homes and ‘non-domestic’ buildings – primarily offices. Building ventilation also has to complywith a number of British
andmaintenance. Standards, covering energy performance, filters
storage systems) and Part P (electrical safety). and power), Part J (combustion appliances and fuel the passage of sound), Part L (conservation of fuel contaminants andmoisture), Part E (resistance to safety), Part C (site preparation and resistance to must complywith Approved Document Part B (fire As part of awider HVAC system, ventilation
Building Research Establishment. industry bodies including the CIBSE and the ventilation guidance available, published by Fortunately, there is also awide range of
13 l/s for a one-bedroom home to 29 l/s for a five- are dependent on the number of bedrooms, from a domestic house, the required ventilation rates example, when designing a ventilation system for different reasons, depending on its function. For require different levels of ventilation, and for stands to reason that different buildingswill Of course, no building is the same and so it
bedroomproperty.
per person. Intermittent extract ventilation will also significant pollutant sources) is generally 10 l/s rates for office ventilation (assuming there are no In comparison, the total air supply and extraction
www.heatingandventilating.net ce for HVAC VENTILATION – THE CO RNERSTONE OF IAQ
to improving indoor air quality and highlights some of guidance engineers should be aware of training manager Martin Passingham argues in favour of that a whole-building approach when it comes HVAC professionals depend on good guidelines to help in their daily duties. Here Daikin UK product and
uidance engineers should be aware of of that a whole-building approach when it comes n their daily duties. Here Daikin UK product and
kitchen areas. showers, printing or photocopying rooms and be required for specific areas, including toilets,
Department of Health. Of course, some healthcare TechnicalMemorandum03-01, published by the also refer to Approved Document Part F: Health environments, such as hospitals, it is important to When designing ventilation for healthcare
environments, such as operating theatres, critical care areas and isolation units,will have additional ventilation requirements, in order to prevent the spread of in fection.
Aswell as the design and placement of the ventilation units inside a building, it is also important to carefully consider the placement of ventilation intakes and exhaust outlets outside. If placed incorrectly, they could negatively impact the performance of the ventilation systemand the indoor environment quality,with the potential for pollutants to enter the interior space.
possible from the main sources of local outside air Ventilatio
pollution, such as road traffic. For HVAC systems, this typicallymeans on the roof of the building, unless there are higher-level pollution sources. Alternatively, air intakes can be installed onwalls, in courtyards and in atria.
It is equal lly important to avoid cross-
contamination fromboiler flues. Exhaust stacks should also be placed as far away as possible from the ventilation intakes, preferably at a higher level, and also downwind. They should not discharge into courtyards or other enclosed spaces and it is recommended that they discharge vertically, to avoid downwash.
d
With ventilation having such an active and crucial role to play in delivering a pleasant, clean and healthy internal environment for occupants to enjoy, designing the systemcorrectly and in accordancewith the relevant Building Regulations and industry guidance is essential. Effective filtrationmeasures and a regular programme of servicing andmaintenance are also important to ensure the systemcontinues to perform as intended.
n intakes must be placed as far away as m the main sources of local outside air
October 2020
www.heatingandventilating.net
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