Modern Building Services

MODERN BUILDING SERVICES JUNE 2022 13 possible that the system’s heat recovery device may not meet ErP 2018’s minimum 73% efficiency for a plate heat exchanger or 68% for a run-around coil. Fitting a larger system with a greater face area to achieve higher efficiency in the current AHU frame may not be achievable, but it is simply no longer acceptable to only achieve some improvement, every effort must be made to comply with the latest regulations which HTM-03-01 2021 now encompasses. Fortunately, with the increase in dimension of AHUs following ErP legislation, allowance has now beenmade for the air velocity to be considered, still achieving no greater than 2m/s but with some tolerance on a project-by-project basis. Illustrated below, a simple 2.5m3/s AHUwith plate heat exchanger has significantly increased in size when the legislation set minimum efficiency requirements in 2016 and again in 2018. Replacing the overall system If refurbishing isn’t a viable option, replacing the overall systemwill come with its own difficulties if space is at a premium. Situating a system externally was often the favoured solution but greater consideration has now been made for safe and long-termmaintenance of the AHU. Rooftop plantrooms or AHUs with corridors are now preferred, which allows the user to maintain the system safely without the challenge of environmental conditions, store spare components and filters complete with a sanitary station to self-contain the system as if it were located indoors. Ensuring the systems selected now are sustainable and future- proofed is imperative as well as considering the financial implications of procuring an entirely new system, with rising labour and material costs continuing to affect the industry. With a new AHU, some users may be steered towards extended warranty and maintenance support offered by a manufacturer, with the entire system provided by one supplier, something a refurbished system cannot be entirely certain of. If there are positives to take from the Covid-19 pandemic, it has made more people both in and out of the industry aware of the importance of good indoor air quality (IAQ). The addition of the recent update to Approved Document F (vol.2) allows designers to assess their ventilation strategies against each individual volatile organic compound (VOC), based on data provided by Public Health England, as well as encourages the use of CO 2 monitors tomeasure levels where the airborne infection is a high risk. Whilst thesemeasures are well received, there is limited consideration given to AHU systems themselves and how the introduction of high-grade filters or deployment of UV, BPI, and other similar systems can aid the improvement of the outdoor air being drawn into the space served. Systems are however discouraged from recirculating, something in place prior to the June update but again reiterated for clarity. Considering that we spend around 85%of our time indoors, it’s crucial that IAQ is continuously improved by addressing the external air quality coming in and reducing the harmful bacteria that could be recirculated. Advantages and disadvantages Both methods have their advantages and disadvantages. Re-using existing systems, maximising the lifecycle, and minimising wastage are at top of most people’s agenda both in and out of the HVAC industry. Refurbishment is often more cost-effective and there is widely published data to showcase the ROI and energy savings made. However, it is critical that within all areas served by mechanical ventilation, particularly in healthcare, a consistent effort is made to ensure compliance to obtain a common level of quality throughout the UK’s built environment. Whether this is by replacing or refurbishing, clear dialogue with industry experts and an objective understanding must be made with the patient and users at the forefront of the design. FEATURE AIR CONDITIONING, COOLING & VENTILATION More information can be found at www.ves.co.uk