Modern Building Services

MODERN BUILDING SERVICES MAY 2022 13 NEWS ANALYSIS The key here for any business or organisation which decides to invest in CO2 monitoring is to not just identify areas where improved airflow is required, but to take action. Building owners, landlords and office managers should remember the main requirement set out at the start of Part F: “There shall be adequate means of ventilation provided for people in the building.” This is the mantra which needs backing up with decisive action. Specific fan powers simplified Let’s move onto Specific Fan Power (SFP) in AD Part L, Volume 2 where, pleasingly, the values and guidance have been simplified, which should result in more effective ventilation. 1 Consultants refer tomaximum SFP values in their specifications and we ensure as a HVACmanufacturer that our product range does not exceed these energy performance ratings, while at the same time ensuring we comply with the Building Regulations. Historically, since 2013, these values have been drawn from the Non-Domestic Building Services Compliance Guide. But they’ve now moved to Part L and have become much clearer (see table 6.9 on page 51). There had been particular ambiguity or confusion over heat recovery units, leading to some consultants specifying at lower values out of fear of contravening the rules. But this has now been resolved: The current 2013 guidance includes allowances to take into account components which offer high resistance to airflow. For heat recovery, this is +0.3 watts per litre per second (w/l/s). For additional return air filter for heat recovery, it is + 0.1 w/l/s. These ‘allowances’ were considered by many to be additions only where heat recovery and filters were not integral to the ‘unit’ and as a result were not included in calculations. For example, to quote the regulations, “zonal supply and extract units, such as ceiling void or roof units serving single room or zone with heating and heat recovery”. The SFP limit is 1.9 w/l/s. However, the new table quotes 2.3 w/l/s. In other words: 1.9 w/l/s + 0.3 w/ls + 1 w/l/s. This confirms that actually the limit for this type of system has always been 2.3 w/l/s, and provides reassuring clarity over ‘allowances’ and whether or not they were already included. Domestic – rates of supply air changes Finally, we move on to Part F volume 1 and look at some key changes to rates of supply air for domestic environments. 1 Again, we are happy to see another example of simplification that should result in better ventilation for the end user. The four main strategies (systems) of ventilation have been abridged to three by the removal of Passive Stack Ventilation from System-specific guidance (page 14). The other main challenge that we felt needed addressing for residential properties was to increase whole building ventilation rates. These are rates for continuous ventilation systems based on the number of bedrooms. Again, simplicity is the key here. The rates are slightly higher than before. For instance, a one-bedroom property previously required only 13 l/s of air (47 m3/h). This has now risen to 19 l/s (68 m3/h). This increase appears to be inspired by Covid and realising improved ventilation is now required. In addition, to simplify calculations, the designer or architect no longer needs to consider any additional occupancy. Previously, the guidance assumed two people in themain bedroomand one each in the others. When determining airflow rates, the designer would have to be aware of the potential for more occupants. We could see on drawings howmany beds were shown in each bedroom, but now there is no need for this, helping to speed up work too. Looking ahead Overall, these are not sweeping new changes that are likely to cause a tidal wave of disruption and despair across the HVAC industry. But they do provide much- needed simplification and clarity to help us navigate the tricky waters of the Building Regulations. Ambiguity is the enemy of the HVAC architect, specifier, technician and installer – and it’s good to see large dosages of such ambiguity removed. At the same time, the new ApprovedDocuments for Part F and L provide the first real update in written guidance since Covid usurped our working lives.They sufficiently encapsulate the industry’s initial learnings fromthe past two years and lay out howwe should apply themto our newpost-Covid landscape. More information can be found at www.solerpalau.com/en-uk/ 1 Source: www.assets.publishing . service.gov.uk/