3 changes to Building Regs Part F and L that you need to know before the summer


3 changes to Building Regs Part F and L that you need to know before the summer


Ian Davis, Technical Manager at ventilation specialists S&P UK, casts his near 40-year expert eye over incoming changes to Building Regulations Part F and L and unpicks three important areas for HVAC professionals before they come into force in Summer 2022.


Almost a decade has passed since the Building Regulations, the holy grail of our industry, underwent a rewrite.


In the intervening nine years, a lot has happened, not least six fundamental amendments and a global health pandemic that has profoundly altered how we view indoor air quality and disease transmission risks inside the buildings where we work, live and play.


And in recent months, you may have heard some rumblings about fresh changes to Part F (ventilation standards and air quality requirements) and Part L (fuel and power conservation).


The changes are being made specifically in response to public consultation on the Future Buildings Standard (FBS). The two-part consultation concluded in April 2021 and the FBS is due to come into force in 2025.


The overarching driving force is the government’s net zero 2050 target, now set in law.


As a result, four new Approved Documents (AD) have been published under Part F and L: volume 1 for dwellings and volume 2 for non-dwellings (commercial and industrial). The rules take effect on 15 June 2022, with a one-year transition for existing planning applications.


Indoor Air Quality (IAQ) monitoring



The first major area to highlight is the introduction of a new ‘Indoor air quality monitoring’ section. Specifically, this covers points 1.21 to 1.23 In AD Part F. Volume 2 (pages 8-9).


We welcome this new guidance on monitoring air quality that has surely been forced into existence – perhaps long overdue – by the pandemic and the failings, shortcomings and opportunities that it has uncovered and turbocharged up everyone’s priority list.


The new section makes repeated reference of ‘Occupiable Rooms’ in places like offices, gyms, theatres, hotels – anywhere where “members of the public are likely to gather”.


It should be noted that the following areas are not considered as occupiable rooms: “bathrooms, sanitary accommodation, utility rooms or rooms or spaces used solely or mainly for circulation, building services plant or storage purposes”.


For offices, outdoor air should be supplied at either 10 litres per second per person (current guidance) or 1 litre per second per m2 floor area (new guidance) – whichever provides the highest total rate. See 1.32 on p10.


The umbrella advice for monitoring IAQ states: “This may be achieved using CO2 monitors or other means of measuring indoor air quality.”


At S&P, we’ve recently launched our AirSens range of intelligent wireless IAQ sensors. They benefit from in-built demand-controlled ventilation and work by sending a signal to ventilation systems to increase airflow rates if a spike is detected in CO2, volatile organic compound (VOC) or relative humidity (RH).


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.


Consultants refer to maximum SFP values in their specifications and we ensure as a HVAC manufacturer 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 p51).


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, S&P supplies, 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.


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 (see 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 the main bedroom and 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 how many 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 Approved Documents 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 from the past two years and lay out how we should apply them to our new post-Covid landscape.


If you would like to benefit from learning more about the new Part F and L guidance, get in touch with Ian at idavis@solerpalau.com