On October 18th, Stephen Anwuzia of Breathing Buildings presented a CPD seminar for the Merseyside and North Wales CIBSE group in Liverpool. The topic of discussion was the recently published Building Bulletin 101 (BB101) which describes the requirements for ventilation, thermal comfort and air quality in schools. The document was refreshed and re-launched in August 2018 following more than 3 years of revision and development by working committees, in which Breathing Buildings played a significant role.
The evening’s talk began with a general introduction to natural and low-energy ventilation systems in school classrooms – the balance between guaranteeing good air quality, comfortable temperatures and compliant acoustics, whilst using as little energy as possible.
The focus of the talk was the recently-published revision of BB101 (2018), centred on major changes from previous design guidance for schools and highlighting the aspects of most interest to building services engineers.
The significant changes from the previous guidance (issued in 2006) include:
• a shift from overheating criteria based on static instantaneous air temperature measurements, to an adaptive thermal comfort model, based on operative temperatures;
• the use of probabilistic future weather files;
• and a marked shift towards hybrid ventilation systems for the twin benefit of providing draught-free ventilation in winter, as well as boosted fresh air flow rates in summer.
Attended by an engaged group of young engineers, experienced engineers and local council authority members, the seminar quickly became a productive discussion regarding the definition of “hybrid” ventilation and the relative suitability of the new design criteria vs the “old” 2006 criteria. Amongst the audience, there was the seemingly general consensus that the new design criteria, based on adaptive comfort (running mean temperature and corresponding acceptable temperatures) and operative temperature, are too conceptual. There was a view amongst the audience that these measures currently have limited quantifiable evidence of their effectiveness. Other well voiced concerns included; the technical complexity of the criteria, the means to accurately assess the values post occupancy and validate modelling, the consequence of failure to comply, and the long-term appropriateness of the criteria.
A healthy discussion followed on whether occupants are more likely to assess their thermal comfort based on dry bulb air temperature or the more complicated operative temperature measure now used in thermal models. The formation of these concerns was based in client and occupant side thinking, especially in regard to the technical complexity of the criteria and the longevity of these standards. One attendee arguing that occupants will not adapt to changes in climate as readily as predicted in the ‘adaptive thermal comfort’ concept. It was further discussed that eventually the external (and internal) temperatures reached will demand cooling regardless of expected adaptation and radiant cooling. Though these points have certainly been considered, the sentiment that there is still much left to be addressed was clear.
The open and frank discussion made for an enjoyable evening and the seminar seemed both informative and well-received. Breathing Buildings look forward to being part of more insightful discussions in future.
To read more about BB101, please visit our page on BB101.
For information on all the products and services offered by Breathing Buildings, please telephone 01223 450 060, or email: firstname.lastname@example.org.