As buildings become increasingly complex to accommodate the aspirations and demands of clients, designers and operators, more and more cases arise where it is difficult for the traditional methods of standard, statutory fire safety guidance (such as Approved Document B) to adequately balance these needs against the fire safety requirements of the Building Regulations. Even in the case of more risk-based design guidance such as BS 9999, potential ‘gains’ in terms of travel distances and exit width will be offset by highly prescriptive recommendations elsewhere.
There is no obligation to adopt the recommendations given in Approved Document B, or any other guidance documents, if the functional requirements of the Regulations are met in some other way.
Modern fire engineering techniques can often provide substantial benefits in preserving architectural aspirations and building functionality, as well as reducing construction and procurement costs whilst maintaining high fire safety standards. Therefore, designers are increasingly turning to a fire engineered approach to provide the best solutions for modern buildings.
As a technical engineering company, Tenos has extensive experience of using all aspects of advanced fire engineering techniques in order to minimise the impact of fire safety on other aspects of the design. One such example is Appleton Academy in Bradford.
Appleton Academy is a £22m building that opened in November 2012 to replace two local schools and with a single, continuous education environment for all learners between nursery and sixth form age. One of the key design aspirations was for the building to provide an open, familiar and accessible space to support the transition of pupils between all education phases. As pupils progress through the school through the various stages of their education, the building grows with them in scale and complexity.
Since its opening, the Academy building has been nominated for several design awards, including a ‘Highly Commended’ award from SCALA (Society of Council and Local Authority Architects) as part of the Civic Building of the Year Awards 2013.
Key fire safety challenge
The standard design guidance in BB100 was not conducive to the architectural and client aspirations for a continuous, open environment. In particular, the means of escape from the feature central courtyard meant that people would have to re-enter the building via a single fire compartment at ground floor level.
Providing adequate justification for this arrangement required modelling of the building’s elaborate elliptical form to predict the smoke movement within the building. Computational fluid dynamics (CFD) modelling of smoke and fire enabled Tenos to predict the passage of fire and smoke throughout the key areas of the building, and determine its impact on the means of escape.
The assessment took the form of a comparison of the Available Safe Escape Time (ASET) against the Required Safe Escape Time (RSET) in the ground floor escape routes.
To determine the RSET, Tenos undertook detailed escape calculations encompassing the fire detection time, human behavioural responses to an alarm, and the travel/ flow time to/ through the exits (see image ‘Factors involved in assessing the total Required Safe Escape Time’).
To determine the ASET, Tenos worked with the design team to identify the reasonable worst-case fire scenarios, taking account of key fire safety measures such as the effect of sprinkler systems. We then reviewed the modelled effects of fire and smoke on the Academy’s escape routes, in terms of visibility and smoke temperatures in the key areas.
The advanced fire engineering analysis indicated that all occupants would be expected to have exited the building before the escape routes were compromised by fire and smoke, and hence demonstrated compliance with the functional requirements of the Building Regulations. Tenos was proud to be able to carry the project and the fire engineering justification through to achieving statutory approvals with respect to fire safety.
For more information about our Advanced Fire Engineering services, click here or contact Tenos Head of Business Development, Geoff Marlow on 0161 872 6798.
Illustration of the 3-D CFD model used to analyse the means of escape
Illustration of fire scenarios
Report excerpt showing results of fire engineering analysis of fire and smoke spread through the building
Factors involved in assessing the total Required Safe Escape Time