Project Description
Application 2: Open Plan Apartment
For the purpose of this animation, we have used open plan living accommodation that is spread over multiple levels. However, the application described is equally applicable to any open plan design. The main issue to be addressed in these buildings is the removal of the protected entrance hall, which often becomes ‘dead space’, so that larger, brighter living spaces can be created within the same footprint.
Guidance – BS 9991
The guidance in BS 9991 often allows open plan apartments, when residential suppression systems are specified. The benefit is that bedrooms can be inner rooms and all internal passive fire protection measures can be removed. However, the guidance is heavily caveated and requests to work outside of the guidance are common. The main issues with the guidance in BS 9991 is that it places restrictions of the overall size of apartment allowed. It does not permit multiple levels with open staircases or those with unenclosed kitchens near to the entrance door.
Our Approach
In order to safely remove protected entrance halls / stairs and justify large open plan living, we have developed our own hybrid deterministic / probabilistic model which is akin to that originally developed by BRE on behalf of NHBC. Our robust modelling approach considers occupant behaviour and uses computational fluid dynamics (CFD), as well as event tree analysis (EVA), to assess the reliability of active and passive fire safety measures.
Active Measures
We are normally able to remove all protected entrance hall arrangements, providing both a fire suppression system and a LD1 fire detection and alarm system are provided. Furthermore, as shown in the figure, it isn’t always necessary to provide fire suppression in every single room when adopting this approach.
Overall Safety Levels
The main benefit with our approach, and the bit we particularly like, is that our model allows us to determine just how beneficial the alternative design approach is, and just what level of reliability is needed by the fire suppression system in order to achieve equivalence to a code compliant approach.
Guidance – BS 9991
The guidance in BS 9991 often allows open plan apartments, when residential suppression systems are specified. The benefit is that bedrooms can be inner rooms and all internal passive fire protection measures can be removed. However, the guidance is heavily caveated and requests to work outside of the guidance are common. The main issues with the guidance in BS 9991 is that it places restrictions of the overall size of apartment allowed. It does not permit multiple levels with open staircases or those with unenclosed kitchens near to the entrance door.
Our Approach
In order to safely remove protected entrance halls / stairs and justify large open plan living, we have developed our own hybrid deterministic / probabilistic model which is akin to that originally developed by BRE on behalf of NHBC. Our robust modelling approach considers occupant behaviour and uses computational fluid dynamics (CFD), as well as event tree analysis (EVA), to assess the reliability of active and passive fire safety measures.
Active Measures
We are normally able to remove all protected entrance hall arrangements, providing both a fire suppression system and a LD1 fire detection and alarm system are provided. Furthermore, as shown in the figure, it isn’t always necessary to provide fire suppression in every single room when adopting this approach.
Overall Safety Levels
The main benefit with our approach, and the bit we particularly like, is that our model allows us to determine just how beneficial the alternative design approach is, and just what level of reliability is needed by the fire suppression system in order to achieve equivalence to a code compliant approach.
Semper Approach
The hybrid deterministic / probabilistic approach that we have developed for this task is more robust than anything we have seen developed elsewhere. We have successfully used it many times and have rapidly gained a reputation for being specialists in this area, so much so that we are regularly asked to act as third party reviewers for designs carried out by others.