Introduction to the RIBA Plan
The RIBA plan of work for fire safety identifies existing fire safety issues and proposes solutions to prevent them. In this blog post, we look at the issues outlined in the RIBA plan and analyse the possible solutions using our years of experience in the smoke control industry. More specifically, we will discuss the problems relating to fire-engineered smoke control systems and how they impact the standard of safety of HRRBs.
Excerpt from RIBA plan:
The RIBA conducted a review of the current industry delivery of fire safe design, construction, and ongoing maintenance of buildings, including the findings from the Independent Review of Building Regulations and Fire Safety, and has identified several issues. Dame Judith Hackitt DBE FREng called for transparency, strengthened accountability and greater collaboration, across statutory authorities, and the client, design and construction teams. A key culture change within the industry is not only greater collaboration between these parties, but including users and residents within design, management and maintenance of the buildings they occupy – with a direct route to the fire and rescue authority at regular reviews. Read in conjunction with the Existing Fire Safety Issues and Proposed Solutions Table and the RIBA Plan of Work for Fire Safety, this process map identifies gaps in necessary involvement, late input, lack of dutyholder responsibilities and limited statutory approvals.
RIBA produced a table of issues raised from the consultation with proposed solutions to each and below we look at these and how they play out in the industry.
Point 19: Late fire safety design from the design team
Late fire safety design occurs at the construction stage.
Fire safety measures are not fully designed or left for contractor design at stage 5 which often results in ambiguities and unintended omissions.
Point 20: No engagement of engineering and specialist consultants in Stage 2
No engagement of Structural Engineer, Building Services Engineer, and Specialist Consultants at Stage 2.
This concept design lacks the necessary and critical input of these services to inform the full fire safety strategy. This can lead to unintended omissions or errors in fire safety design.
A typical scenario from a smoke control point of view
A fire strategy is developed by a fire engineer with some indicative provision for smoke control. This will usually be a fire-engineered system rather than one of the solutions within ADB. As such, the outline proposal will follow the particular preference of the engineer or practice and the level of detail will vary greatly from project to project.
In most cases, the locations of smoke shafts will be identified with a brief design objective and an indication that a CFD model will be required to verify the design. There will rarely be any reference to particular product standards and test evidence to be provided or any competence requirements for the contractor undertaking the work.
Point 21: No Pre-tender construction advice
No pre-tender advice from the construction team prior to contractor appointment results in inadequately resolved or costed MEPH and specialist sub-contractors’ details, solutions, and diminishes robustness of the outline specification for fire safety, leading to changes at the latter RIBA work stages.
At Stage 3 the M&E consultants will be required to produce detailed design information and coordinate services. This will include fan selections, ductwork design, damper sizes, and electrical loads. The consultant will typically approach a specialist for design advice, however, there is often reluctance to give up this information without an order and it is not uncommon that details and dimensions from previous projects are used at this stage.
The smoke control is typically specified as a Contractor Design Portion and only indicative information is included in the detailed design.
Point 22: Late design by Construction Team
Specialist and contractor design portion occurs too late, which often results in ambiguities and unintended omissions that are not coordinated with the original design. A fire-safe specification can be value-engineered by the contractor comprising the integrity of the fire safety design.
The main contractor appointment will spur on the design development and trigger the appointment of sub-contractors through an often lengthy tender process with value engineering frequently being employed to drive down costs to meet the client’s budget. Smoke control may be a direct package or more often part of the M&E subcontract. It is rare to see a requirement for third-party certification of specialists or any other measure of competence in specifications and it is worth noting that the test standards and certification evidence for the system components are routinely overlooked as the primary focus of attention is the model and whether it demonstrates satisfactory conditions in the building. When using a fire-engineered approach, it is of vital importance that all components are independently tested to a relevant standard and appropriate evidence is provided. The Smoke Control Association offers a simple guide to appropriate standards for common systems in table 5.3 of the Smoke Control Association document Guidance on Smoke Control to Common Escape Routes in Apartment Buildings.
By the time the Smoke control specialist has been appointed, there is usually significant pressure to complete the design to obtain approval from the Building Control authority for the proposed solution.
Purpose and outputs of CFD Model
The CFD model is produced to demonstrate that satisfactory conditions are achieved within the stair and lobbies of buildings fire conditions. The fire scenario used for the input to the model is standardised and usually that specified in table 5.3 of the SCA Guide. The main output of the model is the volume flow rate of smoke to be extracted from the lobby which forms the basis of the system design e.g. extract fans, dampers, smoke shaft etc.
The main parameters that influence the extract rate are:
- Length of lobby
- Source of replacement air (e.g. stairwell vent, inlet shaft)
- Location of fire apartment (close to inlet source being worst case)
- Size of door to stairwell
- Size of head above stairwell door
In reality, the majority of residential buildings are similar in design with regards to the common escape areas. This means that the extract rates derived by modeling fall within a small band. The repetitious modeling of individual buildings with very similar parameters is costly, time-consuming, and adds little to the safety of the project.
UniForce Modular Mechanical Smoke Extract
The UniForce approach identifies the parameters within the model that influence the extract rate and specify a range for each of them. It is estimated that this will cover up to 80% of HRRBs based on the Group SCS database of past projects. Extensive modeling was conducted in worst-case scenarios to prove that satisfactory conditions are achieved for buildings within the specified parameters.
The output of the modelling was then used to develop a best-in-class solution that meets all BS-EN testing standards for products and with a third-party assessed open protocol software program that operates the system.
Unique safety features are built in, including remote automatic system testing to ensure the tenants remain protected when we leave the site. As well as that, the automatic firefighter protection removes the need for manual intervention.
A suite of standard building templates is provided to help architects, fire engineers, and consultants utilise the approach at the earliest stage removing the uncertainty of last-minute design.
See how it works
The suite of standard building templates mentioned above is available to view and download for free in the Modular Area of our website. Access to the Group SCS Modular Area is available free of charge to qualifying developers, architects, consultants, and contractors upon request. As well as the final design documents of the system, the Modular Area offers an online System Selector Tool that quickly generates a quote based on your requirements.