The Ditton Walk development wasdesigned in such a way that it prohibiteda 1.5m2 (as recommended by ApprovedDocument B) smoke shaft used tonaturally ventilate smoke from thecommon corridors. Also, due to thelayout of the building at Ditton Walk,the longest corridor (13m) was in excessof the maximum travel distance (7.5m)set out in Approved Document B.Therefore a code compliant solutionwas not viable and a fire engineeredsolution was necessary.

The architect, CMI Consulting and thedeveloper McCann Homes, initially metwith both Birmingham and CambridgeBuilding Control and Cambridge FireServices to discuss the options for asmoke ventilation system. McCannHomes appointed SE Controls to developthe solution.

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Name:Ditton Walk.

Location:Cambridge.

Title:Providing a smoke ventilation solutionwithin a residential premise to providesafe escape routes for occupants in theevent of a fire and to provide clearaccess for the fire service to enter theaffected area, using poweredventilation techniques.

Challenge:To design, install and commission asmoke ventilation system for the threestorey block of nineteen apartments atDitton Walk, Cambridge.

Benefits:The fire engineered solution specifiedhas minimised the impact of the SmokeHeat and Exhaust Ventilation system(SHEVs) on the usable floor space,creating an economic benefit to theclient, through a reduced sized smokeshaft using powered extract rather thannatural smoke ventilation.

The maximum travel distances allowableunder Approved Document B wasincreased by incorporating a fireengineered solution.

Additionally the powered smoke shaftshave effective extract rates considerablyhigher than a natural system resultingin clearer more tenable means ofescape and fire fighting conditions.

Powered Smoke Shaft VentilationSystem for a Residential Development

Case Study

The smoke ventilation system that was demonstratedtoday at Ditton Walk Cambridge, successfully cleared thesmoke to tenable conditions from within the corridorwithin 60 seconds to meet the criteria as set out withinthe design proposal and has been successfully approved.Tim Spittle, Birmingham Building Control

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Design, Cost Planning andApproval

SE Controls were able to look at severalscenarios for their client by usingComputational Fluid Dynamic (CFD)modelling to select the optimumsolution. The ventilation system neededto meet two objectives:

1. Means of escape – Ensure that oncethe door to the apartment has closed,conditions within the corridorbecome tenable, allowing occupantsto reach the stair via the corridor.

2. Fire Service access – Keeping the stairfree of smoke, allowing a safeworking environment for the FireService.

The analysis needed to prove that anyproposed system must perform at leastas well as an Approved Document Bprescribed solution.

CFD modelling analysis

The extensive CFD analysis proved thatusing a conventional naturally ventilatedsmoke shaft system as described inApproved Document B, would fail.SE Controls therefore modelled thescenarios using their SHEVTEC®

Powered Extract Fans to mechanicallyventilate the lobbies via a reduced sizedsmoke shaft. CFD modelling was able tosuccessfully prove that the SHEVTEC®

Powered Smoke Shaft system was ableto perform better than a code compliantsolution and so SE Controls were happyto recommend the system to the clientand Building Control.

The two scenarios were tested separatelyto allow for clearer assessment andclarity.

For the means of escape assessment,figure 2 shows the visibility within thecorridor at different periods of time. Theresults showed that once the apartmentdoor was closed and the systemactivated, visibility increased quickly to10m, and smoke cleared completely ataround 85 seconds, allowing occupantsto exit effectively.

Figure 2: Visibility in the common corridor

Figure 1: The proposed system that was modelled

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Visibility at 70 seconds (10 seconds after apartment door opens)

Visibility at 200 seconds (20 seconds after apartment door closes)

Visibility at 250 seconds (70 seconds after apartment door closes)

Figure 3 looks through the stair (insection) and shows the effect of theextraction fan causing the stair door toact as an inlet and keeps a majority ofsmoke within the corridor.

Figure 4 shows the temperature in thecommon corridor at different intervals.Whilst the apartment door is open,the temperature does not exceedapproximately 90 degrees Celsius,allowing occupants of an adjoiningapartment to exit within the tenabletemperature conditions. The model alsoshows that at approximately 30seconds after the apartment door hasclosed and the system is activated, thetemperature is almost ambient.

Figure 3: Simulation time: 0-600 Seconds – Visibility

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Figure 4: Temperature in the common corridor

Through the extensive analysis of the proposed system within the building envelope,both SHEVTEC® Powered Smoke Shaft systems were found to exceed the requiredcriteria for means of escape and fire service access and exceed the requirements ofthe Building regulations and guidance of Approved Document B. The extendedtravel distances within the corridors were considered adequate based on the smokeclearance system being effective within 60 seconds.

Temperature at 170 seconds (110 seconds after apartment door opens)

Temperature at 190 seconds (10 seconds after apartment door closes)

Temperature at 210 seconds (30 seconds after apartment door closes)

The proposed SHEVTEC® PoweredSmoke Shaft system incorporated theuse of a 1m2 shaft as the mechanicalsmoke extraction shaft. Make up air wasdesigned to come from the escape stairvia low level fire & smoke dampers.Replacement air into the escape stairwas modelled to come via an AutomaticOpening Vent (AOV) at the top of theescape stair.

Due to the limited provision for inletventilation during the means of escapescenario, it was necessary to limit the airextraction rate to an amount that wouldbe provided by the smoke and firedamper. The CFD model identified theoptimum extraction rate of 2m3/s. Thefire service access strategy, enables thefire service to manually increase the fanspeed to 4m3/s via the Manual ControlPoint (MCP). This ensured that the systemis easy to operate for fire service use.

SE Controls solution was accepted bythe client and approved by BuildingControl.

Specification and Tendering

SE Controls provided the client with adetailed specification, systemperformance description, equipmentschedule and wiring schematics toenable them to be sure they wereobtaining competitive and complianttenders.

The correct operation of the systemwas crucial for the system tooperate according to the designstrategy. The system was designed

to operate on a floor by floor basis. Ifthere is a fire on the first floor of theapartment block, only the first floorSmoke Shaft Door should open, with allunaffected floors remaining closed. Inconjunction to the opening door on thefire floor, the SHEVTEC® Damper and theSHEVTEC® Roof Vent to the staircase,will supply the replacement air, whichwill all simultaneously power open. Thisreplacement air is drawn into thebuilding from the SHEVTEC® Roof Vent,through the SHEVTEC® Damper,allowing smoke to be drawn into thesmoke shaft via the extraction of theSHEVTEC® Powered Extract Fans.

The SHEVTEC® Powered Extract Fanswere specified for installation on theroof. The speed of these fans can beincreased by the fire brigade using aManual Control Point (MCP) located atthe base of the escape stair. The proventrack record of SE Controls’ fully testedOS2 control system was specified toensure the system’s control philosophycould be achieved.

Three SHEVTEC®Smoke Detectors oneach floor level are linked to eachnetworked OS2 controller. Whenactivated the OS2 controllerscommunicate to power open thecorresponding Automatic OpeningVents (AOVs).

The fire rated smoke shaft door opensautomatically using a SHEVTEC® SmokeShaft Door Actuator fitted to the backof the door within the shaft. As theAOVs were to be located below 1100mmfrom the FFL, SE Controls recommendedsafety grilles to be installed at each levelto alleviate any further fall protectionand to aid in maintenance.

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Powered Extract Fans

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Smoke Shaft Door Actuator

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Roof Vent

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SHEVTEC® Dampers were specified forinstallation where the staircase meetsthe corridor. The 24v motor drivendamper is certified and compliant and isused for replacement air whilst smoke isextracted.

A SHEVTEC® Roof Vent was specified tobe located in the top of the escape stairto supply replacement air into thebuilding on activation.

Manual Control Points (MCP) werespecified to be situated in each corridorto allow the fire services to manuallyoverride the facilities to operate thesystem and to increase the fan speedfrom the base of the stairs on entry. TheMCPs are coloured orange in accordancewith the forthcoming EN12101-9.

Project Management –Installation Coordination

Coordination of specific site stages is akey element of SE Controls’ effectiveand proven project managementsystem. All of SE Controls’ projectcustomers have a single point of contact(the Project Leader) throughout theentire project duration. Each projectteam has dedicated project administration,coordination and installation resourcesat its disposal to ensure the clientreceives consistency and the highestlevels of customer service and deliverymanagement. SE Controls workedclosely in conjunction with McCannHomes and their electrical subcontractor(who carried out the cable installation),to ensure installation of the system wentsmoothly, to time and to budget.

There were very clear guidelines set out about theanticipated installation process, I’m glad to say that allthe dates were met and everyone is happy with thesystem and we had sign off from the Building Control.We can now go on to get completions for development.Gary FleckneyContracts Manager, McCann Homes

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Damper

PRODUCTS INSTALLED:

2 x SHEVTEC® Powered Extract Fans

SHEVTEC® Roof Vent at the top of stairto create replacement air

SHEVTEC® Dampers to providereplacement air via the stairs into thecorridor

SHEVTEC® Smoke Shaft Door Actuator

SHEVTEC® Smoke detector

Manual Control Point (MCP)

OS2 control system

OSLon network communication

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Service & Maintenance

Smoke ventilation systems are life savingsystems and it is therefore essential thatregular preventative maintenance iscarried out to the required standards bycompetent personnel, who are familiarwith the specification and strategy forthe particular application. Under theRegulatory Reform (Fire Safety) Order2005 legislation this is the responsibilityof the Management Company or ownerof the premises. SE Controls maintenancedivision are able to provide 24 hoursupport for 365 days of the year to itsmaintenance clients to ensure that theirinstallations are always ready to performtheir life safety function whenever theyare called upon to do so.

Commissioning and Handover

It is essential that all smoke ventilation systems are tested via cause and effectanalysis to demonstrate that they actually do what they are designed to do. Oversome 27 years of installing smoke ventilation systems, SE Controls have refined thisprocess and hugely experienced commissioning engineers are able to “get a result” onsite, saving time, money and the need for return visits.

Increasingly SE Controls are utilising smoke tests to satisfy their clients andapproving bodies that fire engineered solutions work in accordance with theirdesign. This methodology was employed at Ditton Walk for the benefit of the client,Birmingham and Cambridge Building Control and Cambridge Fire Brigade.

SE Controls were able to prove that the installed system functioned in accordancewith their design thereby validating the CFD modelling. The approving bodies hadno hesitation in accepting the system, allowing McCann Homes to proceed toformal handover.

Visibility in the corridor after 20 secondsVisibility in the corridor before system operation

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The following regulations apply to asmoke ventilation design:

• Approved Document B – SmokeVentilation design and provision forresidential buildings.

• BS 9999 series – Smoke VentilationDesign

• Regulatory Reform Order (RRO)

• Building Regulation 2009, Regulation7 CE marked products

• EN 60335-2-103 – Finger TrapAvoidance above 1100mm from FFL

• Fire Engineered Solutions – CIBSEGuide E - Fire Engineering

• EN12101 series of smoke ventilationregulations

– Part 1 Specification for Smoke Barriers

– Part 2 Specification for Natural Smokeand Heat Exhaust Ventilators

– Part 3 Specification for PoweredSmoke and Heat Exhaust Ventilators

– Part 4 Fire and Smoke ControlInstallation of Kits

– Part 6 Pressure Differential Systems

– Part 7 Smoke Control Ducts

– Part 8 Smoke Control Dampers

– Part 9 Control Panels

– Part 10 Power Supplies.

SE Controls are able to offer consultationand advice on projects that must performto the design intentions set out inApproved Document B. Their extensiveinvolvement in government sponsoredworking groups has provided a uniqueinsight into the methodology behindApproved Document B, meaning thesolutions proposed are guaranteed tomeet the most demanding requirements.

All SHEV’s components must besuccessfully tested to the BS EN 12101before they can carry the CE mark.

Visibility in the corridor after 35 seconds Visibility in the corridor after 50 seconds

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