Dormers Wells School Sports Changing Pavilion

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The new-build sports changing pavilion for Dormers Wells High School was completed in 2015. It is designed with the same palette of materials as the main school building, (which was completed in 2012 under the BSF programme with Paul Cayford as Client Adviser). Cavity masonry wall construction was selected for its robustness and buildability with an airtight plaster internal finish. The roof structure is a continuous CLT deck exposed on the inside. Airtightness result of 0.3 1/h was achieved on the first test, with energy use of 34 kWh/sqm.year modelled with PHPP.
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Dormers Wells School Sports Changing Pavilion : Project images

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CO2 emissionsPrimary energy requirement
Energy target
AECB Silver

Energy and fuel use

Fuel use by type
Primary energy requirement
CO2 emissions
Renewables

Measured data from renewable generation is not yet available.

Fuel use

 Pre-developmentForecastMeasured
Electricity use 5274 kWh/yr 355 kWh/yr -
Natural gas use- - -
Oil use- - -
LPG use- - -
Wood use- - -
Electric standard tariff - - -
 Pre-developmentForecastMeasured
Primary energy requirement 110 kWh/m².yr 7 kWh/m².yr -
Annual CO₂ emissions 26 kg CO₂/m².yr 2 kg CO₂/m².yr -
Annual space heat demand 34 kWh/m².yr 34 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
Renewables Technology--
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
7 kWh/m².yr -
Annual CO₂ emissions
offset by renewable generation
2 kg CO₂/m².yr -

Calculation and targets

Whole house energy calculation method PHPP
Other whole house calculation method-
Energy target AECB Silver
Other energy targets-
Forecast heating load 16.8 W/m² demand

Airtightness

 DateResult
Pre-development air permeability test--
Final air permeability test08 January 20150.3m³/m².hr @ 50 Pascals

Project description

StageOccupied
Start date09 April 2014
Occupation date13 February 2015
Location Southall Middlesex  England
Build typeNew build
Building sectorPublic
Property typeDetached
Construction typeMasonry Cavity
Other construction type140mm int block, 220mm mineral wool cavity, brick/block ext
Party wall constructionn/a
Floor area 120
Floor area calculation method Treated Floor Area (PHPP)
Building certification  AECB silver standard certified building AECB silver standard certified building

Project Team

OrganisationCayford Design
Project lead personPaul Cayford
Landlord or ClientDormers Wells High School
ArchitectCayford Design
Mechanical & electrical consultant
Energy consultantWill South & Junko Suetake
Structural engineerFluid Structures
Quantity surveyor
Consultant
ContractorSoden Construction Ltd

Design strategies

Planned occupancyTwo separate changing areas are each able to accommodate two full classes, ie 120 student maximum capacity. A central kitchen allows for the dual use as a sports pavilion.
Space heating strategyMVHR system provides fresh air throughout building, and is extracted above WCs and showers in changing rooms. In-duct electric elements provide heating on demand, calculated as being maximum 1.5 kW.
Water heating strategyDirect instant electric heaters are provided for basins, showers and kitchen sinks. Due to the sporadic use of the building, it was deemed inappropriate to heat water in a tank to remain unused for long periods.
Fuel strategyElectric supply from main school building via an underground cable. Whilst it was calculated as being slightly cheaper under current prices to use gas for heating, it was decided not to install a gas supply to the building, for installation cost and safety reasons.
Renewable energy strategySupply comes from main school building
Passive Solar strategyThe orientation of the pavilion was determined by the layout of the existing sports fields. The front of the building faces east-south-east, so some useful solar gain is achieved. However some solar gain is likely in summer early mornings, which can be vented by the opening windows on both sides of the building, aided by the sloping ceiling. Roof-top solar panels were ruled out due to ineffective roof angle and orientation, and for the risk of damage by cricket balls.
Space cooling strategyThe building has quite a high thermal mass (140mm block wall and 100mm screed) and the MVHR system should maintain the building at an even temperature. In the event of heat build-up, the building can be vented by manually operated electric windows. As the roof and ceiling angle is 15 degrees the building will be effectively vented by convection from the windows on both sides of the long elevation. The windows close automatically after 45 minutes, and can easily be re-opened by the teacher of the next class.
Daylighting strategyThere are long lengths of high-level clerestory windows to the front and smaller windows to the rear of the main changing rooms, providing adequate and pleasant daylight. However due to the school use it is likely the electric lighting will be used when activated by motion sensor.
Ventilation strategyMVHR system is used: with a CO2 sensor which activates a boost when required. The system has a manual boost. As required, the building can be vented by manually operated electric windows. As the roof and ceiling angle is 15 degrees the building will be effectively vented by convection from the windows on both long elevations. The windows close automatically after 45 minutes, and can easily be re-opened by the teacher of the next class.
Airtightness strategy Due to the buildings use for school sports changing, robust materials were required which were selected to be airtight. Floor screed, wet plaster on blockwork walls, and Cross Laminated Timber roof are all intrinsically airtight materials. The junctions are sealed with airtight tape. The floor screed is taped to the plaster wall and covered by vinyl floor and coved upstand. The plaster wall is taped to the CLT ceiling and covered with a timber fillet to match the roof; the CLT panel joints are taped and also covered with CLT fillet. Windows and doors are taped to adjoining cils jambs and heads and generally covered with MDF boarding. Service entries are sealed with grommets and taped.
Strategy for minimising thermal bridges Basalt low conductivity ties were used for cavity walls. Continuity between under screed insulation and cavity wall insulation is achieved by proprietary load-bearing thermal insulation block. Windows and doors are located continuously in line with thermal cavity insulation. The thermal connection between the wall insulation and roof insulation above the CLT deck has been mitigated by installing 30mm PIR insulation to the underside of the external soffit.
Modelling strategyPPHP v8.5
Insulation strategyFLOOR: 350mm insulation, made up of 150mm XPS on top of 200mm EPS between floor slab and screed. WALL: Fully filled cavity 220mm glass fibre. ROOF: 200mm PIR insulation above 150mm CLT roof deck
Other relevant retrofit strategiesnew-build
Contextual informationThe building is an integral part of the existing new school, and so the site and orientation was defined. It is a stand-alone building with services provided from the main building. Its use as a school sports changing pavilion require it to be very robust and durable at the same time complementing the architecture of award winning architecture of the main school. Being a stand-alone building operating mainly in school hours it was felt the best environmental strategy was to have a well insulated and ventilated building with heat recovery to maintain constant comfort levels.

Building services

OccupancyTwo separate changing areas are each able to accommodate two full classes, ie 130 people maximum capacity. A central kitchen allows for the dual use as a sports pavilion. There is a separate accessible WC. Due to its main occupancy in school hours the building is designed to be maintained at a constant temperature with MVHR; the ventilation strategy is designed to eliminate smells and humidity whilst maintaining energy efficiency.
Space heatingMVHR system provides fresh air throughout the building, and is extracted above WCs and showers in changing rooms. As electricity is the only energy source electric element heaters are required, maximum load calculated as 1.5kW. Post heating In-duct electric elements provide heating on demand. (these were selected in preference to electric panel radiators, for maintenance and durability preferences). Separate 1kW elements are provided for each side of the building.
Hot waterDirect instant electric heaters are provided for hot water. Individual shower units are provided for each of the four showers, and the six basins are paired with three under counter heater units.
VentilationMVHR system is used: Brink Renovent 400, with a CO2 sensor which activates a boost when required. The system also has a manual boost. Air is inputted into the far ends of both changing rooms and extracted above the showers & WCs. The other rooms are vented via transfer grilles with extracts in the accessible WC and service room. As required, the building can be vented by manually operated electric windows; as the roof and ceiling angle is 15 degrees the building will be effectively vented by convection from the windows on both long elevations. The windows close automatically after 45 minutes, and can easily be re-opened by the teacher of the next class.
ControlsLighting is controlled by automatic occupancy sensor using multi-sensing technology, with a manual over-ride. The MVHR unit is automatically set, timed to run at operating levels during school hours, with a manual over-ride for any out of hours occupancy. The MVHR has a CO2 sensor which provides boost when CO2 levels rise to the trigger point; there is also a manual boost should the atmosphere require it.
CookingThere is a kitchen space where cold food can be prepared. The school may purchase a countertop microwave. Otherwise there are no energy using appliances.
LightingThe main changing space is mainly lit by T5 fluorescent battens with part up-lighting; the areas over the WCs and showers are lit by ceiling mounted LED luminaires. The kitchen, access WC and service room are lit by LED luminaires. Lighting is controlled by automatic occupancy sensor using multi-sensing technology, with a manual over-ride.
AppliancesThere is a below counter fridge, AAA rating, mostly to be used for storing students medicines. There is an AAA rated washing machine for washing sports kit, (it is not yet known how much use this will get).
Renewable energy generation systemNo renewable energy is generated
Strategy for minimising thermal bridgesBasalt low conductivity ties were used for cavity walls. Continuity between under screed insulation and cavity wall insulation is achieved by Marmox Thermoblock thermal insulation block (7kn loading capacity was required), located at base of inner leaf in line with floor insulation. Windows and doors are located continuously in line with thermal cavity insulation. The thermal connection between the wall insulation and roof insulation above the CLT deck has been mitigated by installing 30mm PIR insulation to the underside and edges of the external soffit. Steel wind-posts which give support to the front clerestory windows are fixed to the inner blockwork and have insulation passing in front of them within the cavity; the windposts are insulated on all sides where they pass through the window zone.

Building construction

Storeys 1
Volume 339
Thermal fabric area 550
Roof description The roof structure is formed from Cross Laminated Timber panels spanning the full width of the building of 6.4m, and with a cantilevering eaves the lengths of the CLT panels are 7.8m. (There are 10 CLT panels of 7.8 x 2.3m jointed with grooved joints and a timber tongue). The inner finish is exposed timber finish with a clear fire retardant coating. On top of the CLT is the Alutrix vapour control membrane with 200mm PIR insulation with tight butt joints. A breather membrane is laid on top of the insulation, and VM-Zinc standing seam metal roof for warm roofs is laid directly on top of that, laid by a specialist accredited installer using proprietary VM-Zinc products.
Roof U-value 0.11 W/m² K
Walls description INNER LEAF - painted skimmed 15mm plaster, on 140mm 7N Celcon Hi 7 loadbearing block; stainless steel horizontal joint bed reinforcement at 225mm c/c vertically (Bekaert) was introduced to prevent cracking of internal plaster, to ensure airtight plaster layer remains intact. Cavity Ties Ancon Teplo basalt fibre. INSULATION - 220mm Isover CWS 36 glass mineral wool insulation (Manufactured from up to 86% recycled post-consumer glass that would otherwise go to landfill). OUTER LEAF - part brick and part Sto rendered blockwork, to match appearance of existing school building Buff Handmade from EH Smith above dpc, and blue engineering brick below dpc.
Walls U-value 0.14 W/m² K
Party walls description none
Party walls U-value 0.00 W/m² K
Floor description Coba entry matting at entry lobby with vinyl safety floor finish laid throughout rest of building, with integral coved vinyl skirtings. 95mm mesh reinforced sand cement screed, over 350mm insulation. (made up of 150mm XPS on top of 200mm EPS). 200mm reinforced concrete slab over hardcore.
Floor U-value 0.09 W/m² K
Glazed doors description Outward opening fully glazed Eco-Clad double doors, with side and over panels. 100% FSC laminated finger jointed redwood, with Cora aluminium cladding externally. Triple glazed [4gr.sel/16sw/33.1/14sw/4gr.sel]
Glazed doors U-value 0.92 W/m² K installed
Opaque doors description none
Opaque doors U-value - -
Windows description Inward opening fully glazed Eco-Clad windows. 100% FSC laminated finger jointed redwood, with Cora aluminium cladding externally. Triple glazed [4gr.sel/16sw/33.1/14sw/4gr.sel]
Windows U-value 0.92 W/m² K -
Windows energy transmittance (G-value) 0.5 %
Windows light transmittance -
Rooflights description n/a
Rooflights light transmittance -
Rooflights U-value -

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