Redevelopment scenarios

8.4.1. Scenario selection

A variety of carbon interventions and building redevelopment scenarios were considered for each building, as listed in Table 8.7. Further specifications for each intervention or scenario are given in Appendix B1. The interventions were developed in line with those recommended by HEFCE (2010), those considered by HEIs (as listed in section 2.1.5) and specific interventions being considered for the particular buildings. The interventions considered only related to building energy demand as opposed to building energy supply. For example, the following energy supply-related interventions were not included: voltage optimisation, CHP and renewables. Furthermore, interventions addressing other requirements in isolation such as space planning or accessibility were not included. The interventions were grouped into categories defined as follows:

Existing A baseline scenario with no immediate interventions or refurbishment, although maintenance and replacement of components over the building lifetime.

System or management interventions

Interventions affecting the physical infrastructure or management of the building systems and equipment but not requiring alteration of the building fabric.

Refurbishment Interventions that include some alteration of the building and addition of materials where as a minimum the existing building structure is retained.

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New-build Replacement of the existing building with a new building offering the equivalent function

Table 8.7 Redevelopment scenarios for each case study building (further description is given in Appendices B1 and B2)

Ref-erence Summary Standard intervention

Upper

X1 As existing Baseline scenario with no alterations None None

Systems and management interventions

S1 Boiler upgrade Replacement with boiler to Part L 2013 standards (see Table 8.10)

S2 Chiller upgrade Replacement with chiller to current Part L 2013 standards (see Table 8.11)

70% turndown of ventilation systems outside of occupied periods. Excluding specialist laboratories and workshops with high heat gains

60% turndown 80% turndown

S4 Lighting control Reduction of base lighting load during unoccupied

periods by 75% 50% reduction 100% reduction

S5 Switch-off campaign

Reduction of base equipment load during unoccupied periods by 75%. Excluding research laboratories and heat-based workshops

50% reduction 100% reduction

S6 Set point adjustment Reduction of space heating temperature and

increase of cooling temperature by 1°C 0.5°C change 1.5°C change S7 All management

Addition of 100mm mineral wool insulation to façade and 150mm polystyrene insulation to roof insulation

Insulation 20%

thinner

Insulation 20%

thicker

R2 Glazing upgrade Upgrade to triple glazing with 1.1W/m²K U-value Glazing U-value 20% higher

Glazing U-value 20% lower R3 Insulation and glazing

upgrade As R1 and R2 As R1 and R2 As R1 and R2

R4 External shading devices

Addition of external shading devices to south-facing

facades None None

R5 Façade replacement

Replacement of the existing façade with a new façade to current Part L efficiency standards: U-value 0.21 W/m²/K, airtightness 8 m³/m²/hr. Roof

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N1 Existing form

Replacement with a new building in line with Part L 2013 energy efficiency standards: 40% U-value improvement on limiting values; airtightness 5 m³/m²/hr; lighting 2.5 W/m²/100 lux. Systems as 40% improvement, as given section 8.8.

5% lower N2 Enhanced form As N1 although with an enhanced form to improve

energy efficiency where possible

As N1 As N1

Note: where changes to specific building systems or materials are not described for particular interventions or refurbishment options they remained the same as in the existing scenario.

Paired combinations of interventions in the system/management and refurbishment categories were also considered: the pair with the greatest impact being deemed to be the R5/S8 combination (see Table 8.7). For each scenario, the total life cycle carbon impact was determined in terms of any initial embodied carbon impact plus future recurring embodied carbon impacts and operational carbon impact over the building lifetime.

For each intervention, the uncertainty was defined by calculation of the upper (higher energy use) and lower (lower energy use) limits around the standard intervention. The basis for these limits are given in Table 8.7 and in Appendices B1 and B2.

8.4.2. New building elements

Overview

For the new-build and, where appropriate, refurbishment scenarios, the embodied carbon impacts were assessed separately by element: structure, external walls, floor finishes, ceiling finishes etc. In order to evaluate the sensitivity of carbon impact to material selection, a number of different typical material options were considered for each element. Typically two to four different types of material were considered. Table XIV in Appendix D1 details the materials considered for each building element in the new-build and refurbishment scenarios. The selections for each element are described in the

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following sections. For simplification of the process, the thermal simulation was carried out only using the first material scheme in each case.

Internal element material groups

To account for variability in materials used for internal elements – partitions, floor finishes and ceiling finishes (as described below) - by space type, each material option defined the material specifications for a group of different space types. Nine distinct space types were determined: offices, labs and workshops, general soft finish areas, general hard finish areas, staircases, WCs, stores, plant rooms and risers and lifts. For each option, the material was only applied to space types where considered appropriate, otherwise a base material was used. For example for floor finishes, the carpet option was not applied to lab/workshop areas, WCs and plant areas where hard finishes were deemed necessary.

Additionally, for plasterboard partition walls, these were applied in all general use areas but not in ancillary spaces such as stores, plant rooms, risers, lifts and staircases.

Table XIV in Appendix D1 lists the material schemes for each internal element and the corresponding material specification by space type.

Structural frame materials

The four structural material schemes considered included the three materials commonly used for building structures: concrete, steel frame and timber floor structure. For the concrete frame, an option was also included for 30% cement substitution with pulverised fuel ash (PFA) to assess this as a potential reduced carbon option.

Façade materials

Four common principal façade systems were considered: steel curtain walling with stone cladding, steel curtain walling with aluminium cladding, steel curtain walling with timber cladding and

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brickwork. With the inclusion of natural materials such as stone and timber cladding together with steel support systems and aluminium cladding it was aimed to provide a large range of impacts.

Glazing materials

Only a single option was considered for the glazing – triple glazed in aluminium frame – which is a common option for achieving low heat loss in modern construction. A target U-value of 1.1 W/m²/K was set for the glazing and a G-value of 0.54 was set to give a good balance between solar gain reduction and natural lighting penetration.

Internal partition materials

The partition options for the main occupied spaces were largely similar - plasterboard or blockwork with a wet plaster and paint finish – although for office spaces an option of glass partitions was also included as an appropriate option. For ancillary spaces, partitions were mainly blockwork only except for lift shafts and stairwells where the partitions were reinforced concrete to provide structural lateral support. In WCs, partitions were tiled with ceramic tiles.

Ceiling finish materials

In offices and general hard finish areas such as corridors, a variety of ceiling finishes were considered, including suspended mineral wool tiles, suspended plasterboard and the omission of suspended ceilings and use of wet plaster or bare structure only. For cleanliness and acoustic reasons in other occupied spaces the omission of ceilings was not considered appropriate. In ancillary areas such as stores and plantrooms, ceilings were generally omitted and either wet plaster or unfinished options were considered. In WCs, suspended mineral wool tile ceilings were also considered.

134 Floor finish materials

In the main occupied spaces, stores and staircases a variety of floor finishes were considered including unfinished (bare screed). For labs and workshops and WCs only vinyl and porcelain tiles were considered appropriate. Elsewhere floors were unfinished.