Section D

Framework to review and assess quality, carbon reduction and value

The UK has committed to become net zero carbon by 2050. Most higher education institutions have targets which are more ambitious than this. We are moving out of the phase where the arguments for net zero need to be made and into one where the reality of achieving it needs to be more clearly understood.

The RIBA, LETI and the UKGBC have set out broadly aligned targets for operational and embodied carbon on construction projects, which reduce between now and 2050 to reflect the anticipated decarbonisation of supply chains and energy supplies. The UKGBC has developed a methodology for assessing construction and embodied and operational carbon emissions, which is being widely used in the industry.

The UK electricity grid is decarbonising rapidly and is on track to become net zero by 2050. One of the major strands of the decarbonisation of buildings is transferring space and hot water heating loads from fossil fuels to electricity. For the electricity supply infrastructure to accommodate these additional electrical loads, it's necessary to reduce heating needs by improving the thermal performance of buildings, use heat pumps to efficiently deliver heat from electricity, maximise distributed electricity generation, and facilitate the roll-out of a smart grid to enable generation, storage and peak demands to be dynamically optimised.

In the UK, buildings are replaced at a rate of approximately 2% per year, reflecting an average life of 50 years. Many historically important buildings in higher education institutions have lives well in excess of this. Decarbonising the existing building stock over the next 10–30 years is a significant challenge that we must rise to in order to meet our net zero carbon goals.

The embodied carbon of newly constructed buildings is commonly equivalent to approximately 10–15 years of operational carbon emissions; this is significant in the timescale of our net zero targets. Reusing and adapting existing buildings can reduce this significantly, often by the order of 40%. Coupled with the financial benefits of adaptive re-use over new build, there is a strong imperative to make best use of existing buildings as the starting point for development projects.

Understanding the potential of the existing estate is an essential prerequisite for making good decisions. We present a holistic framework for assessing the potential of existing buildings to create low-carbon, high-quality spaces which function well and provide excellent long-term value.

Each institution is likely to have its own unique set of drivers for carbon reduction, and therefore the value of those drivers should be ascertained to assess an institutional-specific value for each tonne of carbon emissions reduction. Expressing all the values in monetary terms allows the relative merits of carbon reduction projects to be compared on the same basis and in a way which is sensitive to the priorities of the given institution.


A framework for assessing the value of carbon reduction

Drivers for carbon emissions reductions range from purely financial to those which affect reputation and attractiveness to students and staff. The bottom line is that each tonne of carbon emitted creates long term harm for our environment and ourselves.

The value of carbon emission reductions can be expressed in several ways.

Direct financial value is achieved as a result of:


Financial reduction through primary energy purchase.


Financial reduction through carbon offsetting purchases.


Financial reduction through accessing government grants.


Financial reduction in carbon taxation/offsetting.


Financial stability from renewable energy generation, reducing dependence on imported energy.

Achieving energy and carbon savings through development requires upfront investment to achieve long-term benefits. Each institution will have its own view on the appropriate lifetime to consider in the cost benefit analysis, but we recommend that a 50-year life should be considered as the sensible starting point.

Indirect impacts which have financial consequences are those which affect the long-term attractiveness of an institution to the people that are responsible for its success. Ambitious sustainability targets are being increasingly expected by students and staff, and are becoming a significant factor in an institution’s public reputation. We propose that institutions establish a monetised value for this, which can be directly used in the financial analysis of development projects.

There is an as yet mostly unaccounted but real cost in the environmental damage caused by carbon emissions. A 2018 study by the German Environment Agency concluded that the lifetime environmental damage created by the emission of 1 tonne of CO₂ costed €640 to repair in 2016. Carbon offsets can currently be purchased for as little as £10/tonne CO₂. The London Plan 2021 recommends a value of £95/tonne CO₂ be charged for residual emissions. Westminster City Council is reviewing whether to increase this to £850/tonne CO₂. HM Treasury produces guidance for the appraisal and evaluation of projects in the Green Book. The recommended value to use for the emission of 1 tonne of CO2 in 2022 is £241, rising by 1.5%pa. We propose that institutions use this value to illustrate the environmental value of carbon emissions projects alongside the direct and indirect financial costs.


A framework for evaluating and understanding the potential of existing buildings

Existing buildings should be evaluated for the range of parameters that influence their potential for successful adaptive refurbishment. We propose a methodology which considers:


Baseline performance of the existing building.


Functional adaptation potential – attributes and space uses.


Passive design potential.


Potential to create high-quality spaces.


Circular economy potential.


Electrification of heat potential.


Renewable energy generation potential.


Resilience to extreme weather events

Each aspect is scored numerically, and the output of the assessment is expressed graphically in a form which provides an intuitive understanding of the complexity.

Unless indicated otherwise, all aspects of each category should be graded from 0–5 (zero, well below average, below average, average, above average, well above average). While there is inevitably a degree of subjectivity in assigning grades, if applied consistently by a team, the results should be directly comparable.


Fabric thermal performance – assess levels of insulation and airtightness.


Condition and age of existing plant – assess relative to 30-year economic life of most M&E installations and actual condition.


Distribution – assess ability to access and space for installation of new services.


Configuration and condition of controls – assess granularity of control, visibility of system operation, condition and logging facilities.


Heat source – assess carbon intensity of fuel and efficiency.


Operational energy use and carbon emissions – assess based on utility meter data and compare with benchmarks.


Storey height – show typical actual in metres.


Condition of structure – assess relative to 100-year life and actual condition.


Ability to remodel partitions and slabs – assess ability to move partition lines and make new holes.


Ability to create a high-performance envelope – assess ability to replace glazing, add insulation, improve air tightness and address potential cold bridging.


Offices – cellular.


Offices – open plan.


Learning – small groups.


Learning – large groups.


Catering.


Laboratories.


Air quality of site.


Thermal mass of building.


Solar access.


Storey height.


Availability of heat exchange.


Thermal bridging of existing structure.


Form factor.


Suitability for good daylighting.


Daylighting – assess availability of daylight to facade (ie extent of clear view of sky).


Views – assess proportion of facades with views other than closely adjacent buildings.


Noise – assess background noise levels of site.


Air quality – assess distance from roads or fume-generating processes.


Access to nature – assess distance from green spaces.

For each major component, assess the disposal options using the following grading system


Envelope.


Internal partitions.


Finishes.


Fittings and furniture.


Electrical power availability – spare capacity in electrical distribution infrastructure to accommodate heating demands.


Heat rejection/collection potential – local sites available to provide heat exchange with ground, water or air, without causing nuisance.


Existing fabric thermal performance – ability to accommodate reduced heating flow temperature.


Solar – area available for PV or solar thermal array.


Wind – wind availability and low planning risk.


Geothermal – availability and depth.


Hydroelectric – seasonal availability, head and flow rate.


Rainwater – resilience to extreme flow with roof configuration and construction.


Flooding – likelihood of and resilience to flooding.


Overheating – extent of solar shading, thermal mass, roof insulation, natural ventilation and future provision of cooling.


Pandemics – ability to accommodate distancing, extent of natural ventilation.


Carbon reduction in practice

There is a general hierarchy of interventions to existing buildings which may be capable of achieving 2025, 2030 and 2050 building standards for both embodied and operational carbon, depending on the standard and condition of construction of the existing building:

1. Low energy refit – mostly fittings such as lighting and appliances.

2. Low energy refurb – same as low energy refit, plus improvement of thermal performance of fabric.

3. Rebuild with retained structure – as above, plus complete replacement of thermal envelope.

4. Demolish and rebuild.


Embodied carbon

Embodied carbon is the carbon (and carbon equivalent of other greenhouse gases) emitted through the manufacture, delivery, construction, disassembly and disposal of the materials and components of a building. The embodied carbon of a new construction under current building regulations standards typically equates to 10–15 years’ worth of operational carbon. A low-energy refurbishment can reduce this figure by 40%, having a significant impact within the 30-year timescale of complete decarbonisation.

Strategies to minimise embodied carbon in practice

Be materially efficient:


Minimise the quantities of materials used.


Avoid oversizing components and look to design out some elements completely.

Design buildings for longer life:


Reuse existing structures where possible.


Design to allow future flexibility and adaptability.

Disassembly and recoverability:


Minimise interdependency between different layers of a building (eg structural frame and the facade).


Enable dismantling or removal of shorter life components for high-value re-use.

Specify low embodied carbon materials


Operational carbon

Operational carbon is the carbon (and carbon equivalent of other greenhouse gases) emitted through the operation of a building, typically directly by burning fuels used for hot water heating, space heating and cooling, or releasing refrigerant gases, and indirectly by consuming electricity and water.

Requirements to manage the process of achieving defined levels of embodied carbon


Define targets – LETI/RIBA/science-based targets are becoming increasingly adopted.


Undertake a formal low and zero carbon options appraisal to establish effective passive design and MEP approaches.


Use the outputs of the assessment to define design strategies from an early stage, typically during RIBA Stage 2.


Importance of low energy.


Design strategies.


Case studies.

The strategies adopted to minimise operational carbon in practice are:

Low-energy design


Adopt adaptive comfort temperature setpoints which vary according to the weather.


Use methodologies for design and construction which drive energy-focused decisions and provide design and construction QA – eg Passivhaus, EnerPHit, Energy Cost Metric.


Choose appropriate space functions for orientations of facades.


High-performance building fabric to provide comfort while minimising heating and cooling loads – insulation, airtightness, solar control, daylighting, ventilation, etc.


Use diurnal temperature variation and exposed thermal mass to mitigate peak loads and provide passive cooling.


Allow windows to be openable to provide passive ventilation and cooling during temperate parts of the year.


Use evaporation to provide passive cooling.


Low-resistance distribution systems to minimise fan/pump energy.


Select heating and cooling system designs which use circulating water temperatures close to space temperatures.


Link heating and cooling demands to reduce net loads.


Consider active heat storage to reduce peak loads.


Consider active electrical storage to reduce carbon intensity – store energy at times of low demand and utilise during periods of high demand.


Use high-efficiency sources of heating and cooling.

Low-carbon heat sources


Reuse existing structures where possible.


Design to allow future flexibility and adaptability.


Avoid all direct combustion.


Grid-supplied electricity is decarbonising rapidly and is on track to be almost net zero by 2050.


Heat pumps are an efficient way to use electricity for heating and cooling.


Use refrigerants with low GWP and adopt system designs which minimise volume and the risk of leakage.

Renewable energy generation


Take a holistic view of the opportunities presented by the estate – the best capacity, efficiency and value may not be achieved by thinking about the buildings alone.


Avoid tokenism – select approaches that make a significant contribution to the overall energy use of buildings.


Plan for the implementation of the smart grid – the decarbonisation of the electricity supply grid is dependent on the growth of distributed renewable generation capacity, coupled with storage and peak demand control.


Design to allow for the easy replacement of components that have a shorter lifespan than the building.


Select components with the current best-in-class outputs to maximise lifetime generation and carbon reduction.

Long-term value


Test passive design strategies using future weather files – 2050 and 2080.


Plan for the addition of cooling when the passive design is no longer able to provide reasonable comfort in hot weather.


Consider whether the functions/work being carried out in the building could be carried out elsewhere in extreme weather and the extent to which this could be used to manage peak demands and system capacities.


Plan for epidemic periods – allow for higher ventilation rates during epidemic episodes and revert to energy-efficient lower ventilation rates during normal times.