Low-carbon retrofit pathways for airport terminal buildings

Annually more than two hundred million passengers travel through UK airports creating large energy demands. It is anticipated that the majority of terminals serving UK airports until 2050 have already been built. Although carbon dioxide (CO2) emissions from airport terminals are inexorably linked with aviation, they actually contribute to the non-domestic building sector which accounts for approximately 18% of the UK’s carbon footprint. If terminals are to contribute to Government emission reduction targets extensive low-carbon retrofit will be required. The built environment accounts for the smallest proportion of an airport’s carbon footprint but terminals represent the greatest proportion that are within an airport operator’s direct control.

The aim of this thesis is to define financially viable retrofit pathways for existing airport terminals that will progressively reduce their carbon footprint. A retrofit pathway is defined here as a series of retrofit carbon reduction measures (CRMs) that will reduce carbon footprint emissions as they are introduced throughout the life cycle of a building. Detailed whole building dynamic thermal simulation (DTS) models are used to investigate technical and financial impacts of CRMs in existing UK terminal buildings.

To aid understanding of these facilities, common architectural and operational features are described and include large complex building form, lightweight fabric, strict security restrictions, twenty-four operations and a wide range of building zone types. Empirical data collected from case study buildings confirms unitised CO2 emission rates and suggests that benchmarks used in Display Energy Certificate calculations need review as they are unlikely to reflect the median value for UK terminals.

Simulation models are calibrated against monthly utility data from three case study terminal buildings. Calibrated simulation models are a recognised method for more accurately evaluating large scale interactive retrofit CRMs. The process of calibration informed an improved understanding of energy end-use within terminals and found that internal heat gains from lighting and equipment have a large influence on overall building thermal performance. Internal heat gain inputs defined in this work are more realistic than those estimated for existing airport terminals in the UK National Calculation Method which is used in Building Regulation compliance and Energy Performance Certificate calculations.

A group of retrofit CRMs are identified based upon their suitability for terminal buildings. These CRMs are evaluated as single retrofits and as part of retrofit packages and pathways and investment appraisal models are used to estimate financial impacts. Results presented in this thesis demonstrate that it is possible to define financially viable retrofit pathways that significantly reduce the carbon footprints of existing UK terminal buildings. However, the solutions achieving the greatest CO2 reductions and financial performance are not the most energy efficient; results show that solutions including larger biomass fuelled combined heat and power units achieve the greatest reductions but their financial viability is reliant on government subsidies.

Analysis of single technologies and retrofit packages/pathways presented in this document adds understanding to the field of existing non-domestic building research; particularly for large complex facilities such as airport terminals. Estimating technical and financial impacts based upon models that have not been calibrated can lead to large inaccuracies in buildings of this scale. Results in this thesis emphasise the importance of using dynamic thermal simulation when assessing deep retrofit in this type of large complex non-domestic building.