Abstract
Within the UK non-domestic building stock, offices built between 1940 and 1980, are especially in need of retrofit, they can suffer from high energy consumption and thermal discomfort. Many post-war offices will still be in use throughout the first half of this century. This paper evaluates retrofit strategies for post-war office buildings accounting for the improved energy efficiency, thermal comfort and hence productivity, and reduction of capital and running costs. The aim of the paper is seeking optimal, generic retrofit strategies to provide guidance to building owners, occupiers and other decision makers. Dynamic thermal modelling is used to compare retrofit outcomes for existing building standards (PartL2B) and higher standards (Passivhaus retrofit: EnerPHit). The effects of location and orientation and both current and future UK weather conditions (2050) are considered. Multiple combinations of heating and cooling strategies and retrofit measures are assessed. The analysis methodology uses a sophisticated comfort, productivity and cost assessment. An Overall Building Thermal Discomfort (OBTD) index is introduced which enriches the current CIBSE overheating criterion 1 by including the number of occupants. Productivity improvements as a result of better comfort are included in cost calculations. Cost benefits are calculated both for buildings used by the owner (CBO) and for buildings let to a tenant (CBT). On cost and energy grounds, UK building regulation compliant retrofit is optimal provided that passive summertime overheating controls, such as night ventilation, blinds and/or overhangs, are installed. The EnerPHit standard retrofit provides resilience as the climate warms provided summer cooling is available, for example through mixed-mode ventilation.
Highlights
IntroductionThe commitment of the 2006 government that all new non-domestic buildings should be zero carbon from 2019 [1] was scrapped, The Climate Change Act, requires the UK to achieve net-zero emissions “at least %100” by 2050 [2] is in force and legislations towards achieving this target is emerging
By applying the retrofit assessment method adopted in this research, it was possible to create generic retrofit solutions which could be applied to post-war office buildings
The study of Kerdan et al [90], which investigates energy efficient and costly optimal retrofit using exergy-based building simulation tool, suggests that Passivhaus retrofit provides good energy performance but that the approach is not economically viable. They concluded that their study “neglected the quantification of other non-energy related benefits, such as indoor air quality, thermal comfort and building aesthetics improvement; if appropriately quantified, it could enhance the financial viability of the actual retrofit design”
Summary
The commitment of the 2006 government that all new non-domestic buildings should be zero carbon from 2019 [1] was scrapped, The Climate Change Act, requires the UK to achieve net-zero emissions “at least %100” by 2050 [2] is in force and legislations towards achieving this target is emerging. The Energy Performance Certificate (EPC) is a European Union initiative which rates the energy efficiency of buildings (A to G) and is required in all non-domestic (and domestic in some counties) buildings over 500 m2 whenever they are built, sold or rented. In response to The Energy Act 2011, from April 2018 private non-domestic landlords must ensure that the properties they rent out in England and Wales reach at least an (EPC) rating of E before granting a tenancy to new or existing tenants [3]. During the fourth quarter of 2019, 19% of UK nondomestic buildings were rated E or below [4], which could be classified as poorly performing and in the necessity of urgent retrofit
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