The importance of the order of installation of retrofit measures in optimising long term energy and CO2 reductions

The retrofit market for existing domestic properties is gaining increasing importance as the full extent of the challenge to meet the UK government target of an 80% reduction in greenhouse gas emissions by 2050 is being realised. To achieve the necessary reductions will require a multi-faceted approach, employing a package of technologies tailored for each individual dwelling.
The performance of the retrofit technologies is not independent of the other measures in place; therefore the interaction between systems and impact on the property needs to be assessed. Due to a number of factors, such as financial limitations, homeowners often adopt a step-by-step process, taking several years to carry out improvements to reduce their energy consumption.
This paper assesses the energy and CO2 reductions associated with the order in which retrofit technologies are applied over the years, using dynamic thermal modelling to consider the operational performance of an actual semi-detached property; the E.ON 2016 house built to 1930’s standards. The orders for a given range of retrofit technologies are determined by different priorities: ‘demand reduction’, ‘affordability’ and ‘occupant comfort’. The purpose of this paper is to establish the significance of the benefits and drawbacks associated with the varying orders of implementation.
The results indicate that the order in which the same retrofit technologies are installed can result in a 2% difference in final CO2 emissions, however the order with the highest annual emissions can have the lowest cumulative emissions at the end of the 25 year period. The energy reduction potential demonstrated by the simulations indicate a £100 difference in fuel costs per year for a single retrofit measure, dependant on preceding retrofit efforts. This raises some interesting questions for the upcoming Green Deal.