Refurbishment of existing homes to improve energy efficiency not only helps to address CO2 requirements under the Climate Change Act but also has significant impacts on resident energy bills.
We have analysed the impact of a range of energy efficient refurbishment measures for existing homes. Focusing effort on roof insulation and new boilers are expected to be the most cost-effective measures.
We have assessed the cost-effectiveness of different measures based on a typical 3 bed 80m² semi-detached 1960’s poorly insulated home modelled in SAP 2009. Capital costs and fuel prices for gas and electricity have been estimated based on Energy Saving Trust data¹. The results are presented below.
The results show that the following elements should be addressed first as they have the biggest impact and quickest payback:-
- Roof (insulation between joists)
- New boiler
Although the payback period is a crude comparator, it does give a good indication of the highest priorities.
Improving air permeability has a big impact but this will only be achievable by addressing insulation standards first. Installing wall insulation and double glazing provide significant cost savings but are expected to have longer payback periods. Although PV panels have a very short payback period, this is substantially due to the feed-in-tariff, which is payable at lower rates if minimum energy efficiency standards are not achieved. We therefore recommend addressing energy efficiency first.
It is important to note that retrofitting domestic buildings is not a “one size fits all” issue as there are many factors to consider. These include the type of construction, age, size, building form and existing condition (structural, damp, mould, condensation, ventilation quality) as well as the different needs and budgets of the homeowner or investor. Care also needs to be taken when adding thermal insulation to existing buildings without addressing solar shading and ventilation issues at the same time to ensure occupant comfort.
¹ Energy Saving Trust “Home Insulation” www.energysavingtrust.org.uk/domestic/content/home-insulation