Improving Energy Efficiency Through Mitigation
Here you can find links to more detailed advice on how to improve energy efficiency through mitigation measures.
Overview
We use the term retrofit to refer to the improvement of an existing building to ensure it is efficient, resilient and well-adapted to our changing climate.
Successful retrofit projects take into account the construction, condition, significance, occupants, use, exposure and vulnerability of the building, via a whole building approach. The resultant holistic and balanced solutions save energy and carbon, maintain a comfortable and healthy indoor environment, and sustain heritage significance. Certain retrofit measures are not feasible or practicable for historic and traditional buildings.
Energy efficiency hierarchy
The term 'fabric first' is often used to describe prioritising thermal upgrades to building fabric, such as solid wall insulation, over all other interventions. In a historic building, this is often neither practicable nor desirable. It is often not the most technically sound, efficient, or effective approach and may result in unintended consequences.
Effective energy efficiency interventions are far broader than fabric thermal upgrades alone. They also include:
- Repair and maintenance
- Upgrading existing services
- Using efficient heating technology with responsive controls
- Installing new low or zero carbon technologies
Interventions should be implemented in order of priority set out by the 'Energy Efficiency Hierarchy'. This order of priority reflects not only the relative benefits, costs, and technical risks of interventions but the 'three pillars of energy transition' - sufficiency, efficiency, and generation:
- Firstly, reduce energy consumption in real terms (sufficiency)
- Secondly, minimise unavoidable energy use (efficiency)
- Lastly, generate energy from 'renewables', also known as low and zero carbon technologies, where possible (generation)
This stands to support energy security as we transition to electrification, maximise carbon reductions, and minimise negative impact on occupants, fabric, and the environment:
Sufficiency
Eliminating unnecessary energy use and reducing energy wastage will use less energy in absolute terms.
Repair and maintain
Repair and maintenance are not only essential to keep the building in good working use but are also the first steps to reducing energy use, particularly when addressing causes of water ingress. The thermal performance of the building fabric can be enhanced by carrying out prompt repairs and regular maintenance.
Learn more: Maintenance and Repair of Older Buildings
Learn more: Maintenance Checklist
Reduce demand
Insulating hot water storage tanks and pipes and replacing traditional or halogen light bulbs with LEDs are quick and effective energy-saving interventions.
Installing time controls, humidity sensors and light or motion sensors will ensure that heaters, fans, lighting and so on only operate when needed.
Savings can be made by reducing the amount of equipment left on unnecessarily, reviewing how controls are used and taking a more flexible approach to comfort standards in different parts of the building or at different times of the year.
Encouraging occupants to engage with their energy use, be aware of high demand equipment or activities, utilise smart meter technology, and manage comfort levels in ways that do not demand energy use will help reduce energy demand.
Learn more: Tips for lower energy bills - Centre for Sustainable Energy
Reduce uncontrolled air leaks
Draught proofing is unobtrusive and cost effective. Costs will be quickly recovered by energy savings. If draughts are reduced, improved ventilation may be needed. Make sure these requirements are fulfilled to maintain the indoor air quality.
Where practicable, repairing cracked or missing plaster coatings or renders will further increase airtightness.
Learn more: Draught proofing
Incorporate/use passive interventions
Internal shutters, curtains and blinds not only provide privacy, security, and weather protection, they also protect against heat loss through windows. External shutters can reduce the amount of sunlight entering the building, thus minimising solar gain and associated overheating risk. Internal shutters, thick blinds and heavy curtains help to prevent heat loss in winter.
Installing rugs or carpets, with permeable backing materials, can also reduce heat loss or protect against overheating. Carpets and rugs provide draught proofing for suspended timber floors and can easily be removed in the summer months to allow air to flow through timber floors or to expose cool solid floors, thus reducing the risk of overheating. For resilience, rugs also provide removable finishes in case of impending flood risk.
Implementing nature based/planting solutions, such as strategically planting vegetation to the perimeter of buildings for shade. This can also be helpful to reduce flood risk and support biodiversity. Planting plans should consider the setting of the building, particularly if it is listed or in a conservation area.
Efficiency
Increasing a building's efficiency will help minimise unavoidable energy use.
Minimise system inefficiencies
Building services such as heating, hot water and lighting as well as domestic appliances should be designed, selected, sized and run to use as little energy as possible.
Use heating controls
Heating controls help to keep a building comfortable and warm without wasting energy. They should be easy to understand and use. The system may include:
- A programmer (to control when heating turns on and off)
- Room thermostats
- Thermostatic radiator valves
- A cylinder thermostat for the hot water cylinder
Learn more: Heating Controls - Energy Saving Trust
Install secondary glazing
Carefully designed and installed secondary glazing can retain original historic windows and reduce heat loss and draughts. In some situations, secondary glazing can bring even greater energy efficiency improvements than double glazing. Where secondary glazing is installed, it is important to prevent condensation and mould growth in the interspace and within the building itself. Do not draught proof the original window and be sure to fulfil any linked ventilation requirements.
Learn more: Secondary glazing for windows
Replace the heating system
If a heating system is at the end of its serviceable life, replacing it with a new more energy efficient system will be beneficial. Where practicable, switching to a low carbon heating system will enable rapid decarbonisation as the grid reduces its carbon emissions.
Learn more: Heating Historic Buildings
Learn more: Installing Heat Pumps in Historic Buildings
Install/use solar shading
External shutters, awnings and blinds help to prevent overheating in the summer. Installing solar shading can be an extremely effective way to reduce energy demand related to increasing cooling needs. The historical use of external shading solutions is more extensive than generally thought. Planting of trees and shrubs can also make a key contribution to shading, urban cooling and heat resilience. They also provide co-benefits for the future improvement of air quality and nature recovery. Interventions must be designed and integrated sensitively and with the necessary consents.
Learn more: Overheating in Historic Buildings
Improve the thermal performance of the existing building envelope
- Upgrade thermal elements. In some buildings, installing insulation can help improve energy efficiency and reduce the energy demand of the existing heating system. It can also positively impact the size, capital or operational cost, and carbon emissions of heating systems. However, if insulation is not properly considered and installed, or if inappropriate materials are used, it can make a building less energy efficient. It can also undermine climate resilience, risk the health of occupants, cause the building fabric to deteriorate and harm the significance of the building. A thorough risk-based assessment and robust design are key to success.
Learn more: Installing Insulation - Improve the performance of windows or doors. Historic windows and doors are usually durable, functional, and repairable if looked after. There are many ways in which windows can be improved that are not only sensitive to their historic context, but also much more effective in carbon and energy terms than wholesale replacement.
Learn more: Modifying Historic Windows as Part of Retrofitting Energy-Saving Measures
Generation
Generating energy from low and zero carbon systems will reduce carbon emissions. It will also reduce demand on supply networks.
Introduce appropriate low and zero carbon energy technologies
Energy can be generated on site from the sun, wind, water, or ground sources. Before considering any of these, it is important to make sure all practicable energy sufficiency and efficiency interventions have been implemented to minimize the amount of energy needing to be generated. This reduces the system size, saves capital costs and minimises embodied carbon emissions. Introducing low and zero carbon technologies may impact significance, therefore early design and consultation is paramount.
Learn more: Low and Zero Carbon Technologies
Learn more: Generating Energy in Your Home
Building performance evaluation for energy efficiency
Assumptions about the poor performance of buildings of traditional construction are not always justified. This is partly due to inaccurate predictive energy modelling tools, which tend to overestimate heat loss in older buildings. The modelling is based on general assumptions that are not always applicable. Using actual rather than estimated data improves heat loss predictions and identifies better solutions for enhancing energy performance.
To understanding the energy performance of an existing building you need to take a whole building approach and use building performance evaluation (BPE) to identify an accurate baseline, which ensures any interventions are proportionate, cost effective and resource efficient. BPE measures what performance was targeted or expected and compares it to the performance achieved.
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