This is intended to be a collection of tools that can be used in the design of retrofit interventions for individual homes, please note that this is a working progress and mainly includes tools that are developed by others but shared here together save people time. This information will be input into a co-design process trial and adpated oer time - suggested additions, edits and links to new data sources are wecome!
Why retrofit?
Energy use in homes accounts for around a quarter of all energy used in the EU [1]. Heat accounts formost of this and only 10% is produced from renewable energy [2]. Less than 1% of UK homes have a heat pump (MHCLG, 2020) and around 40% of UK electricity required to power heat pumps is still generated by fossil fuels [3]. Reducing heat loss by improving building fabric performance reduces the demand for heat [4]. Many existing buildings were built prior to current standards and hae social, embodied carbon and economic value [5]. There is need for safe retrofit of existing homes to ensure they are climate resilient, healthy to occupy and fit for the future, while reducing energy demand [6]. Retrofit measures can include building fabric and heat interventions [7, 8].
Decision-making for retrofit
There is a lot to consider in making a decision towards retrofit, this guide aims to inform the early stages of the decision-making process to assist in understanding the concepts, the starting place for an individual home and the potential benefits.The first questions focus on the social factors and aimto draw attention to any chalenges with comfort, the phsyical appearance of the home, health concerns and legislation that could be improed or impacted by the retrofit. The second section on environmental tools aims to provide a selection of resources to understand the current energy performance of the home and guide improments, plus consider the embodied carbon of measures. If any areas are particulalrly damp in the home, care should be taken to remedy that or find measures that will not increase the problem by trapping moisture. The economical tools aim to proide insight on potential house price changes resulting from retrofit. The technology questions and links provide an overiew of considerations to guide thinking towards a choice of technologies. The open-data provides insight of monitoring from previous retrofits and wider energy-efficiency data. If you would like to feed into future data resources please get in touch.
Why co-design?
Co-design allows those not trained in design to partake and input ideas from their own knowledge, experience and aspirations. This diagram summarises how this can take place in the home enironment, moving through social, environmental and economical tools.
Social tools
To establish whether there are any environmental conditions that could be improved, sketching the home is recommended, followed by a later walk through the home to identify possible areas of discomfort by evaluating the following parameters on a scale from -3 to +3 (very poor or cold to very good or hot).
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Thermal comfort (any cold areas, draughts, does the home lose heat quickly?)
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Acoustics (any problems with noise ingress, or noisy appliances in the homee?)
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Air quality (any damp problems, or a lack of ventilation, especially when cooking or producing steam in the home?)
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Aesthetics (anything to improve, to adapt the home in line with householder preferences?)
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Health (any conditions which are affected by conditions in the home?
This information can form the basis of post-occupancy evaluation from the householder perspective, used to compare pre and post retrofit
- Legislation compliance (https://interactive.planningportal.co.uk/)
Environmental tools
These tools concern energy and carbon, mainly for space heating. Reducing heat loss through the fabric reduces the demand for heat,and subsequent energy and emissions associated. Here are a few heat flow principles to bear in mind:
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Heat flows from hot to cold by conduction, conection and radiation
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Heat flow cannot be stopped but can be slowed
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Insulation resists heat flow and can be measureed by it’s U-value (W/m2K) - the lower the value, the lower the transfer of heat
This guide has some further concise information relating to heat flow.
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Energy performance and carbon: What is the baseline and what is the target?
Search for an energy performance certificate for an indivodual home here
This open access version of SAP 2012, based on the BREDEM methodology, has been created and shared by Steven Firth and Ben Hall, Loughborough University. This can be used to model poetntial improvements in energy performance from fabric, heat and power interventions to the home, but may require additional support in using
Examples of potetial carbon savings for space heating per insulation upgrades are given here for typical UK housing archetypes and for a variety of heating set points (16C-21C). Variation in heating set points and the construction of the building envelope (floors, walls, windows, doors and roof), plus other variations between data assumptions and reality lead to a gap between typical values shown on Energy Performance Certificates (EPCs) and actual energy use. Therefore, the charts below aim to provide insight based on heating set point and fabric variation, rather than fixed heating set points (e.g. SAP informing EPCs assumes a heating period of nine hours each day at 21C) - though the initial U-value for solid walls of 1.6 may reduce to 1.3W/m2K as a standard steady state variable, so the saving may be less - TO CHECK
This open access version of SAP 2012 is similar to the above but with a user-friendly interface, deeloped by Trystan Lea
This is open material shared by the UK Government on SAP 2012
This is openly shared by Circular Ecology, as embodied carbon is not yet Goverened in the UK the data is not shared centrally
*Embodied carbon of insulation - careful as this data is now quite old
*Products with Enironmental Product Declarations (EPDs)
An example of data per insulation material is given here (to be added -conflicting data found here!):
| Material | Density (kg/m3) | Thermal conductivity (W/m2K) | Fire class | Water resistance | Expected life (years) |
|---|---|---|---|---|---|
| Stone wool | 35-130 | A1 | Water repellant | 50 |
This can assist in sizing a heat pump but takes a little time to think through and may need external support.
This is Part L Conservation of fuel and power for existing buildings, shared by UK Government
- Conservation areas This is the UK guidance on conservation areas, find out if your home is in a local conservation area via your local authority Planning team
Economical tools
To estimate savings in fuel bills the domestic energy model above can be used.
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House price increases as a result of energy improvements This website summarises a UK Government report of house price increases following energy improvements
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To find out if invividual interventions could be cheaper to maintain than at present, check out manufacturers information, or potentially speak to the installer for insight on this
Technology
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What are the preferences for heat provision?
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What are your preferences for insulation?
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Are windows and doors draught-proofed?
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Do you have adequate ventilation or do you notice signs of inadequate ventilation such as condensation, odour or otherwise?
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What are your preferences for electricity provision?
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How do you envisage controlling the heat, power and ventilation systems?
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How much time and finance can you afford to spend on retrofit?
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How much doyou envisage doing now versus future and in relation to maintenance?
Information on insulation, cladding, windows, ventilation, heat and power generation can be found via the Green Spec website.
Further information here: Centre for Sustainable Energy’s Advice for Householders and here: Energy Saving Trust
Heat pump information
Heat Pumps for the Home by John Cantor ebook: https://heatpumps.co.uk/book-heat-pumps-home/
Via Trystan Lea: https://trystanlea.org.uk/
Open access data
- Open access data to inform retrofit This set of data can provide insight on previous retrofit case studies or data to assist in the design of new schemes. There is not a huge amount of open data on energy use in homes so current retrofit projects could encourage this sharing, please get in touch if you think you can contribute here
Further reading:
- European Environment Agency, E. Household energy consumption. 2019 16th April 2021]; Available from: https://www.eea.europa.eu/airs/2018/resource-efficiency-and-low-carbon-economy/household-energy-consumption.
- IEA., I.E.A. Heating. 2021 16th April 2021]; Available from: https://www.iea.org/fuels-and-technologies/heating.
- BEIS, Digest of UK Energy Statistics (DUKES), Chapter 5: Electricity. 2020.
- IEA, I.E.A. Building envelopes, tracking report. 2020 16th April 2021]; Available from: https://www.iea.org/reports/building-envelopes.
- Power, A., Does demolition or refurbishment of old and inefficient homes help to increase our environmental, social and economic viability? Energy Policy, 2008. 36(12): p. 4487-4501.
- CCC., C.C.C., UK Housing: Fit for the Future? 2019.
- Hamilton, I.G., et al., Energy efficiency uptake and energy savings in English houses: A cohort study. Energy and Buildings, 2016. 118: p. 259-276.
- Shah, N.N., et al., Analysis on field trial of high temperature heat pump integrated with thermal energy storage in domestic retrofit installation. Applied Thermal Engineering, 2018. 143: p. 650-659.