Episode 125:

Hello and Welcome to the Part3 with me podcast.

The show that helps part 3 students jump-start into their careers as qualified architects and also provides refresher episodes for practising architects. I am your host Maria Skoutari and this week I will be talking about the Energy Performance Certificate. Today’s episode meets PC3 of the Part 3 Criteria.

Today’s episode is based on the Technical Guidance carried out for Historic England by the Sustainable Traditional Buildings Alliance.

Make sure to stay until the end for a case study example.

Let’s start by defining what an Energy Performance Certificate is, also known as EPC. EPCs were originally introduced as a benchmarking and compliance tool and they are now being used in government policy and programmes to enhance the energy efficiency of buildings including minimum energy efficiency standards for the private rented sector. Making it into a retrofit design tool. EPC’s are valid for a period of 10 years. Key item to note is that Listed buildings are exempt from EPCs however other consents and permissions for works are likely to be required.

It was put into force as a mandatory requirement as part of the Home Information Pack in 2007 by the EU Energy Performance of Buildings Directive to produce an energy certificate whenever a building is constructed, sold or rented and its aim is to detail the current energy efficiency level of a building and to set out recommendations for improvements in energy performance. It was designed to improve the conveyancing process and it must be ordered before the property is marketed. The Home Information Pack was withdrawn in 2010 but the requirement for an EPC was retained. Now the EPC a requirement contained within the Energy Performance of Buildings (England & Wales) Regulations 2012. These Regulations set out the Duties relating to EPCs and specifically how an EPC is required upon sale or rent of a building, what the report must contain, and certain exemptions.

The current aspiration under the Clean Growth Strategy is for all dwellings to reach an EPC band C by 2035, where practical, cost-effective and affordable to do so. A key item to highlight is that EPC is not a substitute for an energy audit and it is becoming increasingly recognised that we need to deliver a sustainable built environment meaning a broader assessment is needed not just an EPC which is where a Whole House assessment will be beneficial. Both together, the EPC and Whole House approach, can assist to have more robust retrofits and provide a fresh approach which would be feasible, effective and sustainable.

Although EPC’s are also required for new buildings, we will be focusing on dwellings only in today’s episode and the EPC’s application to existing dwellings more specifically. Aside from its use in relation to Government programmes, the principal use of EPC’s in existing buildings is as a ready source of information on energy performance for building owners and occupiers, which is why EPC’s are now included in the conveyancing process and estate agents details.

EPCs are increasingly used as a benchmarking tool, such as in the new Minimum Energy Efficiency Standards (MEES) legislation for privately rented buildings. The Energy Efficiency (Private Rented Property) (England & Wales) Regulations 2015 have made provision for the introduction of the Minimum Energy Efficiency Standards.

In 2018, landlords of privately rented domestic and non-domestic property in England or Wales were required to ensure that their properties reach a minimum EPC rating of ‘E’ before granting a new tenancy to new or existing tenants - this is known as the Minimum Energy Efficiency Standards. For private tenancies, the requirement was extended to include all domestic tenancies (i.e. all existing tenancies that are legally required to have an EPC) from the 1st of April 2020. Private rented properties were only required to comply with the Minimum Energy Efficiency Standards if they are legally required to have an EPC. There are certain circumstances where a property may not be required to have an EPC and therefore will not need to meet any minimum standard. Circumstances, where an EPC is not required, is where the landlord or the seller can demonstrate that the building is:

Officially protected as part of a designated environment or because of their special architectural or historic merit where compliance with certain minimum energy efficiency requirements would unacceptably alter their character or appearance which will most likely be determined by a Local Authority Conservation Officer on what is deemed acceptable.
It also makes reference to dwellings in Conservation Areas and listed buildings.

The rating has now increased to a ‘C’, which is the governments target to bring all fuel poor housing up to an EPC rating ‘C’ by 2030.

Now let’s look into the EPC’s function and format more closely:

EPC’s assess running costs for space heating, lighting and hot water and provide a list of recommended measures to reduce these costs. They do not account for elements such as portable heaters or electric showers, or aspects that are more controllable by occupants such as cooking, plugin lighting or appliances; they also don’t include broader aspects of building performance such as maintenance or fabric condition. EPC software makes assumptions about U-values based on the building’s construction, materials and floor area.

The Energy Efficiency Rating (EER) is the most important output of an EPC which states the estimated running costs to occupy a property at assumed comfort levels - an example is, a traditionally-built property with good levels of insulation and comfort and an efficient heating system which may be widely deemed to be efficient, but it can still be allocated a very poor Energy Efficiency Rating if it uses fuel other than mains gas.

Now looking at the EPC’s format, it is a 4-page document, the front page contains headline information such as estimated energy costs, the property’s ‘energy efficiency’ rating and the top three measures recommended by the EPC software to improve efficiency and reduce running costs, together with indicative costs and savings. The front page also makes it clear that it’s only an estimation. Pages 2-4 provide further basic details, including an energy ‘performance’ summary of the various building elements and services, a fuller list of recommended improvement measures, a note on Green Deal finance, background information on the EPC document, the property’s environmental impact and brief addenda as required. The estimated costs on an EPC are all given for a 3-year period.

So when assessing existing dwellings EPC, this is generated by the Reduced Data Standard Assessment Procedure, also known as, the RdSAP assessment methodology, which is a condensed version of a full SAP and it includes a site visit to take the details of the property. The rdSAP is an assessment which uses a set of assumptions about the time the building was constructed. Which then generates the EPC and Energy Efficiency Rating. The site visit is non-invasive and consists of the assessor using a check-list survey and taking the necessary evidence to inform the assessment, such as photographs and documentary evidence. Given that performance characteristics, insulation and so on are rarely visible, this leads to many assumptions being made by the RdSAP methodology. Due to a combination of performance characteristics and assumptions, certain property types are more likely than others to have a low Energy Efficiency Rating, such as detached properties, bungalows, older properties, flat roofs, rooms in roof and properties off the gas network. Properties that tend to score higher includes more modern properties, mid-floor mid-terrace flats, and properties with gas central heating.

Where an assessor has access to sufficient evidence then some of the assumption items are overridden with the actual data, which in term will give a more accurate result. Following the input of the data, the RdSAP software tests for the relevance of a range of improvement measures and includes them automatically where deemed appropriate. It will then provide improvement measures to be considered / recommended under certain given conditions, and the predicted impact of a measure based on the assumed performance. There tend to be many possible improvements, the most common including adding or improving loft insulation, roof room insulation, cavity wall insulation and so on. The key recommendations show a clear promotion of the ‘fabric-first’ approach through a range of insulation measures. Then there are secondary recommendations which can include renewable heating technologies, conventional boiler systems, glazing upgrades, renewable electricity technologies and so on.

Now, EPC’s, unfortunately, are not necessarily deemed as the most accurate and it can often present a misleading picture of both current performance and the most appropriate improvement options for the building. For example:

Relating to Cost & occupancy:

An Energy Efficiency Rating is based on cost, not on energy efficiency, and so is fundamentally misleading
The cost bias makes it much harder for non-gas-fuelled properties to achieve a good Energy Efficiency Rating
The standardised occupancy sizes and relatively intense heating patterns will commonly overestimate fuel consumption

Relating to Thermal performance:

The performance of certain building elements (e.g. solid walls) will commonly exceed that assumed by the software
Many insulation elements / types will not be credited, due to a lack of visual or documentary evidence and a lack of options in the software
Window sizes are generally assumed rather than measured; they are also assumed to face East- West for the purposes of assessing solar gain
If the window installation date is not known, modern timber-framed double glazing will be assumed to have a relatively poor performance regardless of glazing gap
A midway point is assumed for thermal mass, reducing the associated benefits for denser construction types
Open fireplaces are commonly allocated as poorly-performing secondary heating, even where they are not used and have temporary blocking measures installed

Relating to Building & occupant health:

Continuous mechanical ventilation systems, which may be required in order to maintain a healthy indoor environment and manage moisture and pollutants are penalised under the Energy Efficiency Rating

Relating to Fuel cost vs environmental impact:

Little weight is given to the Environmental Impact Rating (EIR), which has been moved to the last page of the EPC and made less visible
Cost is the overriding assessment mechanism, although it is presented in terms of ‘efficiency’
Biomass boilers and stoves often score badly on the Energy Efficiency Rating as the number of models included in the database is limited, default efficiencies are poor and fuel costs are higher than oil, even though they generate a fraction of the CO2 emissions of oil, coal or gas per kWh

Generally, the cumulative impact of just one of these inaccuracies is significant, and these impacts continue into the recommendations made by the EPC which states:

On occasion, some or even many of the recommendations may already have been carried out, but a lack of documentary or other evidence meant that they could not be included in the RdSAP assessment which renders any such recommendations irrelevant
Recommendations may not be viable for a property if they adversely affect its significance, which includes context
Recommendations may also not be viable on technical grounds, for example they may be detrimental to a property and/or its internal environment, for example where its condition – which is not covered by the RdSAP assessment – would give rise to moisture-related problems if certain measures were installed
Capital costs, particularly for higher-quality or specialist versions of any given measure, are likely to exceed those suggested within the recommendations
Running cost savings are likely to be lower than those suggested within the recommendations, due to the intensive ‘standardised’ heating patterns used by the software and an optimistic view of savings
Measures like biomass boilers may be ‘penalised’ due to fuel cost and the difficulty in allocating them a high efficiency in the software, with more environmentally-damaging measures such as oil boilers being presented as a more efficient alternative that would generate a higher Energy Efficiency Rating.

Therefore, the cumulative impact of these issues is significant. At the national/global scale, the improvement measures will not have the required impact on the environment or on fuel poverty and at the same time, property owners are likely to become discouraged by a document that recommends measures that are not appropriate for their home, are extremely expensive or which do not deliver the promised savings. There is a real risk that this could contribute to a negative view of energy efficiency and the wider environmental agenda. Some adjustments, therefore, have been recommended to be made to the EPC enabling it to be a more relevant and reliable assessment process.

So everything I have discussed up to this point relates to traditional buildings as well as other construction types, but there are certain characteristics of older traditionally constructed buildings which have different requirements and ways of assessment.

Therefore, when it comes to assessing an older building’s Thermal Performance:

The older the property the poorer the assumed thermal performance of its elements. Older properties are more likely than newer ones to have been upgraded but where an assessor does not have evidence of insulation depth/performance the software falls back on these assumed performance figures, so an older building would fare worse than a more recent one even where upgrades had taken place. Where double glazing is present but window age is unknown, full glazing details can only be entered where the frame is PVCu. For most traditional properties, timber windows are preferred – this means that if the assessor cannot determine their age they will be allocated a relatively poor U-value even if they perform much better.

In terms of recognising the impact of improvement measures on older buildings – Some improvement measures which are more common in older buildings, such as internal window shutters, chimney balloons and so on are deemed temporary or removable by the RdSAP and therefore cannot be included in the assessment. Some of the least contentious measures for ‘historic’ buildings may not result in significant Energy Efficiency Rating improvements – even if they have a significant impact on thermal comfort and heat losses.

Now in terms of Services relating to older buildings – The predominance of open fireplaces is likely to penalise older properties, even if they are not used for heating. Even where they have been replaced with wood stoves which can be highly efficient, however, as mentioned there is no way to recognise this in the RdSAP software. Similarly for wood boilers which are more common in rural areas where achieving a high Energy Efficiency Rating is notoriously difficult. There are few biomass options included in the RdSAP boiler database, and if the exact model cannot be entered again a generic, relatively low-efficiency option must be used. Biomass also achieves a worse Energy Efficiency Rating than, say, oil, as the fuel costs more – although it achieves a far better Environmental Impact Rating.

It is, therefore recommended, when it comes to older buildings, some of the recommendations made by the EPC, if implemented properly, will reduce ventilation rates, making a property more airtight – in these circumstances it becomes even more important to ensure there is sufficient ventilation, to avoid problems with fabric or indoor air quality. As such, the limitations to the EPC start to become apparent and demonstrate they can have a narrow and limited function, as the risk of problems increases when they start being used in ways that they were not designed for. Its important to distinguish that an EPC assessment is not a building survey and the RdSAP assessment makes it clear that it does not take into consideration the physical condition of any element. Fabric make-up must be properly understood in order to allow for compatible upgrade measures to be chosen.

The EPC’s role and RdSAP assessment, however, can assist with beginning to understand the methodology of starting to address technical risks. But following its recommendations with caution and with the backing up of other assessments prior to integrating any changes.

So, how can the EPC process be improved:

I mentioned earlier that the EPC is not a substitute for an energy audit and a broader assessment is needed which is where a Whole House assessment will be beneficial. The two assessments together can assist to have more robust retrofits and provide a fresh approach which would be feasible, effective and sustainable.

It is, therefore, viewed that the EPC can serve as a useful part of a Whole House Assessment if it implements some changes relating to developing its insulation and ventilation databases, placing more focus on the environmental impact of buildings than energy efficiency in order to provide a more holistic presentation of a building’s characteristics.

The upgrade EPC could then feed into the Whole House assessment process, providing base data on the structure and condition of the building and setting out a series of appropriate informed measures. Alongside the Whole House Approach, the two will be able to provide a more comprehensive energy audit and a retrofit assessment. PAS 2035 is developing the framework within which such an assessment can be carried out.

To sum up:

Energy Performance Certificates are the Government’s legislated rating scheme to summarise and report energy performance of buildings.
In 2020 the Government consulted on increasing the Minimum Energy Efficiency Standards (MEES) for privately rented domestic properties from EPC Band E to EPC Band C for new tenancies from 2025 and all tenancies from 2028
The EPC is a 4-page document and contains information such as estimated energy costs, the property’s ‘energy efficiency’ rating and the top three measures recommended by the EPC software to improve efficiency and reduce running costs, together with indicative costs and savings. The estimated costs on an EPC are all given for a 3-year period.
When assessing existing dwellings EPC, this is generated by the RdSAP assessment, which is a condensed version of a full SAP and it generates the EPC and Energy Efficiency Rating. The rdSAP is an assessment which uses a set of assumptions about the time the building was constructed.
It is recognised that there are issues with the current EPC and it's ability to be used as a tool for delivery policy objectives, a report has been carried out providing actions required to improve the quality, methodology and outcomes of the EPC process, which is mainly making it more straight forward to understand and broadening its database to provide more accurate results and recommendations.
To improve EPC’s it is also recommended that the EPC can serve as a useful part of a Whole House Assessment if it implements some changes relating to developing its insulation and ventilation databases, placing more focus on the environmental impact of buildings than energy efficiency in order to provide a more holistic presentation of a building’s characteristics.

Today instead of a scenario I will provide you with a case study:

Description:

Today’s case study is base on identical renovations of two semi-detached cottages, undertaken three months apart and were rated as C72 and D68 due to updates to fuel costs. The properties were adoining semi-detached three-bedroom farmworkers’ cottages, built in the late 1880s. Materials included Brick under tiled roof, pair of French windows added into gables of both cottages with no other alterations. The total floor area was 78m2 per cottage. The properties were not listed or within a conservation area. One cottage was on protected tenancy and the other on assured shorthold tenancy. Both were historically fueled by open-hearth fires and back boilers and have now been retrofitted with air source heat pumps (ASHPs).

The works:

In December 2009, both Cottages were assessed as part of the estate’s residential portfolio, to allow the estate manager to plan for renovations across the estate. Baseline EPCs were carried out so they could be compared with post-renovation assessments. The first Cottage was rated as G18 and the second Cottage was rated as G16. Both properties were unmodernised prior to renovation and as mentioned both were heated by open-hearth fires and back boilers, with no wall or floor insulation and single glazing throughout. They had outdated kitchens and bathrooms.

Both Cottages were fully renovated using identical work specifications. This included floor insulation and underfloor heating, full internal dry lining with a Kingspan product, loft insulation, replacement double-glazed windows and insulated doors. Both properties were fitted with a Mitsubishi Ecodan ASHP.

The two renovation projects were completed roughly three months apart, starting with the first Cottage. Although it would have been more efficient to do the work simultaneously, staggering the renovations allowed a long-term tenant in the first Cottage to move into the second Cottage during the works. The cost for the energy efficiency measures and associated ‘making good’ came to £63,734 for the first Cottage and £60,784 for the second Cottage. The difference in cost was due to works carried out on the exterior and shared areas and achieving improved productivity while renovating the second property.

The first Cottage’s EPC assessment took place on 19 December 2018 and the property received a rating of C72. The second Cottage’s took place on 1 April 2019 and a rating of D68 was given. The same Domestic Energy Assessor carried out both assessments.

The estimated energy costs for the first Cottage were £2,220 and for the second Cottage they were £2,601. The biggest difference was the energy cost of hot water. Although both properties provide hot water from the main system, the first Cottage was awarded two stars for energy efficiency and the second Cottage only one. Both properties received an environmental impact rating of Band C.

The Domestic Energy Assessor investigated the difference and concluded that an update in fuel prices used to calculate costs in the EPC software had been carried out between the two dates of assessment. Details of fuel price changes within the EPC software are not available beyond January 2018, but previous records indicate these figures are historically updated in January and July each year.

The recommended measures to bring the second Cottage to a Band C included a solar water heating system (£4,000–£6,000) and a heat recovery system for mixer showers (£585–£725.) The landlord said that the former measure was not practicable for the property, and the latter would only move the EPC up one point.

The cottages’ orientation is west, with the first Cottage’s French windows facing north and the second Cottage’s south. The landlord commented that the second Cottages benefits from considerable solar gain via the French doors, making the environment within the second Cottage much warmer than that of the first Cottage, despite its lower EPC rating.