Direct emissions from buildings accounted for around 17% of total UK greenhouse gas emissions in 20191 . As the country looks to achieve net zero emissions by 2050 (2045 in Scotland) it will be essential to significantly reduce these both from new and existing buildings. This will be especially important for healthcare facilities, which are often among the most energy-intensive buildings, both in terms of ‘shrinking’ emissions, and addressing the rapid rises in energy costs
To help drive these reductions, England, Scotland, and Wales, are all in the process of updating the energy performance requirements within their Building Regulations and Standards. In England these were introduced on 15 June, with Scotland’s updates due to come into force on 1 December, and Wales expected to be introduced by the close of the year. These changes are seen as a key steppingstone, laying the groundwork for further updates due in 2024 (Scotland) and 2025 (England and Wales), when virtually all new buildings will need to be ‘net-zero ready’. The NHS has also set its own target to reach net zero on all ‘directly controlled’ emissions by 2040.2
Specific targets
The specific targets that healthcare projects will need to meet differ in each region, and depending on the project type. We’ll take a look at the changes for newbuild projects first.
Part L and Section 6
The energy performance requirements for buildings are contained in Part L of the Building Regulations (separate versions England and Wales), and Section 6 (Energy) of the Building Standards (Scotland). The regulations are accompanied with guidance documents, known as the Approved Documents (ADL) in England and Wales, and Technical Handbooks (TH) in Scotland. These set out the requirements which buildings need to meet to be deemed compliant.
To do this, new healthcare facilities will need to meet three key metrics
Carbon emissions. These need to be 25% lower than under the previous version of Part L in England, at least 16% lower than at present in Scotland, and are expected to be either 22% or 27% lower in Wales. While the uplift is lower in Scotland, the existing requirements are more demanding than those in Wales, and previously in England. As a result, Scottish developments may still need to hit a lower overall level of emissions.
Primary or Delivered Energy. These are new metrics designed to limit the total energy of a building. They’ve been introduced in recognition that as the National Grid is decarbonised, it may be possible for buildings which waste energy, and are expensive to operate, to still reach low levels of carbon emissions. Delivered Energy will be used in Scotland, and will consider the expected energy use by a building. Primary Energy, which is already being used in Wales for non-domestic buildings, and which is now introduced in England, adopts a more in-depth approach. It considers the energy used in upstream activities to prepare a fuel, such as extracting, transporting, and refining, and applies a weighting known as a Primary Energy Factor (PEF) to different fuel types. This may make it more challenging to achieve compliance depending on the fuel types used to heat and power a building.
Worst-case U-values. In recognition that the most effective approach to minimising the long-term energy use of a building is by ensuring that it is well insulated, the different elements of the outer envelope must also meet or be better than worst-case levels of thermal performance (known as U-values). The lower the U-value, the more demanding the target. These are shown in Table 1 for new buildings, and the values set are notably tougher than the existing or previous requirements in all three countries, with Scotland setting slightly more ambitious targets
These values are area weighted, so it is possible to have a worse U-value in certain areas of a construction, providing that this is compensated for with better values elsewhere. In all cases the U-value of individual elements should be no worse than the threshold values shown in Table 1. It is also worth reiterating that these are just worst-case values, and that if all elements in a building are constructed to these levels, it will be extremely difficult to reach compliance.
Notional Building
To calculate the targets for the first two of these metrics, assessors carry out modelling on a proposed building in the SBEM modelling software. This analysis compares the proposed development with a ‘notional building’ of the same dimensions using a set specification, the fabric elements of which are shown in Table 2.
Specifiers are free to vary from these specifications, providing they meet the carbon emission and primary/delivered energy targets and worst-case U-values. It is worth noting that all new buildings will also need to be completed with heating systems designed to operate at temperatures of 55 °C or below. This is to allow a simpler future transition to low carbon heating technologies, such as heat pumps, which operate most efficiently at lower flow temperatures.
Thermal bridges
It’s also important to be aware that changes are being introduced to how heat losses from thermal bridges are considered. Thermal bridges are areas where materials which are more conductive to heat than the insulation layer are allowed to form a path between the inside of the property and the outside. These commonly occur in areas such as around windows and doors, and at junctions between building elements. These paths can form a fast-track for heat to escape, and have been shown to account for as much as 30% of total losses.
To improve practice in this area, the Accredited/Approved Construction Details (ACDs) have been removed, as it was felt they had become outdated. The default heat loss values given where no detail is supplied (either for the junction or globally for the building) have also been worsened. This makes it much more difficult to reach compliance without either having bespoke details calculated, or making use of details from manufacturers or industry libraries.
Impact on Building Specification
While we’re still waiting for the final version of the SBEM modelling software in all three regions to look at how these updates may specifically impact buildings, there are some key points to note. Firstly, the Primary and Delivered Energy metrics allow any energy generated by onsite renewables, such as photovoltaic (PV) roof panels, to be subtracted from a building’s overall demand. This means that use of these technologies is especially beneficial for compliance with this metric
Use of low carbon heating technologies, such as heat pumps, will aid compliance with the carbon emissions metric. However, as the PEF for electricity is currently higher than for natural gas, it is initially expected to be a little harder to achieve compliance with the Primary Energy metric in England and Wales. It’s also worth noting that as electricity is considerably more expensive than gas, the cost of operating these systems is expected to be higher in the near term, so if you choose to go down this route it is especially important to ensure a good level of fabric performance.
Fundamentally, ensuring that the building is well insulated will aid compliance with all three metrics, and – by focusing on this area now – specifiers can minimise long-term operational costs for facilities, and ensure that buildings can be easily transitioned to full Net Zero status through more minor changes to the heating and hot water appliances. It will also help to futureproof buildings against requirements to upgrade the fabric performance of existing buildings at a later date
Fabric performance
When targeting lower U-values, it is especially important to consider the thermal conductivity of the insulation. This is the measure of its ability to prevent heat loss through thermal conduction. The lower the thermal conductivity, the more effective the insulation is at preventing this type of heat loss. This means it may be possible to achieve a desired U-value with a much slimmer thickness of insulation, reducing the overall construction depth. Rigid insulation materials such as phenolic and PIR insulation have notably lower thermal conductivities than alternative materials such as rock mineral fibre.
For example, take a typical flat roof application above a 150 mm concrete slab with 50 mm screeded falls, a vapour control layer, and single-ply membrane. In this construction, it is possible to achieve a U-value of 0.15 W/m2 K with a 140 mm thickness of PIR insulation (thermal conductivity 0.22 W/mK). To achieve this same performance with a typical rock mineral fibre product (thermal conductivity 0.38 W/mK), a total insulation depth of 245 mm is needed – greatly increasing the construction depth and weight.
Other aspects of the design
This increased construction depth can have implications for other aspects of the design, such as the structural support requirements and extent of foundations. In external wall applications, it can also notably reduce the available floorspace which can be achieved within a given footprint due to the additional wall depth. The focus on building fabric also means it is worth specifiers considering the advantages of offsite approaches. For example, structural insulated panels (SIPs) feature a rigid insulation core sandwiched between two layers of oriented strand board (OSB), and can be used to form the roof and walls of buildings. These panels offer excellent ‘out-of-the-box’ thermal performance and insulation continuity, helping to reduce thermal bridging, while their jointing supports the construction of highly airtight buildings.
In addition to these fabric benefits, SIPs can also provide clear programme benefits. The panels are pre-cut to the specific dimensions at dedicated offsite facilities. This means that they can be produced and erected to a predictable schedule, and in many cases the outer building shell can often be erected in 4-6 weeks. Once a breather membrane is applied externally, and windows and doors are fitted, this shell is weathertight, meaning internal fit-out can begin while the external cladding and roofing are applied, further streamlining construction programmes.
Refurbishment and extension work
The requirements for existing buildings depend on the specific work that is being carried out. Where an existing construction, such as a roof, needs to be removed and replaced, or an extension is constructed, these should typically meet the same worst-case U-values as for new build projects (shown in Table 1). Some flexibility is provided in recognition of the challenges that refurbishment work may pose. For example, in ADL2 2021 in England it’s noted that where insulating a floor may create significant access problems with adjoining floor areas, higher U-values may be acceptable, although these should still meet the threshold values in Table 1
Extension work on large buildings (over 1000 m2 ) in England and Wales may also trigger consequential improvements to other aspects of the existing building, such as upgrading the thermal performance of building elements.
In Scotland, where an existing unheated building is converted, or major refurbishment work undertaken, specifiers should look to meet the worst-case values in Table 1 where possible, and the threshold as a minimum in virtually all cases. Finally, in England, and under the expected changes in Wales, work on ‘existing elements’ can be completed to slightly relaxed standards. This applies where there is a change of use in the building, where an unheated building is converted, or if 50% of the surface area of an individual element is renovated, or more than 25% of the surface area of the external envelope is renovated
Ideally, this work should look to achieve the improved values shown in Table 3. Where this isn’t technically feasible, or will not provide payback within 15 years, you should look to achieve the best possible U-values achievable. In all cases, you should reach, or improve upon, the threshold values given in Table 1.
Historic or protected buildings
In all regions, it is recognised that when carrying out work on historic or protected buildings, it may not always be possible to meet even the threshold values. In these cases, the guidance documents recommend that consideration should still be given to how the building can be sensitively improved, rather than adopting a ‘do nothing’ approach. This includes the use of innovative solutions, such as optimal performance insulation, which can help to address ‘problem areas’.
Insulating ‘problem areas’
On all refurbishment applications, it is not uncommon to come across areas where the available depth for insulation is highly limited. Typical examples include when attempting to insulate above an existing solid floor. If the insulation is too thick it can reduce the floor to ceiling height, and also mean that fixtures and fittings need to be raised. Similarly, where existing flat roofs are converted into roof terraces, it can be challenging to ensure that the roof is well insulated while retaining an even transition between the internal and external spaces.
In these applications, vacuum insulation panel (VIP) systems can provide a solution. VIPs feature a microporous core which is evacuated of air and sealed in a gas-tight envelope. This allows the panels to achieve an insulating performance up to five times better than some commonly used insulation materials.
As the VIPs themselves cannot be cut, they’re typically provided in a range of dimensions, and installed in systems along with rigid insulation boards of the same thickness, which can be cut to size to allow for penetrations, and to fill awkward gaps between the VIPs or around the perimeter. VIPs systems are available for both floor and flat roof applications. Additionally, systems are now available which encapsulate the VIP in a protective spray layer, providing a robust solution for inverted roof applications.
Ponding water
Another common problem area for healthcare estates is where water is ponding on flat roofs. This can be caused by a variety of issues, including blocked drains, debris on the roof, or an insufficient drainage fall in the roof itself. Where this issue reoccurs frequently, it may be necessary to re-establish the fall. In this application, tapered roofing systems can provide a simple solution. These systems combine standard flat insulation boards with tapered and hip and valley boards which can be used to provide the drainage fall. They’re typically supported with design services, creating a clear system layout to achieve the desired thermal and drainage requirements. The lightweight boards add minimal structural loading to the deck, can be fitted with a dry installation process, and – depending on the condition of the roof – in some cases can be fitted without having to strip the existing waterproofing layer.
Retrofit framework
Ultimately, refurbishment projects are more complex than new-builds, and there is no one-size-fits-all solution. For this reason, it is important that the improvement work is carefully tailored to the individual building. To support this, a Retrofit Framework has been created, underpinned by two publicly available standards:
PAS 2038:2021 – which covers the assessment of existing buildings, development of an improvement plan and specification, and evaluation of the energy efficiency measures once installed.
PAS 2030:2019+A1:2022 – which covers the installation and commissioning of these measures.
The Retrofit Framework sets out a clear process for each building to be risk assessed, and for a retrofit strategy to be developed. This not only identifies what remedial work is needed, and which energy efficiency measures are appropriate, but also sets out a clear order for them to be installed in to deliver best value. It also provides extensive guidance on how measures should be handed over and evaluated post-installation to ensure that they are performing effectively. This ‘whole building approach’ can help estate teams to plan a clear and logical improvement plan for all buildings, ensuring good value and lasting reductions in emissions and energy demand.
Setting a clear path
As we move toward a zero-carbon future, it is important for specifiers and Estates teams to have a clear understanding not only of all of the updated regulatory requirements, but also the path ahead. By aiming for high standards of fabric performance in new projects, and raising the performance of existing buildings where feasible, it should be possible to limit the operational demand and cost of buildings, and raise them to full net zero performance in the future with minimal cost and disruption.
Jonathan Ducker
Jonathan Ducker is head of Regulatory Affairs at Kingspan Insulation GB. With an extensive understanding of the technical and policy issues surrounding energy efficiency, sustainability, and low and zero carbon technologies, he is regularly involved with construction industry working groups for building regulations and standards relating to new build energy efficiency, net zero, moisture in buildings, and retrofit. He has represented trade associations for English, Welsh, and Scottish building standards, and has contributed to a variety of articles and publications.
References
1 Climate Change Committee. The Sixth Carbon Budget [Internet]. 2020 [cited 01 July 2022]. https://tinyurl.com/2p8wvjba
2 NHS England. Delivering a ‘Net Zero’ National Health Service [Internet]. 2020 [cited 01 July 2022]. https://tinyurl.com/ yc53v4m5