As the UK works towards net zero, the devolved governments are setting various regulatory standards to reduce carbon emissions from our homes and buildings. Specifiers working across the nations need to be aware of these standards when working on both newbuild and retrofit projects.
The Scottish Government aims to reach net zero by 2045, ahead of the rest of the UK in 2050. Heating homes, workplaces and buildings is the third-largest cause of greenhouse gas emissions in Scotland, so this sector must be decarbonised to meet the target.
This will be achieved by improving energy efficiency and switching to low-carbon heat, mandated by two important pieces of legislation – the New Build Heat Standard which came into force on 1 April 2024, and the Heat in Buildings Bill which has recently been the subject of a public consultation.
All you need to know about the New Build Heat Standard
The New Build Heat Standard means new homes and buildings built after 1 April 2024 will not be able to use a polluting direct emission heating system, such as one powered by oil or gas. Instead, new homes must use a clean heating system like a heat pump, or connect to a heat network.
The standard is the result of changes to Section 6 of the Scottish Building Regulations and also covers conversions, where installing a clean heating system is practicable and won’t adversely affect the character of the building.
There are a number of considerations for architects and specifiers working to incorporate low and zero carbon heating systems into building designs, including the heating and cooling requirements and impacts on space, appearance and noise.
What low-carbon heating options are available under the New Build Heat Standard?
Heat pumps are an increasingly popular energy efficient alternative to gas boilers in residential developments. Modern condensing gas boilers are between 92-94% efficient, but a heat pump can produce between 2.5 and 4 units of heat for every unit of energy it uses – an efficiency of between 250 and 400%.
When incorporating an air source heat pump into home design, specifiers must make sure there is space for the unit outside, and may need to work building fabric upgrades into the plans to allow the heat pump to work most efficiently.
Ground source heat pumps can be a good option where there is enough outdoor space to house the ground loops, but the relatively high capital cost of these trenches or boreholes can be prohibitive. Upfront investment can also be a barrier for developers considering district heating or heat networks – another option under the New Build Heat Standard.
However, solutions to this are emerging, such as the new split-ownership model from Kensa Utilities where Kensa install and own the shared ground source heat pump network. The developer purchases the ground source heat pump and connects this to Kensa’s network for a connection fee, then the householder pays an ongoing standing charge, similar to that of a gas network.
Both heat pumps and low-carbon heat networks need additional thermal storage for hot water, for example a hot water cylinder or heat battery. This can be a challenge in space-constrained homes, but specifiers can overcome this by choosing a compact option such as a Sunamp Thermino.
What's included in Scotland's proposed Heat in Buildings Bill?
While the New Build Heat Standard only covers new homes, the Heat in Buildings Bill aims to improve energy efficiency in all homes in Scotland.
The use of polluting heating systems will be prohibited for all homes after 2045. To facilitate this, people purchasing a home which has a polluting heating system will need to replace this with a low-carbon option within a fixed period after completing the sale, likely two to five years.
The bill also proposes minimum energy efficiency standards which should be met by privately rented homes by 2028, and all homes by 2033. The proposed energy efficiency measures include 270mm loft insulation, cavity wall insulation, draught-proofing, heating controls, 80mm hot water cylinder insulation and suspended floor insulation. Homes must have as many of these measures as feasible.
This is an attempt to address the fact that 89% of homes in Scotland are currently using a polluting heating system, while 55% of homes don’t meet what is considered a good level of energy efficiency. By considering energy efficiency measures alongside the heating system, the bill takes a whole-house approach to reducing energy demand.
The creation of Heat Network Zones is also included in the proposals. These zones could cover between 17.1 and 32.1% of Scotland’s total heat demand, and the bill proposes giving local authorities and ministers the power to require buildings in the zone to end their use of polluting heating systems by a certain date. This should encourage developers to invest in, and building owners to join, a low-carbon heat network.
Social housing, which makes up around a fifth of homes in Scotland, isn’t included in the Heat in Buildings Bill. Instead a new Social Housing Net Zero Standard has been consulted on. This proposes a minimum fabric energy efficiency rating and a requirement to replace polluting heating systems with a clean alternative by 2045.
Heat batteries are a great alternative to hot water cylinders and could help complement low-carbon heating systems, boost home energy efficiency, and maximise the potential flexibility of heat networks as this legislation comes into play.
What a new Passivhaus standard for Scotland might look like
Specifiers should also be aware of the development of a Scottish equivalent to the Passivhaus standard. Homes built to Passivhaus principles follow rigorous energy efficiency design standards in their construction, insulation and ventilation, which allows them to maintain an almost constant temperature with very little additional heating or cooling.
A member’s bill was proposed by Alex Rowley MSP in May 2022 which suggested that all new build housing should meet a Scottish equivalent to the Passivhaus standard, to improve energy efficiency and thermal performance. This was supported by the Scottish Government and a consultation on the proposed standard launched on 31 July 2024.
There are many advantages to adopting an equivalent to the Passivhaus standard – it could cut heating bills by up to 90% as well as reducing carbon emissions and creating healthier living environments, as the improved ventilation can eliminate condensation and mould.
How thermal storage can help meet Scotland's new energy efficiency standards
Unlike gas combi boilers, which currently heat up to 80% of UK households, heat pumps and heat networks don’t provide hot water. This means that additional thermal storage for hot water is needed. Choosing a Thermino heat battery to meet this requirement instead of a hot water cylinder has a number of benefits for specifiers, developers and householders alike.
A Thermino is smaller than the equivalent hot water cylinder because energy is stored in our patented Plentigrade phase change material, which is four times more energy dense than water. This compact size maximises space, making it easier to fit into house design, while the cuboid shape and multiple options for pipe connection make for a flexible install.
The vacuum insulation inside makes for lower heat losses than a conventional hot water cylinder, boosting the efficiency of the system. The battery can be charged by heat pumps and solar PV, and by grid electricity which allows householders to benefit from off-peak tariffs.
This solution has been tried and tested in homes across the UK and beyond, fitting seamlessly into newbuilds, retrofits and even Passivhaus projects. In Thurrock, Thermino heat batteries and networked ground source heat pumps replaced old storage heaters in 273 social housing flats. This is expected to cut energy bills by 67% for residents and lead to a 70% reduction in carbon emissions.
Thermino heat batteries are also installed in 10 social housing flats in Dalkeith– four existing properties with electric heating, and six newbuilds which are built to Passivhaus standards. James McLeish, site manager for Morris & Spottiswood on behalf of Midlothian Council, said “The client and the tenant have raved about how much it’s saved on their bills since they’ve moved in.”
In London, MKM Developments chose to include Thermino heat batteries in the eco-friendly Whetstone Green Apartments development. The batteries store energy from solar PV to provide on-demand mains pressure hot water for residents, helping the apartments to achieve EPC A rating.
This versatile system is a great option to include in any net zero home, helping to cut carbon emissions, reduce energy bills and comply with upcoming regulations.
