New homes will have a ban direct emission heating systems (oil & gas) in Scotland from 1 April 2024. The Scottish Government have used the New Build Heat Standard (NBHS) to ban the installation of ‘direct emission’ systems for heating for new build homes and other buildings in Scotland. This means any new build applying for building warrant after 1 April will not be able to use gas or oil boilers.

It also states examples of zero emission heating systems that that might be used:

• Heat Pumps
• Heat Networks
• Electric (resistance) heating
• Solar Thermal
• 100% Hydrogen

It does not state a list of what is a emission generating heating system but the press release from the Scottish Government says it is oil, gas and biomass heating systems.

Basically I think the Scottish Government want to ban oil and gas boilers, but only have powers to control for air quality, hence the ban on ’emissions’ from the heating system. While I agree with the ban on oil and gas for new build there are several questions to address with this change.

““Direct emission heating system”, in relation to a building, means a fixed combustion appliance installation…the purpose of which is to produce thermal energy by which space within the building is heated or cooled, or by which hot water is made available in the building” Technical Handbook – Domestic

The regulations still have a number of ambiguous points that are not very well explained:

1. Ban on biomass but what about stoves?

The handbook says that “there will be situations where some form of fixed ‘emergency heating’ are sought in new buildings and this is recognised. This may be relevant both to buildings where maintaining heating is a critical function and to those in remote and rural areas where there are concerns about the historic resilience of the energy supply” and also that “Emergency Heating” means a fixed combustion appliance installation which is installed to be used only in the event of the failure of the heating or hot water service system which is designed and installed for use during normal operation of the building”.

There are a good few paragraphs on the use of ’emergency heating’ stating that portable heaters are not subject to regulations and it hints that the ’emergency’ is generally around a power cut scenario (although how this is policed is not stated).

In addition, heating for frost protection is not regulated. Generally this would be <12W/m2. Say your main living room space was 45m2 this could allow a 540W stove or gas heater potentially. Most stoves are ~3-5kW so would be banned but you could have gas heater at 0.5kW.

It is not clear (to customers we speak to) if:

a) wood stoves are allowed or not in this category. Some customers are arguing their stove is just for “decoration” and not providing the main or secondary heating to the house. In the software for assessing buildings compliance (the SAP) the stove is added as secondary heating and does have a small impact on the energy and running cost rating of the house. It is also classed as bioenergy, so unless you can argue it is for energy heating in a power cut then it is likely to be banned.

Regulation is via the building warrant, however retrofitting a stove at a later date (after the new build) would still require a building warrant we think as it includes work “associated with a chimney, flue-pipe or constructional hearth”.

However, retrofitting an oil boiler at a later date after the new build could potentially not be subject to warrant as it is exempt under works “associated with a combustion appliance installation” and a “balanced flue serving a room- sealed appliance”. You cannot generally get balanced flues for wood burner stoves as they need a natural draw from a chimney or flue.

b) if the intention is to ban wood stoves why this hasn’t been stated?

The use of wood stoves (whilst widely recognised to having urban air quality issues), can have considerable benefit to homes with say heat pump systems. This is because heat pumps work harder in cold weather and can thus draw more power off the local grid on the coldest days. The use of a wood stove as a back up heater makes very good sense in sub zero cold scenarios on remote rural properties with weak local grid infrastructure. In fact in Sweden you are not allowed to install a heat pump in a rural home without having a wood stove for this reason.

It is also part of the local sustainable rural economy producing wood fuel in the highlands, islands and other areas of Scotland and very well regulated.

It seems to be an exemption for remote rural homes to have a wood burner in the living room is a good idea and would prevent a backlash against the legislation on the main point of the regulation- to ban oil/gas boilers on new build.

When we ask our trade bodies we get told they are banned, but when we ask building control officers they say they are not banned and just not to use them in the SAP calculation for the project. There needs to be urgent clarification otherwise the whole regulation could be called in to question.

2. Can communal or district gas/oil heating be allowed?

There is an exemption for ” fixed combustion appliance installation which is a source of production from which thermal energy is distributed by a heat network”. I think this could allow gas or oil boilers to produce heating for multiple dwellings or blocks of flats.

Again I think the legislation is to allow large district heating schemes to go ahead but will also allow say small numbers of properties (maybe only 2 dwellings ?) to share a gas boiler and be exempt.

The history of communal heating has many poor examples where the design and install has been wrong and we could be artificially creating a new industry in communal gas heating rather than the addressing the point of the regulations to promote heat pumps.

Communal and district heating has its place but needs good design and consideration. This was seen for example by the use of mandatory communal heating in schemes in London resulting in large bills to customers due to the heat loss in the networks being added to their bills.

For new builds with only a few houses they would frankly maybe be better installing individual heating systems such as heat pumps in terms of running costs, however, the builder/developer may not see this and install a cheaper gas communal system.

The legislation should be clearer on where communal oil and gas heating is appropriate.

3. Conversions.

It is clear that new build is not allowed to have gas/oil heating, but some conversions and other buildings maybe allowed to use oil and gas.

The regulations state that alternations and extensions are not affected, however, in a conversion then direct emission systems are not permitted if the heating systems is still in that part that is being converted. This means you can still keep your oil and gas boiler if its in a part of the building that is not being converted.

4. Hydrogen is not ready and does actually produce emissions

I am also sceptical of hydrogen for heating. It could be technically feasible to pipe green hydrogen and burn hydrogen, but the independent research work shows the high cost of this approach compared to heat pumps. Also given that we need to be decarbonised at an accelerated pace, the start point for hydrogen is so far behind: the H2 industry think it may be possible around 2035. We need to have already decarbonised heating by 50-75% by 2030 to reach the 2045 target. There is a role for hydrogen, but it is not in low grade heating for newbuild houses (as per Climate Change Committee’s recommendations). It would help if government could categorically state this, as the use of H2 for industrial heating and transport is much better to use in these sectors that do not have more easily implemented solutions to decarbonise.

Also, there is a key difficulty in classifying hydrogen as ‘zero emission’ in that the burning of hydrogen in air can yield up to six times the NOx emissions as burning natural gas and many of our urban centres are already in poor air quality zones. It doesn’t make a credible policy to ban wood burners under emissions but to then allow hydrogen boilers which do emit emissions.

• Dan Gates MSc BEng IEng MCIBSE is a qualified energy assessor and certifier for building standards for energy in Scotland.