The path to net zero: how our built environment is set to be transformed

In its latest report, the Committee on Climate Change (CCC) has encouraged the government to use the country’s recovery from covid-19 to accelerate the transition towards a net zero carbon economy. The construction industry is likely to be at the forefront of these efforts, with changes to Part L of the Building Regulations (which governs energy performance) for new homes in England and Wales set to be published before the end of the year and consultations on changes for all other buildings expected to open soon. This move will bring both challenges and opportunities for the industry, and to properly prepare, it is important to have a clear vision of what net zero buildings will look like.

Decarbonising supply

One key aspect of the net zero transformation will be the move from traditional gas and oil heating systems to decarbonised sources. This will include increased electrification, through the use of technologies such as heat pumps supported with onsite renewable generation, along with the use of district heating schemes on larger projects.

The Scottish government has stated that all new homes will need to use renewable or low-carbon heating systems from 2024, with these systems also phased in for non-domestic buildings at the same time. Similar changes are expected as part of the revisions to Part L in England and Wales in 2025.

Any move to decarbonise supply must be matched with work to significantly limit energy demand

此举带来了一些明显的障碍。目前，热泵技术的成本很高，而且从长期来看，电力供应的成本明显高于天然气。因此，必须注意确保业主能够负担得起有效地加热他们的物业。

还有一个季节性的问题。在冬季，当需求最高时，较低的温度、较低的太阳角度和较短的白昼降低了空气源热泵和光伏发电的效率。This could place considerable strain on the national grid, particularly as we move to electrified vehicles, potentially raising carbon emissions.

As such, any move to decarbonise supply must be matched with work to significantly limit energy demand.

Fabric first

TheCCC estimatesthat space heating demand for a typical net zero home should be within the range 15-20 kWh/m²/yr – a significant reduction on the current UK average estimated at 130-140 kWh/m²/yr.

为了达到这一目标，性能将需要达到优异的热性能水平。在最近的威尔士L部分咨询(见表1)的概念住宅目标中提供了预期达到的u值的良好指示。这些要求高的目标将更加强调材料的导热系数(lambda值)，因为使用性能较低的绝缘材料(导热系数较高的材料)可能会比按照当前标准建造的材料显著增加施工深度。

Table 1: Proposed U-values for both notional dDwelling options within Welsh Part L domestic consultation

	U-value
Floors	0.11
External walls	0.13
Flat and pitched roofs	0.11

There will also be a greater emphasis on accuracy of design and installation around details to prevent thermal bridges, and tougher airtightness targets with clean air supplied through mechanical ventilation heat recovery systems. This focus on detailing and airtightness is likely to see increased adoption of offsite solutions, such as structural and steel-faced insulated panels, which combine precise fabrication and excellent out-of-the-box fabric performance with a fast-track build programme.

It is likely that measures implemented on new and existing buildings will be expected to be recorded within a digital passport along with monitoring data of the actual building performance

All measures should be designed using a whole-building approach to ensure they function effectively. This is particularly crucial for existing buildings, where the unique characteristics of the property need to be taken into account. PAS 2035 provides a clear framework for how energy improvements can be delivered on domestic retrofit projects while avoiding potential unintended consequences.

It is likely that measures implemented on new and existing buildings will be expected to be recorded within a digital passport along with monitoring data of the actual building performance. This monitoring is seen as key to upholding standards and closing the performance gap.

By adopting this approach, it should be possible to minimise the building’s emissions. Any remaining demand will then need to be met through a recognised offsetting scheme.

Meeting the challenge

The move towards net zero carbon building will require significant upskilling with the construction industry. By meeting this head on and looking to implement best practice now, firms can place themselves well for future opportunities whilst ensuring their buildings form part of the solution to this global effort.