The UK Green Building Council’s ‘Net Zero Carbon Buildings: A Framework Definion’ provides the property and construcon sector with clarity on the outcomes required for a net zero carbon building. It is intended to be used by building developers, designers, owners, occupiers and policy makers to inform the development of building tools, policies and pracces that increase the uptake of net zero carbon buildings.

Beverly Quinn, Environmental Engineer at TÜV SÜD, an international building services engineering consultancy, specialising in sustainable MEP (mechanical, electrical and public health), BIM (Building Information Modelling), lighting design, and vertical transportation.

ENERGY MANAGEMENT Achieving net zero carbon buildings

In the UK, building stock appears to suffer from a ‘performance gap’ where modelled building energy performance does not equate to actual in-use performance. However, the reality is that the results from the calculations carried out to show compliance with Section 6.1 Carbon emissions and Section 6.9 Energy Performance Certificate, under the Building Standards Technical Handbook, should not be viewed as an ‘in use’ prediction as the mandatory standards do not allow an operational energy set up. A building’s in-use energy should therefore be separately calculated during the design stages and be measured and reported on an annual basis while in operation, to accurately address its carbon impacts. Reporting on an annual basis takes into consideration seasonal variations and provides a standard and easily comparable measures between buildings. The building’s annual energy use should be reported as a total (kWh) and in terms of intensity (kWh/m 2).

Wholelife carbon reducon The percepon of energyecient buildings as a business opportunity is growing Net Zero Carbon  Construction

The carbon impacts related to the product and construction stages of a building are significant, in some cases accounting for half a building’s whole life carbon impact.

To determine the building’s carbon impact and drive carbon reductions, a whole life carbon assessment should be undertaken and disclosed for all construction projects, as this addresses a building’s entire carbon impacts throughout its lifecycle. A whole-life carbon assessment should also be undertaken in line with the RICS Professional statement ‘Whole-life carbon assessment for the built environment’. Buildings aiming to achieve net zero carbon for construction should address all embodied impacts from the building’s produce and construction stages, up to practical completion. The carbon to be offset should be determined through the whole-life carbon assessment and undertaken at completion. Developers aiming for net zero carbon in construction should also design the building for net zero carbon for operational energy.

Net Zero Carbon – Operational Energy

Buildings consume more than onethird of total enduse energy


The energy used in the operation of existing buildings represents the most significant carbon impact, contributing 30% of the UK’s total emissions in 2017. So, Net zero carbon operational energy is probably of more direct interest to building-services engineers. The scope of net zero carbon for operational energy is defined as: “all areas under operational control that have been used to demonstrate a net zero carbon balance”. The energy scope should also be disclosed to allow comparability between buildings.

The use on on-site fossil-fuel generation is currently permitted under the framework for net zero carbon operational energy. This is in recognition of the current prevalence of gas heating for the existing building stock and uncertainty about the use of the gas grid for future low-carbon heating.

Investing in energy efficiency and demand reduction is the most cost-effective way to minimise the new infrastructure that will be required to achieve a zero-carbon energy system. The building should target reductions in energy demand and consumption to reduce the amount of total electricity supplied, from both the grid and renewable energy sources. By quantifying the extent to which renewable energy offsets are being used to achieve a net zero carbon building, the market will be empowered to appreciate the building’s energy intensity and autonomy in achieving net zero carbon. The building is considered to be net zero carbon for operational energy when its total annual net CO2e emissions equal zero and these calculations have been audited by a third-party.

The approach used to reduce energy demand and consumption will vary between buildings, but considerations may include: • Building fabric and passive design – reducing the overall energy required to operate the building. Improvements include efficient fabric and shading, natural daylighting, natural ventilation, appropriate sizing of building systems to limit over-engineering.

• Systems energy efficiency – using highly energy efficient building systems across HVAC, lighting, vertical transport etc.

• Energy management – implementing smart energy/building management systems. Improvements include energy auditing, managing occupant behaviour, managing ‘peak loads’, adjusting HVAC temperature set points, achieving ISE 50001 accreditation. The physical wellbeing of occupants should also be considered alongside energy reductions, such as considerations around indoor air quality, daylighting and overheating.

A third and future definition for net zero carbon buildings would be ‘whole-life’. This is defined as: “When the amount of carbon emissions associated with a building’s embodied and operational impacts over the life of the building, including its disposal, are zero or negative.” Net Zero Whole-life would ensure that a lifecycle approach is taken to make informed decisions about building design and operation. This would encourage design for flexibility, adaptation and deconstruction to minimise end-of-life impacts and enable a circular economy within the built environment. However, this approach is not currently covered by the framework due to the limitations in reporting carbon from the maintenance, repair, refurbishment, and end-of- life stages of a building’s lifecycle.

Future reality

While the World Green Building Council is dedicated to supporting market transformation towards 100% net zero carbon buildings by 2050, it does recognise that in most situations, net zero energy buildings are not feasible. It therefore states that buildings that are energy efficient, and supply energy needs from renewable sources (on- site and/or off-site) is a more appropriate target for the mass scale required to achieve Paris Agreement levels of global emission reductions. Our clients are now typically asking for operational energy and carbon calculations to be carried out to assess where their buildings sit in relation to a net-zero carbon future. This gives them a starting point if net-zero carbon is a future aspiration as it indicates their future energy usage.

Going forward, the UK Green Building Council’s report states that on-site renewable energy sources should be prioritised. This means that the UK must increase its total supply of renewable electricity whilst simultaneously reducing demand on the electricity grid. This approach also helps to support a decentralised system, which would see a reduction in transmission losses, making the system more efficient than the more traditionally centralised energy generation systems we mostly rely on today.

About TÜV SÜDgb/realestate

TÜV SÜD’s Real Estate division is an international building services engineering consultancy. Its mechanical, electrical and sustainable design solutions help to ensure that buildings meet evolving legislation and technology requirements. Specialising in sustainable MEP (mechanical, electrical and public health), BIM (Building Information Modelling), lighting design, and vertical transportation, it delivers complex engineering projects across all sectors, from bases in the UK, Ireland and the Middle East.

One of the few MEP consultancies in the UK to be ISO 19650 certified, TÜV SÜD’s Real Estate division is part of TÜV SÜD, one of the world’s leading technical service providers, which has more than 24,000 employees located across over 1,000 locations.


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