energy modelling, ESG,

Hollis has seen a significant increase in the number of developers requesting advice on ESG implementation, this is likely to continue as we see governments introducing post-pandemic green recovery plans. Richard Masters and Katherine Beisler at Hollis explain more

President Joe Biden’s decision to rejoin the Paris climate accord and announce other climate-friendly measures within his first few days in office is evidence that the US will take a much stronger stance on cutting greenhouse gases.

Retrofitting buildings poses a unique challenge. It is important to appoint a specialist design team at the early concept stage, and to involve a sustainability consultant from the inception of the project, to identify the condition of the building and the opportunities to implement renewable or low carbon technologies. Doing so early on can save a lot of time and money being spent later in the project.

Using accurate survey data, a software-based digital twin of the building can be generated to perform building physics simulations and to model energy performance. Supplemented with actual meter readings and sub-metered data, the model becomes a powerful tool to identify consumption patterns, conduct performance analysis and ultimately, achieve zero carbon targets producing healthier and more sustainable buildings.

Building Management Systems (BMS) and control packages are critically important to achieving a low carbon development. They ensure that the building services are operating harmoniously and give alerts where systems are faulty or operating outside of set parameters.

The main issue with predictive energy modelling is understanding the end-users’ occupation patterns and building use. The design team should have a good understanding of the occupiers’ needs and use of the building tailoring building services to the end-users’ requirements.

For significant operational energy savings, the facilities management team should commit to a ‘soft landing’ approach and a period of post-occupancy evaluation, where data is periodically gathered from the BMS/BEMs, and commissioning documents are scrutinised to evaluate the effectiveness of the energy strategy.

There is little doubt that a refurbished building with an A+ EPC or an environmental certification such as BREEAM excellent or very good will have a greater market appeal and the property will inevitably command a higher rental yield.

At Hollis, we recently worked with a fund with a European wide industrial portfolio who wanted to make their assets net-zero carbon. We liaised at length with the fund managers to understand their requirements, their energy management strategy and their budget. We used energy modelling for one building in each country they are active in as a sample of their portfolio.

The energy model compared project efficiency options, compliance with upcoming regulation, predicted savings, and informed actual performance; creating suggestions on how to reduce energy use to meet the clients goals. From this we have been able to provide solutions to reach a 30% reduction in energy usage, to meet upcoming legislation if it applies, or full net-zero carbon.

It’s all in the materials

Understanding the existing building fabric and the construction methodology is critical to the success of any refurbishment and will often require intrusive works to identify the existing levels of insulation and condition of the retained fabric.

Modern high-performance construction systems achieve excellent U -values and are typically airtight by design, featuring an appropriate ventilation strategy that maintains sufficient air changes within the building and incorporating heat recovery. Well-constructed and correctly installed fire safe composite cladding can easily achieve an air permeability of less than 3m3/(m2.h)@ 50 pascal.

Traditionally built or historic buildings are typically the worst performing construction type and can be the most challenging to improve to a level of thermal performance necessary to successfully achieve a net-zero building. They rely on a high degree of breathability and unhindered moisture exchanges within the construction. Retrofitted fabric improvements need to be breathable and maintain the moisture equilibrium to prevent inadvertent moisture build-up and inherent damp issues.

It is, therefore, prudent to involve a historic building specialist or to ensure the design team have a good working knowledge of historic structures and the hygrothermal behaviour of traditional construction types.

A BIM or building physics model can be populated with information relating to individual construction types, including the density and thermal mass of each material as well as the associated embodied carbon. This is useful for establishing quantities and to produce an elemental or whole building life cycle analysis – cradle to grave.

Life cycle analysis can help when deciding whether to retain existing elements of a building or to replace old with new. The process can also produce a comparison between different construction types i.e. concrete frame versus steel portal frame. This enables the design team to make an informed decision based on the embodied energy and associated CO2 of a particular construction.

A sustainability consultant will advise the design team and specify materials with a traceable supply chain/environmental stewardship, or materials that have a qualifying Environmental Product Declaration certificate (EPDs), which can be used to quantifiably demonstrate the environmental performance of that product.

For a developer intending on a BREEAM or WELL Certification, the internal fit out of a building is also important. Internal finishes can be a significant source of VOCs and are inherently difficult to recycle or re-use at the end of life, so exploring new and innovative products – such as paint that captures carbon from the atmosphere – is paramount.

Net-zero carbon case study

We recently completed the refurbishment of a 43,036 sq ft warehouse space in London. Remodelling the layout of the unit and extending the square footage by adding a first floor to the ancillary accommodation.

We achieved our client’s aim of net-zero carbon operationally and an Excellent BREEAM rating, as well as adding value to the property.

Some of the key measures implemented to achieve net-zero carbon and the BREEAM certification include:

  • EV charging points for use by the building occupier and the general public.
  • Solar-powered picnic benches enabling building users to work outside, rich biodiverse growing roofs to the bicycle stores, and nature boxes along a woodland walk to attract wildlife.
  • Photovoltaic panels installed to the roof, provide electricity to the premises and any excess back into the network grid, saving approximately £24,000 per annum.
  • CO2 sensors implemented to the office MHVR units increase/decrease the fresh air supply based on the level of CO2 within the office space.
  • Heat recovery up to 85% for additional energy and cost savings
  • Water reducing products, such as non-concussive taps and rainwater harvesting feeds to the WCs, are anticipated to save over 400,000 litres of water per annum.
  • Reclaimed and reused building materials installed including bio-based carpet tiles – 395 square metres of carbon-neutral flooring (Interface Heuga 727) – resulting in the retirement of 4 metric tons of carbon dioxide – the equivalent of the emissions from a car travelling 15,974 kilometres.
  • Installation of a recycled raised access floor to the additional office space to the first-floor office. Re-using the existing raised access floor to the ground floor.
  • Airlite decoration was used on all wall surfaces, which eliminates bacteria and prevents the formation of moulds. It drastically reduces the amount of solar heat absorbed by buildings, thereby reducing air-conditioning energy costs up to 30% and lowering the associated CO2 emissions that cause climate change
  • New energy-efficient LED light fittings producing 161 luminaire lumens per circuit watt.



Richard Masters

Senior energy and sustainability consultant




Katherine Beisler

ESG consultant



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