Furthermore, with the current building envelope leading to increased energy use, CO₂ emissions and associated operating costs, the building owner identified an opportunity to improve the general performance of the building. To meet these needs, a full strip and re-sheet refurbishment with a built-up steel cladding system was carried out along with an upgrade to the building services.

Prior to the refurbishment, a full analysis of the existing building was carried out including an air pressure test and assessment of the fabric U values.

The existing building

These tables above summarise the cladding and service performance, prior to refurbishment.

Based on this data a full analysis of the building performance was carried out using dynamic simulation modelling software (IES) which indicated a total energy requirement of approximately 300kWh/m₂/year and a CO₂ emission rate greater than 80kgCO₂/m₂/year. .

Further calculations were carried out in IES to determine the potential energy savings following improvements to the building fabric and services of each element of the refurbishment. These included the roof, walls, rooflights, and access doors fabric U values, air-tightness, lighting and heating. These are summarised in the tables below.

Potential energy savings for each element refurbished

Due to the age of the building and the very poor initial U values, enhancement of the fabric insulation gave the greatest benefits. The benefits of air-tightness are most significant once the fabric heat losses have been reduced to a manageable level.

This refurbishment followed current practices and the refurbished building had an achievable CO₂ emission rate of approximately 17.5kgCO₂/m₂/year. This compares favourably with a 2013 Part L compliant building which would have a target emission rate in the region of 15kgCO₂/m₂/year.

Energy and cost savings

Based on National Calculation Methodology occupancy conditions, and current energy costs, a breakdown of the operating cost savings of the refurbished building was carried out. This is summarised in the table below.

Refurbishment saves 75% energy consumption

As well as dramatically improving the overall appearance and longevity of the building by using Colorcoat® pre-finished steel products, the refurbishment has facilitated a 75% reduction in energy consumption, a 75% (625 tonnes) reduction in CO2 emissions, and a 75% reduction in associated operating costs. As a result, the refurbishment delivers an annual cost saving of approximately £130,000 when operated according to the conditions specified in the National Calculation Methodology (NCM). This means that the warehouse now has a better EPC rating so can receive a potentially higher rental income.

Refurbishment saves 75% energy consumption

As well as dramatically improving the overall appearance and longevity of the building by using Colorcoat® pre-finished steel products, the refurbishment has facilitated a 75% reduction in energy consumption, a 75% (625 tonnes) reduction in CO₂ emissions, and a 75% reduction in associated operating costs. As a result, the refurbishment delivers an annual cost saving of approximately £130,000 when operated according to the conditions specified in the National Calculation Methodology (NCM). This means that the warehouse now has a better EPC rating so can receive a potentially higher rental income.

Post refurbishment assessment – how could the refurbishment have been improved?

Our post refurbishment analysis of the project highlighted a number of further improvements that could have been carried out. Using a high reflectivity internal liner product, such as Colorcoat® High Reflect pre-finished steel, with a minimal additional cost initially, could reduce light energy requirements by a further 10% and achieve yearly savings of around £1,500. There were also several thermal cold bridges associated with the original construction and poor installation practices which could be designed out. Plus, alternative rooflights with a lower U value could have been specified at minimal additional cost or significant reduction in light transmission. With minimal additional budget and improved specification, the renovated building could have achieved even better results with regard to energy and cost savings.