Sustainability Series – Project Fitzwilliam

Sustainability Series – Project Fitzwilliam

Design, Sustainability, Work

Project Fitzwilliam – ESB Headquarters – BREEAM Excellent & Near Zero Energy Building

This 45,000 sqm development delivered a Near Zero Energy Building.  It involved the demolition of the existing buildings, the retention and refurbishment of protected Georgian structures and the construction of a new seven-storey office block. The office blocks were developed as grey box for tenant fit-outs.  Key principles of the design were sustainability and energy saving methods.

The design incorporated openable windows to utilise natural ventilation to reduce overall energy use. Heating and cooling in the office space is facilitated through an energy efficient central plant.

One of the key measures is providing cooling and heating in a sustainable way.  This was achieved by 4-pipe heat pumps together with thermal storage. This allows for simultaneous generation of chilled and hot water at optimum external conditions, allowing the energy to be transferred from the cooling process to the heating process and not discharged as waste heat.

Sustainable Strategies

There are several sustainable strategies utilised in the building.  They have addressed building fabric, servicing, water, renewables and overall energy certification.


The building has a series of courtyards which maximise daylight, minimise solar gain and incorporate openable windows to allow the office space to be naturally ventilated. The fabric has been designed to exceed the Building Regulations’ requirements and to maximise the building performance. In addition, the construction of the building has resulted in a high level of airtightness in the order of 2 m3/hr/m2 at 50 Pa.


The office blocks encompassed sustainability and energy saving methods as key principle of the design and the office space was developed as grey box for tenant fit-out.

Heating & Cooling

The servicing strategy involved the provision of cooling and heating by 4-pipe heat pumps with thermal storage.

Phase-change materials are utilised as a thermal store which allows cooling to be stored and generated at the same time as heating. The cooling is stored and then utilised at a time when there is no heat demand to avoid a requirement to run the heat pumps.

The adoption of this storage allows for simultaneous generation of chilled and hot water at optimum external conditions. This allows the energy to be transferred from the cooling to the heating process and not discharged as waste heat – making it as efficient as possible.

Hot Water

Hot water is generated utilising water-cooled heat pumps. The heat pumps are connected to the central heating system and utilise the low-grade heat supplied from the central heat pumps generate hot water centrally.

This process allows for the energy efficient generation of hot water and assists with the simultaneous generation of heating and cooling on the central plant by providing a baseload for the central plant when there are minimal heating requirements.

Water Use

As part of the sustainable strategy relating to the use of potable water, the following strategies have been employed:

  • Low-use fixtures and fittings
  • Use of borehole water for WC flushing
  • Provision of rainwater harvesting for future extension by tenants


As part of the renewable energy drive in the building, heat pumps have been utilised as the primary source of heating and cooling.   In addition, a PV array has been provided to supply energy.


The building sustainable objectives have been measured through the BREEAM assessment process during the design and construction. The development achieved BREEAM Excellent.

Associated Costs

In terms of cost, some of the key expenditure was on the central heating and cooling systems. The rationale behind this was that some of the larger energy uses in the development related to the central plant and key efficiencies could be achieved by utilising thermal storage and energy efficient heat pumps.

In addition, other sustainable measures that impacted on the cost were:

  • A PV array
  • Water boreholes
  • Geothermal collector for use as part of the tenant fit-out works

High-Performance Building

There are several drivers for a high-performance building which include:

  • Demonstrating an all-electric building could be sustainable.
  • Although all electric buildings are more common now with the multinational tech companies driving towards removal of fossil fuel systems on site for their offices, at the time of design most office developments included gas-based heating and hot water generation. The completed building demonstrated this is achievable.
  • Creating a flexible building:
    • The goal was to create a flexible building for tenant fit-out and provide the option to naturally ventilate or comfort cool the building.
  • Improved performance:
    • The goal was based on an allowance for tenant fit-out (currently grey box) that the development would achieve a potential BER of A3. The analysis carried out indicates that a tenant fit-out with comfort cooling on the floors will allow a potential A3 BER to be achieved.

Internal Environmental Quality Strategy

Internal Environmental Quality has been a key consideration for the building in terms of allowing a tenant fit-out to have good access to daylight and high levels of air quality.

To maximise air quality and operate in a sustainable manner, the central ventilation plant is linked to sensors on each floor which can change the air supply rate based on the air quality in the space.

Additionally, openable windows are provided to allow a tenant to employ a naturally ventilated solution should they prefer not to use mechanical ventilation.


In summary, the building has demonstrated that multiple sustainable technologies such as heat pumps, thermal stores and groundwater together with efficient natural or mechanical ventilation can be harnessed together to provide a sustainable building.

The building demonstrated what could be achieved with an all-electric building when they were not common and showed that the on-site use of fossil fuels can be removed. The removal of fossil fuels improves the air quality in our cities and the development has a resulting positive impact.

The all-electric nature of the building allows for the carbon impact of the ongoing operation of the building to be reduced through sourcing sustainable electricity.