How to decarbonise an existing building

There’s no denying the importance of sustainable outputs in all forms of engineering today. According to the Central Statistics Office, Ireland had the second highest emissions of greenhouse gases per capita in the EU27 in 2021 at 12.3 tonnes of CO2 equivalent highlighting the need to transition all buildings, infrastructure, and human settlements to net zero carbon as rapidly as possible. Minimising fossil fuel usage in the built environment can alleviate the ever-increasing carbon emissions, and the global climate change crisis we are constantly facing.

One of Ireland’s leading commercial property companies, IPUT, contacted our Dublin sustainability team to discuss the opportunity to reduce the carbon emissions from Riverside Two in Dublin city centre; a six-storey riverfront office building.

Our team developed a strategy to reduce carbon consumption and optimise the building’s energy use within a live operational working environment.

The challenges

One of the challenges we faced in the early stages of the project, was to provide a solution to decarbonise the building's centralised plant without the need to decant or impact the occupied tenants. To overcome this and ensure continuity of service to the tenants in the building, we implemented a phased approach for the removal of the existing plant and services system on the roof while transitioning to the newly installed plant.

The data

To investigate the current building's energy usage, we carried out a feasibility study through analysis of BMS operational data, and reviewal of utility bills over an 18-month period.

As part of the analysis an Integrated Environmental Solutions Virtual Environment (IES-VE) model was also created to carry out a dynamic thermal analysis of the building to calculate the actual annual cooling and heating demand. The loads were normalised by using utility data for the building and this process allowed us to accurately model the heating and cooling demand and size the heat pumps on actual energy usage rather than on a like-for-like basis.

Our solution

To remove fossil fuel usage for heating and hot water on the site, all-electric heat pumps were installed to decarbonise the building.

Upon reviewing the building’s occupancy form, we discovered that the existing air handling units (AHUs) were selected based on a higher occupancy rate compared to the actual. As a result, smaller AHUs were selected that reduce the running cost while still providing a generous fresh air rate per occupant.

To maximise the lower temperatures from the heat pump the new AHUs were designed to operate at the lower temperatures and recover heat from the exhaust air to increase the system efficiency, lowering the energy used and providing additional cost savings to the client.

The results

As part of the feasibility study, the baseline energy and carbon emission were determined from the building’s utility bills. The baseline energy data was analysed against the proposed system energy usage with the estimated savings shown below.

To verify the reductions a year’s metering data was analysed from the plant in operation. The results for this recorded data show the savings achieved are more than the predicted savings.

For more information on decarbonising pathways or advice on other sustainable initiatives please get in contact.