Pathfinder - Maynooth University John Paul II Library

Objective

The 2023 Climate Action Plan reaffirmed several targets for public bodies that had been originally introduced in previous iterations of the plan.  These include a requirement that all public bodies must reduce their GHG emissions from burning fossil fuels by 51% by 2030, compared to a 2016-18 baseline.  They must also reduce their electricity emissions in line with anticipated supply-side reductions.  SEAI's pathfinder programme has been working collaboratively with public sector organisations to develop scalable solutions to meet these targets, for benefit across the public sector and the wider non-domestic sector. 

The programme of works will ultimately upgrade the building from a C3 to a B2 Building Energy Rating; the scope of works supported under the Pathfinder programme represents the first steps on this journey.  A range of opportunities and options for upgrade were identified by the design team, including core requirements of roof and boiler replacement.  Carbon and financial savings and costs for each option were calculated.  The project team selected the suite of measures described below based on cost, euro/tonne CO2 abated and return on investment in the context of the overall project budget. 

Project Description

The programme of works carried out under this phase of the project included replacement of the end-of-life boilers, Heating, Ventilation and Air Conditioning (HVAC) system and roof fabric. 

The roof fabric required replacement to mitigate further water ingress and material damage.  Under the Pathfinder project, the original 50mm polystyrene roof insulation, which was in poor condition, was replaced with 120mm PIR insulation.  This reduced heat demand in the building by minimising heat loss. 

The existing fixed speed AHUs were sized to meet the demand of all three floors.  These were replaced with newer units incorporating variable speed drive, higher efficiency fans and motors, more suitable flowrates sized to meet the demand of two floors rather than three, and a thermal wheel to recover heat from the return air. 

With only two floors to heat, reductions in the air volumes, air handling unit heat recovery and improvements to the roof fabric, the heat generation capacity requirements were greatly reduced.  This allowed the selection of smaller boilers, circulation pumps and header pipe diameters.  The existing boilers were old, in poor condition, and were not sequence controlled.  A single pump circulated flow through the boilers, domestic hot water calorifier, reheats and AHUs, resulting in operation throughout the summer, and high standing losses at low heating loads.  Seasonal efficiency was judged to be in the order of 55-60%.  The project replaced the 300-350kW boilers with an 85kW air source heat pump (capable of delivering approximately 66% of annual heat demand), in combination with 2 new 125kW modulating condensing gas boilers (gross efficiency >94%) as back-up heat supply.  The size of the heat pump was constrained by the electrical infrastructure of the building. 

Finally, solar panels (10.9 kW photovoltaic (PV) array (50m2))  were installed on the south-east facing pitched roof.  The solar PV system electricity generation offsets a proportion of the increase in electricity demand associated with the heat pump operation. 

Performance

The project was completed in June 2022, compared to the anticipated completion date of August 2021; the delay may be primarily attributed to the impact of the Covid pandemic on the building sector in general. 

A detailed measurement and verification (M&V) plan was developed for the installation in advance of the works to allow the performance of individual items of equipment to be evaluated (efficiency of boilers, seasonal coefficient of performance of the air source heat pump, savings attributable to VSD pumps, PV), in addition to verifying the total energy savings achieved by the works.  Only total electricity and gas supply to the building (original building plus extension) was available for the baseline period.  The formulation of a plan in advance of the works was key to ensuring that any necessary short-term logging was completed on the original equipment to allow the performance of key aspects of the project - space heating, ventilation, insulation - to be evaluated. 

M&V has been completed to assess the energy performance of the retrofitted building.  Savings attributable to the project are summarised in Table 1. 

Project Savings

Insights

This project highlights the significant savings that can be achieved as part of upgrades associated with end-of-life plant replacement. CIBSE guidance gives an indicative service life of 15-20 years for gas boilers and air handling units; the plant that was replaced under this project had been in situ since 1984.   In order to positively contribute to carbon reduction targets for 2030 and beyond, it is vital that energy saving opportunities are identified and implemented as current operating plant reaches end of life. By proactively planning upgrade works as in this case study example, rather than dealing with plant failure in a reactive way, energy saving opportunities can be maximised.