Maynooth University has identified a rolling programme of critical upgrade works in the original Library building.

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. 

 

  • Electricity Savings

    84,050 kWh/y
  • Gas Savings

    570,750k/y
  • TFC Savings

    64 kWh/m2
  • C02 Savings

    133 toness/y (2022 emissions factors)
  • Abatement cost

    €7,260/tC02 (single year's C02 savings)

Background

The John Paul II Library is a higher education facility, completed circa 1984.  The upper two floors accommodate open plan reading areas along the building periphery while the central areas provide the book storage, circulation and ancillary spaces.  The ground floor acts as the administration hub for the library operation activities.  The original design intent for the building was full mechanical ventilation, with separate rooftop air handling units (AHUs) each serving a quadrant of the building down through the 3 floors.  The recirculating AHUs had heating and cooling coils; local reheats provided zone temperature regulation.  Hot water was provided from a 1000 litre calorifier, heated by the main heat generators, two Buderus Logano boilers.

In 2012 a substantial extension was built to the front of the original building.  As part of this project, the ground floor in the original building was upgraded, and new, much smaller, AHUs installed providing tempered air to meet occupancy requirements.  Local fan coil units (FCUs) were installed, providing zoned heating and cooling.  Associated with this was a new heating system, cooling system and separate Hot Water System (HWS) serving the ground floor and extension.  The original AHUs and boilers continued to serve the upper floors of the building. 

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

 Electricity Savings kWhThermal Savings kWhCarbon Savings (tonnes C02)
PV 9,740 - 3
AHU & Circulation Pumps  93,330 - 31
Heating upgrades  -19,020 570,750 99
Total 84,050** 570,750 133

* Based on 2022 emission factors 

** Savings on imported electricity 

Performance of the solar PV system can be compared to predicted performance from PVGIS (photovoltaic geographical information system – software available through the EU Science Hub, which may be used to predict PV performance at any location in Europe), as shown in Figure 3.  Annual generation (normalised to a ‘standard’ year of solar irradiation) was just 0.6% lower than predicted. 

While the heat pump was expected to meet approximately 80% of annual heat demand, analysis indicates that in practice, the heat pump only delivered 22% of annual heat from March 2023 to February 2024.  BMS controls inhibiting boiler operation and allowing sufficient time for the heat pump to respond to changes in heat load are expected to address this issue.  Ongoing problems with the heat meter mean that it has not been possible to calculate an operational Seasonal Coefficient of Performance for the heat pump. 

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.

Learn more about the Pathfinder Programme