Non-domestic buildings - heating systems: research report

5. Impacts of installing zero emissions heating

5.1 Overview

The following impacts of installing or retrofitting ZDEH technologies into new and existing buildings have been identified via our stakeholder interviews for the ZDEH case studies. The table below provides a brief description of these impacts and an overall rating based on scoring across the 16 case studies that are occupied buildings (4 being under construction). Notably, all of these impacts are negative, except for end-users, which were found to be both positive and negative.

b. Impacts on operation

i. Snagging

Four case studies experienced some form of snagging issue on commissioning. Only one case study cited system balancing issues and this was due to internal heating zones needing to be rebalanced to provide enough heat at the entrance vestibule. In one of the biomass boiler case studies, snagging occurred due to the system being located outside, meaning that the internal Building Management System was not able to communicate with the biomass boiler plant. This took approximately a year to fix, and the building’s energy manager felt this issue could have been mitigated through enhanced communication with the building’s IT team prior to the retrofit taking place.

ii. Control

Stakeholder experiences with heating controls varied depending on heating system, size of organisation and control type / set up. The heat pump and biomass boiler systems among the case study projects are all programmed to run automatically. However, one of the biomass boiler case studies noted that its control programme had to be adjusted iteratively to get the right heat output from the biomass boiler. The direct electric systems (panel and space heaters) require manual control, and this had an impact on end user comfort, both suggesting better, and more automated controls would be advantageous.

As well as impacting comfort and heating system operation, controls were also noted to impact costs too. In one case study the building’s sensors had a standing electrical load that was higher than anticipated and the building operator suggested that the control systems had a non-negligible impact on energy costs given this.

iii. Maintenance

Aside from scheduled services (annual for heat pumps and quarterly for biomass boilers), most case studies have not had faults that required unscheduled maintenance. However, specific instances were identified in four case studies. The most extensive maintenance has been required for both of the biomass boiler case studies, including replacement of fuel delivery system parts, but these issues have all been addressed under the boilers’ maintenance contracts. In the leisure centre case study, the placement of the heat pump units in the same plant room as the pool’s water treatment system led to corrosion of the units’ casing and ancillary pipework, due to the corrosive atmosphere created by the chemicals in the treatment system. Additionally, one of the DHN case studies experienced unscheduled maintenance. This should have run smoothly, given the DHN maintenance company is required to provide plug-in electric heaters for unscheduled maintenance, however, staff were not made aware of this initially.

Anticipation of unexpected maintenance was factored into design and decision making, with most case studies having some form of back-up power or resilience designed in, to ensure building operations were not interrupted. For example, the two biomass boiler case studies retained their original gas systems, oil boilers were retained to back-up one off-gas grid heat pump, a backup electric boiler and an oversized heat pump were used in another case study, and diesel generators are used as back-up in one case study.

Another example of designing for maintenance includes the positioning of the system components. One case study mentioned that the underground manifold for the heat pump was designed and positioned to minimise maintenance requirements and provide easy access, if required.

iv. Running costs

Only two of the retrofit case studies provided annual running costs. Total electricity demand fell by a quarter following the replacement of electric boilers with an ASHP in one case study, whereas the gas to biomass boiler retrofit case study saw a 10% increase in fuel costs following the retrofit. Given that we were only able to collect two data sources, it is not possible to quantify or estimate the impacts of installing ZDEH on running costs for other case studies or indeed other buildings. However, anecdotal evidence from stakeholder interviews has been collected, as provided below.

Five case studies reported concerns with operating costs. Three of these have direct electric heating systems and their building owners have considered retrofitting a range of technologies to replace direct electric heating and reduce costs, including gas generators, Solar PV, battery and ASHP. An ASHP was retrofitted in place of direct electric heating in one of the three mentioned previously several years later as electricity costs had been higher than anticipated.

The other two case studies reporting high operating costs (anecdotally) had AHSPs. One was considering undertaking further analysis (if grant funding can be secured) into installing a battery to store the existing excess solar PV to divert into the ASHP, which would allow for reduced electricity costs. The second found through investigation that the kitchen appliances had high electrical loads which were the cause of the high costs and not the ASHP.

v. End user impacts

Various negative end-user experiences were noted in six case studies, including lack of comfort in certain spaces, lack of confidence with controls post-handover and low satisfaction with direct electric systems. For example, the staff at a school found the building to be stuffy, due to ventilation actuators being broken, and remaining so for a long time due to the difficulties in sourcing replacement parts and in getting contractors to the rural location. Another case study mentioned that staff thought they did not receive sufficient education at handover. Two buildings experienced colder temperature and drafts, so plug in electric heaters were installed to raise user comfort in two of these.

Two case studies highlighted positive end-user experiences. Firstly, the building’s elderly occupants of a care centre built relations with the heating contractors during the ASHP retrofit install through taking an interest in the process. This led to a positive learning experience and increased awareness of sustainability among the end users. It also fostered goodwill with the contractor, which led to a thorough handover process and generous post-completion support for staff. Another case study building owner was very involved in the installation of the building’s GSHP, even assisting with construction. They also expressed a desire to learn more about the system so that they could perform future maintenance as necessary.

vi. Additional impacts

For three buildings, the heating system was noted to impact business or building operations. One building was noted to sometimes be too hot in summer, which posed a risk to perishable goods in the building. At the second, the biomass plant and fuel store are in a secure compound and the police require advanced notice of fuel deliveries, so that any impact on access to the compound can be mitigated. At the third, it was discovered during the first year of occupation that extractor fans in the kitchen impacted heating by removing heat from the building. This was easily addressed by ensuring that staff did not leave fans running overnight.