Heat Pumps Today

Preparing existing non-domestic buildings for the energy transition www.acrjournal.uk/heat-pumps 13 T R A I N I N G Ryan Kirkwood or interrogating the Building Management System – are a good starting place. But there is no substitute for measuring real flow rates in different places and conditions, over a given time. This can be extended to include comparing sample heat loss calculations against the sizing of current heat emitters. Similarly, with Domestic Hot Water (DHW) requirements, compare storage volume against peak usage. Using the data With this real data in place, a picture begins to emerge of how the building operates that should enable us to understand: ° the peaks in heating and DHW usage ° how this compares to the current plant sizing ° whether the heat emitters are correctly sized for the rooms. This information can then be weighed up against the project constraints. For example, let’s consider a building with marginal amount of spare electrical capacity and with an assumed high DHW load and low heating load. If the building’s DHW profile shows that the peaks are easily satisfied with the stored volume, it’s reasonable to assume that recovery periods can be stretched. So one possible option may be for a small heat pump to be utilised in DHW generation. When it comes to heating, the transition from a high temperature heating system to a low temperature heating system will be heavily dependent on the data. Options should not be identified without this – a nontrivial problem given the all-too-familiar unknowns in existing buildings. Depending on the building profile, one option might to bracket the space heating system. Take modular Air Handling Units Back in 2010, the term ‘eco-bling’ sprang into the spotlight when Doug King, visiting Professor of Building Engineering at the University of Bath, used it to describe “unnecessary renewable energy visibly attached to the outside of poorly designed buildings.” He argued that simply adding renewable technologies to a building that is poorly designed and energy hungry is unlikely to make it less carbon intensive. A more effective approach, in his view, would be to start by analysing how and where the building uses energy and then design ways to improve its efficiency. A decade later, his reasoning still resonates. Take Air Source Heat Pumps (ASHPs). Along with heat networks and hydrogen, ASHPs have an important role to play in the energy transition. But spending the entire budget on a heat pump to decarbonise an older, draughty non-domestic building without any other preparation will not necessarily guarantee success. As heating professionals are only too aware, a poorly performing heat pump will result in high running costs, an inadequately heated building, and unreliable heating and hot water. So how to avoid this and ensure that customers achieve best value performance for budget from a heating system refurbishment? Setting pathways First, it’s important to recognise that on every refurbishment project, there will be a number of constraints, such as time, budget, available power and physical space, to name but a few. As most existing buildings will need a series of adaptations to make them heat-pump ready, it’s therefore advisable to encourage customers to identify their immediate, medium and long-term goals at the outset. Putting a clear roadmap in place – identifying the overarching goals, the available time to complete the work, the budget and any funding opportunities – will make it possible to plan out and design the various stages of work. Energy efficiency is absolutely critical to reducing emissions and should always be the initial consideration when addressing existing buildings. Passive measures such as roof and wall insulation, draught proofing and improving the thermal performance of windows and doors should be budgeted for first to reduce energy losses and energy usage. Understanding the building profile Next, understand the building profile. As King outlined, this is fundamental to ensure optimal solutions for each individual building. There are a number of ways to go about gathering data. Desktop studies – which might include combing through utility bills Ryan Kirkwood, Heat Pump Business Development Manager at Baxi, discusses the importance of real data and best practice design to prepare existing building stock for low carbon heating.