Modern Building Services

MODERN BUILDING SERVICES OCTOBER 2022 11 FEATURE NET ZERO Upgrading inefficient or ageing heating plant withmore energy- efficient equipment should not be overlooked as an achievablemeans of improving heating reliability and efficiency. Replacing old non- condensing gas boilers withmodern condensingmodels that are up to 20%more efficient, for example, will result in immediate and ongoing energy and carbon savings. To enhance the sustainability of the installation, look for future- ready boilers that are certified to operate on the proposed 20% hydrogen blend and can achieve ultra-low NOx emission levels. Low temperature heating system Inmost projects, it should be possible to address the system’s distribution pipework and heat emitters to operate at lower temperatures than the traditional 82°C/71°C or 80°C/60°C flow and return systemdesigns. This will allow the condensing boilers to operate in condensingmode, where they achieve their maximum efficiencies. It will also future proof the building and prepare the heating system for the integration of low carbon technologies at a later stage, as these operatemost efficiently at low temperature outputs. Comparing energy usage and emissions To understand the savings that could bemade from improving the building fabric and carrying out a boiler replacement, we have carried out comparisons of two energy systems using smart simulation software. For the purpose of the comparison, we have focused on schools, which are, at the time of writing, struggling to absorb a 200% increase in heating bills and remain open without additional funding. We have assumed a secondary school that currently relies on an old 500 kWnon-condensing gas boiler, running at 80%efficiency for heat, with a 1,200 litre indirect hot water cylinder. The school has 40 classrooms, an assembly/sports hall, a shower block with 10 showers and 10 changing rooms, a kitchen, dining area, offices and corridors. The school has 1,000 children on roll. The simulation software calculates the total annual fuel and/or electricity consumption of the old system to be 1,081,994 kWh. Complex retrofit challenges combined with budget constraints mean that the project cannot be engineered fully with just ASHPs at present. The recommendation is to carry out a stepwise refurbishment programme, with each stage designed to be able to be completed during the school shutdown period. The first phase involves carrying out fabric improvements and a boiler replacement to improve the efficiency of the system. Fig.1 Following the implementation of this first phase, the simulation software calculates a fall in the system’s total annual fuel and/ or electricity consumption to 682,380 kWh. That’s a reduction in annual energy consumption of almost 37%. Using SAP 10.2 carbon intensity figures of 0.21 for gas and 0.136 for electric, we calculate that the annual carbon savings from this approach are 83,918 kg. Step three – multivalent solutions Multivalent methods of heat generation cannot be ignored as an important step in the heat decarbonisation process. Returning to our secondary school simulation, the recommendation for the second phase of the heating refurbishment programme is to integrate a ASHP into the system. The simulation reveals that the total annual energy consumption after this phase falls by 134,000 kWh – nearly half the total of the original system. The annual carbon reduction from this latest phase amounts to an impressive 235,006 kg. Fig.2 Clearly, a fully served ASHP buildingwill achieve one of the lowest carbon footprints in new and well- insulated non-domestic buildings. But where an all-electric approach is not feasible due to affordability, budget constraints or technical limitations, these simulations illustrate how a phased approach can achieve important energy and carbon savings at every stage. The heat decarbonisation challenge is far fromnew. But against a backdrop of surging energy prices, unsustainable running costs, rising inflation, higher wages and squeezed budgets, the energy trilemma is more complex than ever. By working together, we can achieve the most appropriate solutions for organisations, balancing best performance for budget value with best practice for heat decarbonisation. In so doing, we can do our bit to help them navigate a course through the energy crisis and continue their journey to net zero. These simulations have been taken from our new guide Schools and the heat decarbonisation challenge. To read the full report, visit: www.baxi.co.uk/knowledge More information can be found at www.baxi.co.uk Fig.1 Fig.2