The construction industry is currently undergoing a transformative period with considerable expectation now placed on the sustainability consultant or team to make core decisions on what technologies will allow a building to achieve sustainability and pass its part L calculation. This level of decision making has handed a great deal of power to the sustainability consultant, but it also puts great pressure on them to be experts on widely varied systems within the building and the legislation that surrounds them.
Where the fabric, renewables, heating and cooling systems should be perceived to be primary, and therefore the most important considerations, domestic hot water (DHW) systems, hybrid integration, controls and current gas procedures (which remain relevant in commercial properties, especially if a building is intended to move to green hydrogen in the long term) could be termed as secondary systems. Designs including non-traditional and secondary systems are where the sustainability team can be at a disadvantage due to the vast amount of changing information that they need to keep abreast of. Any gaps in this knowledge can potentially impact project delivery, optimisation of systems and, importantly, the ongoing running costs across the life of a system.
With DHW applications the primary issues are always going to relate to correct sizing based on the demands generated by a building’s occupants and choice of system. These can be based on application, energy source, suitability, and integration with carbon saving technologies,
Oversizing DHW systems inherently comes from a lack of understanding of hot water demands within the building, diversity, and length of the peak period. Oversizing is exacerbated by the false belief that the building uses more hot water than it really does, and an attitude of ‘better too much than not enough’. Sizing programmes, often employed for a quick sizing early in the design then never reviewed, do not deal well with the many variables and decisions on diversity leading them to oversize to prevent hot water problems. Traditionally the problems with oversizing, such as increased standing losses, increased outlay costs, increased pipe sizes, and increased space use may have been minor in terms of the cost of the whole building, but it now has another important knock-on effect. If the hot water consumption is overinflated, it falsely increases the expectation of the building’s carbon emissions. This then requires greater employment of renewables to reduce emissions which do not actually occur. This can come at great cost and complication and provide little benefit to the building. Access to realistic sizing tools and having the experience to interpret results requires both expertise and time, which specialist application design can bring to a project.
The integration of renewables, such as air source heat pumps (ASHP), heat recovery and solar thermal, will further increase the complexity of a system. Renewable technologies are going to be selected early in the design process to secure the Part L approval, once modelled successfully it is not wise to start changing things too severely. Small changes, such as revising the manufacturer of an appliance is going to make little difference within Part L, but if you have to add, remove and replace a technology, then you are going to be back at the beginning, and will almost certainly need to resubmit your Part L calculations. These early selection decisions increasingly reside with the sustainability consultant before the design engineer is involved, which means they need a broad knowledge of building services systems beyond the renewables themselves. Working together with specialist application design means they can better advise on selecting the right type of renewable to ensure it will integrate with the rest of the system and be controlled to work with traditional technologies. It is very important that renewable heat sources, particularly those that provide low-grade heat, are not held off by traditional boiler systems providing high-grade heat to high-temperature systems. This is not purely a controls issue but one that requires an in-depth understanding of the complete system arrangement to set it up effectively.
Faced with a tremendous number of variables, from technology to regulations, accepting specialist application design aid can be the easiest, and most effective way to gain proven, technically astute advice, regulatory insight, and application modelling which will address the needs and expectations of the contractors working on the building. Working together with a secondary system specialist helps ensure a building’s applications are fit for purpose whilst still helping to meet the requirements for sustainability.