Identification of a Multifaceted Heating Issue

Appropriate Sizing of Radiators

Improvements in Hot Water Delivery and Temperature Consistency


The project involves an urban residential development comprising of 1700 homes. The architectural layout includes multiple high-rise blocks, each equipped with its own substation. These blocks are interconnected through two distinct communal networks, each powered by dedicated energy centres. Within the residences, individual heating units are installed to provide hot water, complemented by radiators for space heating. Additionally, a comprehensive mechanical ventilation system is integrated throughout the development. FairHeat was engaged by the client to carry out dwelling inspections, a comprehensive review of retrofit calculations, and expert oversight during the commissioning phase.


The primary motivation for the project was to address and rectify issues related to domestic hot water and heating delivery in specific residences. An assessment revealed that the radiators were undersized, failing to account for the volume of fresh air introduced by the ventilation system. This oversight resulted in several living spaces struggling to maintain desired room temperatures. In some instances, significant temperature disparities were observed when internal room temperatures were compared with external conditions e.g. some living rooms/bedrooms unable to achieve more than a 16 °C difference between internal and external temperatures during testing. Furthermore, certain outlets, especially those located on higher floors, experienced prolonged delays in hot water delivery. This inefficiency necessitated the continuous operation of an energy-intensive trace heating solution.

FairHeat Solution

Recognising the additional thermal demands imposed by the mechanical extract system, FairHeat advised a resizing of the radiators. They meticulously reviewed the calculations to ensure that the redesigned radiators would deliver the requisite heat efficiently. During the assessment, it was discerned that the contractor had employed a uniform model for several of the dwelling types, irrespective of their size. This approach inadvertently led to the initial selection of undersized replacement radiators in certain flats, compromising their heating efficiency.

To further enhance the heating system’s performance, FairHeat conducted a thorough evaluation of the existing Heat Interface Units (HIUs). This assessment revealed that the HIUs were not optimally equipped to handle the increased heating demands. As a remedy, FairHeat recommended specific valve upgrades to bolster the system’s capacity. Additionally, the Domestic Hot Water (DHW) control valves were replaced to facilitate quicker response times. FairHeat also explored the trace heating settings, ensuring that hot water was delivered promptly without incurring prohibitive costs.

However, the project was not without its challenges. During the recommissioning phase of the DHW system, inconsistencies in water temperatures were observed. Some outlets, especially in the kitchen, dispensed water at alarmingly high temperatures, reaching up to 75 °C. Upon investigation, a lapse was identified in the insulation placement, which was situated between the control sensor and the pipework. This oversight was promptly addressed to ensure safety and efficiency.


The project resulted in the consistent and safe delivery of hot water within an acceptable timeframe. The ongoing upgrades are scheduled for completion before the winter season, ensuring that all residences will benefit from adequate heating during the colder months, thereby guaranteeing resident comfort.

The project’s success was underscored by its ability to thoroughly assess the details of the heating system and identify the core issues. While heating problems can often be attributed to a myriad of factors, the team’s systematic approach and thorough analysis allowed them to pinpoint the primary culprits. This diagnostic precision was instrumental in formulating targeted solutions, ensuring that subsequent interventions were both effective and efficient. By understanding the root cause, the project not only addressed the immediate concerns but also laid the groundwork for preventing similar issues in the future.

One of the key discoveries during the assessment was the realisation that several radiators were undersized for their respective spaces. This oversight was compromising the ability of the system to heat the residences. Recognising this, FairHeat prioritised the resizing of these radiators. By ensuring that each radiator was tailored to the specific needs of its environment, FairHeat effectively addressed one of the primary challenges. This meticulous attention to detail ensured that every room received the requisite heat, optimising comfort levels and energy consumption simultaneously.

The initiative’s impact extended beyond just space heating. A significant portion of the project was dedicated to enhancing the Domestic Hot Water (DHW) system. Prior to the interventions, residents faced inconsistencies in both the temperature and delivery time of hot water. Addressing this, FairHeat implemented a series of upgrades and optimisations. As a result, residents now benefit from hot water that is not only delivered more promptly but also maintains a consistent and safe temperature. This enhancement has significantly improved the daily living experience, ensuring that activities like showers and cooking are seamless and enjoyable.


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