HIU or Heat Interface Unit is a device that transfers heat from a centralised heating system, often found in district or communal heating networks, to individual residential or commercial units providing controllable heating and hot water. Commonly used in apartment blocks HIUs are the backbone of district heating systems providing central heating and hot water in individual properties
Acting as the crucial link between centralised heat sources and individual dwellings HIUs play a vital role in efficient heat transfer, control and distribution within each dwelling. There are various types available such as single plate HIUs, data HIUs, twin plate HIUs and data split HIUs.
With their ability to optimise energy usage and provide tailored comfort through either radiators or underfloor heating, user control with traditional or smart heating controls such as TRVs and room thermostats allows a seamless transition for those used to traditional gas boiler heating systems. In this article we will dive into how these little powerhouses keep us snug while saving energy and providing DHW (domestic hot water)
The Facts & Benefits of Heat Interface Units
Heat interface units (HIUs) are an innovative and energy efficient solution for heating residential and commercial buildings. With their numerous advantages including central boiler compatibility and hot water cylinder connection for direct and indirect hot water capabilities.
Energy Efficiency of HIUs
HIUs offer significant energy saving benefits compared to traditional heating systems. By providing only the required amount of heat to each dwelling or building HIUs help reduce unnecessary energy consumption. This targeted approach ensures that each property receives optimal heating without wasting resources.
As a result, both residential and commercial buildings can enjoy substantial cost savings on their energy bills while minimising their environmental impact. Additionally, HIUs can also be used to provide hot water for domestic use.
Independent Temperature Control of HIUs
One of the key advantages of HIUs is their ability to provide independent temperature control within each property. Gone are the days when residents had to compromise on comfort due to centralised heating systems. These systems were typically set at source and adjusted according to seasons. In effect all occupants of the properties within a communal block were given a predetermined temperature and were not allowed to adjust for personal preference
With HIUs individuals can set their desired central heating or hot water temperature according to personal preferences, ensuring a cosy living or working environment year round
Space Saving Solution of HIUs
Heat Interface Units are typically smaller in size than traditional gas boilers. In addition gas boilers require flues that typically protrude above the boiler casing and require additional consideration both internally and externally. The lack of a need for a flue allows HIUs to be more compact as a unit and can in most cases be easily hidden in a standard sized kitchen cabinet.
Installation Location of HIUs
Unlike gas boilers HIUs do not require internal combustion to take place in order to heat up water. Therefore there are no products of combustion (POCs) and hence no need for an external boiler flue. This allows developers flexibility in choosing the installation location as HIUs do not require close proximity to an external wall nor the need to run lengthy flue extensions in voids that creates issues related to Flues In Voids regulations
Reliability of HIUs:
Unlike gas boilers HIUs contain less mechanical parts such as fans, gas valves and diverter valves, and less electronic parts such as PCBs and sensors. This reduces the number of faults that can arise and typically, HIUs tend to be a more consistent and reliable heat supply. This also reduces the worry for residents about boiler breakdowns or malfunctions
Enhanced Data Accessibility:
HIUs equipped with advanced monitoring capabilities provide valuable data insights for central heating systems. These units collect data on energy consumption patterns, temperature variations and usage trends, optimising overall system performance by identifying areas for improvement or potential maintenance requirements
Landlord Compliance:
The existence of HIUs as the primary source of heating means gas connections and gas appliances are no longer required in rental properties. This reduces the compliance requirements for landlords as an annual gas safety inspection and the need for issuing a gas safety certificate is removed
How Does a Heat Interface Unit Work?
A heat interface unit, commonly known as an HIU, is a crucial component in centralised heating systems. It plays a vital role in distributing heat to individual properties efficiently and effectively.
Receiving Hot Water from the Central Heat Network
At the heart of its operation, an HIU receives hot water from the central heat network through primary pipework. This network serves as the main source of heat for multiple properties within a building or development. The primary pipework carries high temperature water, which is then directed into the HIU for further distribution.
Transferring Heat to Secondary Pipework
Once inside the HIU, the hot water passes through a plate heat exchanger. This device allows for efficient transfer of heat from the primary circuit to secondary pipework connected to radiators or underfloor heating systems within each property. The plate heat exchanger ensures that maximum thermal energy is passed on while maintaining separate circuits for primary and secondary water flows.
Adjusting Flow Rate and Temperature
One of the key advantages of using an HIU in a central heating system is its ability to cater to individual requirements. By incorporating controls such as thermostats, TRVs and flow regulators, users can easily adjust both flow rate and temperature according to their preferences. This flexibility allows residents to create a comfortable living environment while optimising energy consumption in a heat network.
Incorporating Safety Features in HIUs
Safety is paramount and HIUs are no exception. These units come equipped with various safety features that ensure reliable operation while protecting against potential hazards. Pressure relief valves are installed within the HIU to prevent excessive pressure build up in case of malfunction or blockages. Temperature sensors constantly monitor water temperature, providing an added layer of protection against overheating
The Difference between Boilers and Heat Interface Units (HIUs)
When it comes to the heating systems in residential or commercial buildings, the choice often comes down to conventional boiler systems or Heat Interface Units (HIUs). Though these two perform similar functions, they differ greatly in their design, operation and efficiency.
Gas Boilers
A boiler is a self-contained heating system that generates heat by burning fuel, usually natural gas to warm water. This heated water is then circulated throughout the building via radiators, underfloor heating pipes or other heat emitters, providing heat to individual rooms
The boiler also produces hot water for taps, showers and appliances. Each unit or property typically has its own boiler which means each occupant has control over their own heating and hot water timings and temperatures
Boilers have been the traditional method of heating buildings for decades. However they require regular maintenance such as annual services and checks to ensure they are operating safely and efficiently. Each boiler also requires its own flue leading to potential aesthetic and architectural challenges in multi dwelling units
Heat Interface Units (HIUs)
In contrast, an HIU is part of a centralised heating system known as district or communal heating. This type of system distributes thermal energy from a central source to multiple buildings or apartments within a development
Each dwelling has an HIU, which is a mechanical interface that allows users to control the temperature and timing of their heating and hot water. The central source eliminates the need for individual boilers in each dwelling
The main benefit of an HIU is its efficiency. Because the system heats a large volume of water at a central source, it can achieve better energy efficiency compared to individual boilers. This leads to lower CO2 emissions and can also lead to cost savings for users
However, users don’t have complete control over their heating as they do with a boiler because the heat is generated at a central source. Some users may also be concerned about reliance on a single source for their heating and hot water
How are HIUs more energy efficient than gas boilers
Heat Interface Units (HIUs) are considered more energy-efficient than traditional gas boilers for several reasons:
- Centralised Heating: HIUs are typically part of a district or communal heating system, which generates heat at a central source. This central source can be designed to achieve high levels of efficiency, often much higher than can be achieved with individual boilers in each dwelling
- Reduced Heat Loss: Since the heat is generated at a central point and transported to individual units, there is less heat loss compared to individual boilers, especially when the transport pipework is well insulated
- Optimised Operation: Central heating plants can be optimised for the total heat demand of the entire development, operating at peak efficiency more of the time. Individual gas boilers, on the other hand, often have to cycle on and off to meet fluctuating demand, which can lead to inefficiencies
- Integration with Renewable Energy: HIUs can be integrated with renewable energy sources like solar, geothermal or biomass energy. These energy sources are typically more energy efficient and environmentally friendly than burning fossil fuels in a traditional gas boiler
- Reduced Maintenance and Standby Losses: With a traditional boiler, heat is continuously produced and stored, leading to standby losses. As HIUs produce heat on demand, they minimise these losses. Also, maintaining a single centralised heating system can lead to overall higher efficiency levels compared to maintaining multiple boilers
- Minimised Flue Heat Losses: In traditional gas boiler systems, a significant amount of heat can be lost through the boiler flue. This heat is essentially wasted, reducing the overall efficiency of the system. In contrast, centralised heating systems with HIUs typically have flue gas heat recovery systems in place at the central heat source. These systems recover much of the heat that would otherwise be lost through the flue, further enhancing the efficiency of HIUs compared to individual gas boilers
Do HIUs require a hot water cylinder?
Whether or not a Heat Interface Unit (HIU) requires a hot water cylinder depends on the specific type of HIU being used.
There are two primary types of HIUs: direct and indirect.
Direct HIUs directly heat the cold mains water supply as it passes through the unit, similar to a combi boiler. Therefore, these do not require a separate hot water cylinder as the hot water is produced on demand
Indirect HIUs, on the other hand can be connected to an unvented hot water cylinder This stored hot water is then available for immediate use, ensuring a rapid supply when needed, similar to a conventional boiler system with a hot water cylinder
Both systems have their advantages. Direct HIUs can be more space efficient as they do not require a separate hot water cylinder, making them a good choice for smaller properties. Indirect HIUs, with an unvented hot water cylinder can deliver high volumes of hot water rapidly, which can be beneficial in larger properties or those with multiple bathrooms
Importance of Heat Networks and District Heating Systems
Heat networks and district heating systems play a crucial role in efficiently distributing heat from centralised sources to multiple properties or buildings. By connecting various locations through a network, these systems ensure that heat is evenly distributed, providing warmth to homes, offices and other buildings in an efficient manner
One of the key advantages of heat networks is their ability to reduce carbon emissions. District heating systems utilise low carbon or renewable energy sources for heat generation, such as biomass, geothermal energy or waste heat from industrial processes. By moving away from individual boilers and centralising the process of generating heat, these systems contribute significantly to reducing carbon footprints. This shift towards cleaner energy sources aligns with national efforts to combat climate change and to meet UK’s 2050 Net Zero target
In addition to their environmental benefits, district heating systems also promote energy resilience. Traditional heating setups rely on individual boilers within each property, which can be prone to breakdowns or inefficiencies. In contrast, district heating systems provide a more reliable and robust solution by diversifying energy sources and reducing dependence on a single central boiler
District heating systems are instrumental in achieving national carbon reduction targets while ensuring affordable warmth for communities. By pooling resources and sharing the costs associated with infrastructure maintenance and upgrades, these systems can provide cost-effective solutions for both homeowners and tenants in social housing developments
The implementation of district heating involves various components that work together seamlessly. Centralised boilers generate hot water which is then distributed through a network of pipes to individual properties or buildings. Within each property, this hot water circulates through radiators or underfloor heating systems to provide space heating.
Domestic hot water (DHW) requirements are also met by using dedicated hot water cylinders connected to the district heating network. These cylinders ensure that residents have access to a reliable supply of hot water at appropriate temperatures for daily use
Compliance of HIUs with Low Carbon and Renewable Energy Standards
Utilising district heating systems with HIUs is a crucial step in meeting the low carbon standards set by the UK government. These innovative systems are designed to reduce individual energy consumption and promoting sustainability on a larger scale
HIUs play a vital role in ensuring compliance with energy efficiency regulations and standards. These units are equipped with advanced electronic control technology that optimises heat distribution within buildings, minimising wastage and maximising energy savings. By efficiently controlling the supply of hot water and adjusting it according to demand, HIUs promote sustainable heating practices while keeping costs under control
District heating systems contribute to achieving green building certifications like LEED or BREEAM. These certifications recognize structures that meet strict environmental criteria, including efficient energy consumption and reduced carbon footprint. By integrating HIUs into their infrastructure, buildings become eligible for these prestigious certifications, enhancing their reputation as environmentally responsible entities
The benefits of utilising HIUs for central heating extend beyond compliance with low carbon standards. They offer numerous advantages for both residential and commercial properties.
- Energy Savings: District heating systems with HIUs enable significant reductions in overall energy consumption compared to traditional heating methods. By centralising the production of heat and distributing it through an efficient network, less energy is wasted resulting in substantial cost savings for end users
- Efficiency: The electronic control technology embedded within HIUs ensures optimal heat transfer between the central system and individual apartments or buildings. This precise control allows users to maintain comfortable indoor temperatures while minimising unnecessary energy usage
- Cost-Effectiveness: By eliminating the need for individual heating systems in each apartment, district heating with HIUs offers cost effective solutions for property developers and owners. The initial installation costs are often offset by long term energy savings, making it an attractive option for new construction projects or retrofitting existing buildings.
- Reliable Supply: District heating systems provide a reliable and consistent supply of heat throughout the year. With HIUs regulating the distribution of hot water, users can enjoy uninterrupted heating without worrying about boiler maintenance or fuel deliveries
- Planning regulations: With stricter prohibitions planned for the use of gas as a primary heating source and regulations such as the UK Gas Boiler Ban from 2025 on new developments, HIUs have the capacity to meet requirements without the need for gas.
Do Heat Interface Units Need Servicing?
Regular servicing of HIUs ensures optimal performance and efficiency. These units play a crucial role in heating systems, particularly in multi-dwelling buildings where they distribute heat and hot water to individual apartments. Just like any other mechanical equipment, HIUs require regular maintenance checks to ensure they continue functioning effectively
Maintenance checks are essential for central heating units to identify any potential issues or faults in the components. Over time, plate heat exchangers and filters within the HIU can become clogged with debris or scale buildup, leading to reduced heat transfer efficiency. By conducting regular servicing, HIU engineers can clean these filters and remove any obstructions that may hinder the unit’s performance. This not only helps maintain efficient heat transfer but also prevents potential damage to other vital components
Servicing includes checking pressure levels and inspecting valves for proper functioning. Pressure imbalances can occur within the HIU system due to various factors such as airlocks or faulty valves. Regular servicing allows HIU engineers to identify such issues and rectify them promptly. Properly functioning valves ensure smooth operation of the HIU, preventing problems like overheating or inadequate hot water supply
Timely servicing extends the lifespan of HIUs and reduces the risk of breakdowns or costly repairs. Neglecting routine maintenance can lead to more significant problems down the line, resulting in higher repair costs and inconvenience for residents. By investing in regular servicing, property owners and landlords can avoid unexpected breakdowns and ensure uninterrupted heating and hot water supply for their tenants
To provide a comprehensive service for central heating and HIUs, HIU engineers follow a series of steps during maintenance checks.
- Cleaning: HIU engineers thoroughly clean plate heat exchangers and filters by removing any accumulated debris or scale buildup.
- Inspecting: Valves are inspected for leaks or signs of wear and tear that could affect their functionality.
- Testing: Pressure levels are checked using specialised tools to identify any imbalances within the system.
- Functionality: Moving parts, such as circulating pumps and valves, are checked and to ensure continued operation.
- Calibrating: If necessary, HIU engineers calibrate temperature sensors and control settings to optimise performance.
Regular servicing of HIUs is crucial for their longevity and efficient operation. It not only helps maintain optimal performance but also reduces the risk of unexpected breakdowns or costly repairs. By investing in routine maintenance, property owners and landlords can ensure the comfort and satisfaction of their tenants while maximising the lifespan of their heat interface units
So, if you have an HIU installed in your building, make sure to schedule regular servicing to keep it running smoothly and efficiently throughout its lifespan.
Are heat interface units suitable for both residential and commercial buildings?
Heat Interface Units (HIUs) are suitable for both residential and commercial buildings. They are especially effective in multi-dwelling developments, such as apartment buildings, office complexes or mixed-use buildings, where heat can be efficiently and centrally produced and then distributed to individual units
Residential Buildings
In the case of residential buildings, especially multi-dwelling units like apartment buildings or housing complexes, Heat Interface Units (HIUs) are highly effective. They eliminate the need for each residence to have its own individual boiler for heating and hot water. This can save space, reduce maintenance requirements, and improve energy efficiency, which can lead to cost savings for residents. The centralised heating source provides heat and hot water to each unit as needed, and residents can still control the temperature and timing of their heating and hot water.
This also has benefits in terms of safety and aesthetics, as there is no need for individual flues from each apartment. Plus, with the growing importance of sustainability, the improved energy efficiency of HIUs contributes to reducing the overall carbon footprint of the building
Commercial Buildings
In commercial buildings such as offices, retail complexes and mixed-use developments, HIUs also play a vital role. The central heating system can effectively manage the larger scale heating requirements of these buildings. The HIUs allow for individual control within each unit or zone, which is particularly beneficial in mixed use or multi tenancy buildings where different tenants may have different heating needs
Using a central heating system with HIUs can lead to substantial energy savings, particularly in larger commercial properties. It also simplifies maintenance since there’s only one central heating system to maintain, rather than multiple individual boilers. Additionally, HIUs in commercial settings can contribute to a more sustainable operation, supporting the achievement of green building standards and regulations
Can an HIU be integrated with renewable energy sources?
Heat Interface Units (HIUs) can be integrated with renewable energy sources, making them an excellent choice for sustainable and environmentally friendly heating.
Central heating systems that utilise HIUs are quite versatile in terms of the energy sources they can use. The central heating plant can be powered by a variety of methods including traditional gas or oil, but it can also utilise renewable sources such as biomass, geothermal, air source heat pumps or solar energy.
For instance, in a district heating system, the central plant could use a large-scale solar thermal array, a biomass boiler, or a heat pump system that draws energy from the ground or air. The heat produced is then distributed to the individual units via the HIUs
This integration with renewable energy sources not only reduces the carbon footprint of the heating system but can also lead to lower operating costs in the long term, thanks to the reduced reliance on fossil fuels. It’s an effective way to meet sustainability targets and adhere to increasingly stringent energy efficiency regulations.
Therefore, the use of HIUs can be a key component of a holistic approach to green building design and operation, contributing significantly to energy efficiency and sustainability goals
Can an HIU be Retrofitted in an Existing Property?
Heat Interface Units (HIUs) can be retrofitted into existing properties, although the process can be quite complex and requires careful planning and implementation.
When retrofitting HIUs, the existing individual heating systems (like boilers) within the property will need to be replaced. This usually involves removing the old system and then installing the HIU, which will be connected to the new centralised heating source
The feasibility and cost-effectiveness of retrofitting HIUs in an existing property will depend on several factors, including:
- The existing heating infrastructure: The current layout and condition of the building’s heating infrastructure will play a major role. If the existing systems are old or inefficient, it might make economic sense to replace them with HIUs. However, if the current systems are relatively new and efficient, the cost benefits might not be as significant
- The building layout: The structure and layout of the building can influence the ease and cost of installation. For instance, if the building is difficult to navigate or if the units are widely spread out, it may be more complex and costly to install the necessary piping for the centralised heating system
- Access to a central heat source: The building must have access to a central heating source, or one must be installed. This could be a central boiler, a district heating network, or a renewable energy source.
- Regulatory requirements: There may be specific local building regulations or codes that need to be complied with when retrofitting a heating system, which could impact the process and costs.
Therefore, while retrofitting HIUs is technically possible, it’s essential to conduct a thorough feasibility study to determine whether it is the most suitable and cost-effective solution for the specific property.
Final Thoughts
In conclusion, heat interface units (HIUs) offer significant advantages in terms of reduced installation and maintenance requirements in district heating systems. By efficiently transferring heat from a central source to individual properties, HIUs eliminate the need for separate boilers and reduce the complexity of heating installations.
The use of HIUs simplifies the overall design and installation process, saving time and resources. With fewer components involved, there is less room for error during installation, leading to smoother implementation and reduced costs. HIUs require minimal maintenance compared to traditional heating systems, resulting in lower ongoing expenses for homeowners or property managers.
Heat networks and district heating systems play a crucial role in achieving energy efficiency goals and reducing carbon emissions. HIUs contribute to this objective by optimising heat distribution within communities. By connecting multiple properties to a central heat source, these systems promote more efficient energy usage while minimising waste.
HIUs also support compliance with low carbon and renewable energy standards. As the UK government prioritises sustainable practices, adopting technologies like HIUs becomes increasingly important. These units facilitate the integration of renewable energy sources into district heating networks, making them an essential component of environmentally friendly infrastructure.
Take action today by considering the adoption of HIUs in your next heating project or discussing their implementation with your local authorities or property management company. Embracing this technology will not only enhance your comfort but also contribute towards building more sustainable communities.