Heat Interface Units Explained.

What is a Heat Interface Unit (HIU)?

Heat interface units (HIU), or Packaged Plant Rooms like the QuadraTANK, are typically installed in large apartment complexes with multiple dwellings. Rather than each dwelling being fitted with a boiler, a central boiler provides heating and domestic hot water energy to the entire complex.

Heat interface units (HIU) act as a bridge between the central boiler and the heating and hot water systems of the individual apartments. 

HIU ExplainedHIU Explained



Why use district heating?

1. Opportunities for renewable energy

One of the primary considerations in modern construction is conserving energy through the use of energy-efficient plant. In Dutypoint Heat Interface Units (HIU), hot water produced by a centralised district heating plant (generally powered by renewable energy sources) is transferred via integral heat exchangers, to provide on-demand heating and hot water. Dutypoint Packaged Plant Rooms deliver eco-friendly temperature control to the building occupants. 

Heat interface units (HIU) give building services engineers the option to design multi-dwelling complexes with district heating systems, which can use energy sources such as CHP, solar or heat pumps. This can be done without the constraints of attempting to equip each individual dwelling with its own renewable energy source.  Domestic hot water provided by a plate heat exchanger is provided rapidly, ensuring a high level of comfort for building occupants. 

2. Greater level of luxury

Domestic hot water can be provided by heat interface units (HIU) or Packaged Plant Rooms on-demand, without the requirement for cylinder storage, and at a higher flow rate than a typical domestic combi boiler. Heat interface units from Dutypoint Systems are available at standard capacities up to 80kW; most domestic combi boiler ranges have a maximum output of 45kW. Higher capacity units can be configured on request.

3. Reduced investment costs and ongoing maintenance

Rather than supplying each apartment with gas, and installing numerous domestic boilers,  heat interface units (HIU) require only a hot water riser connected to each apartment and a central boiler plant. This alone leads to a significant saving.

In addition, there will be no building-wide gas network to install or maintain on an ongoing basis. Heat Interface Units are also easier to install than boilers and no gas training qualifications are required for installers; there is no gas connection and no flue pipe, so ventilation routes are not required. Less ongoing maintenance is required for heat interface units themselves, and maintenance need not be conducted by gas-qualified personal. This also means less disruption for building occupants.

Heat Interface Units 28HIU29- Product Overview

Heating Type

Indirect Heating

Indirect heat interface units facilitate separation between the primary and secondary systems, with a plate heat exchanger to transfer energy from fluid in the primary system to fluid in the secondary system. In installations where the separation between the primary and secondary systems is required, indirect heat interface units provide this.

Control Type

A further distinction can be made between heat interface units that are thermostatically controlled like our Packaged Plant Rooms and those which use proportional hydraulic control.

Thermostatic Control
Proportional Hydraulic Control
The majority of heat interface units on the market employ thermostatic control. These units have the advantage of a lower initial cost, but in many cases, the users will notice a fluctuation in hot water temperature. Dutypoint heat interface units (HIU) address this problem by using a fast-responding thermostat specifically designed for use in heat interface units (HIU). Proportional hydraulic control provides a much more constant domestic hot water temperature, fully eliminating the use of thermostatic control. There is a slightly higher initial cost, but a better experience for building occupants as water temperature stabilises very quickly.

Why Dutypoint?

Because Dutypoint units are batch-produced to your project specification we also have the option to include in-built metering, with an option for wireless usage monitoring, and to configure units for either radiator-based or under-floor heating. We can also offer customised configurations outside of our standard range, and higher capacities if required. Our units also feature first fix connection rails, allowing pre-plumbing prior to the heat interface units (HIU) or the Packaged Plant Rooms, for example, the QuadraTANK, being installed, ensuring heating circuits remain free from debris and allowing contractors to delay delivery and payment for heat interface units until later in the project timeline.


We're here to help.

We have been involved in a wide range of projects including small domestic developments, high rise residential, hotels, commercial and industrial properties, highways and education. Whether it's a basic pump station or a complex bespoke system, we help you create a solution for your specific project!

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