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What is a Heat Transfer Kit? How Does it Work? 

Heat generation is a process that consumes a lot of energy. But in many Australian homes, a lot of the residual heat gets wasted due to various reasons we’ll discuss.

Making the maximum utilisation of the generated heat can be an economical way to heat up other rooms in your home that may not have a heating system. Installing a heat transfer kit is one of the easiest ways of doing it and making your home more energy efficient.

You might be thinking:

  • How does a heat transfer kit work?
  • How much money can it save me?
  • What other benefits does it offer?

Perfect, here you go:

What is a Heat Transfer Kit?

As described above, the basic mechanism of heat transfer kits remains the same. However, the size of the unit changes based on the number of rooms and the volume of air to be transferred.

For this reason, many brands sell their transfer kits based on the number of rooms to be heated. Each kit includes all the components including the fan, duct, and other accessories. 

The kit capacity depends on the amount of heat transfer and the area to be heated. These kits are designed to ensure low running costs and some are also sold as a part of DIY systems.

It goes without saying that the larger the system, the higher the price. In general, the kits can be classified as:

  • 1 room heat transfer or single room heating
  • 2 room heat transfer
  • 3 room heat transfer
  • 4 room heat transfer

Usually, more than 4 rooms are not considered since the heat loss increases over larger distances. With larger distances and more area, the efficiency of the system also drops.

Why Use a Heat Transfer Kit?

With the idea of sustainable living on the rise, a heat transfer kit is a great way to make your home more energy efficient. If the winters are not extreme in your location, this kit is a great heating solution.

Many Australian homes do not have a heater in the kitchen or the bedrooms. Using a transfer kit is an easy and efficient way to distribute the excess heat across your house. 

Here are some of the main benefits:

  • Heat transfer allows you to make better use of the available heat while reducing the energy consumption rate. In addition, it is also an economical option with lower running costs. In general, such a kit can pay for itself within one or two years. If you live in a location where you have access to free wood as fuel, your cost savings can be even higher. 
  • Since the heating kits are available at affordable prices, you do not need to install separate heaters or heat pumps to warm up the chilled spaces. Such a cost-effective system can be good enough to cut down the chill factor and allow you to spend a comfortable night.
  • A heat transfer kit ensures better air circulation throughout your home, especially during winter. It also reduces the formation of cold air pockets and condensation from excess humidity. As a result, the risks of mildew, mould, and musty smells are reduced.
  • The process of heat recovery will reduce the carbon emissions from your home. So, your home’s environmental footprint will come down.

How Does a Heat Transfer System Work? 

A typical heat transfer system is a combination of a fan and air ducts to transfer the generated heat to different areas of a home. The primary source of heat can be a wood fire or a space heater. 

Depending on the size of the kit the warm air can be transferred to one or more rooms.

In many homes, the heat distribution is uneven and some rooms remain colder or warmer than others. In some cases, rooms with vaulted ceilings can be difficult to warm up. 

For example, the hot air from a heated living area can rise to the second or third floors, making them too warm. The heat trapped at these high spots raises the temperature of that area to an uncomfortable level and serves no practical purpose. Redistributing this heat can ensure that the warm air reaches all the occupants in the house.

The process involves drawing the warm air through a ceiling vent in the warm room. It then passes through the insulated ducting to the other rooms and is let out through an outlet vent. The good news is that you can customise a heat transfer kit to recirculate the heat back to the living space or any necessary zone.

Obviously, there will be a certain amount of heat loss during the transfer. But the goal of the transfer system is to warm up a room and not act as a primary source of heat. In fact, not all rooms in a home require a direct heat source.

Moreover, the power consumption of the entire process is also on the lower side. For transferring heat to a single room, the power consumption of the system can be as low as 40W.

The following are the main components of a standard heat transfer kit:


The system uses a thermostat to start the fan after the room temperature has reached a specified value. When the temperature drops below that value the fan shuts down to stop the hot air transfer.

Modern digital thermostats contain a device called a thermistor. It measures temperature by detecting the change in electrical resistance. Some thermostats also have programmable settings that allow you to control the temperature settings.

Insulated Ducting

The quality of ducting plays a vital role in heat transfer to the other rooms with minimum heat loss. For that purpose, the metal body of the ducting is insulated to minimise heat loss. 

Ducts used in transfer kits come with a metalized inner core covered by a polyester thermal blanket. The outer layer is made of flame-retardant materials to reduce fire hazards. The ducting diameter depends on the rate of flow of the hot air in the room.


The fan generates the necessary pressure required for transferring hot air. The size of the fan is chosen based on the amount of airflow and the length of the ducting. By using a controller, the speed of the fan can also be controlled.

In most cases, a mixed-flow fan is used for heat transfer kits. These fans have two types of blades that can make the air move in both axial and radial directions relative to the fan shaft. 

Mixed-flow fans can develop higher static pressure and generate low noise which makes them suitable for indoor use. The installation and maintenance of these fans are much simpler too.

Ceiling Grilles

There are a wide variety of grilles and diffusers used at the terminal points of the ducting to direct the airflow. These diffusers have vanes that disperse the warm air and allow it to mix effectively with the cold air in a room.

Depending on the geometry of the room and heat requirement, the grilles can deliver a horizontal, or vertical air discharge. 

Note, sizing the grilles based on the airflow is an important process. Undersized diffusers can make the discharge noisy, whereas an oversized grille will reduce the pressure of the warm air outflow.

Types of Heat Transfer Systems 

As we know, heat will naturally flow from a hot area to a cold area; the temperature difference between the two points being the driving force.

Basically, all heat transfer can be classified into three categories

  1. conduction
  2. convection
  3. radiation


During conduction, heat is transferred through the contact between solid materials. Think of the heat you feel when you touch a cup of hot coffee. Metals like copper and aluminium are the best conductors of heat.


Convection is caused by the movement within fluids (like liquids or gases) and facilitates heat transfer between hotter, and less dense materials to colder and denser materials.


Radiation is the process of heat transfer through electromagnetic waves. Solar heat or the heat generated by a fire are examples of radiation.

In heat transfer kits used in homes, the method of transfer is through convection. Whenever a fluid comes in contact with a surface that is hotter or cooler than itself, convection occurs. Here, air acts as the medium for conducting heat, resulting in either cooling or heating.

Since this air is forced through the duct, the process is forced flow convection. A free-flowing convection system or natural convection, that works based on temperature gradients, is also used in various engineering applications.

Keep in mind, heat exchangers are also a type of heat transfer mechanism that uses both conduction and convection. However, they are not used for indoor heat transfer units. More on that later.

Heat Transfer vs Heat Exchanger

General users might get confused by the differences between a heat exchanger and heat transfer. Fundamentally, both processes result in the transfer of heat, but the mechanisms are different.

In various engineering applications, heat exchangers are used to transfer heat or thermal energy from one fluid to another. The two fluids might be separated by a partition wall or can get mixed. Based on this, heat exchangers are classified into direct and indirect types.

Some of the most common appliances where it is used are refrigerators, HVAC systems, power plants, automobiles, waste heat recovery units, and chemical plants. You can also find them in commonly used heat pump water heaters.

If we take the example of a vehicle, the radiator acts as a heat exchanger to transfer heat from the engine. The coolant collects heat from the engine, makes its way to the radiator tubes, and transfers the heat to the ambient air. For high-performance engines, the right level of radiator efficiency is a must.

The primary goal of using a heat exchanger is to improve a system’s energy efficiency. It transfers the redundant heat from one system to another one, where heat is needed. Besides, they can be used for both heating and cooling processes.

As the fluids flow at higher speeds, the primary mechanism of heat transfer is forced convection. This results in pressure loss in both fluids. For modern heat exchangers, the design goals are to minimise pressure drops and maximise heat transfer. In addition, flow rate, heat loads, and corrosion are other factors that are considered.

As you can see, heat exchangers are more complex devices used to transfer heat between two media. Mass transfer of fluids may or may not occur in a heat exchanger. 

However, in a residential heat transfer system, a portion of the hot air is collected and transferred to another space through ducts. This is a simple system where heat transfer rate is not influenced by the temperature difference between two media. 

In fact, the system is for moving heat and not for heat exchange between two fluids.

Frequently Asked Questions

How much does it cost to install a heat transfer system?

The cost of a heat transfer system depends on the number of rooms that you want to heat and the length of the ducting required. The prices can range between $250 to $800.

Do heat transfer kits work with heat pumps?

Not unless the pump was selected for that purpose. Most heat pumps are best for heating the area of the room in which they are installed (and some are used for hot water or heating pools). Connecting it to a heat transfer system will result in the pump working at full capacity to heat up the extra volume of air. This will not only raise the power bill but will also shorten the life of the pump. Also, since heat pumps deliver heat more evenly there are lower chances of hot air gathering at the roof area for transfer.

Will the system heat up another room to the same temperature in the living room?

No, the secondary room will not be as hot as the primary room. Even though insulated ducts are used in the process, there will be some loss of heat during the transfer. Ideally, these systems are best for providing warmth in rooms that do not need constant heating.

Can you install a heat transfer system yourself?

If you are familiar with the installation of ducting and fans then you can handle most of the installation on your own. However, you might need the help of a professional electrician to make the electrical connections and install the thermostat.

Final Thoughts

Modern technology has developed a variety of heating and cooling systems. But a few are as simple and economical as a heat transfer kit.

If you want to maintain a comfortable and cosy temperature throughout your home without spending much on power bills, this is a great solution.

It is a simple system and can work for large as well as small spaces while consuming minimum power. You can even direct the air up or down depending on your preferences.

However, make sure that you choose a brand that delivers dependable products and ensures the right sizing of the fan and duct. While standard kits are cheaper, it might be best to choose a customised system that ensures the best long-term benefits.