Types of Warm Air Heating Systems

All warm air heating systems operate by pushing warm air around a duct network using low-power fans; the difference is found in the ways in which the air is warmed.

gas flame

Warm air heating systems, much like various other systems, come in a variety of different configurations. All of the systems operate by pushing warm air around a duct network using low-power fans; the difference is found in the ways in which the air is warmed.


These traditional warm air heating systems simply draw cold air across a gas flame in order to warm it – typically in a heat exchanger. This method is simple and very effective.

Air-to-Air Heat Pumps

These are largely similar to air conditioning units as they tend to be reversible so that they can either heat or cool the air. The systems can be standalone units or they can be used with a ventilation system. Either method is very inefficient.

Heated Ventilation

These types of warm air heating systems could use air-to-air heat pumps, a wet heat exchanger from a boiler, or an electric resistance heater, located in the ventilation system. Usually a very small heat source is used, ranging from 1kW to 3kW capacity, meaning that such systems are only really suitable for homes with a very low heat load close to or at the PassivHaus standard. Companies such as Genvex use exhaust air or loft space heat pumps in these kinds of warm air heating systems.

In-Ground Pre-Heating

The ground-air heat system supplied by ADM Systems in the UK makes the most of the fact that at depths greater than 1.5m, ground temperature is relatively consistent at 8-12 degrees C. Air is drawn through a network of pipes and is brought into line with the temperature of the ground. Pre-heated air is used in an air-source heat pump connected to the ventilation system or air which has been cooled is used to cool the home in summertime. This removes any need for air conditioning as well as making the overall efficiency of the heat pump much greater.

The Key Facts about Warm Air Heating Systems

What you read in the advertising of warm air heating systems won’t give you the whole picture. Read through these key facts to make sure you have all the information necessary before going ahead with warm air heating.


These systems run quietly, with noise levels depending upon the quality of the ducting and installation. Today’s fans are almost completely silent, but ducting which is flexible or has been poorly installed can cause noise.

Short heat-up Times

This is something you will see advertised often, and it’s very true. Additionally, as insulation and airtightness levels improve the cool-down time becomes less of an issue.

High Controllability

This is one of the major benefits of warm air heating systems. Once the system is switched on, heat almost immediately enters the room. Once it is switched off, the heat stops coming. Radiator systems can take thirty to forty minuets to achieve the same levels of heat, whilst underfloor heating can take up to two hours.

Cheap Installation

The cheap installation of warm air heating systems is a massive benefit in single storey homes. However, installation costs increase as floors are added. Make sure to carry out detailed cost comparisons where several floors are involved.

Fuel Efficiency

In comparison to conventional wet systems, warm air is less efficient. The best of the warm air heating systems available today will achieve efficiencies of around 80%, whereas the average wet system boiler will easily reach 85% efficiency with the potential to achieve much higher rates. This may seem like a small difference, and air will inevitably cool as it is moved through the ducting.


There are many claims to be read about warm air heating systems being detrimental to our health. The worries are that warm air spreads coughs and colds, spreads dust, and dries the air to an uncomfortable degree. These claims are unfounded, and the air in a warm air heating system is filtered just as it is in any other system.

Image by Paul Kretek

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