What is the best way to heat an indoor swimming pool?

The environment in an indoor swimming pool installation is controlled by an Air Handling Unit that allows the following parameters to be set:

• Pool hall air Relative Humidity
• Pool hall air Temperature
• Pool water Temperature

The AHU also provides fresh air (normally 6 complete air changes per hour) and is very efficient because it also extracts the heat energy from the air going to waste outside and adds the heat back to the incoming fresh air or the pool water.
In the UK for 8 to 9 months of the year, very little heating is required if heat loss is minimised by a floating cover on the pool. During this period an Air Source heat pump can be provided to provide the heat.

However during the winter, when the ambient outside air temperature can drop very quickly, up to 40kW of heating power can be required to maintain the pool hall environmental conditions. This instantaneous response can only be provided by gas, fuel oil or electric heating. This requirement subsantially reduces the economy and sustainability of the heat pump because of the doubling up of the heating plant required.

An Air Source Heat Pumps will cost about a third of the cost of a Ground Source heat pump. Ground Source heat pumps are the cheapest to operate but the installation costs are horrendous.