With the proliferation of renewable sources of energy there is a desire to comply with both the Building Regulations, ethical and economic motivations when specifying heating for buildings. Whilst the cost of retrofitting domestic properties with renewable heat sources is often prohibitive we are seeing an increase in the retrofit of commercial buildings with such heat sources such as heat pumps. For new builds in both domestic and commercial applications the numbers stack up more favourably due to the higher capital cost of the heat sources compared to more traditional heat sources being offset by the significantly lower running costs.
Getting back to the question about whether you can get enough heat output from heat pumps. It’s a good question. Most traditional gas fired, or oil fired, boilers generate a flow temperature of around 75°C to provide a temperature at most heat emitters, or radiators, in the heating system. The system is designed around this temperature output and the heat emitters are sized accordingly. However when you consider that the average flow temperature of a Heat Pump, ground-source, or air-source, there is a significant shortfall in the flow temperature. Most efficient ground-source and air-source heat pumps produce a flow temperature of around 40-45°C. Consequently the traditional radiators cannot provide the required heat output to heat the space at this flow temperature of just 40-45°C, without increasing their size by up to 4 times. More often than not doing this is not practical, nor is it desirable. Imagine increasing a radiator from a commonly used width of 1.2m to 4.8m, or doubling its width to 2.8m and doubling its depth so that it protrudes into the room much further.
All is not lost though. Replacing the traditional radiators with fan convectors overcomes the need to increase the size of radiators. Fan convector technology is designed to be used at flow temperatures from 40-80°C. It is true to say that for very large spaces using a heat pump as a heat source a large fan convector running at 45°C would be required. However the point is that because the fan convector uses a near-silent fan to blow the warm air created by passing the hot flow water from the heat pump through the heat exchanger into the room the temperature of the room heats up more quickly and efficiently. Another benefit of fan convectors as opposed to traditional radiators is that because the room heats up quicker, you can schedule the heating to come on as and when you need it rather than waste energy heating the radiators, which then rely on natural convection. Think about how quickly the radiators at home get very hot and how long afterwards the room becomes warm. The problem is much worse in larger spaces. Conversely when you no longer need to heat the space the fan convectors can be switched off and no energy is wasted. Traditional radiators keep heating the space long after the heating has been turned off.
So, back to the original question. The answer is yes you can most definitely heat an office, or indeed any space, large or small, using heat pumps as a heat source.