So when we reach the 2030s, ordinary central heating boilers, as we know them today will be banned. We will need to replace gas boilers with heat pump systems - expensive at the outset. And that is not all. The water temperature produced by heat pumps is not as high as that produced by gas central heating boilers. So we will need to replace our radiators with larger and thicker ones, to gain the same heat from cooler water. This it turn means that we will need stouter pipes to feed those radiators, so the piping will need to be replaced - even more expense and considerable disruption.

That at any rate is the gloom prophesied by the news media. I decided to look beyond the media and see what alternatives are available.

I started by examining the present alternatives. The media seem to focus on the common idea of a central heating system, with a central boiler and radiators. Our present house has such a system.

In our previous house, the central boiler heated air, which was sent to the various rooms via ducts. Individual rooms could be shut off if heating was not required therein. An advantage of this system is that if a room is suddenly needed, opening the air shutter causes the room to heat up very quickly. The benefit of the heat can be felt in less than five minutes and the room can be comfortably warm in about 15 minutes. Radiators cannot respond as quickly as this. Their thermal mass means that they take time to warm up before they begin to deliver heat in appreciable quantity, and they rely on natural, instead of forced, circulation. Conversely, if the room becomes too hot, the heat from and air duct can be shut off immediately, whereas a radiator continues to give off unwanted heat while it cools. A disadvantage of ducted air is that the air flow can be accompanied by a hissing noise, which can be intrusive, though there are ways to suppress this.

Our house previous to that had gas fires in fireplaces. These could produce noticeable heat quite quickly and get the room quite warm and cosy in time. They did not do much for the hall and landing areas, however. We later addressed this by having a through-the-wall-flued gas convector heater fitted, and this was very effective.

So here are three ways to heat a house. Can we draw parallels with heat pump technology?

The system using radiators has been well-publicized. I found some very useful information from the Energy Savings Trust.

energysavingtrust.org.uk/.../

If heat pumps are limited in respect of how well they heat water for radiators, why do things that way? Why not pump the heat directly to air instead?

It seems that this option could be possible, especially where ducted air heating is already installed. It would require the main equipment to be on an outside wall; however; this will not always be the case for gas fired systems. If a ducted air system is not already installed, the practicality of installing one would depend on the size and layout of the house. A bungalow would usually take such an installation easily; the ducts could run through the roof space and serve nearly all of the rooms. For a house of more than one storey, installation would be less easy. Ideally, it could be installed easily in a new house as part of the building process. Bear in mind that water has a much larger thermal capacity for conveying heat than air. Also it is more effective in transferring heat in a heat exchanger. We need hot water for taps, so provision would be needed to take off some of the pumped heat for this purpose. However hot tap water is usually heated to about 60 °C, whereas radiators need about 75 °C, so this could be achievable. Another advantage of this system is that it could operate in reverse in hot weather to provide cooling. Radiators cannot do that.  

Could there be an equivalent for an individual through-the-wall gas heater? I do not see why not. Through-the-wall cooler units have been used in hot countries for many years. Could not these be adapted as heat pumps? I think they could be very cost-effective, because they would avoid the upheaval of replacing radiators and associated piping. A good sized fridge-freezer can be bought for around £400, so why should these, mass-produced, be more expensive? Around eight could serve a 3-bedroomed semi.

The BBC recently ran a program about heat pumps, interesting and instructive on some points, but again it focused on radiator systems. I imagine that in the coming years all three systems I have described will be employed, sometimes in combination, according to the type of premises where they can be installed. Engineers will find cost-effective measures, as always. What do to others think?