Electric Heatpumps.

Peter Bernard Ladkin: 
 

. . . 

Denis McMahon:

When we moved to Hampshire, in the mid-1980s, we saw ducted air heating installations in several houses, including in the one we eventually bought. ……..

There are some downsides to ducted air heating…… this system can be easily designed and built into a new house but adapting to an older house, …..is less easy and probably very expensive.

There are individual devices for individual rooms which exchange air with the outside, and which exchange heat during the air exchange. They are not large. The specs for one device I have been looking at are roughly 38cm^2 cover, sticking out 5cm into the room (you get a 35cm to 60cm hole in your outside wall). They claim 82% thermal efficiency through heat exchange, and you can get them to exchange 15 m^3/hr to 55 m^3/hr for the same wall space. They are not noisy – claimed 25dB at 30 m^3/hr.

You just have to find that 38 cm^2 patch per room outside wall. 

It solves both problems of course: heating and air exchange.

. . .

We once had a through-the-wall gas convector heater in a former house. It heated the room quite effectively, without telling other rooms all about it. It is not suprising that this through-the-wall idea has been applied to heat pumps. Really, they are similar to the air conditioning units one sees in hot countries, but working in reverse.

The is some merit in heating rooms individually rather than centrally; it calls for more-accurate control of temperature and avoids the problem of radiators with water not really warm enough. However the cost of several of these units is likely to be more than that of a central system. And what about heating the water?

Peter Bernard Ladkin: 
 

. . . 

Denis McMahon:

When we moved to Hampshire, in the mid-1980s, we saw ducted air heating installations in several houses, including in the one we eventually bought. ……..

There are some downsides to ducted air heating…… this system can be easily designed and built into a new house but adapting to an older house, …..is less easy and probably very expensive.

There are individual devices for individual rooms which exchange air with the outside, and which exchange heat during the air exchange. They are not large. The specs for one device I have been looking at are roughly 38cm^2 cover, sticking out 5cm into the room (you get a 35cm to 60cm hole in your outside wall). They claim 82% thermal efficiency through heat exchange, and you can get them to exchange 15 m^3/hr to 55 m^3/hr for the same wall space. They are not noisy – claimed 25dB at 30 m^3/hr.

You just have to find that 38 cm^2 patch per room outside wall. 

It solves both problems of course: heating and air exchange.

. . .

We once had a through-the-wall gas convector heater in a former house. It heated the room quite effectively, without telling other rooms all about it. It is not suprising that this through-the-wall idea has been applied to heat pumps. Really, they are similar to the air conditioning units one sees in hot countries, but working in reverse.

The is some merit in heating rooms individually rather than centrally; it calls for more-accurate control of temperature and avoids the problem of radiators with water not really warm enough. However the cost of several of these units is likely to be more than that of a central system. And what about heating the water?