What is energy saving?

[Stoday]

In my house I have both heat recovery and air source heat pumps. The heat pumps are Mitsubishi air conditioning units run in reverse. They never freeze up because they have a defrosting cycle, rather like the defrosting cycle on a frost-free refrigerator. I use them more in heat pump mode than cooling mode.

The heat recovery unit recovers some 75% of heat or cool. I ventilate my rooms with about 4 air changes per hour and replace 25% with outside air through the heat exchanger.

In the five years since I built my house, I have not met a problem with the temperature gradient; I keep my bedroom at 26°C but it can easily make this when the outside temperature's well below freezing.

 

[bernardgreen]

Heat pumps are a good way to reduce energy usage but as with most things some careful thought is needed as to how they are used. I can imagine a small village in a valley where all the houses use heat pumps for heating water turning the valley into a frost hollow as the houses pump out all the warmth from the air to be poured down the drains in waste hot water. I recall the New York subway stations where the passenger areas were over heated by the hot air coming out of the air conditioning units installed for the comfort of staff in the ticket booths and other offices.

Heat pumps used to recover heat in a ventilation and drainage system together with top up from an outside source seem to be the best option if one can accept the high initial cost to purchase and the disruption during the installation.

An early ground source heat pump using a ground coil made the earth so cold that the grass above the pipe grew slower and left a clear indication where the coil was. That coil had to be dug out and re-laid several feet deeper. It was later found that the cost of a deep bore hole to reach warm water for the low grade source would have been less than the cost of re-laying of the coil.

 

[ericmark]

bernardgreen has put it well. I have also seen where people have jumped to a solution with out considering all factors.

I was not amused at the amount of times condensate rained on me from air conditioning units while working in Hong Kong.

And yes streets were hotter as a result of making shops cooler.

Even in UK in Chester we fitted 14 x 7kW air conditioning units on the roof just to remove the heat produced by lighting in the shop. The only heater was a curtain on the entrance.

Clearly with that shop the NEXT time they do a re-fit maybe they should use more discharge lighting.

There is the exception to every rule but for a guy living in Suffolk to comment on a North Wales or even worse Scottish household way of saving energy is not really valid as the latitude is so different.

This is the whole point we can't isolate what is being done but must look at it as a whole. And it seems that is not being done.