Heat recovery

[toscal]

Since we seems to be having a lot of heating based topics I thought this would be a good one. Been thinking about heat recovery.
Been monitoring temps at various heights in my lounge and have noticed a 1.5 to 2 degree difference between where the thermostat is and where I have one of my thermometers. The thermometer is about 20cm higher. This has got me thinking about trying to utilise this wasted heat.
The idea I have is to have some sort of extractor fan based system sucking the heat from the ceiling and putting back into the room at floor level.Must admit my wife doesn't like the idea of tubes/ grills in the lounge and the amount of work needed to chase it into the walls would mean lots of dust so at the moment WAF is quite low. Then I was thinking in the summer you could reverse it so the cooler floor temp could be pumped tot he ceiling.
But I guess the bottom line is cost would it save money or would the install and the cost of running the fans out way any cost saving.
And has any one done this or similar.

[MrFluffy]

They do that here, you can buy kits for it in the local diy chains in fact for a few hundred euro's upwards for the more basic systems right up to computer controlled sophisticated valved units which are designed to serve huge houses.
They call it VMC (venitilation mechanical control) and in fact even have vmc's which take cool air in from outside and pass it through a heat exchanger along with the wasted hot used air so you have warm fresh air in the house.
Yes the ductwork is fairly invasive. Its actually mandatory for bathrooms and kitchens here on new builds I think...

[Gangsta]

Is this not precisely the reason that ceiling fans have a reverse switch? So that in winter the warm air at ceiling level is pushed back into the room. Or have i missed the point and you don't want/cant have fans

[MrFluffy]

The vmc kits use real duct fans back at the vmc box which sits in the loftspace, so actual presence in the room is down to a few duct grilles. Once youve knocked big lumps out the walls channelling in the isolated ductwork that is

Which then leads you into thinking youve almost got enough to make a canadian style underground ventilated warmth system for it. Which you have.
The canadian duct is like a form of geothermal, in that you bury a large diameter duct deep underground and take in fresh air for the house some metres away, by dint of the ground being slightly warmer in winter and cooler in summer, the intake of air has already warmed up before you start, which all helps and you can pass this through a exchanger a few times to get it up to temperature to provide the bulk of energy for heating the house with only the cost of the fan electricity.
I believe they use special coated pipework for it which has a anti fungal coating to stop it furring up and causing lots of diseases...