Hi, I'm building an extension to a small garage and considering experimenting with underfloor heating using a used fridge or freezer compressor as a heat pump. I want to do this on the cheap.

I'm not a refridgeration expert but have a general engineering back ground.

The building is small and well insulated and will only need about 1kw of heat.

I can't find any information of anyone whose done something like this on the web. Could any one advise of:
1) How do you find the output of a domestic freezer compressor and would one be big enough - i was thinking of getting one from a large chest freezer but can't find any info on output?
2) Should i use a specific refridgerant / compressor with a specific refriderant.
3) What size and length of coils you should use inside / outside the building. I was thinking of about 6mm coil and about 15-20m long.
4) What material the coils should be. I was thinking of using copper inside and out with it possibly PVC coated. The coils inside will be in concrete and the coils outside in sand.

I'm doing this partly out of fun. Any guidance would be greatly appreciated.

Regards Mark