Other heat pumps

To the real estate editor: In the Ask a Builder column of Dec. 21 you had a question about heat pumps. Your reply dealt only with air-to-air systems.

I have a friend here who extracts heat from, and adds heat to, water from a deep well which at present runs to waste. Another friend extracts heat from a solar-heated swimming pool located in a greenhouse which is attached to his house. In the summertime he heats the swimming pool with the pump.

The local paper a year or two ago described a system which extracted heat from both the crawl space and the attic which were connected in some way. Donald W. Goodwin Oak Ridge, Tenn.