We are having closed loop system installed for a new 2k sf foot home in Iowa (winters can get below zero). Are there any worries about using a flammable fluid running into the mechanical room where heaters, electrical etc is located? From searching the forum it sounds like glycol while safer may not be so good in colder climates. Thanks!

In Iowa the last I knew methanol was allowed in shallow horizontal systems as the circulating fluid, but not vertical systems, you'll have to check with reputable installers in Iowa. If they are licensed with the state, they should know. Methanol is allowed in some states in all geothermal systems, horizontal or vertical, but the percentage is typically 20% or less to keeps the fluid from being flammable once mixed. It is true that if methanol can be used legally, it does pump easier requiring less power, and has better heat transfer properties. Hopefully this helps.
Dan

Go with your installer's recommendation. Dan's right, once mixed with water flamability is moot. If a leak occurs the water could easily cause as much or more damage than the antifreeze used. Oh and methyl is cheaper.
J