[drcoastline]

Porsche-O-Phile, If I recall when buying a barbeque the sales person explained propane doesn't burn as hot as Natural Gas and the better units are Natural gas as the heat is more controllable and get hotter. If that is true that could be part of the problem with your propane heaters.

When I first opened my office I heated the entire building with vent free Natural Gas heaters. The original radiator heat had all the radiators removed at some point. The vent frees were the quickest and most cost effective fix at the time. We used a single fireplace style on the first floor and smaller vent free heaters in each of the 4 offices on the second floor and an electric oil radiator in the bathroom. More then adequate heat for all but the coldest days. The building now has central forced hot air heat and AC but all the heaters are still operable and used on occasion. .