Its amazing how much heat an iron puts out into a room. I have a basement sewing room , and this time of year its a bit chilly. Once I turn on my iron.. the room gets warm very quickly.. so much so I don't need a space heater. I think you have several heat sources. Incandesent light bulbs put out alot of heat, so switch to the flouresant type where ever possible. Your iron if not needed should be off ( I know this is a tough one ..as I want my iron hot and ready). The motor of the machine does reject some heat into the room , but not very much. I think your issues are the iron, the lights and ... people. Remember we are all about 98.6 degrees and the more people in a room the warmer it gets.
You need to exhaust the hot air .. can you open a window? A fan to help move cooler and circulate cooler air should provide some relief... but you need to draw air from a cooler source.