I am in the process of building a horse barn. I had a contractor do the shell, and I am doing all the interior work. I chose galvanized steel stall kits from Triton (this is going well). Well anyway the reason for the post. It has been cold outside (20-35 degrees F) while my daughter and I work. I got a 75,000 btu kerosene space heater from the Tractor Farm Supply folks and it has kept us reasonably well comfortable. The barn is 34X44 with 10 ft ceilings, and the heater generally will heat the barn to 30 degrees warmer than outside.
In planning the barn, I was trying to meet desires of future owners, so I included a heated wash stall. I am now regretting it a bit, thinking that the space heater would have done a more than adequate job.
I am not a horse person, but perhaps a downside to a space heater is that is does make a fairly loud "woosh" as it runs, which could spook a horse.
I thought I would put this in for the benifit of others, and also get some opinions!