It was about 6' x 6' corner in a room. it did get warmer in there but usually only when I had the room closed off, if a door was open it wasn't so bad. Usually it does best with a temperature around 74-76°F, but I recall mine sometimes went up into the 80's. The fan helped a lot to bring it down. as far as affecting the plants, it can if it gets too hot but sometimes depends on the strain, some are more heat resistant then others... Cinderella 99 was a hearty one I remember. but i would start with some bagseed.