I've had a number of solar tubes in my homes. I never had any problems in AZ with them heating up my home, but when it's over 100 outside you've still got the AC on. When we had a new roof put on in OR, my DH thought he would have a solar tube put into the hall bathroom. I don't know if it's the paint or the way they placed the tube or even if it's because it's in a smaller area, but it does heat up that bathroom. I find that in the summer (this summer for sure), that I keep the doors closed on the hall bathroom (1 door into the hallway and 1 door into the laundry room). So to answer your question in most cases it doesn't, but it can sometimes.