might. i would think that all of the pours in the fabric would absorb as much light as it reflects. painting i would think would be better. panda film would be best.
No the frabic would absorb heat. Grow tents are made of fabric yes but they have a mylar coating to they reflect it. White paint is a much better option for you.
yea, if it's just cloth and doesn't have a reflective surface its just going to absorb the heat and light. if you dont want to paint it you can always put up sheets of mylar or just go the ghetto way and put up foil
i made a diy grow room and used a 20x20ft heavy duty canvas tarp (ones used for keeping tar hot) and then hung black/white mylar on the inside