Do not let the room temperature get over 35 C (95 F) as this hurts growth. Optimal temperature is 27-30 C (80-86 F) if you have strong light with no CO2 enrichment. Less than 21 C (70 F) is too cold for good growth. Low temperatures at night are OK down to about 60 degrees outdoors, then start to effect the growth in a big way.
Flickr: Wolf Rock. For god's sake, this is simple. A pizza is cooked in a pizza oven, not a pizza skillet. So to reheat pizza, you attempt to replicate a pizza oven. Place a baking sheet in your oven, blasting the heat as high as your oven will go. Once the baking sheet is hot, place the pizza on it. The bottom will be crispified by the hot baking sheet.
Another option might also be to let them set out at room temp, and then reheat them in the oven when you're ready to serve them. Pizza shops that sell pizza by the slice usually leave whole pizzas out at room temp, and just put them in the oven for a few minutes to reheat them. That might work better, since they won't be continually heated & drying out in the oven for hours.