My set up for bottom heat. If basement temperature is 68 to 70 F, only one bulb is turned on to start new cuttings. If the room temp. is 65-66 F, 2 bulbs are on. A dish-pan will fit over each cutout. I can lower the temp 1 or 2 degrees by moving the dish-pan sideways one inch to let some heat escape through the top. Always keep temperature between 70 and 74 F.