I use incandescent lights. They give off all the heat you may need. I also check temperature with a thermometer every few days, in every box and keep the light high enough so the box is 95f the first week, 90f the second week, about 5 degrees lower each week, until they are well feathered, then keep it at their comfort level until they can go without the extra warmth. Because sometimes there are as many as 5 boxes of chicks in a spare bedroom, at a time, the whole room is lovely and warm and I add new sheets of rough paper toweling 3 or 4 times a day, for the first weeks, then newspapers a number of times a day, layering them, then every day or so, roll up the dirty papers and dispose. The room smells like warm fuzzy chicks, and not stinky.
Chicks stay clean.
A thermometer checks the right temperature at floor level of each box. When the chicks are a couple of weeks old, one lamp may warm 2 boxes. I know you have your chicks inside, but I'm just curious. Folks ask why I do not use Heat Lamps. Heidi, Absolutely not true.