You need good air exchange, inside your house there's no breeze to help that occur, you might need to open up the top more, what are you using for heat, that can quickly build up in an enclosed space, it's a fine line between not enough ventilation but too much chicken dander all over your house. I like brooding in an unheated shed that has better air exchange. The kids toys are throwing me off a bit, poultry give off a lot of dust you don't want your children breathing in too much, I'm sorry, you did a good job building it, what's the inside look like and what are the dimensions.