thats a nice wee stup mate.. love the camera to.you best bet is just to wait till the seedlings pop up then put ur light on. humidity wont be a problem. if youve fans on..the attic looks big thats good to. means the heat will spread out. honestly dont worry about humidity or temps.. yet.. pics look sweet.. ps dont let the soil get cold or it will slow growth.. Looks greaet sorry i couldnt get bak to you earlier.. Peace TBB