Is your heat lamp a light-emitting bulb, or just a ceramic bulb? One of the members of the forum on here has been doing some experimenting with his snakes and I believe has found out that they don't need light at all (paging Aaron) and in fact seem to do better in complete darkness, as far as feeding goes. But you don't have to leave a light on for them during the day. The light coming in through the windows is fine, but if the heat bulb emits white light, I would switch to a ceramic or red bulb.