At those temperatures I wouldn't use any heat. Generally it's those first few weeks they need extra heat for temperatures below 80-85. I think I ran my heat lamp for two weeks 24/7 than only at night for another week or so before stopping. I moved mine out to my shed at 6-8 weeks.
I believe it's the same formula of 85-90 degrees the first week, than lower the temperature by 5 degrees a week until you hit ambient temperature whatever that is for you. Use your geese as your guide. If they are constantly under the light they are too cold. Happy geese move around, both below the heat, and away from it.