I roast on a Giesen 1 K and as I lve in the UK the most part we have an average of 70 - 80 % humidity and cool temperatures.
As spring arrives and the humidity drops I am trying to work out if I should drop my charge temperatures 5c or how I can adjust my profiles. Am I right in thinking that if the humidity drops the transfer of heat will change? Will the beans be holding less water due to the rising heat and if so should I apply less heat?
Yes, you're correct. The moisture content does affect the heat transfer. However (experientially, not scientifically), the relative humidity of your local environment will take a while to have a noticeable roast affect...several weeks to a couple of months. 5c seems like a big shift. I would try closer to 5f when you start noticing quicker times.