You will want to know how much of a change to make to the exterior styling. If it is an older church with a long history, you might not want to deviate much from the current style just to preserve the tradition. In fact, if the building is located in a historic district, you may be forced to keep the styling the same.
After you settle on an architectural style for the exterior, you then need to look at accessibility. Many older buildings were constructed before the days when people gave much thought to things like wheel chair accessibility. During the renovation, there needs to be things like ramps installed where needed. The door width must also be considered, especially at the entrances near the ramp.
Thought must be given to the way the foot traffic will flow, both before and after the service and for things like getting from the Sunday school rooms to the sanctuary. You will also need to think about how people may go from their seats to the alter and back again during Holy Communion services. The Communion table location may depend on whether the pulpit is in the center or to the side. The pulpit should never be in front of the table. Therefore, for sanctuaries with the pulpit in the center, the Communion table must be in front of the pulpit, not behind it.
Once the layout and architectural style have been decided upon, you can begin to think of ways to do the renovation in ways that make the building more energy efficient. This will not only save money on the energy bill, but it is good stewardship also.
There are a lot of decisions to make when renovating a church. Enlisting the help of a company that specializes in this kind of thing will avoid a lot of frustration as the project moves forward.