This weekend, I plan to remove all the old batt insulation, and in the medium-term have new insulation installed.

In the medium term, Life can get in the way of the best laid plans. I would leave the insulation in place for now.

There are a few reasons to insulate pipes:

1. To prevent them from freezing (you put the insulation between the cold wall and the pipe)

2. To prevent heat loss from hot water lines

3. To prevent water from condensing on cold water lines in humid areas

If you live somewhere that the outside temps get significantly below freezing, that insulation will protect the copper pipe from freezing (and bursting).

In many areas of the country, the threat of frozen pipes has mostly passed for the winter.

You will be fine temporarily. I like to use "R-Max" foil faced foam board between plumbing and an outside wall for the highest R value in the smallest amount of space.

If one of those pipes is a hot water line, you want to use foam pipe insulation around the entire pipe (in addition to R-Max between the pipe and the wall).

The short answer is: if the temperature doesn’t reach freezing where the pipes are located, there is nothing to worry about.