Sheathing Question

[Barb P]

A small section of sheathing, about 2x4, approx, got wet from leaking window.
Sheathing got warped, and needs to be replaced, in the section of wall, under large window.
It was a bay originally, but replaced with a triple, double hung.

The original sheathing seems to be 1/4 inch cardboard, foil on one side, facing inside.
There is plastic between sheathing and aluminum siding.

It doesn't look like it can be done from inside....bear with me please, I'm an old lady with no knowledge of this construction stuff.
My son is planning the work. He has not yet seen it.

I need to know what to buy for sheathing. I saw what looked like foam with foil around it, in a home store. Is this what I will be using?

What do we buy for sheathing, is my question, please. Thank you.

[Greg]

Can you get a couple of pictures and post them? It may be foam board with foil as flashing to seal the window but without seeing it it is impossible to say.

Greg

[Barb P]

Thanks Greg. I am going to see if I can get the window installer to make good on this damage from leaking, expensive window, only one year old.

The stuff already in my wall, looks and feels like cardboard. . Sheathing is 1/4 inch thick.
My home is 28 years old

I wanted to know what sheathing, people use in their walls, if the window installer won't make good on it and we have to do it.

[Greg]

It does look like foil coated foam board to me also. I have heard of using it, but personally I have never seen it.

Greg