My first house I owned with my ex-husband had a porch added onto the side of one of the bedrooms, and they left the window in, so it overlooked the new stairs down into the basement. Frankly, it just looked bizarre, and made setting up furniture on that wall very difficult.

You don't say what the rooms are going to be where you are "losing" the windows, but if you are concerned about the loss of light, I would recommend "replacing" the window with a tubular skylight in the ceiling over where the windows are gong to be walled over--they add a shocking amount of light, and I love mine. In my kitchen, which had been very dark, now I keep thinking the lights are on when they are not, it's just the tube bringing in the sun.

Carla in Sac

I saw the same situation in a magazine. The owners ended up creating a hallway between the new addition and the outside of the home so the light could flow through the new outside windows into the old outside windows. The hallway ended up being a much used path in the home. Good luck!

A hallway is the logical solution, since you are required to provide a min. value of natural light and ventilation.
The other option requires opening the adjoining wall 50% as well as increasing the window area in the new exterior wall to accommodate both areas.

Love the hallway idea. Are you working with an architect? If not, the contractor should be able to suggest how that might fit. Just make sure it's proportional to the house and not just a narrow strip that looks like it was added to bring in light. Should be functional too, from a walking perspective.