Covering the moss is a waste of time and effort. It is easily removed with a water and ammonia solution. No need to seal the brick, if the moss wants to grow, usually in a wet and dark environment it will grow back on the sealed brick. As for your respiratory issues please consult a physician, you won't get any medical answers on a home forum on the internet, and if you do I wouldn't take it.

Thank you for the info.

You are most welcome, I hope things work out for you and you get your respiratory problem in check.

Are you sure that this is moss? Moss needs light to grow. Any green plant needs light to grow. They also need water to grow. Is water pooling on the brick? The real solution needs to be proper drainage first and then, maybe, sealing.

You respiratory problems are probably not caused by anything growing on the outside of the window, but may be related to it. If the windows are not draining properly on the outside, you may be getting water in the walls. That will cause mold to grow which is a more likely cause for indoor air quality issues.

Please, inspect your windows carefully to see that water is draining properly. I think that 10% bleach (from 6% hypochlorite stock) will work better to kill moss than ammonia will.