My neighbour just informed me that they had to change the vent on their high efficiency furnace. The furnace vents between our two houses and it used to have an elbow on it directing it along the walkway but she said the elbow was icing up and they had to change it. It is now directed straight at the brick on our house. She wants to lean a sheet of plastic, the type that's used as roofing material on decks, against our house to protect it. My question is, will the emissions cause damage to our brick over time? We are about four feet away. I don't want to have a sheet of plastic leaning there.