투습정항계수 때문인데요.. 역전지붕의 경우 평지붕에 사용하셔도 되어요.
홈페이지의 질문답변 중 하나 입니다.
Can you use ice and water shield on a flat roof?
Yes, you can use an ice and water shield on flat roofs. It provides two necessary layers of protection for your roof that will absorb small amounts of moisture under the membrane if any water passes through the leak barrier.
아래 글이 도움이 되실 것 같습니다.
http://www.phiko.kr/bbs/board.php?bo_table=z10_02&wr_id=440
지붕용과 벽체용만 나옵니다
홈페이지의 질문답변 중 하나 입니다.
Can you use ice and water shield on a flat roof?
Yes, you can use an ice and water shield on flat roofs. It provides two necessary layers of protection for your roof that will absorb small amounts of moisture under the membrane if any water passes through the leak barrier.