| 摘要 |
<p>The invention relates to a roof covering for cleaning and keeping the roofs of buildings clean, in particular of plant growth, or pollutants, comprising a sheet-like material (1) which reacts in co-operation with moisture. The sheet-like material forms a partly closed chamber, when in the state of being set upon an inferior roof element (5) and slowly releases the moisture accumulated in said chamber to the exterior.</p> |
