How is zmesh installed under existing asphalt shingles or do you just put it on top?

How is zmesh installed under existing asphalt shingles or do you just put it on top?

ZMesh is installed under shingles for several reasons.  Heatizon offers a long term solution to winter roof problems and we believe in do the project once and do it right.  ZMesh is protected when it is installed under the shingles and in most cases will outlast the roofing above. Thinking long term we offer an invisible solution as well as the longevity of a system that will perform for the long term so the customer will never have to worry again about winter roof problems. To install ZMesh existing shingles will need to be removed by a roofing contractor so it can be installed on the sub-roof with a layer of ice and water shield over the top of the system before shingles are installed back over it.