use as building material

"use as building material", in relation to a renewable energy installation utilizing solar photovoltaic as its renewable resource, means the use of the solar photovoltaic modules serving the function of a principal building material with no secondary building material beneath such solar photovoltaic modules serving the same function.
PU(A) 385/2011 - RENEWABLE ENERGY (FEED-IN APPROVAL AND FEED-IN TARIFF RATE) RULES 2011
2. Interpretation