The present invention relates particularly to photovoltaic roofing systems in which photovoltaic elements are integrated on a roof deck with conventional roofing materials. In one aspect, a photovoltaic roofing system includes a two-part tee element disposed on a roof deck, the two-part tee element comprising a base piece including a central portion; two opposed horizontally-extending first and second flanges extending from the central portion, and a top piece attachment feature formed in the central portion, and a top piece including a base piece attachment feature mated with the top piece attachment feature of the base piece; and a vertically extending portion extending from the base piece attachment feature. A first photovoltaic element can be disposed on the roof adjacent the base piece with its edge disposed on the horizontally-extending first flange of the base piece of the two-part tee element.