We really love this PPT slide because we really feel it demonstrates the importance of first considering the building envelope. The slide shows a large PV array on a project that we completed a few years ago. The project is a renovation of South Hills High School and we have a 26,ooo kW array on the roof. The array produces a small amount of PV for the project and is nearly the size array that would be required to power the average Pennsylvania home, 28,ooo kWh . In fact you can see the houses adjacent to the school and the area of our PV array spread out over the roofs of 5 houses. Yes that's right- if you want to power an average house using PV you need the roof space of your own plus 4 of your neighbors! If you consider the envelope first and design to Passive House standards you can make a house that requires an array small enough to fit on your own roof. We cannot just put PV on every building and solve our energy problems, we need to address the envelope first!