A Solar Integrated Roofing System is typically thin film photovoltaics integrated with a new roofing system. The decision to go solar (or not go solar) will have a direct impact on the type of roofing system that would be specified for a given building. In other words, if you're going to be installing a small power plant on your roof, one which has a life expectancy of 25+ years, then it is necessary to make sure that the roofing system selected is one that is going to be watertight for at least that long, in order to avoid having to remove/replace the solar PV system when the useful life of the roof expires.

In the case where a new roofing system is warranted, Pfister Energy believes that a Solar Integrated Roofing System is the most appropriate choice for photovoltaics. The system specifications, which were developed in partnership with Soprema and UniSolar, call for the following components:

• Insulation (minimum 2" - polyisocyanurate)
• 1/8" SopraBoard
• Sopralene Torch Flam180 Base
• Sopralene Flam 250 FRGR Cap
• UniSolar PVL-136 (Thin-Film PV Laminates)

Pfister's solar integrated roofing system offers the following principal advantages:

• The Soprema 2-Ply SBS Modified Bitumen roof represents a superior roofing system as compared with a standard (single-ply) TPO, PVC or EPDM alternatives. The 2-Ply SBS modified bitumen roofing system will have a longer lifespan (30+ years) compared to a single-ply roofing system, which generally begins to fail in ~17 years on average.
• And unlike a conventional glass panel PV system, a thin-film, integrated approach entails no brackets, roof penetrations, or mounting hardware, enabling the avoidance of any potential roof leaks through PV related-penetrations and reducing the amount of labor to install the system.
• Tax laws allow any supporting structures for the solar panels and integral parts to be included in the federal tax incentives for solar. With a solar integrated roofing system, since the basic roof system and solar are in effect one unit, a large percent of the cost for the roof can be included in the incentives.
• The thin-film (amorphous silicon) photovoltaic modules are relatively light weight, adding only ~0.7 lbs. per square foot, as compared with a hard (glass) panel system which can add as much as 8 to 10 lbs. per square foot.
• Amorphous silicon PV is deposited on a substrate of stainless steel in three separate layers. These layers are called multi-junctions, and unlike conventional mono-crystalline PV panels, they enable these modules to utilize all ends of the light spectrum to produce electricity.
• Because of their multi-junction construction, thin-film products therefore produce more energy under low light conditions than glass panels. For example, as the sun rises and sets, the thin film panels will continue to produce energy when the glass panels will not.
• The thin-film modules are also shadow tolerant, with a large number of integrated bypass diodes enabling them to operate even when partially shadowed.
• In addition, amorphous silicon PV yields improved energy production under high-heat conditions (i.e. thin-film panels will not have as drastic a drop-off in production when the temperature rises as glass panels do).
• The end result of these features is that the UniSolar panels provide more energy production (kWh per rated Watt) when compared to conventional glass panels.