Optimizing for Speed in Commercial Rooftop Applications: Page 2 of 3

Standardize Products and Procedures

Standardizing your company’s offerings on a small set of products and vendors should be a no-brainer. To provide vendors with the volume commitments necessary to drive down unit costs as much as possible, every solar company should work with a select few partners for modules, inverters and racking. Having a standard set of products also allows everyone to learn how to efficiently design and install projects utilizing those products. (See Table 1, “Low-Slope Mounting System Vendors,” for an overview of commercial mounting system product lines.)

To work faster and reduce errors, each solar contractor should be working toward standardizing its drawing templates, sheet notes, details, specifications, contracts and scope-of-work documents. It is also beneficial to standardize basic design parameters such as tilt angle and row spacing for similar projects. The sales team can standardize on the amount of roof area held for contingency. Companies may even want to establish standard practices for equipment locations and ac collection strategies, or for when to upsize conductors. Though standardization is not a substitute for design optimization, it is important to optimize the system design as much as possible before sending out proposals.

Create Value Engineering Guidelines

Pair standardizations with clear guidelines for determining when it makes sense to spend time and resources on value engineering activities, as well as metrics for evaluating different design options. As a guideline for the project team, consider putting a value on project time as a means of determining when to invest in value engineering. Placing a value on time, and making sure the project team understands how to use that number as a guideline for devoting resources to value engineering, is a simple way to align the project team with company goals.

For instance, imagine that a project manager hears of a new wire management system that she thinks can save $4,000 in material and labor for a 1 MW project. After a quick review, the design engineer determines that it will take one engineer about 4 days to establish whether the solution is viable and to integrate it into project specifications and details. If the value of the electricity generated by the PV system is $600 per day and the burdened cost of an engineer is $800 per day, then the cost to integrate the new wire management system into the project is $5,600  ($1,400 per day times 4 days). This review suggests that even though the new hardware option could reduce project hard costs, it is not a wise investment, as the savings ($4,000) are less than the costs ($5,400).

The team also needs easy-to-follow and relatively accurate metrics and rules of thumb for estimating cost savings for design alternatives. Make sure the design team has access to simplified per-unit cost estimates—for equipment, conduit, wire and labor—and knows how to use them quickly. These metrics can help prevent the dreaded “analysis paralysis.”

Do Your Due Diligence

It is critical to meet with permitting officials early. Never assume that it is better to ask for forgiveness later than to seek permission in advance, or that a new AHJ might not have the same concerns you have encountered in other jurisdictions. Do not hesitate to ask questions of building or fire officials, even if you are afraid of drawing their attention to a disputed code interpretation. It is far better to get their opinion early on than to have them find something they do not like late in the game.

This is especially true when dealing with fire officials on commercial roof-mounted PV projects. In spite of the best efforts of industry stakeholders, including the Solar America Board for Codes and Standards (solarabcs.org), a number of areas in the fire codes remain open to interpretation, such as whether to apply commercial or residential setbacks to a sloped roof at an apartment complex. Moreover, fire officials have every right to ask for something that goes above and beyond minimum code requirements if they believe it will improve safety. Some fire officials object to pathways that dead-end, even if the pathways terminate at skylights or mechanical equipment. Others insist on straight pathways, even where the design requires a jog to keep the access path over a structural member. You can expedite project timelines by clarifying these types of issues before starting on a design.

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