A key part of the DC Construction Code Supplement of 2017 requires that newly constructed commercial buildings meet certain renewable energy requirements. Though there are various pathways to compliance, we will focus on the onsite renewable energy codes for the purpose of this post. Under this code, new multi-level commercial buildings above 10,000 square feet of floor area must either build systems that produce a certain amount of energy OR design their rooftops with 25% of the horizontal space designated as “solar ready”. Any property that lacks sufficient exposure to the southern sky may be exempted from this mandate AND they also purchase certified renewable electricity credits (RECs) proportionate to the building’s electrical usage.
Section 13: The Prescriptive Renewable Path
The pathway that requires the actual installation of a PV array is referred to as the Prescriptive Renewable Path and located in section 13 of the DC Code. The Prescriptive Renewable Path requires PV systems to produce 32 kWh per year per square meter of total roof space. To provide some context around this, today we would estimate that a roof that is fully built out with solar (and has few obstructions) would produce around 130 kWh per year per square meter. Given that 32 kWh is just shy of 25% of the fully built out PV system, this pathway would seem to be roughly commensurate to the “solar ready” pathway from a design requirement perspective. If a building uses high efficiency appliances, the production threshold would be reduced to 22 kWh or an expected 17% of the total roof space. Thus, if you are tight on roof space and using high efficiency appliances, it may be easier for you to take this pathway.
Section 5.44: “Solar Ready” Area Requirements
The 25% “solar ready” pathway is Section 5.44 of DC’s Construction code. Though “solar ready” is not explicitly defined in the code, the term is generally understood as open space that would allow for the integration of a complete solar PV system without requiring significant structural changes. A preliminary design would still be expected to verify compliance with this code, but will not require an electrical diagram or shading analysis. The space dedicated to solar should include not only the panels, but all of the balance of system components, such as the racking system and inverter.
It’s common for laws and codes as written to have ambiguity in their mandates, with responsibility delegated to corresponding agencies, in this case the DC Department of Consumer and Regulatory Affairs, to interpret code to achieve the goals of the legislation. In some cases, the agency will report back to City Council and request that the legislation be amended to better accommodate the reality on the ground. Given that this process is still ongoing, note that the statements below reflects the latest feedback we’ve received from the DCRA and are still subject to further review.
DCRA will allow for vertically mounted panels to count towards the 25% solar ready area, but the counted area of the panel face will be discounted by 20-50%, depending on the orientation of the panel. A shading analysis will be required if vertically mounted panels are expected to be used in the solar ready space.
It is currently not clear as to whether bifacial panels (panels that both produce electricity from light coming directly from the sun and from light reflecting back off the roof) could count both sides of the panel toward the 25% solar ready area, but it seems like a longshot.
Other Considerations for DC Solar Code Compliance
DCRA has indicated that all green roof space that has adequate room for panels may qualify as part of the 25% solar ready area. This is because the soil in a green roof acts as a ballast for the solar PV system. Without the weight of a ballast, PV system would need to be directly attached to the roof to withstand strong gusts of wind.
If the rooftop is still lacking sufficient space to meet the “solar ready” requirements, the use of a rooftop canopy system may be critical to comply with the code. These systems allow for panels to be suspended above rooftop equipment and amenity space. For very tall buildings, be mindful of DC’s infamous height restrictions! Your “solar ready” roof area must still comply with all other zoning restrictions.
Additionally the requirements listed above apply only to multilevel commercial buildings, with lower standards applicable to single story commercial buildings.
These codes can be pretty daunting at first. Thankfully, DC has some of the most generous incentives for solar available in the nation. Honeydew Energy Advisors are available to help make sense of this code and provide financial analysis on the proposed systems. For more information, please email [email protected] or fill out the form below.