At the May 8, 2018 meeting of the Board of Supervisors, a public hearing was held to consider changes to the General Plan and Zoning Code. The proposed Zoning Code changes included the removal of a requirement of one covered parking space for each residence in multi-family residential developments. After final action was taken to adopt the proposed change, the Board directed staff to provide further information on parking lot shade structure requirement for multi-family residences and their potential use for mounting photovoltaic solar panels at a future meeting. Staff was also directed to look into the costs to development and possible alternatives.
BACKGROUND
The Yolo County Zoning Code requires one (1) parking space for each one-bedroom multi-family residential unit and one and one-half (1 ½) parking spaces for each two or more-bedroom unit, as per Table 8-2.1306 in the Off-Street Parking and Loading Ordinance. Prior to the 2018 adopted Zoning Code changes, the Table also required that, “one (parking space) shall be covered per dwelling unit.” It should be noted that Section 8-2.1312 of the Zoning Code still requires tree plantings that will result in 50 percent shading of the parking lot surface within ten years of commencement of the permitted land use. This requirement may be waived, “if the parking lot proposal includes solar panels or a paving technique that radiates significantly less heat than traditional asphalt.”
The intent of covered parking requirements is primarily to protect residents’ vehicles from heat and weather. Sheltered vehicles are much cooler which reduces the air conditioning load on vehicles and protects them from UV damage. Wear and tear on vehicles is likely to have a greater impact on residents of multifamily housing who often have more limited incomes and resources. This does add a nominal cost to construction of the residences though. Although most installers will only give personalized quotes, the internet source, Homeadvisor, lists the typical price range for a steel carport for two vehicles as between $2,043 and $4,350 and another website quoted $2,500 to $3,500 (Understandsolar, 2018). In addition to protecting residents’ vehicles, a carport this size could support 5 kW worth of 300 W solar panels.
Placing solar on a carport does not increase the cost of the solar array because rooftop and carport installations use the same type of panels. A benefit of placing solar panels on a carport rather than a roof however is that there is greater flexibility in the location, angle, and size of the array, which can all increase the efficiency of the panels to help offset the added cost of the carport construction (Understandsolar, 2018).
Whether shade structures are used for solar installations or not, the covered parking requirement for multifamily residential development was compatible with the County Strategic Plan goal of a sustainable environment. Besides protecting vehicles from deterioration, the other major benefit of shade structures is to reduce urban heat island effects that result from the asphalt surfaces typically used to pave parking lots. Hotter urban areas can negatively affect health and increase energy use. Besides the obvious effects of heat stress on people, higher air temps impact air quality by increasing production of smog and ground level ozone. Energy use increases as the use of air conditioning and refrigeration rise due to warmer temperatures (Guan, 2011).
Alternatives to carport shade structures include tree canopy cover over parking areas, underground parking, or a ground-level parking garage within the residential building. Of these, underground parking and parking garages are prohibitively expensive at the densities of development currently found in the County. Tree planting to provide canopy cover to parking areas is the most affordable alternative and as mentioned above, the County currently has tree cover requirements in the Code; however, staff does not think that this is sufficient to take the place of the removed carport requirement given the problems associated with relying on tree canopy for parking lot shading.
Parking Lot Shade Comparison
| Type of Shade Structure |
Expense |
Effectiveness |
Additional benefits |
| Tree Canopy |
Low |
Low |
Water retention, Transpiration, Carbon storage |
| Carports |
Moderate |
High |
Solar Mounting |
| Parking Garages |
Very High |
High |
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Although tree planting is the most economical means of shading parking lots and can produce many benefits beyond shade, the likelihood of tree canopy cover providing the required 50% shaded parking area surfaces is poor. As shown in the attached review of parking lot shade ordinances (Attachment A), actual tree shade for projects after ten to fifteen years is more likely to approach 25% shade cover for the parking area rather than the 50% typically required by these ordinances.
Though shade structures are more expensive than tree plantings, trees are typically neglected after planting which lowers their ability to provide the expected amount of shade. Maintenance and replacement of damaged or lost trees, which are rarely enforced, would increase their costs. Shade structures may have a higher initial cost, but can provide the required amount of shade immediately and when paired with solar panels, they can recuperate some of their cost in the long term through energy savings. Solar parking canopies are growing in popularity for public and business parking lots, but are less likely to be found in residential applications. They are appropriate for multi-family parking areas and may even be necessary with the new solar requirements for residential development proposed for the update of the California Building Code.
Outreach
This report was shared with Lisa Baker, Executive Director of Yolo County Housing Authority. Ms. Baker's commented that covered parking structures are not always feasible for "deeply affordable housing" at a the standard previously required in the Zoning Code.
Conclusion
Staff concludes that parking shade structures are an effective and relatively economical means of shading paved parking lot areas. Staff recommends that the requirement for one covered parking space per residential unit in a multifamily development should be restored to the zoning code with flexibility to exempt the requirement in cases of very low income units or other similar special circumstances. Additionally, strategies to better ensure the effectiveness of trees for shading parking areas should be further studied for all parking areas.
Cited Sources
Guan, K. K. 2011. Surface and ambient air temperature associated with different ground material: a case study at the University of California, Berkeley.
https://nature.berkeley.edu/classes/es196/projects/2011final/GuanK_2011.pdf
Homeadvisor. Referenced Oct 10, 2018. How much does it cost to install a metal carport?
https://www.homeadvisor.com/cost/garages/metal-carport/
Richardson, L. Posted March 2018. Solar carports: How do they work and how much do they cost? Energysage. https://news.energysage.com/what-is-a-solar-panel-carport/
Understandsolar. Referenced Oct 10, 2018. What is a solar carport, and how much does it cost? https://understandsolar.com/solar-carport/
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