Chapter 7.5
Energy Conservation and Efficiency

• ALL
• Remove Code Barriers
• Create Incentives
• Fill Regulatory Gaps

Site & Solar Orientation

INTRODUCTION

The design, orientation, and layout of a structure directly affect the efficiency of solar energy generation.[1] Solar energy regulations may require solar-ready lot and building orientation,[2] and site plan regulations may require a site layout that provides a minimum length of time for solar energy systems to have access to sunlight.[3] Optimum solar capacity can be achieved, in part, by adopting regulations that require street and building orientation to have the long axis running from east to west in order to maximize sunlight exposure emanating from the south.[4] Codes can allow flexibility in their setback requirements, as well as limit the height and location of structures, so as not to interfere with a development’s capability to harvest and produce solar power.[5] Communities that adopt solar siting ordinances into their site development standards may control the height and location of buildings through stricter minimum setbacks to ensure neighboring lots maintain solar access.[6]

The effectiveness of site orientation is heavily dependent on ordinances, which combine the concept with shade prevention or “solar fences”.[7] For ordinances addressing off-property shading and off-property shading disputes see Process to Resolve Tree Interference with Solar Access and Limiting Off Property Shading of Solar Energy Systems.

EFFECTS

Site orientation is a critical component to “passive” solar energy collection, a process that involves harnessing solar energy to heat a building without the use of panels or other instruments. The ideal orientation for buildings to harvest solar energy is within five degrees of true south, though placement within 30 degrees still garners a considerable solar contribution.[8] Aligning a house in accordance with the recommended axis, combined with design features such as thermal mass material and the installation of glazed southern facing windows, can reduce heating costs for homeowners by as much as 25 percent without the need to install additional solar energy collection equipment.[9] Proper placement of sunspaces or glass rooms on the southern end of properly aligned structures can account for up to 60 percent of a residence’s heating.[10] Placing an awning or similar covering instrument over windows in homes utilizing passive solar energy reduces cooling costs in the summer because of the sun’s higher trajectory.[11]

Using photovoltaics (PV) and other solar collectors to store energy for later use is known as “active” solar energy collection. The orientation of a structure affects the effectiveness of solar energy equipment.[12] Solar panels on roofs facing the east or west will return approximately 20 percent less energy than south facing panels.[13] North facing panels offer little to no energy production.[14] An array aligned to face south reduces the amount of time it takes for a PV system to provide a full return on the cost of the investment.[15] In one study, an east facing, 10 kilowatt PV array in Golden, Colorado increased the simple payback period by over three years over a similar north facing array, while a west facing array increased the payback period by over five years.[16]

Building a home with the long walls aligned on the east-west axis provides the residents with a better perception of cardinal direction, time, weather conditions, and aids understanding of “the world outside the building.”[17] The costs associated with constructing buildings with elongated south facing walls are minimal, and can be outweighed by the positive effects of lighting and energy consumption.[18] Utilization of passive solar carries the additional benefit of promoting health and adding comfort to buildings by reducing dependency on furnaces. Forced air heating systems used in typical construction create discomfort for occupants by pulling dry air from outside of the structure, significantly decreasing the level of humidity inside.[19] This can lead to a sensation of dry skin, while also creating an environment conducive to the well-being of viruses and bacteria.[20] By requiring only sunlight and proper design, passive solar heating can circumvent the risks associated with traditional heating systems.

EXAMPLES

Boulder, CO

Boulder is divided into three “Solar Access Areas.”[21]  Areas I and II protect existing access to sunlight for south facing yards, walls and rooftops, while Area III calls for a permit process to be employed when granting unfettered solar access would unduly hinder development.[22] The City utilizes solar fences to preserve the right to sunlight in Solar Access Areas I and II.[23] Flexibility is offered in the form of an application for an exception when developers wish to deviate from the code’s solar requirements.[24]

Solar siting requirements for new subdivisions and planned unit developments require residential units to have a roof surface oriented within thirty degrees of a true east-west direction and to be either flat or sloped in a southern direction.^[25] Each residential unit in a Solar Access Area must also have an exterior wall surface that is oriented within thirty degrees of a true east-west direction and located on the southernmost side of the unit.[26] All nonresidential buildings with an anticipated hot water demand of one thousand or more gallons per day must have a roof surface that is flat or oriented within thirty degrees of a true east-west direction.^[27]

When subdividing land, Boulder’s municipal code requires subdivision plats to maximize solar energy use by requiring solar siting criteria for new subdivisions.^[28] The development must orient streets, lots, open spaces and buildings to ensure that each principal building on the lot is able to realize its solar potential.[29] The code also requires lots to be designed to avoid shading by nearby structures and minimize off site shading of adjacent properties.^[30] Additionally, developers must design the building shape to maximize utilization of solar energy and must utilize open space areas to protect buildings from shading by other structures.^[31]

To view the provisions, see Boulder, CO Municipal Code § 9-9-17, Boulder, CO Municipal Code § 9-12-12(a)(1)(O)(i-iv).

Eatonton, GA

Eatonton allows rooftop solar energy collectors as a by-right accessory structure in every district with the exception of its Downtown Business Overlay zone.[32] In the Downtown Business Overlay zone, solar energy collectors are permitted pursuant to the regulations of the underlying district.[33] The City requires that new structures be built ready to exploit solar energy, and developers must take into account building orientation, the effects of shading and wind-screening by vegetation, and the possibility of shading nearby properties.[34] Streets in a new development are to be aligned on an east west axis where feasible to encourage maximum sunlight exposure when erecting new buildings.[35]

Within reasonable bounds, new subdivisions should be platted to maintain or improve the quality of active and passive solar energy systems.[36] Cluster subdivisions must be designed to promote solar energy for dwellings, and should consider placing high-density units on south facing slopes and low-density units on north facing slopes.[37] To reduce shading, structures should be placed on the northern end of lots, and larger structures should be placed on the northern side of smaller ones.[38] Eatonton’s planning and zoning commission is required to consider if approval of new projects will block an existing solar collector’s access to sunlight during peak daylight hours.[39] Both the City and the planning and zoning commission have the right to reject platting and subdivision plans that are prohibitive to the reasonable development of solar collectors or other renewable energy devices.[40]

To view the provision, see Eatonton, GA Code of Ordinances §§ 53-4, 53-(9-10).

ADDITIONAL EXAMPLES

North Las Vegas, NV Code of Ordinances § 17.24.140-1: Menu of Sustainability Options (offering density bonuses through a point system, including for orienting lots and streets to maximize solar efficiency).

Anchorage, AK Code of Ordinances § 21.07.110(C)(8)(e) (requiring residences with eight or more units to select three items from a list, including the provision of windows or primary entrances on twenty percent of a solar oriented wall which is likely to have six or more hours of sunlight from March through September).

ADDITIONAL RESOURCES

Planning for Solar Energy Briefing Papers, American Planning Association (2013), https://perma.cc/VE54-W5PE (providing a comprehensive overview of many solar energy related topics).

John R. Nolon, Mitigating Climate Change by Zoning for Solar Energy Systems: Embracing Clean Energy Technology in Zoning’s Centennial Year, Pace Law Faculty Publications (Dec. 2015), https://perma.cc/5ESR-DAWT (detailing strategies for local governments to promote solar energy).