City of Lake Oswego, Oregon

 

50.06.007 SOLAR ACCESS

1. SOLAR ACCESS FOR NEW DEVELOPMENT

a.    Purpose

The purposes of the solar access provisions for new development are to ensure that land is divided so that structures can be oriented to maximize solar access and to minimize shade on adjoining properties from structures and trees.

b.    Applicability

The solar design standard in LOC 50.06.007.1.d shall apply to applications for a development to create lots in the R-7.5, R-10, and R-15 zones and for development which creates lots intended for single-family detached dwellings in any zone, except to the extent the hearing body finds that the applicant has shown one or more of the conditions listed in LOC 50.04.004.1, Exemptions from Solar Design Standard, and LOC 50.04.004.2, Adjustments to Solar Design Standard, exist and exemptions or adjustments provided for therein are warranted.

c.    Development Review

The review procedures for a solar access permit are located in LOC 50.07.004.9, Solar Access Permit.

d.    Solar Design Standard

At least 80% of the lots in a development subject to this section shall comply with one or more of the options in this section. In order to be included in the 80% requirement a lot must also comply with LOC 50.06.007.1.e.

i.    Basic Requirement

A lot complies with this section if it:

(1)    Has a north-south dimension of 90 ft. or more; and

(2)    Has a front lot line that is oriented within 30° of a true east-west axis.

ii.    Protected Solar Building Line Option

In the alternative, a lot complies with this section if a solar building line is used to protect solar access as follows:

(1)    A protected solar building line for the lot is designated on the plat, or documents recorded with the plat; and

(2)    The protected solar building line for the lot is oriented within 30° of a true east-west axis; and

(3)    There is at least 70 ft. between the protected solar building line on the lot to the north and the middle of the north-south dimension of the lot to the south, measured along a line perpendicular to the protected solar building line; and

(4)    There is at least 45 ft. between the protected solar building line and the northern edge of the buildable area of the lot, or habitable structures are situated so that at least 80% of their south-facing wall will not be shaded by structures or non-exempt vegetation.

iii.    Performance Option

In the alternative, a lot complies with this section if:

(1)    Habitable structures built on the lot will have their long axis oriented within 30° of a true east-west axis and at least 80% of their ground floor south wall protected from shade by structures and non-exempt trees; or

(2)    Habitable structures built on the lot will have at least 32% of their glazing and 500 sq. ft. of their roof area which faces within 30° of south and is protected from shade by structures and non-exempt trees.

e.    Protection from Future Shade

Structures and non-exempt vegetation must comply with the Solar Balance Point provisions, LOC 50.06.007.2, for existing lots if located on a lot that is subject to the solar design standard in LOC 50.06.007.1.d, or if located on a lot south of and adjoining a lot that complies with the solar design standard.

(Ord. 2579, Repealed and Replaced, 03/20/2012)

2. SOLAR BALANCE POINT

a.    Purpose

The purposes of this section are to promote the use of solar energy, to minimize shading of structures by structures and accessory structures, and, where applicable, to minimize shading of structures by trees. Decisions related to these provisions are intended to be ministerial and not subject to a public hearing and are to be processed as a part of the consideration of the minor development permit for the affected structures.

b.    Applicability

This section applies to an application for a building permit for all structures in the R-7.5, R-10 and R-15 zones and all single-family detached structures in any zone, except to the extent the City Manager finds the applicant has shown that one or more of the conditions listed in LOC 50.04.004.3, Exemption from the Maximum Shade Point Height Standard, and LOC 50.04.004.4, Adjustments to the Maximum Shade Point Height Standards, exists, and exemptions or adjustments provided for therein are warranted. In addition, non-exempt vegetation planted on lots subject to the provisions of LOC 50.06.007.1.e, Protection from Future Shade, shall comply with the maximum shade point height standard. Solar plan procedures are located in LOC 50.07.004.9.

c.    Maximum Shade Point Height Standard

The height of the shade point shall comply with either subsection 2.c.i or ii of this section.

i.    Basic Requirement

The height of the shade point shall be less than or equal to the height specified in Table 50.06.007-1 or computed using the following formula. If necessary, interpolate between the five-ft. dimensions listed in Table 50.06.007-1.

TABLE 50.06.007-1: CALCULATION OF HEIGHT OF SHADE POINT
H	=	(2 x SRL) – N + 150
		5
Where H	=	The maximum allowed height of the shade point.
SRL	=	Shade reduction line (the distance between the shade point and the northern lot line); and
N	=	The north-south lot dimension; provided, that a north-south lot dimension more than 90 ft. shall use a value of 90 ft. for this section.

Provided, the maximum allowed height of the shade point may be increased one ft. above the amount calculated using the formula or Table 50.06.007-2 for each ft. that the average grade at the rear property line exceeds the average grade at the front property line.

TABLE 50.06.007-2: MAXIMUM PERMITTED SHADE POINT HEIGHT
Distance to Shade Reduction Line from Northern Lot Line (in ft.)	North-South Lot Dimension (in ft.)
	100+	95	90	85	80	75	70	65	60	55	50	45	40
70	40	40	40	41	42	43	44
65	38	38	38	39	40	41	42	43
60	36	36	36	37	38	39	40	41	42
55	34	34	34	35	36	37	38	39	40	41
50	32	32	32	33	34	35	36	37	38	39	40	41	42
45	30	30	30	31	32	33	34	35	36	37	38	39	40
40	28	28	28	29	30	31	32	33	34	35	36	37	38
35	26	26	26	27	28	29	30	31	32	33	34	35	36
30	24	24	24	25	26	27	28	29	30	31	32	33	34
25	22	22	22	23	24	25	26	27	28	29	30	31	32
20	20	20	20	21	22	23	24	25	26	27	28	29	30
15	18	18	18	19	20	21	22	23	24	25	26	27	28
10	16	16	16	17	18	19	20	21	22	23	24	25	26
5	14	14	14	15	16	17	18	19	20	21	22	23	24

ii.    Performance Option

The proposed structure, or applicable non-exempt vegetation, will shade not more than 20% of the south-facing glazing of existing habitable structure(s), or, where applicable, the proposed structure or non-exempt vegetation complies with LOC 50.06.007.1.d.ii or iii. If the protected solar building line is used, non-exempt trees and the shade point of structures shall be set back from the protected solar building line two and one-half ft. for every one ft. of height of the structure or of the mature height of non-exempt vegetation over two ft.

d.    Analysis of Allowed Shade on Solar Feature

i.    The applicant is exempt from this section if the lot(s) south of and adjoining the applicant’s property is exempt from LOC 50.06.007.2.c, Maximum Shade Point Height Standard.

ii.    Applicants shall be encouraged to design and site a proposed habitable structure so that the lowest height of the solar feature(s) will not be shaded by buildings or non-exempt trees on lot(s) to the south. The applicant shall complete the following calculation procedure to determine if the solar feature(s) of the proposed structure will be shaded. To start, the applicant shall choose which of the following sources of shade originating from adjacent lot(s) to the south to use to calculate the maximum shade height at the north property line:

(1)    Existing structure(s) or non-exempt trees; or

(2)    The maximum shade that can be cast from future buildings or non-exempt trees, based on Table 50.06.007-3. If the lot(s) to the south can be further divided, then the north-south dimension shall be assumed to be the minimum lot width required for a new lot in that zone.

TABLE 50.06.007-3: ADJACENT SHADE CALCULATION
North-south lot dimension of adjacent lot(s) to the south (in ft.)	100	95	90	85	80	75	70	65	60	55	50	45	40
Allowed shade height (SH) at the north property line of adjacent lot(s) to the south (in ft.)	12	12	12	13	14	15	16	17	18	19	20	21	22

iii.    The height of the lowest point of any solar feature of the proposed structure shall be calculated with respect to either the average elevation or the elevation at the midpoint of the front lot line of the lot to the south.

iv.    The applicant shall determine the height of the shadow that may be cast upon the applicant’s solar feature by the source of shade selected in subsection 2.d.ii of this section by using the following formula or Table 50.06.007-4.

SFSH	=	SH – (SGL/2.5)
Where: SFSH	=	The allowed shadow height on the solar feature.
SH	=	The height of the shade at the northern lot line of lot(s) to the south as determined in LOC 50.06.007.2.
SGL	=	The solar gain line (the distance from the solar feature to the northern lot line of adjacent lot(s) to the south).
Table 50.06.007-3 may be used to determine (SH) in the above formula.

TABLE 50.06.007-4: MAXIMUM PERMITTED HEIGHT OF SHADOW AT SOLAR FEATURE
Distance from Solar Gain Line to Lot Line (in ft.)	Allowed Shade Height (SH) at Northern Lot Line of Adjacent Lot(s) to the South (in ft.)
	22	21	20	19	18	17	16	15	14	13	12
50	2	1
45	4	3	2	1
40	6	5	4	3	2	1
35	8	7	6	5	4	3	2	1
30	10	9	8	7	6	5	4	3	2	1
25	12	11	10	9	8	7	6	5	4	3	2
20	14	13	12	11	10	9	8	7	6	5	4
15	16	15	14	13	12	11	10	9	8	7	6
10	18	17	16	15	14	13	12	11	10	9	8
5	20	19	18	17	16	15	14	13	12	11	10

v.    If the allowed shade height on the solar feature calculated in subsection 2.d.iv of this section is higher than the lowest height of the solar feature calculated in subsection 2.d.iii of this section, the applicant shall be encouraged to consider any changes to the house design or location which would make it practical to locate the solar feature so that it will not be shaded in the future.

e.    Solar Balance Point

If a structure does not comply with the maximum shade point height standard in LOC 50.06.007.2.c and the allowed shade on a solar feature standard in LOC 50.06.007.2.d, then the solar balance point of the lot shall be calculated. The solar balance point is the point on the lot where a structure would be the same from complying with both of these standards.

f.    Yard Setback Adjustment

A yard setback may be adjusted for solar access according to the provisions of LOC 50.08.001.3, Solar Access Yard Setback Adjustment.

(Ord. 2579, Repealed and Replaced, 03/20/2012)