Chapter 18.160
SOLAR BALANCE POINT
Sections:
18.160.010 Purpose.
The purposes of this chapter 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 this chapter are intended to be ministerial. [Ord. 810, 2000; Code 2000 § 11.40.34.]
18.160.020 Applicability.
This title applies to an application for a building permit for all structures in all single-family zones and for detached single-family structures in any zone, except to the extent the approval authority finds the applicant has shown that one or more of the conditions listed in subsection (C) or (D) of this section exist, and exemptions or adjustments provided for there are warranted. In addition, nonexempt vegetation planted on lots subject to the provisions of CMC 18.155.020(E) shall comply with the shade point height standards as provided in subsections (B) and (C) of this section.
(A) Solar Site Plan Required. An applicant for a building permit for a structure subject to subsections (B) and (C) of this section shall submit a site plan that shows the maximum shade point height allowed under subsection (B) of this section, and the allowed shade on the proposed structure’s solar features as provided in subsection (E) of this section. If applicable, the site plan also shall show the solar balance point for the structure as provided in subsection (F) of this section
(B) Maximum Shade Point Height Standard. The height of the shade point shall comply with either subsection (B)(1) or (2) of this section.
(1) Basic Requirement. The height of the shade point shall be less than or equal to the height specified in Table A or computed using the following formula. If necessary interpolate between the five-foot dimensions listed in Table A.
H = (2 x SRL)-N+150
5
Where:
H = the maximum allowed height of the shade point (see Figures 4 and 5 following Chapter 18.165 CMC).
SR = shade reduction line (the distance between the shade point and the northern lot line, see Figure 6 following Chapter 18.165 CMC); and
N = the north-south lot dimension; provided, that a north-south lot dimension more than 90 feet shall use a value of 90 feet for this section, and provided the maximum allowed height of the shade point may be increased one foot above the amount calculated using the formula or Table A for each foot that the average grade at the rear property line exceeds the average grade at the front property line.
|
Table A Maximum Permitted Shade Point Height (in Feet) |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
North-South lot dimension (in feet) |
|||||||||||||
|
Distance to reduction line from northern lot line (in feet) |
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 |
|
|
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 |
20 |
24 |
(2) Performance Option. The proposed structure, or applicable nonexempt vegetation, will shade not more than 20 percent of the south-facing glazing of existing habitable structure(s) or, where applicable, the proposed structure or nonexempt vegetation will comply with CMC 18.155.020(A). If CMC 18.155.020(B), Protected Solar Building Line Option, is used, nonexempt trees and the shade point of structures shall be back from the protected solar building line two and one-half feet for every one foot of height of the structure or of the mature height of nonexempt vegetation over two feet.
(C) Exemption from the Maximum Shade Point Height Standard. The community development director or his or her designee shall exempt a proposed structure or nonexempt vegetation from subsections (A) and (B) of this section if the applicant shows that one or more of the conditions in this section exist, based on plot plans or plats, corner elevations or other topographical data, shadow patterns, suncharts or photographs, or other substantial evidence submitted by the applicant.
(1) Exempt Lot. When created, the lot was subject to Chapter 18.155 CMC and was not subject to the provisions of CMC 18.155.020(E).
(2) Pre-Existing Shade. The structure or applicable nonexempt vegetation will shade an area that is shaded by one or more of the following:
(a) An existing or approved building or structure;
(b) A topographic feature;
(c) A nonexempt tree that will remain after development of the site. It is assumed a tree will remain after development if it is situated in a building setback required by this code; is part of a developed area or landscaping required by this code, a public park or landscape strip, or legally reserved open space; is in or separated from the developable remainder of a parcel by an undevelopable area or feature; or is on the applicant’s property and not affected by the development. A duly executed covenant also can be used to preserve trees causing such shade.
(3) Slope. The site has an average slope that exceeds 20 percent in a direction greater than 45 degrees east or west of true south based on a topographic survey by a licensed professional land surveyor.
(4) Insignificant Benefit. The proposed structure or nonexempt vegetation shades one or more of the following:
(a) An undevelopable area; or
(b) The wall of an unheated space, such as a typical garage; or
(c) Less than 20 square feet of south-facing glazing.
(5) Public Improvement. The proposed structure is a publicly owned improvement.
(D) Adjustments to the Maximum Shade Point Height Standard. The community development director shall increase the maximum permitted height of the shade point determined using subsection (B) of this section to the extent it finds the applicant has shown one or more of the following conditions exist, based on plot plans or plats, corner elevations or other topographical data, shadow patterns, suncharts or photographs, or other substantial evidence submitted by the applicant.
(1) Physical Conditions. Physical conditions preclude development of the site in a manner that complies with subsection (B) of this section due to such things as a lot size less than 3,000 square feet, unstable or wet soils, or a drainage way, public or private easement, or right-of-way.
(2) Conflict Between the Maximum Shade Point Height and Allowed Shade on the Solar Feature Standards. A proposed structure may be sited to meet the solar balance point standard described in subsection (A) of this section or be sited as near to the solar balance point as allowed by subsection (F) of this section if:
(a) When the proposed structure is sited to meet the maximum shade point height standard determined using subsection (B) of this section, its solar feature will potentially be shaded as determined using subsection (E) of this section; and
(b) The application includes a form provided by the city that:
(i) Releases the applicant from complying with subsection (B) of this section and agrees that the proposed structure may shade an area otherwise protected by subsection (B) of this section;
(ii) Releases the city from liability for damages resulting from the adjustment; and
(iii) Is signed by the owner(s) of the properties that would be shaded by the proposed structure more than allowed by the provisions of subsection (B) of this section;
(c) Before the city issues a permit for a proposed structure for which an adjustment has been granted pursuant to this subsection, the applicant shall file the form provided for in this section in the office of the county recorder with the deeds to the affected properties.
(E) Analysis of Allowed Shade on Solar Feature.
(1) The applicant is exempt from this subsection if the lot(s) south of and adjoining the applicant’s property is exempt from subsection (B) of this section.
(2) 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 nonexempt 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:
(a) Existing structure(s) or nonexempt trees; or
(b) The maximum shade that can be cast from future buildings or nonexempt trees, based on Table C. 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.
(3) 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.
(4) 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 this subsection by using the following formula or Table B.
(SFSH) = SH-(SGL/2.5)
Where:
SFSH = the allowed shadow height on the solar feature (see Figure 8 following Chapter 18.165 CMC).
SH = the height of the shade at the northern lot line of lot(s) to the south as determined in this subsection.
SGL = the solar gain line (the distance from the solar feature to the northern lot line of adjacent lot(s) to the south; see Figure 7 following Chapter 18.165 CMC).
|
Table B |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
Maximum Permitted Height of Shadow at Solar Feature (in feet) |
|||||||||||
|
|
Allowed Shade Height at Northern Lot Line of Adjacent Lot(s) to the South (in Feet) |
||||||||||
|
Distance from Solar Gain Line to Lot Line (in Feet) |
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 |
Table C may be used to determine (SH) in the above formula.
|
Table C |
|||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
North-south lot dimension of adjacent lot(s) to the south |
100 |
95 |
90 |
85 |
80 |
75 |
70 |
65 |
60 |
55 |
50 |
45 |
40 |
|
Allowed shade height at the north property line of adjacent lot(s) to south |
12 |
12 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
(5) If the allowed shade height on the solar feature calculated in this subsection is higher than the lowest height of that calculated in this subsection the applicant shall be encouraged to consider any changes to the house design or location which make it practical to locate the solar feature so that it will not be shaded in the future.
(F) Solar Balance Point. If a structure does not comply with the maximum shade point height standard in subsection (B) of this section and the allowed shade on a solar feature standard in subsection (E) of this section, then the solar balance point of the lot shall be calculated (see Figure 8 following Chapter 18.165 CMC). The solar balance point is the point on the lot where a structure would be the same from complying with both of these standards.
(G) Yard Setback Adjustment. The city shall grant an adjustment to the side, front, and/or rear yard setback requirement(s) by up to 50 percent if necessary to build a proposed structure so it complies with either the shade point height standard in subsection (B) of this section, the allowed shade on a solar feature standard in subsection (E) of this section, or the solar balance point standard in subsection (A) of this section (see Figure 8 following Chapter 18.165 CMC). This adjustment is not intended to encourage reductions in available solar access or unnecessary modification of setback requirements, and shall apply only if necessary for a structure to comply with the applicable provisions of this chapter. The following list illustrates yard adjustments permitted under this section:
(1) R-7 Zone:
(a) A front yard setback may be reduced to not less than 10 feet.
(b) A rear yard setback may be reduced to not less than three feet. A side yard setback may be reduced to not less than three feet.
(2) R-10 Zone:
(a) A front yard setback may be reduced to not less than 13 feet.
(b) A rear yard setback may be reduced to not less than 13 feet. A side yard setback may be reduced to not less than five feet.
(H) Review Process. Compliance with the standards in this chapter shall use a Type I procedure specified in CMC 18.15.010(A). [Ord. 810, 2000; Code 2000 § 11.40.35; Ord. 841 Exh. 2, 2003.]