4.1.6.16. Roofs with Solar Panels

(See Note A-4.1.6.16.)

(1)

Where solar panels are installed on a roof, the snow loads, S, shall be determined in accordance with Sentences (2) to (6) or with the requirements for roofs without solar panels, whichever produces the most critical effect.

(2)

For the purposes of this Article, solar panels shall be classified as

(a)

Parallel Flush, where the panels are installed parallel to the roof surface with their upper surface less than or equal to C_b C_w S_s /γ above the roof surface,

(b)

Parallel Raised, where the panels are installed parallel to the roof surface with their upper surface greater than C_b C_w S_s /γ above the roof surface, or

(c)

Tilted, where the panels are installed at an angle to the roof surface with their highest edge greater than C_b C_w S_s /γ above the roof surface.

(3)

For sloped roofs with solar panels, the snow loads, S, shall be determined in accordance with the requirements for roofs without solar panels, except that the slope factor, C_s, shall be

(a)

taken as 1.0 for roof areas extending upslope from the downslope edge of a panel or array of panels at an angle of 45° from each side edge of the panel or array, and

(b)

as specified in Sentences 4.1.6.2.(5) to (7) for all other roof areas. (See Note A-4.1.6.16.(3))

(4)

For sloped roofs with Parallel Flush solar panels, the snow loads, S, shall be determined in accordance with the requirements for roofs without solar panels, except that

(a)

C_s shall be determined in accordance with Sentence (3),

(b)

where the gap width, w_g, between the panels along the roof slope is greater than or equal to the panel width, w_p, along the roof slope, the accumulation factor, C_a, shall be taken as

(i)

0.0 for the panels,

(ii)

2.0 for roof areas within a distance of w_p downslope from a downslope panel edge, and

(iii)

1.0 for all other roof areas, and (See Note A-4.1.6.16.(4)(b))

(c)

where the gap width, w_g, between the panels along the roof slope is less than the panel width, w_p, along the roof slope, C_a shall be taken as

(i)

0.0 for panel areas within a distance of w_g downslope from an upslope panel edge,

(ii)

1.0 for other panel areas,

(iii)

2.0 for roof areas in gaps between the panels, and

(iv)

1.0 for all other roof areas. (See Note A-4.1.6.16.(4)(c))

(5)

For roofs with Parallel Raised solar panels, the snow loads, S, shall be determined in accordance with the requirements for roofs without solar panels, except that

(a)

where the roof is flat, C_a shall be taken as

(i)

1.0 for the panels,

(ii)

1.0 for roof areas not under the panels,

(iii)

1.0 for roof areas under the panels within a distance of min (2h_g,2w_g) from a panel edge, where h_g is the gap height between the lower surface of the panels and the roof surface, and w_g is the gap width between the panels, and

(iv)

0.0 for other roof areas under the panels, and (See Note A-4.1.6.16.(5)(a))

(b)

where the roof is sloped, the snow loads, S, derived from Clause (a) shall be used, except that

(i)

C_s shall be determined in accordance with Sentence (3),

(ii)

S shall be taken as 0.0 on the panels, and

(iii)

S for all roof areas shall be taken as the sum of S on the panels, as derived from Subclause (a)(i) and shifted by a distance of w_p downslope onto the roof, where w_p is the panel width along the roof slope, and S on the roof areas, as derived from Subclauses (a)(ii) to (a)(iv). (See Note A-4.1.6.16.(5)(b))

(6)

For flat roofs with Tilted solar panels, the snow loads, S, shall be determined in accordance with the requirements for roofs without solar panels, except that

(a)

C_a shall be taken as 0.0 for the panels,

(b)

C_a shall be taken as 1.0 for roof areas beyond a distance of 5(h – C_b C_w S_s /γ) from the lowest edge of the panels, where h is the height of the highest edge of the panels above the roof surface,

(c)

except as provided in Clauses (d) and (e), for roof areas within a distance of 5(h – C_b C_w S_s /γ) from the lowest edge of the panels, C_a shall be taken as

(i)

1.25 for (h_g – C_b C_w S_s /γ) ≤ 0.3 m, where h_g is the gap height between the lowest edge of the panels and the roof surface,

(ii)

1.294 – 0.1471(h_g – C_b C_w S_s /γ) for 0.3 < (h_g – C_b C_w S_s /γ) ≤ 2.0 m, and

(iii)

1.0 for (h_g – C_b C_w S_s /γ) > 2.0 m, (See Note A-4.1.6.16.(6)(c))

(d)

except as provided in Clause (e), Ca shall be taken as 2.0 for roof areas within a distance of w_ph beyond the lowest edge of the panels, where w_ph is the horizontal projection of the panel width, w_p, along the sloped panel edges, and

(e)

where the panels, panel supports or back plates obstruct snow from sliding under the panels, the load of the increased volume of snow in the gaps between the panels shall be considered to be uniformly distributed. (See Note A-4.1.6.16.(6))