4.1.7.13. Roof-Mounted Solar Panels on Buildings of Any Height

(1)

Where solar panels are installed on a roof, the roof wind loads shall account for the wind loads on the solar panels, as determined in accordance with Sentences (2) to (7), or shall be determined in the same way as for the roof without solar panels, whichever approach results in the most critical effect.

(2)

For an array of solar panels where the panels are installed close and parallel to the roof surface with their upper surface not more than 250 mm above the roof surface and with gaps around the panels of not less than 6 mm, the net positive or negative pressure difference between the upper and lower surfaces of a panel or the array shall be calculated as follows:

where I_W, q, C_e, C_t, C_g, C_p = as defined in Sentence [[b-4.1.7.3.#^1hplca|4.1.7.3.(1)]], determined in the same manner as for the roof cladding, E = edge factor, as provided in Sentence [[b-4.1.7.13.#^4hplca|(4)]], and γ_a = pressure equalization factor, as provided in Sentence [[b-4.1.7.13.#^3hplca|(3)]].

(3)

The pressure equalization factor, γ_a, in Sentence (2) shall be

(a)

for a panel or an array where the panel chord length, L_p, is greater than 2 m or for a panel or an array that is within a distance of 2h2 from the roof edge or ridge, where h2 is the height of the panel’s highest point above the roof surface, taken as 1.0, and

(b)

for other panels or arrays, determined from Figure 4.1.7.13.-A based on the area of the panel or array over which the wind load is being calculated.

Figure 4.1.7.13.-A

γ_a Forming Part of Clause 4.1.7.13.(3)(b)

(4)

The edge factor, E, in Sentence (2) shall be taken as

(a)

1.5 within a distance of 1.5L_p from an exposed edge of the array of solar panels, as defined in Sentence (5), and

(b)

1.0 elsewhere.

(5)

For the purposes of Clause (4)(a), an exposed edge of the array of solar panels shall be considered to occur

(a)

where the distance to the next row of panels or the distance across a gap in the same row of panels exceeds 4h2 or 1.2 m, whichever is greater, or

(b)

where the distance to the roof edge exceeds 4h2 or 1.2 m, whichever is greater, and exceeds 0.5h, where h is the reference height of the roof.

(6)

For an array of solar panels mounted on a roof with a slope, α, less than or equal to 7°, where the panels are tilted relative to the roof surface, have a chord length, L_p, not greater than 2 m, and are installed such that the height of their lowest point above the roof surface, h₁, is not greater than 0.6 m, the height of their highest point above the roof surface, h2, is not greater than 1.2 m, and their tilt angle relative to the roof surface, ω, is not greater than 35°, or where the panels are installed parallel to the roof surface with their upper surface greater than 250 mm above the roof surface and with gaps not less than 6 mm between the panels, the net positive or negative pressure difference between the upper and the lower surfaces of a panel or the array shall be calculated as follows:

where I_W, q, C_e, C_t = as defined in Sentence [[b-4.1.7.3.#^1hplca|4.1.7.3.(1)]], determined in the same manner as for the roof cladding, and (C_g C_p)_net = net gust pressure coefficient, as provided in Sentence [[b-4.1.7.13.#^7hplca|(7)]].

(7)

The net gust pressure coefficient, (C_g C_p)_net, in Sentence (6) shall be calculated as follows:

where γ_p = parapet factor, determined as the lesser of 1.2 and (0.9 + h_pt /h), γ_c = chord factor, determined as the greater of (0.6 + 0.2L_p) and 0.8, E = as defined in Sentence [[b-4.1.7.13.#^2hplca|(2)]], and (C_g C_p)_n = normalized gust pressure coefficient, determined from [[b-4.1.7.13.#^figure-41713-bhplca|Figure 4.1.7.13.-B]] based on ω and A_N, where h_pt = height of the parapet above the roof surface, in m, h = reference height of the roof, in m, L_p = panel chord length, in m, ω = panel tilt angle relative to the roof surface, and

A_N = normalized panel or array area, calculated as

where A = panel or array area over which the wind load is being calculated, in m2, and L_b = normalized *[[a-1.4.1.2.#building|building]]* length, in m, determined as the lesser of

, h and W_S, where W_L = longest horizontal dimension of the *[[a-1.4.1.2.#building|building]]*, in m, and W_S = smallest horizontal dimension of the *[[a-1.4.1.2.#building|building]]*, in m.

(1) H = height of the.

(2) h = reference height of the roof.

(3) (C C) values are for both positive and negative values.

(4) For panels with 5° < w < 15°, linear interpolation is permitted.