Choose the combination that results in the highest U, use U in your calculations.
$$U = 1.4(D+F)$$
$$U = 1.2(D+F+T) + 1.6(L+H) + 0.5(L_r or S or R)$$
$$ U = 1.2D + 1.6(L_r or S or R) + (1.0L or 0.8W)$$
$$ U = 1.2D + 1.6W + 1.0L + 0.5(L_r or S or R)$$
$$ U = 1.2DL + 1.0E + 1.0L + 0.2S$$
$$U = 0.9D + (1.6W or 1.0E) + 1.6H$$
D = Dead Load, L = Live Load, T = self-straining, H = earth pressure, \(L_r\) = roof live load, S = Snow Load, R = rain load, E = earthquake load