模拟建筑物热负荷和冷负荷的计算机程序通常要求人工照明负荷成为数据的一部分，通常以小时为单位，以单位面积的功率为单位。因此，没有规定外部光线在多大程度上可以满足周边区域的照明要求。我们在本文中表明，这种运行模式会带来严重的能量损失。本文首先描述了大气模型和辐射数据集，从中我们计算了太阳在可见光带中直接和漫射辐射对水平和垂直表面的影响。 接下来，描述了一种计算周界区域自然光的新模型。最后，本文给出了两个例子，说明了自然光在很大程度上可以满足照明要求，并由此节省了大量成本。引文:密歇根州底特律ASHRAE学报第85卷第2部分研讨会

Computer programs which simulate the heating and cooling loads in buildings usually require the artificial lighting load to be part of the data, generally specified by hour in units of power per unit area. Consequently, no provision is made for the degree to which outside light could satisfy the illumination requirement in a perimeter zone. We show in this paper that there is a severe energy penalty for that mode of operation. The paper begins by describing the atmospheric model and radiation datasets from which we have calculated the direct and diffuse solar radiation in the visible band impinging upon horizontal and vertical surfaces. Next, a new model for calculating the natural light in a perimeter zone is described. Lastly, the paper gives two examples which demonstrate the significant degree to which natural light can satisfy the illumination requirements, and the large cost savings which result.