Simulation tools for predicting building thermal performance and solar system performance must accurately calculate solar irradiance to surfaces of arbitrary orientation. This is imperative to correctly predict passive solar gains to buildings and to accurately estimate thermal and electrical production of solar collectors. In cold climates, where snow covers the ground for long periods of time, ground reflected radiation can represent a substantial fraction of the total incident irradiance to highly tilted and vertical surfaces (e.g. windows). A new model has been developed to improve the calculation of ground-reflected radiation in simulation tools. The model is based upon empirical observations taken at a measurement site in Ottawa (Canada), and has been validated using disjunct data from the measurement site, and with published data from two other sites in the USA. The model was found to increase the accuracy of ground reflectivity predictions for cold and humid climates.

用于预测建筑物热性能和太阳系性能的仿真工具必须准确计算任意方向的表面上的太阳辐射。必须正确地预测建筑物的被动太阳能增益，并准确地估计太阳能收集器的热和电产量。在寒冷的天气中，积雪长时间覆盖地面，地面反射的辐射可能占到高度倾斜和垂直表面（例如窗户）的总入射辐射的很大一部分。已经开发了一种新模型来改进仿真工具中对地面反射辐射的计算。该模型基于在渥太华（加拿大）的测量地点获得的经验观察，并已使用来自测量地点的离散数据进行了验证，以及来自美国其他两个站点的已发布数据。发现该模型可以提高寒冷和潮湿气候下地面反射率预测的准确性。