Effects of roof size, heat transfer, and climate on snow loads: studies for the 1995 NBC

Abstract

As roof sizes increase, the ability of the wind to reduce the uniform snow loads is diminished, thus resulting in higher uniform loads. Results of recent research into this size effect and the influence of heat loss through roofs in four Canadian cities (St. John's, Montreal, Saskatoon, and Edmonton) using the finite area element method are described and snow load formulae for uniform loads on large roofs are proposed. Also, the drift loading on lower roofs adjacent to large area upper roofs has been studied using similar techniques, and revised formulae for the peak loading in the drift at the step are put forward taking into account the size of the upper roof and the presence of parapets. The snow load provisions developed in this paper have been proposed for the 1995 edition of the National Building Code. Key words: snow loads, drift loads, uniform loads, large flat roofs, size effect, heat loss, finite area element method, computational fluid dynamics.