A Simple Method for Computing the Dynamic Response of Passive Solar Buildings to Design Weather Conditions

In contrast to the lengthy computations required to simulate hour-by-hour building performance using response-factor or thermal network models, design-day performance can be analyzed simply by using a method developed based on Fourier transforms. This paper describes how Fourier response functions are derived from the buildings thermal properties and shows how approximations can be made which allow the results to be expressed as algebraic formulas which can be computed rapidly using a hand-calculator.

A program written for a hand-calculator which can perform this analysis requires as inputs building design parameters such as UA products (conductances), specific heats of materials, and weather parameters. Since similar materials (e.g. frame walls and ceilings) can be lumped together, data for only a few different construction types are needed. Weather parameters are: daily solar gains for sunny and cloudy design days, length of cloudy design weather cycle, average ambient temperature of the design day and typical diurnal temperature fluctuation. Output from the program is hourly room temperatures for each of the design days.