This study determines the glazing area in direct gain passive systems
needed to ensure thermal comfort inside a building (room air temperatu
re 20 +/- 2-degrees-C). A 4 m X 4 m X 3 m single zone isolated house i
s analyzed in three different types of climates namely composite (8-de
grees-C to 20-degrees-C, New Delhi), cold-cloudy (-2-degrees-C to 5-de
grees-C, Srinagar), and cold-sunny (-14-degrees-C to -3-degrees-C, Leh
). The analysis is based on the periodic solution of the heat conducti
on equations describing heat transmission in the building components,
floor, walls, and roof, and the Fourier representation of the ambient
temperature and the total solar radiation intercepted by the building
envelope. Two types of construction are analyzed: the first type is a
traditional construction with 22-cm-thick brick wall, plastered 15 mm
on both the sides (U = 2.0 W m-2 K-1); and the second one is of the sa
me type but with 10 cm of expanded polystyrene insulation on all the f
our walls and the roof (U = 0.31 W m-2 K-1). It is found that for trad
itional construction with U = 2.0 W m-2 K-1, the glazing U value has a
lmost no effect on the room temperature even for large variation of th
e glazing area ( 10% to 40%, expressed in terms of percentage of floor
area). For a well-insulated house (U = 0.31 W m-2 K-1), the glazing U
value has no effect upon the room air temperature if the glazing area
is small (less than 10%). The position of the insulation on the exter
nal surfaces is more effective in reducing large in-room air temperatu
re. Finally, for an insulated house, we recommended glazing is 30%, 20
%, and 10% for cold-sunny, cold-cloudy, and composite climates, respec
tively.