Question

A summer time temperature analysis of a relative zone of the building, estimating the cooling load and a comparative study for a different type and a different percentage size of glazing

Answer 1

In dealing with heat insulation of exposed windows and doors, suitable methods should be adopted to reduce:

(a) Incidence of solar heat, and

(b) Reduction of heat transmission.

(a) Reduction of incidence of solar heat:

This may be achieved by any one of the following means :

(i) External shading, such as louvered shutters, sun breakers chhajjas, and

(ii) Internal shading, such a curtains and venetian blinds.

(b) Reduction of heat transmission. Whene glazed windows and doors are provided, reduction of heat transmission may be achieved by providing insulating glass or double glass with air space or by any other suitable means.

The development of different cases to represent different glazing types, orientations and areas. The optical properties and thermal characteristics of different glazing materials used are listed in Table

The reason behind selecting such
glazing types was that their properties cover a wide range of commonly-used glazing, including high- performance types double Electro chromic reflective coloured.

Effect of window to wall ratio:-

For the seven models representing the seven main cases, the discomfort hours and the lighting electricity results were obtained for 20, 40, 60 and 80 WWRs. The results indicate a positive correlation between WWR and discomfort hours as shown in Fig. 9. To be more precise, the percentage change in discomfort hours compared to the discomfort hours in the best WWR is listed in Table 6. As indicated in Table 6, WWR of 20 gives the best thermal comfort (minimum discomfort hours), and when WWR is increased to 40, the discomfort hours increase by more than 20% except in L case 2 where the increase is 17.8%. When the WWR is increased to 60, the thermal discomfort increases by 30–40% and in 80 WWR the percentage increase in discomfort hours is 45–55% except in L case 2 where the change is 41.48%. It is further evident that the difference in percentage change is only 10% between the 60 and 80 WWRs, where between other ratios the difference is more than 20%.