Q4. In a building environmental performance assessment, credits are given for better daylight performance and reduction in energy use for air-conditioning.

Assuming that daylight performance is assessed by the window-to-wall ratio (r) and energy for an air-conditioned space is assessed by the percentage reduction in annual thermal energy consumption (TEC, kWh/m2 year). The credit scales for these two assessment criteria are given in Table Q4.1. Given also are the baseline and design parameters in Table Q4.2 for the environmental assessment.

Table Q4.1 Credit scale for the two assessment criteria (No interpolation; credits are in integer values)

R	No. credit(s)	% reduction in TEC	No. of credit(s)
0.9	3		0
0.7	2	10	4
0.5	1	20	8
	0	30	12
		40	16
		50	20

Table Q4.2 Summary of baseline and design parameters of the building

Parameter	Baseline	Design	Parameter	Baseline	Design	Additional capital cost HK$/m	Additional maintenance cost HK$/m2
T	25	25	r	0.3	0.5	?	?
A	1000	1000	U	40	34	6 / 1	1 / 1
V	4000	4000	S	0.8	0.6	4 / 0.1	0.25 / 0.1
L	40	40

(a) Determine the % reduction in the TEC of the air-conditioned space for the design, and hence the number of credits to be scored by the design. (4 marks)

You are given the equation below for prediction of annual thermal energy consumption E for the air-conditioning space in kW/myear, where I is indoor air temperature in C, A and V are area and volume of the floor in m and m respectively, r is window-to-wall ratio, L is the characteristic length in m, U is overall U-value in W/mK, and S is the shading coefficient. E=27749 7-0.88 A-0.79 70.22 0.39 0.37 0.36 50.49, where L=max(Width, Depth) of a floor plan. You are given the equation below for prediction of annual thermal energy consumption E for the air-conditioning space in kW/myear, where I is indoor air temperature in C, A and V are area and volume of the floor in m and m respectively, r is window-to-wall ratio, L is the characteristic length in m, U is overall U-value in W/mK, and S is the shading coefficient. E=27749 7-0.88 A-0.79 70.22 0.39 0.37 0.36 50.49, where L=max(Width, Depth) of a floor plan