Faculty of Engineering and Information Sciences
School of Mechanical, Materials, Mechatronic & Biomedical Engineering
| Student to complete: |
| Family name |
| Other names |
| Student number |
| Table number |
ENGG947
Advanced Building Design for Energy Efficiency and
Sustainability
Wollongong
Examination Paper
Autumn Session 2020
| Exam duration Weighting |
2 hours 35% (+ a 10% oral exam to be arranged with subject coordinator) |
| Items permitted by examiner | Open book |
| Aids supplied | None |
| Directions to students | All questions are to be answered. All questions are of equal value. Upload your answers on Moodle. Name your files to include your student number and your name. Electronic files are preferred but hand written answers are also acceptable, however, make sure your writing is clear. |
Honour Statement
By proceeding to attempt this exam, you are acknowledging that you are aware of the exam
requirements and that any work submitted is your own. This means that you agree to the following:
• I understand all requirements for this exam and have been given an opportunity to ask questions
regarding exam procedures.
• I am the individual enrolled in this subject.
• I understand that at no point during or after the exam am I to discuss, collude, or share
information about the exam with any other individual or group, with the exception of official UOW
IT/Exam Support channels.
• I understand that, as a member of the UOW community, I am responsible for maintaining the
quality and rigour of the institution.
• I understand that if I am found in violation of this agreement that I will be subject to university
Academic Misconduct Procedures.
By commencing this exam you acknowledge that you agree with the above statements.
QUESTION 1 (25 Marks)
a. The walls of a house have a composite construction of bricks (thickness = 330mm, thermal conductivity
= 0.8 W/mK) and 20mm thick plaster (thermal conductivity = 1.2 W/mK). The inner and outer surface
resistances are 0.067 m2K/W and 0.033 m2K/W, respectively. Determine:
| i. | the heat loss per m2 of the wall surface area if the temperature inside the room is 22°C and |
| the outside temperature is -5°C; | (7 marks) |
| ii. | the increase in the heat loss when the wind blows fast and the outside surface resistance |
| decreases to 0.005 m2K/W. | (3 marks) |
b. A building surface has a temperature of 30°C and loses 250 W/m2 of heat to the surrounding air by
convection. If the surrounding air is at 5°C, calculate the convective heat transfer coefficient.
(2 marks)
c. Calculate the Solar Heat Gain Coefficient (SHGC) of a glazing pane when the total amount of solar
heat gains from a 3m2 glazing pane (without a frame) are 1785 W and the total incident solar radiation
on the glass is 700 W/m2. (2 marks)
d. A building has only one space and an internal volume of 720 m3. The mean inside air temperature of
the space is 22°C. The air change rate between inside and outside is 2 Air Changes per Hour (ACH).
From the data listed in Table 1.1 and when the outside temperature is 4°C, calculate:
i. the steady-state fabric heat loss rate and; (7 marks)
ii. the ventilation heat loss rate. (4 marks)
| Table 1.1: Physical and thermal properties | ||
| Surface | Area (m2) | Thermal transmittance U-Value (W/m2K) |
| External Walls | 234 | 0.5 |
| Windows | 30 | 5.6 |
| Roof | 120 | 0.3 |
| Doors | 4 | 2.0 |
| Floor (assume it faces the outdoor environment) |
120 | 1.0 |
QUESTION 2 (25 Marks)
a. Explain briefly the meaning of the term “thermal bridges” and provide two examples of thermal bridges
in buildings. (3 marks)
b. A masonry wall consists of 100mm brick outer face with 10mm mortar joint, a 200mm concrete wall
and a 10mm insulating board on the inside as shown in Fig. 2.1. The outside and inside air
temperatures are 40°C and 25°C, respectively.
Determine the heat flux per unit area through the wall if the outside surface resistance is 0.067 m2K/W
and the inside surface resistance is 0.2 m2K/W. Thermal conductivities given are: bricks, kb = 1.2
W/mK; mortar, km = 0.6 W/mK; concrete, kc = 0.8 W/mK; insulating board, kbo = 0.05 W/mK.
(11 marks)
Figure 2.1: Section of the masonry wall (not to scale)
c. An existing two-storey house is of brick veneer construction with a timber upper floor and a concrete
slab ground floor. The initial total embodied energy of the major elements of the house is 1400 GJ.
The energy needed for heating, cooling, lighting, appliances, hot water and cooking (i.e. operational
energy) is given in Table 2.1. The annual recurring embodied energy in the materials required for
maintenance and refurbishment of the house was found to be equal to 1.5% of the initial embodied
energy of the house. The energy needed to demolish the building at the end of its life has been
estimated to be 600 GJ.
Assuming that the annual recurrent embodied energy and the operational energy do not change every
year, determine the life-cycle energy consumption of the house over a 50-year period.
(11 marks)
| Table 2.1: Operational energy demand | |
| Operational Energy Use Category | Amount of Energy |
| Heating | 33 GJ / year |
| Cooling | 6000 kWh / year |
| Lighting | 3 kWh / day |
| Appliances | 4.8 kWh / day |
| Hot water and cooking | 0.04 GJ / day |
| Note: 1 kWh = 3.6 10-3 GJ |
QUESTION 3 (15 Marks)
a. Propose an air-conditioning system that would suit the hot and humid climate of the Solar Decathlon
Middle East 2018 competition in Dubai and explain your reasons. (6 marks)
b. The T8 fluorescent lamps in a typical floor of an office building were replaced with T5 fluorescent
lamps. The total number of lamps is 20. The power consumption of a T8 fluorescent lamp is 40 W
while the power consumption of a T5 fluorescent lamp is 28 W. The annual operating hours of the
lamps before replacement are 2920 hours.
| i. | How much energy can be saved annually due to the replacement of the lighting systems if the annual operating hours after replacement are increased to 3285 hours? (5 marks) Select an appropriate measurement and verification (M&V) option suitable for determining the |
| ii. |
energy savings and explain why you chose this option.
(4 marks)
QUESTION 4 (35 Marks)
You are to consider ventilation of the building space shown in Figure 4.1 by either wind driven ventilation or
buoyancy driven ventilation. The space is 5 m high with a flat roof and has only two openings between inside
and outside: i) a door measuring 900 mm wide and 2100 mm tall on the north wall and ii) a window measuring
1800 mm wide by 1200 mm tall on the south wall with the bottom of the window being 3000 mm above the
floor level. The window and door have the same discharge coefficient of CD=0.60 when open.
a. Determine the air flow through the window and the indoor in litres per second that would occur when
the two openings are open and only wind effects are considered. In this situation, assume a wind of
6.0 m/s blows from the northwest and results in the following pressure coefficients, Cp, of +0.3 and –
0.55 on the north and south faces of the building, respectively. Hence, determine the rate of heat loss
through this ventilation process if the building is located in Wollongong and the inside and outside
temperatures are 21oC and 7oC, respectively. (15 marks)
b. Carry out the same analysis to determine the air flow and the rate of heat loss when the window is
open but the door is closed (again considering only wind effects). When closed, the door has a gap
around its circumference with a loss coefficient k=0.8 (with units of L/s per meter of crack at 1 Pa) and
a flow exponent n=0.65. When the door is closed, it can be assumed that all the pressure drop will be
across the door crack as the other opening is relatively very large. (10 marks)
c. Now consider the situation with no wind and both the door and window fully open and where internal
heat gains in the space have raised the inside temperature to 32oC while the outside ambient
temperature is 22oC. Calculate the rate of air flow through each opening as a result of the stack effect.
(10 marks)
Figure 4.1: Plan view of building space. (not to scale).
Wind
Door
Window
N
5.0m
10.0 m
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