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S U L T A N Q A B O O S U N I V E R S I T Y
Oman Eco-House Project
Comfort Final Report
ENGINEERING FACULTY & STUDENTS TEAM
February 2016 www.oman-ecohouse-squ.com
Al Khoudh, Muscat 123
S U L T A N A T E O F O M A N
i
Executive Summary
This report describes the building systems, the design features, and the implication on comfort.
Several passive and active systems have been installed in the SQU’s ecohouse during phase-1 of
the TRC’s ecofriendly house competition. Passive systems include building form and geometry,
courtyards on south and north sides, small and large windows opening for natural ventilation,
mechanically assisted fans for hybrid ventilation, water fountain in the south courtyard for
evaporation effect, double-shell wall and roof systems, shading systems using vertical and
horizontal canvas, date palm tree shading screens, bio-green wall, and the greenery landscape
that modifies the microclimate of the house. The passive systems have largely helped in reducing
the impact of the outside aggressive and harsh hot climate on indoor environment. Since they
consume energy and require continuous maintenance, installations of complementary active
systems were minimized at the SQU’s ecohuse. Mini-split air conditioning systems are provided
in each space for extreme control flexibility. LED lights are selected as a source of light. They
are installed indoor and outdoor to minimize power consumption, yet at higher lighting output.
For phase-2, mist spray system is proposed and installed on the east and west cavity areas inside
the double shell wall and in the south and north courtyards. This system is intended to reduce the
ambient air temperature by evaporation. Finally, the report outlines and describes the operation
strategies for all systems to maintain comfort at low energy consumption in the ecohouse.
ii
Table of Contents
Executive Summary ......................................................................................................................... i
List of Figures ................................................................................................................................ iv
List of Tables ................................................................................................................................. vi
1 Building Systems in the SQU Ecohouse ..................................................................................1
1.1 Mist Spray System in the double-shell façade .....................................................................1
1.1.1 Background ..................................................................................................................1
1.1.2 Design of Mist spray system ........................................................................................2
1.1.3 Operation and control strategy .....................................................................................6
1.2 Air conditioning (AC) Systems ...........................................................................................7
1.2.1 AC description .............................................................................................................7
1.2.2 AC modes of operation ................................................................................................8
1.3 Ventilation Systems for cooling, thermal comfort and indoor air quality .........................11
1.3.1 Background ................................................................................................................11
1.3.2 Natural Ventilation.....................................................................................................13
1.3.3 Mechanically-assisted Ventilation .............................................................................15
1.3.4 Mechanical Exhaust fans ...........................................................................................16
1.4 Other systems used for thermal comfort ............................................................................18
1.4.1 Ceiling fans ................................................................................................................18
1.4.2 Water Fountain Heat Exchanger ................................................................................21
1.4.3 Double-Shell system concept .....................................................................................23
1.4.3.1 Double-roof design ............................................................................................23
1.4.3.2 Double-wall design ............................................................................................24
1.4.4 Shading systems attached to the double-shell system................................................25
1.4.4.1 Vertical Canvas ..................................................................................................25
1.4.4.2 Horizontal Canvas ..............................................................................................25
1.4.4.3 Date palm shading screens .................................................................................26
1.5 Building Illumination Systems ..........................................................................................27
1.5.1 Artificial lighting Systems .........................................................................................27
1.5.2 Daylighting Considerations .......................................................................................29
iii
1.6 Building Acoustical Systems and Noise Control ...............................................................31
2 Operation Strategies for Comfort ...........................................................................................32
2.1 Thermal comfort ................................................................................................................32
2.1.1 Operation strategy #1: Natural ventilation .................................................................32
2.1.2 Operation strategy #2: Natural ventilation + Ceiling fans .........................................33
2.1.3 Operation strategy #3: Natural ventilation + Ceiling fans +mechanical ventilation
fans 33
2.1.4 Operation strategy #4: Mechanical cooling using AC systems .................................34
2.2 Indoor air quality................................................................................................................37
2.3 Visual Comfort...................................................................................................................37
2.3.1 Artificial lighting Systems .........................................................................................37
2.3.2 Daylighting control ....................................................................................................38
2.4 Acoustical comfort .............................................................................................................39
REFERENCES ..............................................................................................................................40
iv
List of Figures
Figure 1.1 TRNSYS model and results for potential of evaporative cooling in Muscat ...............2
Figure 1.2 The double shell façade system in the SQU Ecohouse and the potential location to
alter the microclimate area ...............................................................................................................3
Figure 1.3 The proposed location of the mist nozzles in the double shell façade ..........................4
Figure 1.4 Schematic diagram showing the components of the proposed Mist system .................5
Figure 1.5 Air conditioning split systems in SQU Ecohouse .........................................................7
Figure 1.6 Main components of the indoor unit of AC split system in the SQU Ecohouse ...........9
Figure 1.7 Available mode of settings and operations of the AC split system in the Ecohouse ..11
Figure 1.8 Climate analysis of Muscat city using TMY weather file from Meteonorm ...............12
Figure 1.9 Passive and active ventilation systems in the ecohouse ..............................................13
Figure 1.10 Natural ventilation concept in SQU ecohouse ...........................................................14
Figure 1.11 Mechanical Ventilation systems in the SQU ecohouse .............................................15
Figure 1.12 Fan model used for ventilation system installed at first floor ...................................16
Figure 1.13 Fan models used for exhaust in the kitchen and toilets .............................................17
Figure 1.14 Fan model used for ventilation installed in the control room at ground floor ...........18
Figure 1.15 Locations of ceiling fans in the SQU ecohouse .........................................................20
Figure 1.16 A ceiling fan model similar to those installed in the SQU ecohouse ........................21
Figure 1.17 Water fountain located in the South courtyard of the house ....................................22
Figure 1.18 Roof shade using PV panels ......................................................................................23
Figure 1.19 Bio-wall system on east and west side of the ground floor level ..............................24
Figure 1.20 Vertical canvas as a shading system on outer wall shell at first floor level ..............25
Figure 1.21 Horizontal canvas as a shading device on outer south wall shell at first floor level .26
Figure 1.22 Date palm shading screens on external walls shell and roof periphery .....................27
Figure 1.23 Lighting layout in ground and first floor of the SQU ecohouse ................................28
Figure 1.24 Candle power distribution curve for the LED lighting luminaire .............................28
Figure 1.25 Daylighting systems in SQU Ecohouse .....................................................................30
Figure 1.26 Outside fence and landscape for noise control in SQU Ecohouse ............................31
Figure 2.1 Operation strategy#1: Natural ventilation ...................................................................33
Figure 2.2 Different operation modes for mechanical and natural ventilation in the family area 34
v
Figure 2.3 Thermal comfort evaluation in Majles room based on measurements from 1st-8th Sep
2015 36
vi
List of Tables
Table 1-1 Characteristics and features of the Mist spray Pump ......................................................6
Table 1-2 Schedule of air conditioning system ...............................................................................8
Table 1-3 Measured power consumption of the ceiling fan in the Majles ....................................19
Table 2-1 Schedule of operations for AC systems ........................................................................35
Table 2-2 Target illumination level and the measured lighting level in different spaces .............38
1
1 Building Systems in the SQU Ecohouse
1.1 Mist Spray System in the double-shell façade
1.1.1 Background
Evaporative cooling using mist spray has been known for reducing the ambient air in hot
climates. Although Muscat’s climate is known to be humid in summer, evaporative cooling can
potentially be used in some summer months. This is true in outskirt of Muscat especially in the
SQU’s campus where it is located few kilometers away from the coastline. The climate in this
area tends to be dryer than the coastal area due to the close vicinity of the mountains on the south
of Muscat city and close to the interior side of Oman. The potential of evaporative cooling in
Muscat city was evaluated using a weather file, a TMY2 format, generated by the Meteonorm
software [1]. This weather file was utilized in TRNSYS [2]. TYPE506, a component for
evaporative cooling device, was subsequently used within TRNSYS simulation package. The
implementation in TRNSYS and the results are shown in Figure 1.1. Regardless of air flow, the
ambient air temperature can be reduced by as much as 10 K in a hot day if the saturation
efficiency is 90%. This approximation methodology shows that there is a potential in using
evaporative cooling in Muscat city.
2
a) TRNSYS model
b) The correlation between inlet and outlet air temperature across the evaporative cooling
device
Figure 1.1 TRNSYS model and results for potential of evaporative cooling in Muscat
1.1.2 Design of Mist spray system
The SQU’s ecohouse is equipped with a double shell façade on east and west sides. The house is
featured with shaded courtyards on south and north side. Using mist system, this area can be
utilized to alter the microclimate of the house as illustrated in Figure 1.2.
y = 0.5441x + 9.6092R² = 0.891
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50
Outle
t Tem
pera
ture
[°C]
Inlet Temperature [°C]
3
Figure 1.2 The double shell façade system in the SQU Ecohouse and the potential location to
alter the microclimate area
Figure 1.3 shows the location of the mist nozzles in the double shell façade. The nozzles are of a
size of 0.2 mm spaced between 0.80 to 1.0 meters. It is also important to mention that each
outdoor condenser unit will have one nozzle to spray water at the inlet hot air. The inlet air
temperature will be reduced and subsequently the coefficient of performance (COP) of the unit
will increase.
North
Courtyard
Microclimate Area
Courtyard
4
Figure 1.3 The proposed location of the mist nozzles in the double shell façade
Figure 1.4 shows the schematic plan of the proposed mist system in the SQU’s Ecohouse. The
water from the main city line can be used directly without treatment provided that appropriate
filters are utlized. Mist pump is needed to increase the water pressure to 70-105 Bar. The
maximum total daily water consumption is estimated to be 1864 gal (i.e., 9.8 l/min x 12 hr x 60
min x 0.2641721 gal/l). The characteristics and the main features of the mist system are provided
in Table 1-1. The mist pump can work up to a maximum of 12 hours per day and can be
controlled by a scheduled intermittent timer or using temperature/humidity sensor through
embedded controller. The temperature/humidity sensor will be installed in the south courtyard.
Mist Nozzle
North
Courtyard
Courtyard
5
a) Schematic of the mist system
b) Mist distribution from a 0.2 mm nozzle
Figure 1.4 Schematic diagram showing the components of the proposed Mist system
6
Table 1-1 Characteristics and features of the Mist spray Pump
Model E216
Pressure (Bar) 70-105
Nozzles Number (0.2 mm) 20-150
Pump SIMMM AXA
Min Flow Rate (l/min) 1.9
Max Flow Rate (l/min) 9.8
Motor Speed (RPM) 900
Voltage (Volts) 230/50Hz
Power (kW) 0.92
Max daily use (hours) 12
1.1.3 Operation and control strategy
Due to the cost implication, one temperature/humidity sensor is installed in the south courtyard.
This sensor controls the operation of the mist pump based on the humidity/temperature values in
the courtyard. The pump can work up to a maximum of 12 hours in a day. The temperature rises
during the day time at which the relative humidity is low. During this time, the mist system is
utilized to reduce the microclimate environment of the house. The pump will be controlled to
7
regulate the water flow to the nozzles. No major intervention is expected from the occupants
except switching on/off the electrical switch in the pump room.
1.2 Air conditioning (AC) Systems
1.2.1 AC description
The SQU Ecohouse is divided into 10 thermal zones based on many factors such as the
occupant’s activity, orientation, the level of system control as illustrated in Figure 1.5.
a) Ground floor indoor units b) First floor indoor units
c) Roof plan showing the corresponding
outdoor units
d) Indoor and outdoor units connection in a
typical zone
Figure 1.5 Air conditioning split systems in SQU Ecohouse
1
2
3
4
56
7
8
910
1
6
2
7
8
4
10
9
3
5
8
Each zone is equipped with 1 Ton split system except the familyroom where 1.5 tons of air
conditioning is installed as summarized in Table 1-2. The COP of the split AC system is
calculated using the following equation:
Equation 1-1
Table 1-2 Schedule of air conditioning system
Location Thermal
Zone
Cooling Capacity
[kW]
Model COP
Majles (GF) 1 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Dining Area (GF) 2 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Family Area (GF) 3 5.28 CS/CU PC18MKF 2.65-2.58
Guest Room (GF) 4 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Kitchen(GF) 5 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Master Bedroom (FF) 6 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Living Room (FF) 7 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Girls Room (FF) 8 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Lobby Area (FF) 9 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Boys Room (FF) 10 3.52-3.54 CS/CU PC12MKF 2.85-2.91
Notes: GF: ground floor, FF: First floor, All units are split AC Manufactured by Panasonic,
Malaysia
1.2.2 AC modes of operation
All AC split systems are controlled using an ON/Off controller. A typical schematic of Panasanic
indoor unit is illustrated in Figure 1.6. The occupants can use the wall-mounted controller to set
the desired operation mode. For the controller to work properly, it has to be within 8 meters
distance from the indoor unit. To maintain acceptable indoor air quality, air filters are to be
cleaned every two weeks. The Panasanic AC split system in SQU ecohouse has several modes of
operation. When ECONAVI mode of operation is selected, a human activity sensor is activated
and the source of heat inside the space is tracked. This will maintain the indoor air temperature to
the setpoint temperature. When no source of heat is detected, the air temperature will gradually
increase to 2°C above the setpoint temperature, subsequently saving energy consumption. If
9
thermal comfort is of importance, the occupant can select the AutoComfort mode. A maximum
thermal comfort level will be maintained. More settings and configurations are fully described as
illustrated in Figure 1.7.
Figure 1.6 Main components of the indoor unit of AC split system in the SQU Ecohouse
10
11
Figure 1.7 Available mode of settings and operations of the AC split system in the Ecohouse
1.3 Ventilation Systems for cooling, thermal comfort and indoor air quality
1.3.1 Background
Using the free outside cooled air has an impact on thermal comfort, energy consumption and
indoor air quality. When adaptive thermal comfort criteria is used, natural ventilation can be
utilized for 29% of the time for thermal comfort (i.e., 2576 hrs of the 8760 hrs) for Muscat city
as show in Figure 1.8. The figure shows that in almost every month, outside air can be used. The
utilization of outside air for natural ventilation is however a challenging task for this climate.
12
a) Dry bulb Temperature Versus Relative humidity using adaptive thermal comfort criteria
b) Design Strategies when using adaptive thermal comfort criteria
Figure 1.8 Climate analysis of Muscat city using TMY weather file from Meteonorm
13
The SQU ecohouse provides a variety of passive and active means for full harvesting of outside
cooled air for cooling purposes, maintaining the thermal comfort and providing an acceptable
indoor air quality as shown in Figure 1.9. To meet the ventilation requirement of ASHRAE 62.2
(Table 4.1a of 2013 version), the SQU’s ecohouse needs between 135-150 CFM of fresh air [3].
This rate can easily be achieved by the current passive and active systems in the ecohouse. The
following sections provide further details about these passive and active systems.
a) Ground Floor ventilation systems b) First Floor ventilation systems
Figure 1.9 Passive and active ventilation systems in the ecohouse
1.3.2 Natural Ventilation
In the SQU’s ecohouse, natural ventilation can be achieved using windows and doors that are
located in strategic locations. Cross natural ventilation is promoted due to differential pressure
between windward and leeward sides that can be created by closing and opening windows and
doors at ground and first floor. Lessons are learned from traditional Omani architecture in which
natural ventilation was achieved by long vertical windows that contained lower openings to inlet
Exhaust Fans
Ventilation Fans
Ceiling Fans
Windows
Doors
Exhaust Fans
Ventilation Fans
Ceiling Fans
Windows
Doors
14
cool breeze, and upper openings to exhaust hot air. The windows and doors are located on North
and South walls that respond to day and night variations of Muscat prevailing wind and sea
breeze as previously shown in Figure 1.9. Outside landscape is designed so that outside air is
directed toward the house as shown in Figure 1.10.
Figure 1.10 Natural ventilation concept in SQU ecohouse
15
1.3.3 Mechanically-assisted Ventilation
When the outside air can’t be driven naturally using passive means, the ecohouse has 5
ventilation fans on the first floor to promote air flow as clearly shown in Figure 1.9 and Figure
1.11. These fans are mainly installed to drive the air flow in the family area located in the ground
floor. As per the manufacturer data sheet provided in Figure 1.12 , each fan can provide a total
flow rate of 550 CFM with a fixed speed. Since both ground and first floor are connected
through the void in the core of the house, the fans serve a total volume of 345.8 m3 (floor
area=52 m2, height for the two floors= 6.65 m). All five fans can provide a total of 13.5 ACH
(i.e., every fan can achieve 2.7 ACH).
North Courtyard South Courtyard
Cross Section Inside photo
Figure 1.11 Mechanical Ventilation systems in the SQU ecohouse
Ventilation fans Ventilation fans
Ventilation fans
16
Model: 30 ALFT (50 Hz) used
for ventilation located at first
floor
Figure 1.12 Fan model used for ventilation system installed at first floor
1.3.4 Mechanical Exhaust fans
Indoor air quality is an important factor for the residents. One source of odors is generated in
toilets and kitchen. ASHRAE 62.2 [3] mandates acceptable ventilation rates for residential
buildings. According to the ASHRAE standard, local mechanical exhaust shall be installed in
each kitchen and bathroom. This local exhaust can either be based on a demand-controlled which
should be operated as needed by the occupants or should be operated continuously. The local
exhaust system at the SQU ecohouse is designed to be operated by occupants as needed.
17
According to ASHRAE 62.2 (Table 5.1 demand-controlled local ventilation), an air flow of 100
CFM (50 L/s) and 50 CFM (25 L/s) for kitchen and bathroom should be provided respectively.
All toilets and the kitchen in the SQU ecohouse are equipped with exhaust fans as shown in
Figure 1.13. The kitchen and all first floor toilets are provided with wall mounted fans; model
20AUHT-50 Hz. Each fan delivers a flow rate of 341 CFM. All ground floor toilets are using
glass mounted fans with model 20WUD-50Hz. Each fan provides 212 CFM. Therefore, all local
exhaust ventilation provided by these fans meet the air flow rate recommended by ASHRAE
62.2 for residential buildings.
Wall mounted: 20AUHT-50 Hz
(Kitchen and first floor toilets)
Glass mounted model: 20WUD-
50Hz (ground floor toilets)
Figure 1.13 Fan models used for exhaust in the kitchen and toilets
The control room in the ground floor is provided with fan model 30KQT 50 Hz that delivers 718
CFM as shown in Figure 1.14. The distribution panel board (DP), PV invertor and data
acquisition system (DAS) are all located in this room. A total of 62 ACH can be provided by this
18
fan which deemed satisfactory (i.e., 3.2 m height x 1.8 m width x 3.4 m length = 19.584 m3=
691.6024 ft3, flow rate= 718 CFM, ACH=718(ft
3/min)/691.6024(ft
3) x (60 min/hr) = 62.3 ACH).
Model: 30KQT
Control room
Figure 1.14 Fan model used for ventilation installed in the control room at ground floor
1.4 Other systems used for thermal comfort
Thermal comfort and indoor air quality can also be influenced by many other systems installed in
the SQU’s ecohouse. Examples include ceiling fans, outdoor water fountain in the south
courtyard, shading system, double shell systems, and green bio-wall. The following sections
provide further details about these systems.
1.4.1 Ceiling fans
Ceiling fans are very common in residential buildings in Oman. They are installed in the ceiling
of every space. The speed of the ceiling fan can be controlled using a wall mounted electronic
regulator where occupants can manually select the desirable speed. The fans provide a good
means to mix room air and as well as increases the air speed. Since the air velocity is one
important factor for thermal comfort, the thermal comfort can be achieved at higher temperature.
19
For the SQU’s ecohouse, the ceiling fans are installed in Majles, Dining room, Kitchen, Guest
room, all bedrooms on the first floor, and the living room in the first floor as shown in Figure
1.15. The ceiling fans have 5 speeds where the number of rotation varies according to the
selected speed. The ceiling fan model is AX56XK from KDK. A similar model type (M56XG 50
HZ) is found from the KDK website and shown in Figure 1.16 for illustration purposes. The
power consumption of the installed model was measured using the real time data acquisition
system as shown in Table 1-3 which is closer to the model provided as per Figure 1.16.
Table 1-3 Measured power consumption of the ceiling fan in the Majles
Fan Speed Electrical Power (Watts) Difference between speeds (Watts)
1 (Low) 18
2 29 11
3 42 13
4 56 14
5 (High) 73 17
20
a) Ceiling fans in Ground Floor
b) Ceiling fans in First Floor
Figure 1.15 Locations of ceiling fans in the SQU ecohouse
Ceiling Fans
Ceiling Fans
21
Figure 1.16 A ceiling fan model similar to those installed in the SQU ecohouse
1.4.2 Water Fountain Heat Exchanger
Heat exchanger water fountain is located in South courtyard as shown in Figure 1.17. It has a
deep water reservoir that dissipates heat from water to deep soil. The cooled water is pumped up
to the fountain to cool air that flows into lower inlets of the house.
22
Figure 1.17 Water fountain located in the South courtyard of the house
Water Fountain
North
23
1.4.3 Double-Shell system concept
External surfaces of buildings get heated due to the combination of air temperature and solar
radiation. For example, when the surface temperature in the shade is 40°C, the exposed surface
to the sun could be few degrees. These extra heat could add considerable thermal load to the
building with consequences of added AC load and cost. Conventional design concepts are to
shade window to prevent sun rays from penetration through glass, while the concept double-shell
system is to shade all the building. A secondary light shell wraps around the house providing full
shade of all external surfaces (i.e., roof and walls). It intercepts solar radiation and removes its
thermal load before it reaches the building. The outer shell must be of light weight material, and
air currents in the interim space are maximized to avoid stagnation of hot air.
1.4.3.1 Double-roof design
The roof is shaded by a shell lifted up from the roof with 60cm cavity space, and the upper shell
comprises Photovoltaic (PV) panels tilted at 23.5° oriented towards the South to maximize the
received solar radiation. This tilt could also help to scoop prevailing North-Easterly wind and
directed towards roof cavity to maximizing cooling effect. Wooden lattice are inserted between
PV panels to complement roof shading, and to be used as walkways for maintenance as shown in
Figure 1.18.
a) Snapshot on the wooden walkway b) Snapshot from the roof cavity below the PVs
Figure 1.18 Roof shade using PV panels
24
1.4.3.2 Double-wall design
Walls are surrounded and shaded by date palm wood screens, canvas vertical strips, and climber
plant trellises. Two types of spaces are designed in this Eco-house. On the East and West are 80
cm wide colonnades. The South space extends into lively courtyard surrounded by plants and
flowers, with a central fountain that cools the space and introduces cool breeze to the living
room. It is shaded like the above plus a roof plate extended southwards. Climber plants on
trellises surround East and West colonnades providing full shade all year round. The plants climb
on vertical cords to a height of one floor only creating a bio-wall system as shown in Figure
1.19.
Figure 1.19 Bio-wall system on east and west side of the ground floor level
25
1.4.4 Shading systems attached to the double-shell system
1.4.4.1 Vertical Canvas
Canvas strips are used as vertical shading devices on the East and West colonnades. But they are
floppy and they get wing flutter. They were therefore stretched vertically in order to gain
maximum stability as illustrated in Figure 1.20. The end of each strip is wrapped around a
galvanized hollow metal bar. A screw bar connects the middle of each bar to support channel
being anchored to the beams. The screw is tightened by nuts into final stretching positions.
Figure 1.20 Vertical canvas as a shading system on outer wall shell at first floor level
1.4.4.2 Horizontal Canvas
Canvas strips are use as horizontal shading devices to protect South courtyard as illustrated in
Figure 1.21. Horizontal canvas strips in horizontal position sag and cannot be used as horizontal
shading devices. A curved galvanized hollow tube is therefore introduced at which the end of
each strip is wrapped around. Two screw bars connect the curved tube it to support anchor which
in turn is anchored to the columns. The screws are tightened by nuts into final stretching
26
positions. Three caved tubes are also introduced along the horizontal strip to maintain its
curvature.
Figure 1.21 Horizontal canvas as a shading device on outer south wall shell at first floor level
1.4.4.3 Date palm shading screens
Date palm wood screens are applied at the external wall shell and roof periphery as shown in
Figure 1.22. Local craftsmen were employed for on-site manufacturing and construction of these
screens. Research is to be conducted to treat date palm wood with protective materials to
improve durability. Study is conducted on accumulated heritage of handcraft of date palm
products to develop it into modern production processes in order to obtain economically feasible
products and promote them as viable sustainable building material.
27
Figure 1.22 Date palm shading screens on external walls shell and roof periphery
1.5 Building Illumination Systems
1.5.1 Artificial lighting Systems
The lights in the SQU’s Ecohouse are of LED type; model Portland 15W LED IP54 white Opal
(NPO15LED/WH/O/850), from NVC lighting UK. Each lighting luminaire produces 1040
lumens and the color rendering index (CRI) is 80% with a nominal correlated color temperature
(CCT) of 5000 K (measured CCT is 4134 k). Each LED lighting fixture has a 64 PC LED light.
The lights can be switched on/off using wall mounted switches in each space as shown in Figure
1.23. The candlepower distribution curve for this lighting luminaire is shown in Figure 1.24.
28
a) Ground floor b) First floor
Figure 1.23 Lighting layout in ground and first floor of the SQU ecohouse
Figure 1.24 Candle power distribution curve for the LED lighting luminaire
29
1.5.2 Daylighting Considerations
Daylighting can better be introduced to the indoor space in a diffuse form. No shading is
provided on north side of the house allowing the diffuse north light to enter the spaces on this
side easily. On other sides of the house, the double skin façade of the SQU’s ecohouse is
rationally designed to block all direct sunlight. The shading systems attached to the double skin
façade (vertical, horizontal canvas, GRC screens, bio-wall, and date palm screens) allow the
direct and diffuse light to penetrate into the south courtyard, east and west cavities. The lights are
then introduced to the interior spaces through clear glass windows and glass doors distributed in
all zones as shown in Figure 1.25. Moveable cloth curtains are provided in all transparent
envelope system where occupants can manually open and close them as needed.
30
a) Windows and glass doors in ground floor
b) Windows and glass doors in first floor
Figure 1.25 Daylighting systems in SQU Ecohouse
Windows
Glazed Doors
Windows
Glazed Doors
31
1.6 Building Acoustical Systems and Noise Control
In interior spaces, is generated from different sources such as equipment and appliances. The
ecohouse is designed with interior walls that are composed of 200 mm hollow block. In addition,
thick wooden doors are used in interior spaces. Inside the rooms, wide closets are attached to the
exterior walls providing another means for noise mitigation. Main source of noise comes from
mechanical and electrical systems. The systems are located away and isolated from the quite
area. For example, the noisy compressor units of the air conditioning systems are located on the
roof. Fountain pumps in the south courtyard are located in a special slump below the ground.
Special room is designed for mist pump system. Double skin façade in the SQU ecohouse is also
a helpful design feature to mitigate the propagation of exterior noise. Climbing trees and the soft
canvas on the exterior side of the double-shell can absorb significant amount of noise. In
addition, the ecohouse is surrounded by a concrete block fence of a 2 m height. This fence is
helpful to reduce the noise that comes from the nearby road. Tall trees are planted in the
landscape of the ecohouse as shown in Figure 1.26. These trees will absorb significant amount
of noise that comes from exterior environment.
Figure 1.26 Outside fence and landscape for noise control in SQU Ecohouse
32
2 Operation Strategies for Comfort
2.1 Thermal comfort
Thermal comfort is a basic requirement for occupants to perform their day to day activities.
According to ASHRAE 55, thermal comfort is defined as “that condition of mind which
expresses satisfaction with the thermal environment” [4]. It is influenced by many variables that
can be divided into environmental parameters: air temperature, mean radiant temperature,
humidity, relative air velocity and personal parameters: clothing and activity level [5]. Proper
combinations of these variables have to be sought to provide a thermally comfortable
environment. Several strategies using passive and active systems are available to maintain
thermal comfort. However, the thermal comfort criteria will change based on what system or
combination of systems is used. The following sections provide further details on operation
strategies to achieve thermal comfort.
2.1.1 Operation strategy #1: Natural ventilation
Natural ventilation can provide outside free cooled air that flushes and dissipates the internal
generated heat. Cross ventilation can be achieved by opening exterior and interior doors and
windows in the house. Under this scenario, the thermal conditions can be regulated primarily by
the occupants through opening and closing of doors and windows. All spaces in the house are
equipped with operable windows which can primarily be regulated by occupants. If occupants
are uncomfortable, they should open the windows and doors at both north and south side for
cross ventilation as shown in Figure 2.1.
33
Figure 2.1 Operation strategy#1: Natural ventilation
2.1.2 Operation strategy #2: Natural ventilation + Ceiling fans
When operation strategy #1 is not sufficient for thermal comfort, operation strategy #2 using
ceiling fans can alternatively be followed by occupants. The ceiling fans are provided in every
space in the house except in the family room at ground floor. Occupants can select between 1-5
speed levels of ceiling fans. This strategy will alter the air velocity inside the space and therefore
thermal comfort is enhanced.
2.1.3 Operation strategy #3: Natural ventilation + Ceiling fans +mechanical
ventilation fans
Mechanically assisted fans installed on the upper level (i.e., first floor) can be operated to create
negative pressure inside the house and promote the air flow movement. Occupants can primarily
operate the mechanical fans and open/close windows based on the wind direction, speed and the
desirable thermal comfort level. Figure 2.2 illustrates the concept of this strategy where
occupants have to select which mode is favorable as per the weather conditions.
Courtyard
North
34
a) Natural ventilation only b) Mechanical and natural ventilation are both
on from both sides
c) Mechanical ventilation on south and
natural ventilation on north
d) Mechanical ventilation on north and natural
ventilation on south
Figure 2.2 Different operation modes for mechanical and natural ventilation in the family area
2.1.4 Operation strategy #4: Mechanical cooling using AC systems
In hot climates, air conditioning systems are commonly used by occupants to achieve thermal
comfort. AC systems can be used to manipulate few of the environmental parameters; air
temperature, humidity and air velocity. Ten AC units, one in each space, manufactured by
Panasonic are provided for extreme control flexibility in the SQU’s ecohouse. Different
operation modes are available as described previously in section 1.2.2. In order to define the
optimal operation mode to maintain the desirable thermal comfort (-0.5<PMV<+0.5), site
measurements were performed in the Majles area from 1st -8
th of September 2015 using HD32.1
Thermal Microclimate instrument from Delta OHM as illustrated in Figure 2.3 (a) [6]. The
Courtyard
on
on
Courtyard
off on
off
Courtyard
offon
off
Courtyard
35
measurements for air temperature, relative humidity, air velocity and globe temperature were
taken at 15 minutes time interval for this week interval. Predicted Mean Vote (PMV) values were
calculated based on a clothing level of 0.5 clo and various activity levels, typical domestic values
for tropical climate similar to that experienced in Oman is provided by Mallick as depicted in
Figure 2.3 (b) [7].
The room air temperature was set at 24°C, cool mode was selected (refer to Figure 1.7 for
available modes), and the indoor unit fan was set to single speed by utilizing the wall mounted
controller. In all cases, the ceiling fan was operated at 1st speed to mix the air inside the space.
The results of PMV are shown in Figure 2.3 (c). It is clear from the figure that as the activity
level increases above 1.2 MET (i.e., to 1.5 MET) or decreases below 1.2 MET (i.e., to 1.0 MET),
the thermal comfort (-0.5<PMV<+0.5) is slightly out of range. The occupants in this case should
change the temperature setpoint or/and the ceiling fan speeds as desirable until thermal comfort
is achieved. Clothing level could also be reduced or increased as a way to achieve thermal
comfort. This strategy should be used throughout the house. It is also found through trial and
error that not all ACs in the house are necessary but ceiling fans are needed at 1st speed setting.
Table 2-1 provides the schedule of operations and conditions to operate the ACs in the ecohouse.
Table 2-1 Schedule of operations for AC systems
Location Thermal Zone Operation
[yes or no]
Comments
Majles (GF) 1 Yes When Majles/dining and/or living
rooms are occupied or under testing.
Dining Area (GF) 2 No When needed only.
Family Area (GF) 3 No When needed only.
Guest Room (GF) 4 Yes When occupied or under testing.
Kitchen(GF) 5 Yes When occupied or under testing.
Master Bedroom (FF) 6 Yes When occupied or under testing.
Living Room (FF) 7 No When needed only.
Girls Room (FF) 8 Yes When occupied or under testing.
Lobby Area (FF) 9 Yes When occupied or under testing.
Boys Room (FF) 10 Yes When occupied or under testing.
36
a) HD32.1 Thermal Microclimate
instrument from Delta OHM
b) Typical domestic activity and clothing values [7]
c) PMV calculations for a clothing level of 0.5 CLO and various activity levels
Figure 2.3 Thermal comfort evaluation in Majles room based on measurements from 1st-8th Sep
2015
0 96 192 288 384 480 576-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
Time [minutes]
PMV
[-]
Activity Level=1.5 MET
Activity Level=2.0 MET
Activity Level=1.2 MET
Activity Level=1.0 MET
37
2.2 Indoor air quality
Indoor air quality is an important factor for occupants’ health and wellbeing. There are many
sources of contaminants inside the house. Occupants produce moisture and CO2 through
inhalation and exhalation. Cooking produces many gases and contaminants. Toilets are also
another source of contaminants. Due to the construction quality, fresh outside air can be
introduced through air infiltration to maintain good indoor air quality. Although air infiltration is
not measured, it is expected that a value from 0.35 to 0.5 ACH of infiltration is possible. In
addition to uncontrolled fresh air entrainment, controlled air ventilation can be supplied through
either natural or mechanical ventilation or a combination of both as described previously in
section 1.3. Exhaust fans are installed in all toilets and kitchen at source generation. The fans
should be operated when these spaces are occupied or when specific activity is in operation.
2.3 Visual Comfort
2.3.1 Artificial lighting Systems
Illumination is important for occupant’s visual task. IESNA (Illuminating Engineering Society of
North America) has a set of requirements for building illumination. Illumination level generated
by artificial ambient lights has been measured at 60 cm x 60 cm grids in all spaces at 0.8 m
above finished floor (AFF) as shown in Table 2-2. In general, the ambient lights using the
ceiling LED luminaires meet the target illumination level mandated by IESNA. However, the
shaded cells in Table 2-2 shows that these spaces need task lighting to meet the IESNA target
level. Ceiling LED lights shall be operated when spaces are occupied. Task lights should be
operated when specific task is done in the space to complement the ambient lighting.
38
Table 2-2 Target illumination level and the measured lighting level in different spaces
Floor Space name Target Illumination Level
according to IES 10th Edition
Table 33.2 [Lux]
Average measured
Illumination at 0.80
m AFF [Lux]
Window
area [m2]
Gro
un
d F
loo
r
Majlis 100 at 1.5 m AFF (similar to
family room) 120 1.8
Dining room Formal: 50 at table plane
Informal: 100 at table plane 96 1.2
Family room 100 at 1.5 m AFF 100 4.625
Guest room General: 50 at 1.2 m AFF
Bedhead=200 168 1.2
Guest
Bathroom
Showers/Tubs=50
Toilets and Bidets=100 at top of
plumbing fixture
136 0.263
Kitchen
General: 50 at 1.5 m AFF
Counters= 500
Sink, cooktop= 300
65 1.2
Control room Storage frequent use: 50 at 1.2 m
AFF 144 0.6
Majles
Bathroom
Showers/Tubs=50
Toilets and Bidets=100 at top of
plumbing fixture
180 0.263
Staircase 50 at treads 79 0.6
Fir
st f
loo
r
Master
Bedroom
General: 50 at 1.2 m AFF
Bedhead=200 Not measured
Lobby Circulation Corridors: 30 at 1.5
m AFF 88 0.96
Living room 30 at 1.2 m AFF 62 1.2
Girls Bedroom General: 50 at 1.2 m AFF
Bedhead=200 62 1.2
Boys Bedroom General: 50 at 1.2 m AFF
Bedhead=200 67 1.86
Bathroom
Showers/Tubs=50
Toilets and Bidets=100 at top of
plumbing fixture
71 0.263
2.3.2 Daylighting control
In addition to artificial lighting, daylighting can be utilized as a complementary lighting source
when cloth curtains are fully open. During the measurements performed in November 2015,
daylighting was able to provide an extra average value of 40 lux.
39
2.4 Acoustical comfort
Appliances and electrical equipment can be a source of noise. The possible sources of noise in
the ecohouse are the PV invertor in the control room, exhaust and mechanical ventilations, fans
of the indoor units of AC, water fountains and water pumps. While the noises from many of
these systems are typical and unavoidable, the noise from the PV invertor in the control room is
significant and can be reduced by closing the control room’s door. The door of the control room
shall always be kept closed. Exterior doors and windows shall be kept close if the source of noise
is from exterior environment.
40
REFERENCES
[1] Meteonorm 7, URL: http://meteonorm.com/, [Accessed: May/23/2015], (2015).
[2] Thermal Energy System Specialists LLC -TESS Libraries - Individual Component Libraries,
URL: http://www.trnsys.com/tess-libraries/individual-components.php [Accessed:
October/23/2012].
[3] ASHRAE, Ashrae Standard 62.2-2013: Ventilation and Acceptable Indoor Air Quality in
Low-rise, Ashrae, 2013.
[4] American Society of Heating Refrigerating Air-Conditioning Engineers (ASHRAE), A.N.S.I.
(ANSI), Thermal Environmental Conditions for Human Occupancy, American Society of
Heating, Refrigerating and Air-Conditioning Engineers, 2004.
[5] P.O. Fanger, Thermal comfort: analysis and applications in environmental engineering,
McGraw-Hill, 1970.
[6] Delta OHM, URL: http://www.deltaohm.com/ver2012/download/HD32.1_D_uk.pdf,
[Accessed: Jan/30/2016], (2016).
[7] F.H. Mallick, Thermal comfort and building design in the tropical climates, Energy and
Buildings, 23 (3) (1996) 161-167.
