appln assignment #2
Post on 13-Jul-2015
23 Views
Preview:
TRANSCRIPT
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 1/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou Student ID: g201004120
King Fahd University of
Petroleum & MineralsCollege of Environmental Design
Architectural Engineering Department ARE 510 Computer Utilization in Architectural Engineering
Syed Ashraf Tashrifullahi
Application Assignment #2
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 2/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 1 Student ID: g201004120
Contents
1. Introduction ..................................................................................................................................... 3
1.1 Building Envelope........................................................................................................................... 3
1.2 Importance of Assessing Building Envelope .................................................................................... 3
1.3 Software Tool................................................................................................................................. 4
2. Modeling & Simulation of the Best Overall Wall System ................................................................. 5
2.1 Simulation Results of Previous Assessments .................................................................................. 5
2.2 Modeling of the Best Wall System .................................................................................................. 6
2.3 Simulation of the Modeled Wall System......................................................................................... 7
2.4 Assessing the Results ..................................................................................................................... 9
2.4.1 Temperature and Moisture Content ........................................................................................ 9
2.4.2 Total Moisture Content ......................................................................................................... 11
2.4.1 Transfer Rate of Heat ............................................................................................................ 12
3. Comparison with Previous Assessments......................................................................................... 13
4. Conclusion ..................................................................................................................................... 14
References............................................................................................................................................. 15
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 3/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 2 Student ID: g201004120
List of Figures
Figure 1: Wall Systems #2 & #3 respectively. .................................................................................................................... 5
Figure 2: (a) Exterior Option Selection, (b) Interior Data Setting ........................................................................... 7
Figure 3: Simulation of Wall Assembly .................................................................................................................................. 8
Figure 4: (a) Simulation of Wall Assembly (January), (b) Simulation of Wall Assembly (June) ........... 10Figure 5: Total Moisture Content ........................................................................................................................................... 11
Figure 6: Heat Transfer ............................................................................................................................................................... 13
List of Tables
Table 1: Materials selection of Wall #2 ................................................................................................................................. 6
Table 2: Moisture Content by Layer ..................................................................................................................................... 12
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 4/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 3 Student ID: g201004120
1. Introduction
1.1 Building Envelope
For the design, construction and operation of a facility, there is an especially important
interface between the indoor and outdoor environments which is known as building envelope. Itis one of the most important elements in ensuring comfort and is comprised of the outer elements
of a building such as foundations, walls, roof, windows, doors and floors [1]. The main function
of the building envelope is to manage the flow of air, moisture and heat between different
environments, typically exterior and interior. This helps prevent material deterioration, corrosion,
mold growth and heat loss [2]. Besides this, the building envelope serves many prime functions
of which the functions of interest for the present study are thermal control and moisture control.
1.2 Importance of Assessing Building Envelope
Sustainability now-a-days is an increasing priority for facilities [1]. Building construction
and operation have an enormous direct and indirect impact on the environment in terms of many
factors of which one that I feel the most important for the current study is energy use. The impact
of both thermal and moisture transfer could be accountable for this. The fact, increase in the heat
gain increases the cooling load and results in higher use of energy, does not support the issues
pertaining to sustainability. Similarly, moisture transfer within a wall assembly could result in
concealed condensation and is accountable for increased rate of heat transfer, mold growth and
air quality.
Heat is conducted most easily through solid materials. The goal for any wall should be to
minimize the amount of conductivity through the materials in the wall, including the framing
materials and the insulating materials. Also, the potential for condensation occurring in walls is
one of the most important considerations when deciding on the building envelope system. This
decision for the selection of the best envelope system, for example a wall system, requires an in
depth assessment and can be accomplished by state of art tools.
Recent trends in North America towards green buildings resulted in the development and
increased popularity of several green building assessment tools. These tools were primarily
developed to assess, or measure specific aspects of a building, pertaining to sustainability goals
[3]. The tools emphasize on early design phase of the building. The initial design ideas are
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 5/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 4 Student ID: g201004120
conceptualized with the formulation of building project requirements. Most tools focus on three
main areas; energy, water and material use in buildings. The conceptual approaches adopted and
technical implementation of these tools varies significantly [4]. The former area of study
(energy) is of primary interest to this report.
1.3 Software Tool
For the present study of hygrothermal (moisture and thermal) analysis, one of the tools
available to assess the flow of heat and moisture through the wall section is hygIRC. It is a 1-D
state-of-the-art hygrothermal model developed to help building design professionals in
simulating the response of each element to environmental conditions on either side of the
envelope on an hourly basis by allowing them to choose optimal building envelope components
and systems. It produces information on the temperature and relative humidity distributions
within the wall assembly. The program is targeted to engineers, architects, building scientists,
contractors, and students in investigating the transfer of heat, air, and moisture through common
construction materials [5].
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 6/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 5 Student ID: g201004120
2. Modeling & Simulation of the Best Overall Wall System
2.1 Simulation Results of Previous Assessments
Previous assessments constituted the analysis of wall systems #2 and #3, as shown in
figure 1, from the point of view of thermal and moisture transfer using the state of art
CONDENSE.
Figure 1: Wall Systems #2 & #3 respectively.
Both wall systems were analyzed for the given conditions of Dhahran city taking into
consideration the heat gain, thermal resistance, cost aspect and most importantly the purpose for
which the software tool ³CONDENSE´ was built, i.e., the risk of condensation. The assessmentdid not reveal any sort of condensation in any part of the wall assembly for the given conditions
and resulted in the selection of wall #2 based on the heat gain, thermal resistance and cost
aspects. A sensitivity analysis was also carried out to assess the behavior of wall #2 by varying
the thickness of insulation while keeping relative humidity constant and vice-versa.
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 7/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 6 Student ID: g201004120
Condensation was observed on the exterior surface of wall #2 where changes to relative humidity
were found accountable [6].
For the present study/assessment, the best wall system, i.e., wall #2, as per the assessment
results of CONDENSE, the same wall system was modeled using hygIRC. This was
accomplished by considering either same or similar materials while constructing the wall
assembly depending upon the material database of hygIRC compared to the material database of
CONDENSE. The thickness of various layers in this analysis was considered the same as it was
in the previous assessment. Same boundary conditions were imposed and the assessments were
carried out from the point of view of thermal and moisture transfer only.
2.2 Modeling of the Best Wall System
As mentioned earlier, the best wall was considered for the purpose of thermal andmoisture analysis. The wall #2, as shown in figure 1, is composed of a brick with an air gap,
rigid insulation and concrete block in between followed by interior finish from outside to inside
along its cross-section. This type of wall system is known as ³Cavity Wall Insulated in Cavity´
meaning that the insulation is installed within the cavity in between the wall. Table 1 shows the
selection of materials for various components of wall #2 depending upon the material database of
hygIRC compared to CONDENSE.
Table 1: Materials selection of Wall #2S. No. Component Material Thickness (mm)
1 Brick (Outer Wythe) Concrete brick 100
2 Rigid Insulation Extruded Polystyrene 50
3Concrete Block
(Inner Wythe)Aerated Concrete 75
4 Interior Finish Gypsum 13
The materials selection for inner wythe and interior finish in this analysis had to be different
compared to the previous assessment because of their unavailability in hygIRC materials
database. The properties of the selected materials for hygIRC were first observed and compared
by using the ³value´ command in CONDENSE. The materials very close to the materials in
CONDENSE were selected based on their density. The thickness of all components of the wall
assembly was kept the same.
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 8/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 7 Student ID: g201004120
2.3 Simulation of the Modeled Wall System
The modeled wall system was simulated for the simultaneous thermal and moisture
transfer under the weather conditions of Dhahran city, (2002). The simulation variables were set
to temperature and total moisture content. The exterior conditions were set and analyzed using
the Dhahran weather file of the year 2002. Preference to time selection, as shown in figure 2 (a),
was given to ³years´ and the input type selected was ³system input´ as it was instructed to assess
the wall assembly using Dhahran 2002 weather file. The selection of system input option in
hygIRC constructs the weather file from the database and does not require inputting constant
environmental conditions by the user. This helps in the analysis of the wall assembly taking into
consideration the real life environmental conditions of the year 2002 for Dhahran city.
(a) (b)
Figure 2: (a) Exterior Option Selection, (b) Interior Data Setting
With respect to the data pertaining to the interior space, constant values were given as
input to the software tool. This was purposely done in relation to the assessment carried out in
application assignment #1 [6]. The indoor data settings there were as shown in figure 2 (b). This
helped in the preparation of a base for the comparison of the two wall assemblies using the two
software tools which is discussed later in this report.
Over to the structure of the wall assembly, its orientation and inclination are east oriented
and 90o
respectively. The layers of the wall assembly were selected as described in the modeling
part of this report. The indoor ventilation pressure in the air diffusion tab was provided with a
value of 5 Pa. The internal pressure need only be slightly higher than ambient on average to
achieve the goal of excluding humid outdoor air from building cavities. In any case, internal
pressure shall not be greater than 10 Pa [7]. There are some suggestions of recommended
pressurization levels of the order 5 Pa to perhaps 10 Pa. Each building¶s pressurization strategy
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 9/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 8 Student ID: g201004120
should be designed based on the climate, the building height and the envelope leakage [8].
Because the pressurization varies from 0 to 10 Pa, average value of 5 Pa was selected for the
current study. The initial conditions were set based on temperature and RH. Constant conditions
were set for the whole structure of the wall keeping in mind the time constraints for the report.
The simulation parameters were set for the complete year of 2002 for Dhahran city. The
simulation was then started and observations were made.
Figure 3: Simulation of Wall Assembly
Figure 3 shows the temperature and total moisture content within the wall assembly for the
complete year. The temperature is found to be at its peak during the summer months with themoisture content being at its minimum values. This implies that at the verge of completion of
winter season, the total moisture content gradually decreases and reaches its minimum value
during the summer season. The location of Dhahran city being very close to the coast results in
increased humidity levels even reaching up to around 95% during the summer period. The
decreased levels of moisture content within the wall during this period are an appreciation of the
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 10/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 9 Student ID: g201004120
wall system to be suitable for the climatic conditions of Dhahran city from the perspective of
moisture transfer. This is an indication of reduced risk of concealed condensation.
Figure 4 (b) shows the variations in temperature and moisture content during the month of June.
It can be seen that the exterior temperature is high compared to interior. There was gradual
decrease in the temperature in the air gap. The presence of insulation resulted in an increase in
the slope of the curve depicting in much more decrease in the temperature. Decrease in the
moisture content was observed. This was as a result of the insulation material.
2.4 Assessing the Results
The results were assessed considering the following indicators:
y Temperature and Moisture Content
y Total Moisture Content
y Transfer Rate of Heat
2.4.1Temperature and Moisture Content
Shown in figure 4 are animation stills of the simulation carried out on the wall assembly.
In order to report on the performance of the assembly during the simulation period, two stills
were captured and analyzed. The first one, as shown in figure 4 (a), was for the month of
January. Gradual increase in the temperature from outside to inside can be seen. A sudden
increase in the temperature was observed in the thermal insulation layer. Because the indoor
environment is at a higher temperature compared to outside during the winter season, the
insulation reduces the amount of heat to pass through to the outer environment. Higher value of
moisture content was observed in aerated concrete layer as it has high moisture absorbing
capacity. The sudden increase in the curve in that layer may be due to the presence of moisture
(45%, as given as input for the interior space) in the interior space.
Figure 4 (b) shows the variations in temperature and moisture content during the month
of June. It can be seen that the exterior temperature is high compared to interior. There was
gradual decrease in the temperature in the air gap. The presence of insulation resulted in an
increase in the slope of the curve depicting in much more decrease in the temperature. Decrease
in the moisture content was observed. This was as a result of the insulation material.
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 11/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 10 Student ID: g201004120
Figure 4: (a) Simulation of Wall Assembly (January)
Figure 4: (b) Simulation of Wall Assembly (June)
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 12/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 11 Student ID: g201004120
2.4.2Total Moisture Content
Data pertaining to total moisture content within the wall assembly was first exported to a
specialized application ³Surfer´ in the form of a ³.dat´ file. This data contained information
about moisture content for various layers of the wall on an hourly basis for the complete year.
Average values were derived for every 30 or 31 days respectively using basic application ³MS
Excel´ in order to summarize the data for a monthly basis as shown in table 2. This was then
used to assess the performance of the layers of the wall assembly. Besides this, total moisture
content was analyzed and is shown in figure 5.
Figure 5: Total Moisture Content
It was observed that initially the moisture content was higher during the winter months and
decreased to its minimum during August. This is an indication that the wall selected based on the
previous assessments and selected materials is not absorbing the moisture during the summer
conditions when the temperature outside is high. This could also be seen in figures 4 (a) and 4
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 13/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 12 Student ID: g201004120
(b) in which the moisture content is high and low respectively. It could be said that, for the
combination of wall assembly and the materials selected, the moisture is being accumulated on
the higher temperature side (either interior or exterior) based on winter or summer conditions
respectively. The use of insulation in between the wall assembly holds good for the summer
conditions of the region selected.
Table 2: Moisture Content by Layer
Time
(Months)
Concrete
brick
(Layer 1)
Air Space
(Layer 2)
Extruded
Polystyrene
(Layer 3)
Aerated
Concrete
(Layer 4)
Gypsum
(Layer 5)
January 6.849242 0.079336 2.138081 0.84875 0.000344
February 7.157829 0.075673 0.734786 0.83105 0.000367
March 6.819879 0.064564 0.217681 0.819391 0.000518
April 6.31128 0.063175 0.19747 0.816866 0.00062
May 5.484105 0.064691 0.192752 0.813914 0.00089
June 4.704008 0.062631 0.190473 0.812935 0.000869
July 4.226199 0.056615 0.183783 0.811556 0.000734
August 4.036284 0.054081 0.181963 0.81181 0.000612
September 4.255493 0.052847 0.182756 0.812843 0.000501
October 4.838691 0.052588 0.184202 0.813775 0.000441
November 5.144714 0.054014 0.193228 0.817678 0.000298
December 6.408029 0.056783 0.200802 0.820065 0.000264
The moisture content in the concrete brick was observed to be maximum compared to all other
layers. This could be due to the fact that the concrete has higher tendency to absorb moisture.
The air gap/space provided after the brick does not allow the moisture to pass through and
reduces its level to negligible values throughout the year. The insulation layer on the other hand
initially absorbs moisture and as time passes allows limited amount of moisture to pass through
compared to the first layer. The fourth layer being aerated concrete has a tendency to absorb
moisture and has higher values of moisture content compared to layer 3. Moisture transfer is
almost zero in layer 5.
2.4.1Transfer Rate of Heat
The heat transfer through the wall is shown in figure 6. It can be seen that the majority of
heat transfer occurs from outside to inside along the wall assembly during the summer season
and is depicted by positive readings. Less amount of heat transfer is observed from inside to
outside. Maximum heat gain was observed during the end of February and during October. This
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 14/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 13 Student ID: g201004120
means that the wall system designed does not allow the flow of heat along its cross-section
throughout the summer season. Less heat gain results in decreased cooling loads.
Figure 6: Heat Transfer
3. Comparison with Previous Assessments
The capabilities of the software tool CONDENSE are limited to the thermal transfer and
identification of condensation in any part of the wall assembly at a particular instant of time.
CONDENSE does not deal with the dynamic aspects of weather conditions. On the other hand,
hygIRC is capable of simulating the modeled wall assembly throughout a complete year (or even
more than a year) taking into consideration the dynamic aspects of the surrounding atmosphere.
The assessments carried out by the two tools had one similarity. The assessments using
the state of art tool CONDENSE didn¶t reveal any sort of condensation in the selected wall for
the given conditions. Sensitivity analysis carried out resulted in the identification of
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 15/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 14 Student ID: g201004120
condensation on the exterior surface. In the case of hygIRC, maximum amount of moisture
content was observed in layer 1 (Concrete Brick). Both these assessments revealed the
accumulation of moisture and maximum accumulation of moisture in the first layer, i.e., either
on exterior surface or within layer 1 using the software tools CONDENSE and hygIRC
respectively.
4. Conclusion
Based on the analysis of the selected wall system, it could be concluded that the wall is
suitable for the summer conditions of Dhahran city. While assessing the results it was found that
the moisture accumulation in layer 1 was high. The concrete brick acting as the first layer needs
to be replaced by some other material which is cheap and absorbs less moisture. The air space
and thermal insulation suit well in restricting the flow of moisture and heat respectively, or both.
The simulations done by hygIRC have many results compared to CONDENSE.
Limitation in hygIRC is that it assesses the thermal and moisture transfer in only one dimension
based on certain assumptions. Use of much more advanced software tool such as WUFI 2D is an
appreciation as it is capable of executing hygrothermal analysis in two dimensions.
5/12/2018 Appln Assignment #2 - slidepdf.com
http://slidepdf.com/reader/full/appln-assignment-2 16/16
_____________________________________________________________________________________
Course Instructor: Dr. Adel Abdou 15 Student ID: g201004120
References
[1] Rob Bolin, ³Sustainability of the Building Envelope´, National Institute of Building
Sciences. Last updated: December 14, 2009.
[2] The Challenger Series, Canada. Information available at: http://www.thechallengeseries.ca/chapter-04/building-envelope/#importanceofenvelopes.
[3] Jamie McKay, ³Green Assessment Tools: The Integration of Building Envelope
Durability´, 11th
Canadian Conference on Building Science and Technology, Banff,Alberta, 2007.
[4] Khee Poh Lam, Yi Chun Huang and Chaoqin Zhai, ³Energy Modeling Tools
Assessment for Early Design Phase´, Center for Building Performance and Diagnostics,Pittsburgh, December 31, 2004.
[5] hyg IRC 1-D User¶s Guide.
[6] Syed Ashraf Tashrifullahi, ³Building Envelope Preliminary Design & Assessment´,
Evaluation Based on Introduction of CONDENSE Software Tool, K FUPM, October 16,2011.
[7] US General Services Administration. Information available at:
http://www.gsa.gov/portal/content/101291.
[8] Andy Persily, ³Building Ventilation and Pressurization as a Security Tool´,ASHRAE Journal, September 2004.
top related