_____________________________________________________________________________________ Course Instructor: Dr. Adel Abdou Student ID: g201004120 King Fahd University ofPetroleum & Minerals College of Environmental Design Architectural Engineering Department ARE 510 Computer Utilization in Architectural EngineeringSyed Ashraf Tashrifullahi Application Assignment #2
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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
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.
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
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