An Assessment of External Wall Retrofitting Strategies Using GRC Materials in Hot Desert Regions
Abstract
:1. Introduction
2. Material and Method
- The climatic characteristics of New Aswan city were determined, along with detailed descriptions of the studied building model;
- Model validation was performed by comparing measured and extracted simulated data;
- A comparison between the investigated building envelope options, in terms of environmental conditions, energy savings, and economic feasibility, was performed.
2.1. Location and Specifications of the Study Case Model
2.2. Meteorological Data and Study Framework
2.3. Model Validation
2.4. Description of the Proposed Wall Options
3. Results and Discussion
3.1. The Effect of Proposed Design Options on the Indoor Thermal Conditions
- ▪
- The indoor monthly mean air temperatures were only completely positioned in the thermal comfort zone for three months (January, February, and December). In March and November, only four options provided thermal comfort (O5, O6, O3, and O4).
- ▪
- All alternatives were less efficient without air conditioning. However, among the examined options, O5 and O6 were the most successful.
- ▪
- As previously demonstrated, New Aswan utilized more energy for cooling during the hottest months. Consequently, none of the investigated options could provide thermal comfort without the use of air conditioning, as the majority of passive climate solutions do. This result is consistent with previous studies [27].
- ▪
- Regarding the mean air temperature inside the investigated building, all studied options showed nearly the same trend, with some options showing a minor improvement in their performance. In addition, the mean air temperature values were lower than the outside dry bulb temperature in all studied options from April to October, while it was higher in the other months.
- ▪
- All the studied external wall options provided adequate thermal comfort for the occupants throughout the year. The average air temperature ranged from 21.6 °C to 29.1 °C.
- ▪
- In general, the simulations generated satisfactory results, exhibiting that (O5) has the best thermal performance and monthly energy consumption and, as a result, the best total annual energy cost among other options.
- ▪
- Following (O5), it was noticed that (O6), (O3), and (O4) demonstrate the best results in terms of the mean air temperature, the monthly energy needed for cooling, and hence the annual energy cost.
- ▪
- Among the investigated options, (O2) was the least efficient option. It had the highest mean temperature variations of more than 28 °C from May to September.
- ▪
- Focusing on the months between April and October, compared to outside dry bulb temperature, (O5) improved the mean air temperature by 8.93%, 15.76%, 19.74%, 21.96%, 21.11%, 17.64%, and 10.83% for the months from April to October, respectively.
- ▪
- In terms of the mean air temperature, (O6) was the second best option, with an improvement rate ranging from 7.84% to 20.79%. (O2) had the lowest improvement rate, with improvements ranging from 2.55% to 16.37%.
3.2. The Effect of Proposed Design Options on the Energy Required for Cooling
- ▪
- As presented in Figure 8a, the monthly results show that (O5) performed slightly better than O6 in all months. However, (O2), which presents the integration of GRC and the common brick layer with an air cavity in between, had the worst performance among the options containing GRC material.
- ▪
- Despite the use of GRC material, the monthly energy required for cooling increased dramatically in the case of (O2). This may be because the U value was high, and there was a heat trap between the GRC and the common brick layer in the external wall option that lacked ventilation.
- ▪
- The U value significantly impacted the energy demand for cooling in the studied area, as shown in Figure 8b. With R2 = 0.8961, a clear relationship between the U value and cooling energy demand was discovered. This means that U values could be responsible for more than 89% of the energy consumption for cooling purposes, as they play a key role in reducing heat transfer from the exterior to the interior spaces, lowering the amount of energy required for cooling.
- ▪
- As shown in Figure 8c, (O1) was used as a benchmark against which the other options were compared. The annual energy needed for cooling in the case of using (O5) was the most efficient option among the studied options, with a 41.21% improvement rate. Then there is (O6), which enhances energy efficiency by 37.96%. (O3) and (O4) performed similarly, with (O3) exhibiting slightly higher efficiency, increasing energy efficiency by 31.24%. Among the options studied, including the reference option (O1), (O2) was the least efficient. With an improvement rate of 9.43%, (O2) was the least efficient advised option.
- ▪
- As shown in Figure 8d, the amount of energy used for cooling had a greater impact on energy costs (EGP). The best performance was in (O5), which was followed by (O6), (O3), and (O4) in that order.
3.3. The Cost–Benefit Analyses (CBAs) of Proposed Design Options
4. Conclusions
- -
- Thermal performance could be improved using a glass fiber-reinforced cement (GRC) material and an insulating material as the third and fourth wall options, rather than using GRC material and cement brick with a vacuum between them. An explanation for this discovery might be found in the second wall option’s high U value (GRC material followed by air cavity, cement brick, and cement plaster), as well as a heat trap in the air cavity layer and a lack of apertures in the cross-sectional layers of the wall themselves.
- -
- Embedded GRC materials with insulation materials could improve thermal and energy efficiency while expanding the area of interior spaces due to their thinner thickness compared to conventional exterior walls.
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- The fifth wall option (O5), which represents an external wall option with the following layers: (cement plaster, cement brick, glasswool, and GRC), was proven to be the most energy-efficient option in terms of internal thermal conditions and required cooling energy, with an improvement rate of approximately 41.21%. Moreover, the fifth option (O5) was the most economically feasible option among those examined, with a simple payback period of roughly 11 years.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Item | Specification |
---|---|
Type | Communal social hub |
Location | New Aswan city |
Floor area (m2) | 1056 |
NO of floors | 3 |
Floor height (m) | 4 |
Density (people/m2) | 0.2 |
Windows glazing | Single-glazed (6 mm) |
(HVAC) | split air conditioning for each space |
Cooling set-point | 25 °C |
Heating set-point | 18 °C |
Material Name | Abb. | Thickness (m) | Density (kg/m3) | Thermal Conductivity (W/mK) | Specific Heat (J/kg K) | Thermal Resistance (m2 K/W) | Total Thermal Resistance (Rt) (m2 K/W) | U-Value (W/m2 K) |
---|---|---|---|---|---|---|---|---|
Cement plaster | O1 | 0.02 | 1762 | 0.721 | 840 | 0.028 | 0.558 | 1.793 |
Cement brick | 0.25 | 600 | 0.752 | 1000 | 0.332 | |||
Cement plaster | 0.02 | 1762 | 0.721 | 840 | 0.028 | |||
Cement plaster | O2 | 0.02 | 1762 | 0.721 | 840 | 0.028 | 0.575 | 1.74 |
Cement brick | 0.12 | 600 | 0.752 | 1000 | 0.159 | |||
Air cavity | 0.1 | 1000 | 0.3 | 1000 | 0.333 | |||
GRC | 0.025 | 2000 | 0.67 | 1100 | 0.037 | |||
GRC | O3 | 0.025 | 2000 | 0.67 | 1100 | 0.015 | 4.237 | 0.236 |
Glasswool | 0.12 | 120 | 0.03 | 840 | 4 | |||
GRC | 0.025 | 2000 | 0.67 | 1100 | 0.037 | |||
GRC | O4 | 0.025 | 2000 | 0.67 | 1100 | 0.037 | 3.676 | 0.272 |
Foam | 0.12 | 20 | 0.035 | 1400 | 1.667 | |||
GRC | 0.025 | 2000 | 0.67 | 1100 | 0.037 | |||
Cement plaster | O5 | 0.02 | 1762 | 0.721 | 840 | 0.028 | 4.386 | 0.228 |
Cement brick | 0.12 | 600 | 0.752 | 1000 | 0.159 | |||
Glasswool | 0.12 | 120 | 0.03 | 840 | 4 | |||
GRC | 0.025 | 2000 | 0.67 | 1100 | 0.037 | |||
Cement plaster | O6 | 0.02 | 1762 | 0.721 | 840 | 0.028 | 4.292 | 0.233 |
Cement brick | 0.12 | 600 | 0.752 | 1000 | 0.159 | |||
Foam | 0.12 | 20 | 0.035 | 1400 | 1.667 | |||
GRC | 0.025 | 2000 | 0.67 | 1100 | 0.037 |
Materials | Unit Cost EGP/m2 |
---|---|
Cement plaster | 100 |
Cement brick | 500 |
GRC | 2000 |
Glasswool | 50 |
Foam | 100 |
Options | Wall Cost (EGP) | Additional Investment (EGP) | Energy Cost (EGP/year) | Annual Saving (EGP/year) | SPP (year) |
---|---|---|---|---|---|
O2 | 2,171,426.4 | 1,586,811.6 | 329,698.60 | 34,342.57 | 46.21 |
O3 | 3,382,414.2 | 2,797,799.4 | 250,327.61 | 113,713.56 | 24.60 |
O4 | 3,424,172.4 | 2,839,557.6 | 259,091.88 | 104,949.30 | 27.06 |
O5 | 2,213,184.6 | 1,628,569.8 | 214,036.59 | 150,004.59 | 10.86 |
O6 | 2,254,942.8 | 1,670,328 | 225,842.24 | 138,198.93 | 12.09 |
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Ragab, A.; Abdelhafez, M.H.H.; Touahmia, M.; Alshenaifi, M.; Noaime, E.; Elkhayat, K.; Alghaseb, M.; Hamdy, O. An Assessment of External Wall Retrofitting Strategies Using GRC Materials in Hot Desert Regions. Buildings 2022, 12, 1194. https://doi.org/10.3390/buildings12081194
Ragab A, Abdelhafez MHH, Touahmia M, Alshenaifi M, Noaime E, Elkhayat K, Alghaseb M, Hamdy O. An Assessment of External Wall Retrofitting Strategies Using GRC Materials in Hot Desert Regions. Buildings. 2022; 12(8):1194. https://doi.org/10.3390/buildings12081194
Chicago/Turabian StyleRagab, Ayman, Mohamed Hssan Hassan Abdelhafez, Mabrouk Touahmia, Mohammad Alshenaifi, Emad Noaime, Khaled Elkhayat, Mohammed Alghaseb, and Omar Hamdy. 2022. "An Assessment of External Wall Retrofitting Strategies Using GRC Materials in Hot Desert Regions" Buildings 12, no. 8: 1194. https://doi.org/10.3390/buildings12081194