Unlocking the Residential Retrofitting Potential in a Three-Degree World: A Holistic Approach to Passive Design in Hot Climates
Abstract
:1. Introduction
- (1)
- Can significant energy savings be achieved with traditional retrofit techniques? Is there a need for the introduction of more novel alternatives?
- (2)
- Which of the packages are more successful in the current conditions?
Objectives and Paper Structure
- (1)
- Translating the SBC requirements into an ideal building model and/or a performance benchmark for a comparative assessment of the selected baseline model and the optimised scenarios.
- (2)
- Test a range of retrofit strategies addressing key performance requirements and energy savings measures against SBC benchmarks.
- (3)
- Formulate further optimisation arrangements based on potential alternatives that combine the favoured tested individual strategies.
2. Background Review
2.1. Case Study Country Profile: Kingdom of Saudi Arabia
2.2. The Current and Future Role of the Built Environment Sector
- The high portion of non-thermally insulated housing stock (nearly 70%).
- The low electricity bill (<100 SR/month for 65% of consumers) disincentivises conscious consumption.
- Lack of public awareness led to a low general tendency to purchase high-efficiency devices and/or the replacement of existing less efficient devices.
- There is a weak supervision protocol for the assessment and maintenance of these products.
2.3. Engineering Design Solutions
2.3.1. Region of Study
2.3.2. Type of Housing Stock
2.3.3. Age of Model
2.3.4. Design Target
2.3.5. SBC Regulations
2.3.6. Local Research: Passive Design Strategies and Precedents
2.3.7. Wall and Floor Systems
2.3.8. Roof Systems
2.3.9. Fenestration and Shading Systems
- Canopies on top of windows (e.g., overhangs, fins, egg-crates, louvres).
- Planting shades instead of steel shades.
- Sun reflective design techniques.
- Increasing glazing thickness (with air/argon-filled cavity).
- Highly air-tight windows.
2.3.10. Landscaping Design
2.3.11. Additional Features and Considerations
3. Research Methodology
3.1. Identification of Selected Methodology Frameworks
3.2. Energy Modelling: Formulation of Test Scenarios
3.2.1. Energy Modelling: Identifying Restrictions
3.2.2. Energy Modelling: Defining Input Parameters
3.2.3. Energy Modelling: Design Procedures and Performance Indicators
3.2.4. Shading Design Strategies
3.2.5. Fenestration Design Optimisation: Heat Gain Reduction Versus Daylight
- Reflectance and transmittance values are extracted from IES-VE packages.
- No surrounding obstructions for ground floor (Gf) windows and the overhangs were considered for first floor (f1) windows.
- Only 75% of each floor (see Table 3) is accounted for, and also, assuming that half of the gross floor area is subjected daylighting in each direction.
3.2.6. Green Design and Modelling
3.2.7. Photovoltaic Solutions
3.2.8. Energy Modelling: Performance Benchmarking
4. Key Findings and Discussions
4.1. Baseline Model Assessment
4.2. Upgraded Model Assessment
4.3. Single-Strategy Energy Performance
4.3.1. External Walls: W1
4.3.2. Fenestration: F1 versus F3
4.3.3. Roof: R1 versus R3(a)
4.3.4. Microgeneration: Shading Versus Generation (M1)
4.3.5. Landscaping: L1
4.3.6. Section Overview: The Selection and Formulation of the Retrofit Packages
4.4. Energy Performance of Retrofit Packages
5. Conclusions and Further Recommendations
5.1. Conclusive Statement
5.2. Research Limitations and Further Recommendations
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Appendix A. Supporting Data
Opaque Elements | Residential Conditioned | Residential Unconditioned | |||
---|---|---|---|---|---|
Assembly | Insulation | Assembly | Insulation | ||
Max U-Value W/m2 °C | Min R-Value m2 °C/W | Max U-Value W/m2 °C | Min R-Value m2·°C/W | ||
Roofs | Insulation Entirely Above Deck (Continuous Insulation) | U-0.202 | R-5.0 C.I. | U-0.4 | R-2.5 C.I. |
Wall | Above-Grade Mass (Continuous Insulation) | U-0.342 | R-2.92 C.I. | U-0.453 | R-2.2 C.I. |
Below-Grade | C-0.678 | R-1.3 C.I. | C-6.473 | NR | |
Floors | Mass | U-0.496 | R-1.5 C.I. | U-0.78 | R-0.7 C.I. |
Steel-Joist | U-0.296 | R-3.3 | U-0.296 | R-3.3 | |
Other | U-0.188 | R-5.3 | U-0.288 | R-3.3 | |
Slab-on-Grade Floors | F-0.90 | R-2.6 | F-1.263 | NR | |
Doors For 60 cm | All Assemblies | U-2.839 | U-2.839 |
Fenestration | Assembly | Assembly | Assembly | Assembly |
---|---|---|---|---|
Max U-Value W/m2 °C | Maximum SHGC | Max U-Value W/m2 °C | Maximum SHGC | |
Vertical Glazing, 25% of Wall All Assemblies | U-2.668 | SHGC-0.25 | U-3.695 | NR |
Skylight with Curb, Glass, % of Roof 0–3% All Types | U-4.259 | SHGC-0.35 | U-10.22 | SHGC-0.35 |
Building Air Tightness | (ACH50) 4.0 | NR |
Appendix B. Additional Methodology Considerations
157.50 | 1.63 | 310 | 33.25 | 90–450 |
Shading factors | 15% | 30% | 45% | |
23.63 | 0.25 | 70.88 | ||
No. of panels | 14 | 28 | 41 | |
4.34 | 68 | 12.71 | ||
3.26 | 6.51 | 9.53 | ||
Series × parallel | 2 × 7 | 2 × 14 | 13 × 3 | |
Actual no. of panels | 14 | 28 | 39 | |
22.78 | 45.55 | 63.45 | ||
Covered ratio without spacing between panels | 14% | 29% | 40% |
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Country | Saudi Arabia |
---|---|
Geographical footprint | Approximate coordinates of 16–32° N, 34–55° E, Approximate area 2,252,500 km2 |
Natural resources [12] | Hydrocarbons: Ranks 5th in proven reserves of oil and natural gas globally at a combined estimate of 204.5 trillion cubic feet (2016) |
Renewables: High solar resource (3245 daylight hours of solar radiation at over 2200 kWh/m2) and attractive wind resource in the Eastern provinces (e.g., a mean annual wind speed of 6.7 m/s at 50 m above ground in Yanbu) | |
Case study city | Riyadh City |
Location | Coordinates: 24.714° N, 46.675° E |
Overview | Semi-to Hyper Arid, with Exceptionally Low Rainfall and High Evapotranspiration | |
---|---|---|
Zonal breakdown | Zone 1 | Subtropical, Mediterranean subzone, mountainous subtype |
Zone 2 | Hot and dry with a maritime desert subzone | |
Zone 3 | Hot and dry with maritime subzone | |
Zone 4 | Cold and dry with a desert subzone | |
Zone 5 | Hot and dry with a desert subzone | |
Zone 6 | Al-Rub Al-Khali is not inhabited and has no weather data |
Floor Dimensions (L × W) | Number of Floors | Building Height | Gross Floor Area | Gross Wall Area | Window-to-Wall Ratio (WWR) | Building Capacity | Operations Parameters |
---|---|---|---|---|---|---|---|
15 m × 17.5 m | 2 | 7 m | 525 m2 | 455 m2 | 13% | 6 occupants | Check Figure 4 |
Lighting Power | Equipment Power | Domestic Hot Water Requirement | Temperature Setpoint | HVAC System | Energy Efficiency Ratio (EER) | Typical Operation of Conditioning Plants |
---|---|---|---|---|---|---|
4 W/m2 (~600 L×) | 3.5 W/m2 | 11.4 L/person/day | 22 °C (heating), 25 °C (cooling) | Split DX | 7.5 (low) | 24 h/day |
Element & Composition | Thermal Performance | |
---|---|---|
Actual | SBC | |
Walls (20 mm plaster-150 mm hollow concrete block-20 mm plaster) | U-value: 0.5450 W/m2K | U-value: 0.340 W/m2K |
Roof (10 mm built-up roofing-200 mm concrete roof slab-13 mm plaster) | U-value: 0.5821 W/m2K | U-value: 0.202 W/m2K |
Glazing (clear single pane, wooden frame) | U-value: 3.8701 W/m2K | U-value: 2.670 W/m2K |
SHGC: 0.5470 | SHGC: 0.25 | |
Floor (ceramic tiles-100 mm concrete slab on grade) | U-value: 0.6085 W/m2K | U-value: 0.900 W/m2K |
Door (oakwood) | U-value: 1.3783 W/m2K | U-value: 2.840 W/m2K |
CODE | VARIANTS | SPECIFICATIONS | JUSTIFICATION |
---|---|---|---|
W1 | External insulation | Add a 100 mm-thick polyurethane board to all the exterior sides of the walls. | These variants are investigating whether the cool wall model and higher building envelope airtightness can reduce or eliminate the reliance on wall insulation. |
W2 | Internal insulation + reflective coating | Add a 50 mm-thick insulation board to all the interior sides of walls and paint a coating with an albedo of 0.6 (from an assumed 0.4 for baseline). | |
W3 | Airtight envelope + reflective coating | Impact of lowering infiltration down to 0.5 ach and a reflective coating of 0.6. | |
R1 | Reflective roof | A roof coating with an albedo of 0.6. | The presented roof strategies were selected as they were reported less frequently, especially in local literature. |
R2 * | Flying roof | Placing a 40 mm thin concrete shading south- facing platform at a 15° tilt to cover 50% of the flat roof area. | |
R3 * | Green roof | See Section 3.2.6 for specifications. | |
R4 | Shaded roof | Measures the shading effect of rooftop PV integration (M1) on solar gains. | |
F1 | Double-glazing system | Increasing the glazing thickness by using two panes with reflective low-E surfaces and an argon-filled cavity. | Comparing the individual potential of reflective surfaces, glazing thickness, and external shading devices to derive the case’s optimum solution. |
F2 | Triple-glazing | Uses three clear panes and an air cavity. | |
F3 * | F1 + Overhang | Test 1 m overhang projections with the double-glazing system from F1. | |
L1 * | Green courtyard | Change surrounding surfaces from hard concrete to a green surface. | These were proposed to investigate the influence of surface materials properties on cooling load reduction |
L2 * | Green shading | Cover F3 with a green surface. | |
M1 * | Rooftop PV system | PV south-facing array that covers 15–45% of the accessible roof surface area. | The balance between its roof shading impact and generation potential was studied. |
M2 * | PV shading device | F3 + PV panels integrated on top of the shading device’s surface (tilted and flat). | Very few reports were found on the potential of other PV solutions besides rooftop systems in local literature. |
M3 * | PV windows | Semi-transparent PV cells integrated as part of the south-facing windows. |
Window Type | 1 | 2 | 3 |
---|---|---|---|
Dimensions | 2.75 m × 1.25 m | 1.25 m × 1.25 m | 0.75 m × 1.25 m |
Orientation | West (270°)/East (90°)/South (180°) | South (180°) | East (90°)/West (180°) |
Target shading period (peak conditions) | West: Equinox (21 Mar/Sep), afternoon | ||
East: Equinox (21 Mar/Sep), morning | |||
South: Summer solstice (21 Jun), midday |
F1 | F2 | F3 | ||||
---|---|---|---|---|---|---|
Gf | f1 | Gf | f1 | Gf | f1 | |
0.34 | 0.34 | 0.78 | 0.78 | 0.34 | 0.34 | |
41.88 | 29.38 | 41.88 | 29.38 | 41.88 | 29.38 | |
90 | 90 | 90 | 90 | 51.34 | 51.34 | |
0.32 | 0.32 | 0.07 | 0.07 | 0.32 | 0.32 |
Element | Technical Specifications |
---|---|
Vegetation cover | Shrubs at 0.1 m high; Surface solar absorptance of 0.7; Green colour reflectivity of 0.29; Has an R-value of 1.610 m2K/W |
Growing medium | A 200 mm thick layer; Has moisture content of 40% and thermal conductivity of 1.580 W/m·K; A minimum 3 inch (76.2 mm) layer to avoid root damage; Vegetation and the soil layer were modelled as a one |
Filter | Assumed to be 30 mm thin; Often plastic and modular |
Insulation (Variant R3(a)) | A 50 mm polystyrene layer; Conflicting views were found regarding its necessity. Supporting argument states that it acts as an additional protective barrier against condensation and physical damage |
Waterproofing | 10 mm thin; Thermal conductivity of 0.033 W/m·K |
Roof deck | The existing roof specification were kept constant |
Parameter | Criteria | Selection |
---|---|---|
Model | − | G Solar (GSM310) |
Size | − | 0.992 m 1.640 m |
Cell technology | Maximum power output (module efficiency, ) | Mono-Si310 ; 19.05%, (@STC *) |
Electrical parameters | IV performance | 33.25 V, 9.33 A 40.63 V, 9.85 A** |
Operating environment | Efficiency temperature coefficient () | −0.393 (@NOCT ***) |
Reputation & warranty | Long 25-year life and low power degradation rate | Manufactured and designed by G solar. |
Parameter | Inverter Model | Inverter Efficiency | Warranty | ||
---|---|---|---|---|---|
Description | Single-phase Eversol TL2000 | 97% | 15 years | 11 A | 90–450 V |
FOR 640 mm × 1240 mm PANEL | ||||
---|---|---|---|---|
GLAZING PARAMETERS | ||||
Layer | STPV layer | Air gap | Clear pane | |
Thickness | 4 mm | 9 mm | 5 mm | |
Solar transmittance at normal incidence | 0.224 | − | 0.811 | |
Visible transmittance at normal incidence | 0.225 | − | 0.887 | |
Thermal conductivity | 0.0415 | − | 0.0133 | |
SEMI-TRANSPARENT PV WINDOW (STPV) SYSTEM PARAMETERS | ||||
13% | 6.986 A | 85.6 V | 6.221 A | 68.3 V |
ELEMENT | CONDUCTION GAINS | Differences (Reference to Baseline) | |
---|---|---|---|
Baseline (MWh) | Upgrade (MWh) | ||
Roof | 8.85 | 5.33 | −40% |
Exposed floor | 7.59 | 7.59 | − |
External walls | 10.04 | 6.70 | −33% |
Fenestration | 5.10 | 3.96 | −22% |
Door | 0.14 | 0.14 | − |
Code | F1/F3 | F2 |
---|---|---|
U-Value (W/m2K) | 2.651 | 1.876 |
SHGC (-) | 1.185 | 0.618 |
Thickness (mm) | 24 mm (pane: 6 mm × 2/cavity: 12 mm) | 42 m (pane: 6 mm × 3/cavities: 12 mm × 2) |
F1 | F2 | F3 | ||||
---|---|---|---|---|---|---|
Gf | f1 | Gf | f1 | Gf | f1 | |
2.18% | 1.53% | 4.50% | 3.16% | 1.24% | 0.87% |
Target Element (Code) | Reviewed Description | Percentage Reduction |
---|---|---|
External walls (W3) | Envelope airtightness of 0.5 ach and reflective wall coating with an albedo 0.6. | −6.1% |
Fenestration (F1) | Double-glazing system with reflective low-E surface and an argon-filled cavity. | −9.9% |
Roof (R1) | Reflective roof coating with an albedo of 0.6. | −3.2% |
Microgeneration (M1) | South-facing rooftop PV array that covers 30% of the accessible roof area. | −14.4% |
Landscaping (L1) | Green courtyard with three wide-canopied tall trees covering the Western wall and a collection of shrubs surrounding the North-western side. | −0.5% |
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Aldabesh, A.; Soufi, J.; Omer, S.; Haredy, A. Unlocking the Residential Retrofitting Potential in a Three-Degree World: A Holistic Approach to Passive Design in Hot Climates. Buildings 2021, 11, 228. https://doi.org/10.3390/buildings11060228
Aldabesh A, Soufi J, Omer S, Haredy A. Unlocking the Residential Retrofitting Potential in a Three-Degree World: A Holistic Approach to Passive Design in Hot Climates. Buildings. 2021; 11(6):228. https://doi.org/10.3390/buildings11060228
Chicago/Turabian StyleAldabesh, Abdulmajeed, Jassmen Soufi, Siddig Omer, and Abdullah Haredy. 2021. "Unlocking the Residential Retrofitting Potential in a Three-Degree World: A Holistic Approach to Passive Design in Hot Climates" Buildings 11, no. 6: 228. https://doi.org/10.3390/buildings11060228