Design Optimization of Energy-Efficient Residential Buildings in Morocco

Abstract

In this paper, an optimization-based analysis approach is presented to cost-effectively improve the energy efficiency of residential buildings in Morocco. This study introduces a unique focus on the Moroccan context, where a comprehensive application of energy efficiency optimization has not yet been undertaken. This analysis considers the interactive effects among various energy efficiency measures to determine optimal combinations for designing high-energy performance, as well as net-zero energy, residential buildings for six climate zones in Morocco. In particular, the design analysis approach combines a whole-building simulation with the sequential search technique, providing a novel, integrated cost–benefit analysis that minimizes lifecycle costs (LCC) while maximizing energy savings for each climate zone. This study also includes an unprecedented comparison of optimized designs, reference designs, and current Moroccan building regulations (RTCM), highlighting potential improvements to the existing regulatory framework. While the sequential search method has been applied elsewhere, its specific application to achieve net-zero energy homes in the Moroccan context with comparable LCC is a new contribution. The analysis results show that houses in Morocco can be cost-effectively designed to achieve annual energy savings of 51% for Zone 1, 53% for Zone 2, 60% for Zone 3, 67% for Zone 4, 54% for Zone 5, and 56% for Zone 6 compared to the current construction practices considered as reference designs. Moreover, the results indicate that houses can reach net-zero energy building designs with almost the same LCC as the reference design cases for all the climate zones in Morocco.

1. Introduction

If current trends continue, global energy consumption is predicted to increase by up to 62% between 2022 and 2050 because of demographic and economic growth, particularly in Asia and Africa, where energy consumption in residential and commercial buildings is even expected to triple [1]. During 2021, the building sector accounted for 34% of final energy demand and contributed 37% of energy-related CO₂ world emissions, as depicted in Figure 1 [2]. Using proven and cost-effective energy efficiency measures, and according to the Net Zero Scenario presented by the International Energy Agency (IEA), energy consumption in the building sector is projected to drop by 24% by 2030 [3]. It is also a highly strategic sector due to the long lifetime of buildings; today’s buildings will shape the consumption of tomorrow in the long term. A building’s well-thought-out design is much more effective and less expensive than a posteriori renovation. If the renovation sector is crucial regarding existing housing stock, new construction must be exemplary.

In Morocco, according to the latest Moroccan national energy efficiency strategy for 2030, the building sector accounts for 33% of the total energy consumption, as shown in Figure 2 [4]. Moreover, the energy consumption of buildings is expected to increase steadily during the coming years in Morocco for two main reasons, as follows:

• An evident housing deficit expressed by a continuous building stock production over the past 10 years in the country, as depicted in Figure 3;
• An increasing use of energy-intensive equipment in buildings, including appliances, as well as space heating, air conditioning, and domestic hot water heating, due to the improvement in living standards and reduction in deployment costs of such equipment [5].

Figure 2. Final energy consumption by sector in Morocco in 2020 [4].

Figure 2. Final energy consumption by sector in Morocco in 2020 [4].

Figure 3. Yearly housing unit production over the last decade in Morocco [6].

Figure 3. Yearly housing unit production over the last decade in Morocco [6].

To improve the energy sustainability of its economy, in 2009, the Kingdom of Morocco launched a national energy strategy and deployed mandatory regulations to meet its ambitious energy and environmental targets set for 2020. These targets consisted of (i) increasing the share of Morocco’s electricity production from renewable resources to 43% and (ii) reducing Morocco’s energy demand by 12% [7]. To achieve these targets, the Kingdom of Morocco has set mandatory national targets for the deployment of renewable energy and energy efficiency measures in all sectors, including buildings. In 2020, the Kingdom of Morocco noted that the objectives relating to energy efficiency were far from being achieved; it subsequently revised its energy strategy so that it could honor its commitments to a reduction in greenhouse gas emissions and overcome the challenges of the energy sector, which are characterized by the strong dependence on fossil fuels, with the import of 93% of its energy demand and the binding access costs due to the weight of the energy bill, which was USD 8 billion in 2019, equivalent to about 10% of national GDP. Thus, Morocco is now targeting a new strategy that will allow it to increase the share of renewable electricity to about 52% of the total installed capacity and achieve 20% of energy savings by 2030 through the implementation of an energy efficiency plan in various economic sectors, notably, transport, building, industry, and agriculture [8].

The main reasons for an energy efficiency action plan implemented in buildings, whether during the planning phase or as a modernization strategy, are the reduction of the energy bill [9] and the mitigation of environmental impacts. However, the thermal regulation of construction in Morocco (RTCM), which is now mandatory, only considers the building envelope, the objective of which is to reduce the need for heating and air conditioning.

Given that the building sector has considerable potential for energy savings, several studies and a significant amount of research have been conducted to improve its energy performance. In addition to conventional energy efficiency measures, the contributions concerned the bioclimatic design of the building [10], the production of hot water [11,12,13], and heating and air conditioning [14,15].

A wide range of studies have been conducted to assess the impact of design and operating conditions on the energy efficiency of residential buildings worldwide. Some studies have evaluated the impact of only a few design features, including the shape and geometry of the building [16], the thermal resistance and thermal inertia of the envelope elements [17,18,19], natural ventilation [20,21,22,23], orientation [24,25], and window size [26,27].

Several analysis approaches have been used to optimize the design of buildings [28,29,30,31,32]. For instance, Evins [33] conducted a review of computational optimization methods applied to sustainable building design. Nguyen et al. [34] reviewed optimization methods based on simulation in the analysis of building performance. Machairas et al. [35] discussed the different algorithms used in the optimization of performance-based building design. Attia et al. [36] reviewed the gaps and integration needs of building performance optimization tools in the design of buildings at net zero. Moreover, a multi-objective optimization study was carried out by Abdou et al. [37] to achieve net-zero energy buildings in Morocco, in which the authors used passive energy efficiency measures to achieve this end.

Very limited research has focused on the cost-effectiveness of combining a wide range of energy efficiency measures to design energy-efficient buildings in the MENA region [38,39,40,41]. They have developed a complete energy simulation environment to select optimal building envelope characteristics and designs, as well as operating parameters for heating and cooling systems in residential buildings, that minimize the lifecycle cost (LCC). Romani et al. [42] carried out an optimization of the building envelope in Morocco using the Nelder–Mead simplex algorithm. This method was used successfully to achieve the rapid operational optimization of building envelopes to improve the implementation of low-energy buildings in Morocco.

Globally, there are many studies on the optimization of building performance. Anderson et al. [43] used the BEopt 2.8 software to explore the design of new homes, with a peak of zero cooling demand. Griego et al. [44] used the same software for the optimization of residential buildings in Salamanca. Polly et al. [45] described a method of analysis to determine the optimal solutions for improving residential energy efficiency, which has been applied as the method of analysis in eight American cities. Spencer [46] explored the utility of EnergyPlus as a simulation engine for the energy optimization of residential buildings. The BEopt software developed by the National Renewable Energy Laboratory (NREL) is a computer program designed to identify optimal building designs at different levels of energy savings, going from a reference building to zero net energy (ZNE). BEopt has been used by researchers at NREL and in other works [43,44,45,46,47].

This study presents an optimization-based analysis approach to evaluate and optimize the design and operation of residential buildings in Morocco across six climate zones. The objective is to explore cost-effective design and operating options that maximize energy savings while minimizing lifecycle costs (LCC).

This study employs a sequential search optimization method, which has previously been used for energy optimization. This study uniquely applies it to the context of Moroccan residential buildings across six climate zones, integrating detailed energy simulations and lifecycle cost analysis to develop region-specific solutions for net-zero energy buildings (NZEB). This approach systematically evaluates design and operational characteristics—such as building orientation, insulation, air leakage, setpoint temperatures, lighting density, and energy efficiency levels of systems—to achieve net-zero energy designs. A particular feature of this study is its integrated cost–benefit analysis, which accounts for Morocco’s distinct climate zones and construction practices, alongside a comparison with the current Moroccan building regulations (RTCM).

The results of this analysis provide important insights into energy-efficient building design for Morocco, revealing opportunities for substantial energy savings, with potential improvements to existing building standards. This study lays the groundwork for the further development of Morocco’s thermal regulations and energy efficiency policies.

2. Analysis Methodology

This study employs a combination of methods to achieve its objectives. The DesignBuilder v5.5 software (a state-of-the-art whole-building energy analysis tool) based on the EnergyPlus v8.6 simulation engine is used to calculate hourly energy demands for heating and cooling, accounting for the building’s operational and design characteristics across six Moroccan climate zones. These simulations are integrated into a sequential search optimization framework, which systematically evaluates energy efficiency measures (EEMs) to minimize lifecycle costs (LCC). This approach ensures that the optimization process considers both energy performance and economic feasibility, resulting in cost-effective and region-specific solutions for Moroccan residential buildings. A three-step analysis approach is considered in this study to design energy-efficient residential buildings, as illustrated in Figure 4, for all six climate zones in Morocco. In the first step, an analysis of the effect of the parameters required by the Thermal Regulation of Construction in Moroccan (RTCM) on the improvement of the energy performance of the Moroccan prototypical residential building is carried out using the DesignBuilder software. The second step involves applying the sequential search optimization technique to identify the most cost-effective set of EEMs to minimize the lifecycle cost of the prototypical building. This optimization is grounded in iterative dynamic simulations performed in EnergyPlus, where parameters such as building orientation, insulation, window-to-wall ratio (WWR), air leakage, lighting density, and HVAC system efficiency are systematically varied. Simulations are conducted using hourly weather data specific to each of the six climate zones, ensuring that the outputs are region-specific. In the final step, the findings from the first two stages are integrated into a comparative analysis. This analysis assesses the energy and cost benefits of the RTCM requirements compared to the optimal design packages. The NZEB designs are then determined for each climate zone, including the required sets of EEMs and the needed rooftop PV system sizes.

2.1. Description of the Prototypical Residential Building

The prototypical single-family house considered in the study consists of a ground floor and 2 floors with glazed facades, with a total living floor area of 300 m² and a ceiling height of 3 m [48]. Figure 5 shows a 3D rendering of the house, including the glazed facades.

Table 1. Exterior wall construction layers for the prototypical house.

Materials	Thickness (m)	λ (W/m·°C)	CP (J/kg·°C)	ρ (kg/m3)	R Value (m2K/W)
Cement plaster	0.015	0.42	1000	1800	4.48
Red brick	0.07	0.34	1000	1800
Air blade	0.1	0.025	1012	1
Red brick	0.07	0.34	1000	1800
Cement plaster	0.015	0.42	1000	1800

,

Table 2. Roof construction layers for the prototypical house.

Materials	Thickness (m)	λ (W/m·°C)	CP (J/kg·°C)	ρ (kg/m3)	R Value (m2K/W)
Tile	0.007	1.4	1000	2500	0.35
Chape	0.015	0.42	1000	1800
Reinforced concrete	0.04	2.3	1000	2350
hollow block	0.16	0.6	880	1000
Cement plaster	0.015	0.42	1000	1800

and

Table 3. Floor construction layers for the prototypical house.

Materials	Thickness (m)	λ (W/m·°C)	CP (J/kg·°C)	ρ (kg/m3)	R Value (m2K/W)
Tile	0.007	1.4	1000	2500	0.10
Chape	0.015	0.42	1000	1800
Reinforced concrete	0.04	2.3	1000	2350

summarize the construction details of the exterior walls, roof, and floor of the prototypical building, including the thermal properties of various construction layers. The main entrance door of the building is made of steel with a thermal transmittance of 1.13 W/(m²·K), and the windows are single-glazed, with a U-value of 5.7 W/m² and a solar gain factor (FGS) of 0.82. This typology reflects the most common form of residential construction in Morocco, encompassing both existing and new buildings. Thus, the findings of this study are relevant for retrofitting the current housing stock and guiding the design of new energy-efficient homes. Throughout this study, the prototypical building is assumed to be facing south and to be occupied by a family of 4 members. Figure 6 displays the occupancy profile considered for the building. The internal heat gains from occupants are set to be 75 W/person.

2.2. Climate Zones

Morocco has a remarkably diverse climate, reflecting the various geographic zones within the nation. In the far north, the cities of Tangier, El Hoceima, and their like experience a purely Mediterranean climate, while the eastern part of the Middle Atlas, including cities like Oujda, Taourirt, and Outat Lhaj, is characterized by an arid eastern climate. The Central Atlantic region has a semi-arid climate, while the Northern Atlantic region presents a subhumid to semi-arid climate. Furthermore, the country’s sub-Saharan parts and the Southern Atlantic region have dry climates, in contrast to the mountainous sections, which have a distinct mountain climate. Finally, a typically highly arid Saharan climate prevails in the extreme south at the stations of Laayoune, Sidi Ifni, Guelmim, Smara, Dakhla, etc. [49].

Following that, a climate zone mapping project was carried out in close collaboration between the National Meteorology Department and the Moroccan Agency for Energy Efficiency (formerly known as the National Agency for the Development of Renewable Energies and Energy Efficiency), with assistance from international expertise. The country was divided into climate zones as a result of the analysis of climate data gathered by 37 weather stations between 1999 and 2008 (10 years). As illustrated in Figure 7, the construction of the zones was carried out according to the criteria of annual heating degree days (HDD), with a base temperature of 18 °C, and annual cooling degree days (CDD), with a base temperature of 21 °C [50].

Based on this information and the outcomes of yearly simulations of building heating and cooling requirements, a single climate zoning was created to meet thermal regulatory requirements. This led to the creation of six final climate zones, each represented by a city, as shown in Figure 8 [50].

The average monthly variations in ambient air temperature (Ta), wind speed (Vwind), and horizontal global solar radiation (G) for the six Moroccan climate zones are illustrated in Figure 9. These weather data are generated by METEONORM software [51].

2.3. Optimization Approach

2.3.1. Sequential Search Technique

Several optimization techniques can be used to design energy systems for buildings, including minimizing the lifecycle costs while maximizing energy savings. The optimization methods commonly used in the literature include the genetic algorithm (GA), particle swarming optimization (PSO), and the sequential search approach [29,30,31,32,43,44,45,46,47,52]. A. Razmi et al. used the genetic algorithm to predict the most optimal design solutions in an integrative process to enhance a dormitory building’s main performances, combining speed with a high level of accuracy [30]. Furthermore, A. Yahiaoui et al. developed a PSO-based algorithm to identify the optimal configuration and decrease the cost of a PV–diesel–battery system in South Algeria [53]. In this study, the sequential search optimization technique is used to determine the set of energy efficiency measures (EEMs) to minimize the lifecycle costs, as well as the combination of EEMs and rooftop PV system to achieve an NZEB design for the prototypical residential building for the six Moroccan climate zones. The sequential search optimization technique offers a significant advantage by efficiently identifying optimal solutions with minimal computational effort. Its key strength lies in its utilization of the Pareto path, which systematically guides the search process toward the most desirable solutions, ensuring both precision and efficiency in multi-objective optimization scenarios. [54,55,56].

2.3.2. Lifecycle Cost Analysis

The optimization-based analysis used throughout this study considers designs to minimize the lifecycle cost (LCC) through the lifetime of the prototypical residential buildings, as defined by Equation (1) [57].

LCC = IC + USPW(N, rd) × EC

(1)

where

• IC is the initial cost of implementing all design and operating features;
• EC is the annual energy cost required to maintain indoor comfort in the residential building;
• USPW is the uniform series present worth factor used to convert future recurrent costs into present costs and depends on discount rate rd and lifetime N as expressed by Equation (2), as follows:

  $$\mathrm{U}\mathrm{S}\mathrm{P}\mathrm{W}(\mathrm{N},\mathrm{r}\mathrm{d})={\displaystyle \frac{{1-(1+r_d)}^{-N}}{r_d}}$$

  (2)

For the optimization analysis presented in this study, the lifetime is set as N = 30 years, and the discount rate is considered to be rd = 5%. These values are based on typical life cycles of Moroccan buildings, as well as the economic parameters common in the MENA region [54].

3. Discussion

3.1. The Thermal Regulation Code of Morocco

The thermal regulation code of Morocco (RTCM) acts as a mandatory document for projects involving the construction, expansion, and retrofitting of buildings. It is the first decree putting into operation Moroccan law 47-09, which is related to energy efficiency. The RTCM was hence implemented in 2014 and established as mandatory as of November 2015 in order to improve the thermal performance of buildings [7]. The RTCM has the following four objectives:

-

Reducing the need for heating and air conditioning;

-

Improving the comfort of non-air-conditioned buildings;

-

Reducing the installed power of heating and air conditioning systems;

-

Reducing the building sector’s emissions of greenhouse gases.

The RTCM solely concerns the building envelope and covers both the housing and service sector buildings, as it sets performance levels using two approaches: a functional and a prescriptive one. These levels of performance depend on the building type, but also the climate zoning. Hence, for each climate zone, the RTCM establishes performance criteria for the building’s envelope components.

Following the functional approach, specifications are stated as maximal allowed loads for annual heating and cooling requirements, as shown in

Table 4. RTCM functional approach.

Climate Zone	Representative City	Maximum Annual Loads Allowed (kWh/m2/year)
Z1	Agadir	40
Z2	Tangier	46
Z3	Fez	48
Z4	Ifrane	64
Z5	Marrakech	61
Z6	Errachidia	65

below.

On the other hand, the prescriptive approach sets limitations for the building’s envelope by specifying the allowed thermal transmission values for external walls, roofs, windows, floors, and slabs, as well as the equivalent solar factor of glazed openings, as expressed in

Table 5. RTCM prescriptive approach.

Climate Zone	Window-to-Wall Ratio (WWR)	U-Value of Roofs (W/m2·K)	U-Value of Exterior Walls (W/m2·K)	U-Value of Windows (W/m2·K)	Minimum R Value of Floor on Slab (m2·k/W)	Glazing Solar Factor
Z1: Agadir	≤15%	≤0.75	≤1.20	≤5.80	Unrequired	Unrequired
	16–25%	≤0.75	≤1.20	≤5.80	Unrequired	North: Unrequired Other: ≤0.7
	26–35%	≤0.75	≤1.20	≤3.30	Unrequired	North: Unrequired Other: ≤0.5
	36–45%	≤0.65	≤1.20	≤3.30	Unrequired	North: ≤0.7 Other: ≤0.3
Z2: Tangier	≤15%	≤0.75	≤0.80	≤5.80	Unrequired	Unrequired
	16–25%	≤0.65	≤0.80	≤3.30	Unrequired	North: Unrequired Other: ≤0.7
	26–35%	≤0.65	≤0.70	≤3.30	Unrequired	North: Unrequired Other: ≤0.5
	36–45%	≤0.55	≤0.60	≤2.60	Unrequired	North: ≤0.7 Other: ≤0.3
Z3: Fez	≤15%	≤0.65	≤0.80	≤3.30	≥0.75	Unrequired
	16–25%	≤0.65	≤0.80	≤3.30	≥0.75	North: Unrequired Other: ≤0.7
	26–35%	≤0.65	≤0.70	≤2.60	≥0.75	North: Unrequired Other: ≤0.5
	36–45%	≤0.55	≤0.60	≤1.90	≥0.75	North: ≤0.7 Other: ≤0.5
Z4: Ifrane	≤15%	≤0.55	≤0.60	≤3.30	≥1.25	Unrequired
	16–25%	≤0.55	≤0.60	≤3.30	≥1.25	North: Unrequired Other: ≤0.7
	26–35%	≤0.55	≤0.60	≤2.60	≥1.25	North: ≤0.7 Other: ≤0.6
	36–45%	≤0.49	≤0.55	≤1.90	≥1.25	North: ≤0.6 Other: ≤0.5
Z5: Marrakech	≤15%	≤0.65	≤0.80	≤3.30	≥1.00	Unrequired
	16–25%	≤0.65	≤0.70	≤3.30	≥1.00	North: Unrequired Other: ≤0.7
	26–35%	≤0.55	≤0.60	≤2.60	≥1.00	North: ≤0.6 Other: ≤0.4
	36–45%	≤0.49	≤0.55	≤1.90	≥1.00	North: ≤0.5 Other: ≤0.3
Z6: Errachidia	≤15%	≤0.65	≤0.80	≤3.30	≥1.00	Unrequired
	16–25%	≤0.65	≤0.70	≤3.30	≥1.00	North: Unrequired Other: ≤0.7
	26–35%	≤0.55	≤0.60	≤2.60	≥1.00	North: ≤0.6 Other: ≤0.4
	36–45%	≤0.49	≤0.55	≤1.90	≥1.00	North: ≤0.5 Other: ≤0.3

.

Following Table 5, the prescriptive approach is conditioned by a WWR percentage that should remain under 45%. As the WWR increases, meeting the requirements becomes more demanding.

3.2. Parametric Analysis Results

In this section, the effects of design parameters specific to insulation levels for the building envelope, as well as the window types and sizes, are evaluated for the prototypical residential building [58,59]. The main objective of the analysis is to assess the potential energy efficiency improvement levels for residential buildings and contextualize them in terms of the RTCM, depending on the different climate zones in Morocco.

3.2.1. Effect of Envelope Insulation

The objective of this analysis is to determine the specific influence of different insulation thicknesses on energy consumption, depending on climate specifications. It is generally accepted that added insulation lowers energy demand; this research, however, presents precise data on the amount of energy that may be saved following each Moroccan climate zone. This analysis is essential to designing specific energy efficiency solutions, since the ideal insulation thickness changes depending on the area. In order to evaluate the impact of adding thermal insulation to the exterior walls and roof of residential buildings in Morocco, four design scenarios are considered for the prototype house in Figure 5, as follows:

-

The reference building without any insulation in the walls and roof;

-

Scenario 1: the addition of 2 cm-thick polystyrene layers to both the walls and roof;

-

Scenario 2: the addition of 3 cm-thick polystyrene layers to both the walls and roof;

-

Scenario 3: the addition of 4 cm-thick polystyrene layers to both the walls and roof.

For each design configuration, the total annual heating and cooling energy end-use requirements for the prototype are estimated and normalized by the total building floor area (i.e., kWh/m²/year) for all of Morocco’s six climate zones, as illustrated in Figure 10.

As expected, the addition of thermal insulation to the building envelope is beneficial and reduces both the heating and cooling loads for all climate zones of Morocco. Figure 10 indicates that the climate zone has a significant impact on the heating energy end-uses, even for the reference design case without any wall and roof insulation. Specifically, the reference house located in Climate Zone 4 (Z-4), represented by the city of Ifrane, has the highest heating energy consumption. However, when located in Agadir (Zone 1), the reference house requires the lowest annual heating energy demand. The reference house heating requirements of Fez (Zone 3), Errachidia (Zone 6), Tangier (Zone 2), and Marrakech (Zone 5) are moderate. The addition of thermal insulation to the walls and roof reduces the heating needs for the prototypical house, regardless of its location. A greater reduction in the heating demand is achieved with thicker insulation layer additions.

Figure 10 shows similar trends for the cooling energy end-uses, that is, the residential building with and without insulation has the highest air conditioning needs when located in the city of Errachidia (i.e., Zone 1, featuring the hottest summer among all six cities). On the other hand, when the house is located in Ifrane (i.e., Zone 2, with the mildest climate among the six cities), its cooling energy end-use is the lowest, regardless of the insulation level. The cooling energy demand is reduced as a thicker insulation layer is added to the walls and roof of the prototypical house for all six cities, as depicted in Figure 10.

Figure 11 shows the total annual building energy consumption for the four design configurations considered in the analysis. As expected, the energy demand of the house is reduced with a thicker insulation layer added to both the walls and roof. The percent reduction relative to the reference design case of the annual energy consumption achieved by the prototypical house due to the addition of thermal insulation is summarized in

Table 6. Rate of reduction of the energy requirements of the 1st, 2nd, and 3rd CS compared to the reference scenario in the six climate zones.

City (Climate Zone)	Present Energy Savings Relative to the Reference Design (i.e., no Insulation in Walls or Roof)
	2-cm Polystyrene	3-cm Polystyrene	3-cm Polystyrene
Agadir (Zone 1)	12.16	20.27	24.54
Tangier (Zone 2)	7.14	13.54	17.16
Fez (Zone 3)	7.48	14.56	18.64
Ifrane (Zone 4)	6.95	14.63	19.53
Marrakech (Zone 5)	7.33	13.47	17.69
Errachidia (Zone 6)	5.15	12.98	16.97

.

For Zones 2, 3, and 5, which are represented by the cities of Agadir, Tangier, and Marrakech, respectively, the addition of a 2 cm-thick polystyrene layer results in a reduction in annual total energy consumption of 8%. However, for Zone 6, which is represented by the city of Errachidia, the house experiences only a 5.15% decrease in its annual energy use. When the house is located in Agadir, which is located in Zone 1, the total energy demand is reduced by 12.16%, which is the highest level among all six climates in Morocco. When thicker insulation layers are added, higher savings in total house energy demand are achieved for all cities. Specifically, the addition of a 3 cm-thick polystyrene layer in both the walls and roof reduces the total house energy consumption by 20.27%, 13.54%, 14.56%, 14.63%, 13.47%, and 12.98% successively for Zones 1, 2, 3, 4, 5, and 6. For a 4 cm-thick polystyrene layer, the energy use reductions for the prototypical house are 24.54% for Agadir, followed by Ifrane (19.53%), Fez (18.64%), Marrakech and Tangier (17.69%, 17.16%), and, finally, the city of Errachidia (16.97%).

3.2.2. Effect of Window Size

Similarly to the insulation effect, the detailed impact of window size on the heating and cooling energy performance of the prototypical house is evaluated for all six climate zones. For this analysis, the insulation of the building envelope has been fixed to 4 cm, while the window-to-wall ratio (WWR) is set to three options: WWR = 10%, WWR = 25%, and WWR = 40%. The annual heating and cooling energy end-uses for various WWR values when the prototypical house is located in cities representing the six Moroccan climate zones are presented in Figure 12. As shown in Figure 12, the annual heating needs are reduced as the window size is increased due to the increase in solar heat gains. On the other hand, the cooling energy end-use increases with the window size. The impact of varying window sizes on heating energy consumption is minimal across all climate zones, with negligible differences observed among the three WWR scenarios. This can be attributed to the lower intensity and shorter duration of solar radiation during winter, which inherently limits the potential for solar gains to offset heating needs. As a result, variations in WWR have only a marginal effect on heating energy demand. In contrast, WWR has a significant impact on cooling energy consumption, as larger window areas allow more solar radiation to enter the building, substantially increasing cooling loads. This effect is particularly pronounced in hotter climates, such as Marrakech and Errachidia, where high solar intensity and prolonged cooling seasons further amplify the influence of WWR on energy performance.

Figure 13 shows the annual total building energy consumption for different WWR values and cities representing the six climate zones. For all the climates, the total energy consumption increases with the window size, which is driven by higher cooling thermal loads, especially when the house is located in Marrakech or Errachidia, which are characterized by warmer climates.

Table 7. Reduction in total house energy use due to setting WWR = 10% instead of WWR = 25% and WWR = 40% for the six climate zones.

City (Climate Zone)	Percent Reduction in Annual Energy Demand
	WWR = 10%/WWR = 25%	WWR = 10%/WWR = 40%
Agadir (Zone 1)	31.67	49.6
Tangier (Zone 2)	21.03	36.71
Fez (Zone 3)	15.70	29.22
Ifrane (Zone 4)	5.08	12.13
Marrakech (Zone 5)	51.16	61.36
Errachidia (Zone 6)	30.39	35.27

summarizes the results of the effect of the window size on the heating and cooling energy demands when the prototypical house is located in each of the six Moroccan cities. The results provide the percent reduction in annual total house energy consumption when the WWR is set to 10% instead of WWR = 25% and WWR = 40% for the six climate zones. As indicated in Table 7, smaller windows (i.e., WWR = 10%) significantly reduce the energy demand for the house in all Moroccan climates, compared to the case of larger windows. Specifically, when the WWR is reduced from WWR = 40% to WWR = 10%, the annual energy consumption for the house is reduced by 49.60% for Agadir, 36.71% for Tangier, 29.22% for Fez, 12.13% for Ifrane, 61.36% for Marrakech, and, finally, 35.27% for Errachidia. Ifrane exhibited the lowest percentage reductions of only 5.08% and 12.12%. This can be explained by its cold climate conditions, in which heating dominates the energy demand. In such conditions and as mentioned previously, the limited intensity and duration of solar radiation during winter reduces the effectiveness of measures aimed at increasing solar gains, such as adjusting the WWR. Consequently, these measures have a minimal impact on reducing heating energy needs.

3.3. Optimal Designs

In this section, the optimal designs for the prototypical house are identified considering a wide range of options for the building shape, building orientation, insulation thickness in the walls and roof, window size/type, and energy efficiency of the heating/cooling systems. All these design parameters affect the energy performance of the house and can be modeled using detailed simulation engines, such as DOE-2 [60] or EnergyPlus [61]. In this section, an optimization-based analysis is carried out to identify the set of design options that minimizes the lifecycle cost, as defined using Equation (2) [62,63,64].

Table 8. List of design features and their implementation costs for the prototypical house [66,67,68].

Design Features	Options		Implementation Costs (USD)
Orientation of the building	0°		USD 0 for all options
	45°
	90°
	135°
	180°
	225°
	270°
Insulation Level for the Exterior Walls	No insulation		USD 26.53/m2
	Extruded Polystyrene (2 cm)		USD 33.36/m2
	Extruded Polystyrene (4 cm)		USD 35.03/m2
	Extruded Polystyrene (6 cm)		USD 36.62/m2
Insulation Level for the Roof	No insulation		USD 74,07/m2
	Extruded Polystyrene (2 cm)		USD 80.9/m2
	Extruded Polystyrene (4 cm)		USD 82.57/m2
	Extruded Polystyrene (6 cm)		USD 84.16/m2
Window Size (WWR)	25%		USD 0 for all options
	Scenario 1: 10%
	Scenario 2: 20%
	Scenario 3: 30%
	Scenario 4: 40%
Window Glazing type	Single clear (6 mm; U = 6.17 W/m2·°C FGS = 0.82)		USD 14.86/m2
	Single bronze (6 mm; U = 6.17 W/m2·°C; FGS = 0.61)		USD 24.41/m2
	Single low-e (6 mm; U = 4.27 W/m2·°C; FGS = 0.5)		USD 46.7/m2
	Double clear (6/12/6; U = 3.163 W/m2·°C; FGS = 0.72)		USD 21.23/m2
	Double bronze (6/12/6; U = 3.16 W/m2·°C; FGS = 0.49)		USD 31.84/m2
	Double low-e (6/12/6; U = 1.65 W/m2·°C; FGS = 0.61)		USD 100.83/m2
Lighting Power Use	Typical (7.3 W/m2)		USD 0.42/m2
	30% reduction		USD 0.74/m2
	50% reduction		USD 1.16/m2
	70% reduction		USD 1.59/m2
Air Leakage (ACH)	Typical (0.84 ACH)		USD 0/m2
	25% reduction		USD 0.7/m2
	50% reduction		USD 1.4/m2
	75% reduction		USD 2.09/m2
Heating Setpoint Temperature	22 °C		USD 0 for all options
	20 °C
	18 °C
Cooling Setpoint Temperature	26 °C		USD 0 for all options
	25 °C
	24 °C
Power Rating for the Refrigerator	412 kWh/an		USD 360/unit
	(20% reduction)		USD 529/unit
	(40% reduction)		USD 740/unit
	(60% reduction)		USD 1270/unit
Efficiency for Heating/Air Conditioning Systems	COP = 2.6	EER = 2.85	USD 7407.41/unit
	COP = 3	EER = 3.25	USD 8465.61/unit
	COP= 3.3	EER = 3.60	USD 9523.81/unit
	COP = 3.5	EER = 3.85	USD 10,582/unit

lists 11 design features and the associated options considered in the optimization analysis in this study [41,57]. The options used for the reference house design are highlighted in bold in Table 8. Moreover, it provides the costs of implementing the different options for all the design features. For estimating the energy costs, a flat rate of USD 0.20/kWh for electricity is considered in this study [65].

Figure 14 shows the lifecycle cost optimization results for designing the energy systems of the prototypical house located in Agadir (Figure 14A), Tangier (Figure 14B), Fez (Figure 14C), Ifrane (Figure 14D), Marrakech (Figure 14E), and Errachidia (Figure 14F). For each location, the optimization results are represented via the optimal path (i.e., red curve), as well as several design options considered using the sequential search technique (i.e., blue points). Furthermore, four design configurations are specified: the reference design (i.e., black point), the RTCM-based design (i.e., green point), the LCC-based optimal design (i.e., gray square), and the NZEB design (i.e., orange triangle).

Figure 14A shows the optimization results and design cases for when the house is in the city of Agadir. The lifecycle cost of the reference design is USD 107,614. The optimal LCC design can reduce the annual energy consumption of the house by 51% and lower the LCC from USD 107,614 to USD 87,500, which is an 18.7% reduction. Compared to the RTCM design, the optimal LCC design can improve energy efficiency by 42.37% and lower the LCC by 18.53%. To achieve the NZEB design in Agadir, additional energy efficiency measures and a rooftop PV system are needed, resulting in an LCC of USD 108,255, which is slightly higher than the reference design.

Figure 14B indicates that the optimal LCC design when the house is in the city of Tangier provides an annual energy saving of 53%, with a 19% reduction in LCC compared to the reference design. The RTCM-based design represents an improvement of only 10% in energy efficiency and a 1% reduction in LCC compared to the reference design. The NZEB design slightly increases the LCC to USD 112,760 from USD 110,680 for the reference design.

The results of Figure 14C,D show that the optimal LCC designs can reduce the annual energy consumption by 60% and 66% when the prototypical house is in Fez and Ifrane, respectively. The same optimal designs lower the LCC costs relative to the reference designs by 23% in Fez and 25% in Ifrane. Moreover, Figure 14C indicates that for Fez, the optimal LCC design saves 21% of the annual energy demand compared to the building that meets the requirements of RTCM, with an LCC reduction of 16%. Similar findings are obtained when the house is in Ifrane, as shown in Figure 14D, with the optimal LCC design resulting in a 25% reduction in energy demand and a 15.8% reduction in LCC compared to the RTCM-based design.

Figure 14E illustrates the optimal path when the prototypical house is located in the city of Marrakech. The optimal LCC design results in 54% annual energy savings and a 19.5% reduction in LCC compared to the reference design. When compared to the RTCM-based design, the optimal LCC design achieves 39% energy savings and an 11.5% LCC reduction. The LCC required for the NZEB design is USD 138,277, which is equivalent to 9% more than the reference design and around 25% more than the optimal LCC design.

For the city of Errachidia, Figure 14F shows the optimal LCC design for the prototypical house. The building achieves annual energy savings of 56% and an LCC reduction of 23% relative to the reference design. The same optimal LCC design results in 19% energy savings and an 8.5% LCC reduction relative to the RTCM-based design. The LCC required to reach the NZEB design is estimated to be USD 143,524, which is a 5% augmentation relative to the reference design and a 27% augmentation compared to the optimal LCC design.

Table 9. Required rooftop PV capacities and installation costs required for NZEB designs of the prototypical house in six Moroccan cities.

Climate Zone/City	PV Power Capacity (kW)	Number of PV Panels	PV Installation Cost (USD)
Z1/Agadir	1.92	7	11,530
Z2/Tangier	2.94	11	13,717
Z3/Fez	3.91	14	16,856
Z4/Ifrane	6	22	25,731
Z5/Marrakech	5.84	21	25,191
Z6/Errachidia	5.97	22	25,731

summarizes the power capacity for the rooftop PV system required for the prototypical house to achieve the NZEB design for the six cities considered in the analysis. The listed capacities can easily be placed on the 90-m² roof of the house, regardless of its location. The variance in the number of PV panels is primarily due to variations in local solar irradiance, along with the needed power capacity [69]. Table 9 shows the installation costs for the listed PV systems, including PV panels and inverters, based on prevalent installation practices in Morocco [70].

Figure 15 compares the optimal Pareto paths to achieve optimal LCC and NZEB designs of the prototypical house located in all six cities representing different climate zones of Morocco. From the LCC comparison between the reference designs in all cites (refer to points of the Pareto paths with 0% energy savings), the lifecycle costs required by the prototypical house located in Agadir, Tangier, Fez, and Marrakech are lower than those needed when the house is in Errachidia and Ifrane. Indeed, because the reference designs are situated in Errachidia and Ifrane, which are Morocco’s most extreme climate zones, their LCC values, which are USD 136,718 and USD 129,743, respectively, are much higher than those of the other cities due to the higher annual energy use and the costs associated with high heating and cooling energy demands.

As illustrated in Figure 15, the annual energy savings achieved by the optimal LCC designs range from 51% to 66% for all Moroccan cities. The LCC values for the NZEB designs also vary significantly, with the climate zone of the prototypical house with the lowest value achieved in Agadir and the highest value in Errachidia.

Table 10. Lifecycle costs and annual energy saving associated with the optimal LCC designs for six Moroccan cities.

City (Climatezone)	LCC Optimum Design		LCCreference/LCCoptimal (%)	LCCRTCM/LCCoptimal (%)
	LCC (USD)	Energy Savings (%)
Agadir (Zone 1)	87,503	51	22.98	22.91
Tangier (Zone 2)	89,383	53	23.94	22.71
Fez (Zone 3)	92,162	60	30.50	19.68
Ifrane (Zone 4)	101,131	67	33.80	18.79
Marrakech (Zone 5)	96,970	54	24.29	13.00
Errachidia (Zone 6)	105,730	56	29.31	9.24

summarizes the annual energy savings and the LCC values for the optimal LCC designs compared to the reference and the RTCM-based designs for the prototypical house in six Moroccan cities. As indicated by the results presented in Table 10, the energy savings for the optimal LLC designs are maximal when the house is in Ifrane due to the significant energy efficiency benefits of insulating the building envelope in the hot climate zone. The reductions in LCC values for the optimal LCC designs compared to the reference designs are 22.98%, 23.94%, 30.50%, 33.80%, 24.29%, and 29.31% when the house is in Agadir, Tangier, Fez, Marrakech, Ifrane, and Errachidia, respectively.

Table 11. Design options for the optimal LCC designs of the prototypical house located in six Moroccan cities.

Design Feature	Agadir	Tangier	Fez	Marrakech	Ifrane	Errachidia
Orientation of the Building	180° (North)	0° (South)	0° (South)	0° (South)	0° (South)	0° (South)
Insulation Level for Exterior Walls	No insulation	Extruded Polystyrene (2 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)
Insulation Level for Roof	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)	Extruded Polystyrene (6 cm)
Window Size (WWR)	WWR = 10%	WWR = 10%	WWR = 10%	WWR = 10%	WWR = 10%	WWR = 10%
Window Glazing Type	Single clear	Single clear	Single clear	Double bronze	Double low-e	Double bronze
Lighting Type	100% CFL	100% CFL	100% CFL	100% CFL	100% CFL	100% CFL
Refrigerator Energy Rating	A++	A	A++	A+++	A+	A+++
Air Leakage (ACH)	0.84 ACH	0.21 ACH	0.21 ACH	0.21 ACH	0.21 ACH	0.21 ACH
Heating Setpoint Temperature	18 °C	18 °C	18 °C	18 °C	18 °C	18 °C
Cooling Setpoint Temperature	26 °C	26 °C	26 °C	26 °C	26 °C	26 °C
Energy Efficiency for Heating (COP)/Air Conditioning (EER)	COP = 2.6 EER = 2.85	COP = 2.6 EER = 2.85	COP = 2.6 EER = 2.85	COP = 2.6 EER = 2.85	COP = 2.6 EER = 2.85	COP = 2.6 EER = 2.85

lists the options of various building features required to achieve the optimal LCC designs for Morocco’s six climate zones. For cities located in temperate zones, including Tangier and Agadir, the optimal designs need no or little insulation for exterior walls since it is beneficial to allow heat trapped indoors to escape outdoors, especially during cool nights, in these climates [56]. For cities where the climate is extreme, that is, very hot in summer or very cold in winter, a well-insulated building envelope is required to optimize the performance of residential buildings.

For all climates, except that of Zone 1, of Morocco, an airtight building envelope is needed to achieve the optimal LCC designs, including reducing the air infiltration rate to below 0.21 ACH. Other common options for the optimal LCC designs in all climate zones include high-efficiency lighting and appliances and smaller window sizes (WWR = 10%), a low heating temperature setpoint (18 °C), a high cooling temperature setpoint (26 °C), and standard and least-costly heating/cooling systems (COP = 2.6/EER = 2.85).

The type of window glazing needed to realize the optimal LCC designs varies with the climate zone, as shown by the results presented in Table 11. In particular, the double bronze-glazed windows with a solar gain factor are selected for Marrakech and Errachidia to reduce the cooling thermal loads. For Agadir, Tangier, and Fez, single clear-glazed windows are sufficient, while for Ifrane, double low-e glazed windows are needed for the optimal LCC designs.

Table 12. Energy savings and LCC changes of RTCM, optimal LCC, study, and NZEB designs relative to the reference design.

	Energy Saving (%)		% LCC Increase (+)/Decrease (−) Compared to the Reference Design
Climate Zone: City	RTCM	Optimal Point	RTCM	Optimal Point	NZEB Design
Z1: Agadir	8.63	51	−0.17	−18.7	+0.7
Z2: Tangier	10	53	−1	−19	+1.8
Z3: Fez	39	60	−7	−23	−0.7
Z4: Ifrane	41	66	−9.2	−25	+2.6
Z5: Marrakech	15	54	−8	−19.5	+10
Z6: Errachidia	38	56	−16	−23	+5.2

summarizes the improvements offered by the RTCM, optimal LCC, and NZEB designs relative to the reference design for the prototypical house located in the six Moroccan cities considered in this study. As clearly indicated by Table 12, the LCC values for the optimal designs are lower than those for the reference designs in all cities. The RTCM-based designs offer a reduction in energy demand and LCC relative to the reference designs, but without reaching the potential offered by the optimal LCC designs. Moreover, NZEB designs can generally be achieved with LCC values comparable to those of the reference designs.

Building on the LCC analysis of optimal designs, it is important to consider the economic situation of users, which plays a crucial role in the adoption of these energy efficiency measures, particularly for existing buildings. While the proposed designs demonstrate significant lifecycle cost savings, the high upfront costs of retrofitting measures, such as rooftop PV systems and advanced insulation, may be prohibitive for economically constrained households. To address these challenges, phased renovation strategies and targeted government interventions, such as subsidies or low-interest loans, are critical. Furthermore, prioritizing low-cost, high-impact measures like air sealing and energy-efficient lighting can provide immediate energy savings while remaining accessible to a wider range of households. These socio-economic considerations are essential for ensuring that the benefits of energy efficiency improvements can be equitably realized across Morocco’s diverse population.

4. Summary and Conclusions

The Kingdom of Morocco is one of the predominant countries in the North African region, not only in terms of population and economy but also the size of the building sector. In this region, Morocco and Tunisia are the only countries that have developed a mandatory thermal regulation for the building sector, and therefore they can play a leading role in driving this region toward an efficient building sector. However, as shown by the present work, the RTCM only takes into account the need for heating and cooling and not the energy consumption of the building. To achieve the objectives of its energy transition and honor its commitments to reduce greenhouse gas emissions, more than ever, it is necessary that Morocco revises its thermal regulations, which were launched more than seven years ago, to incorporate requirements for energy consumption and energy equipment that consume the most electrical energy, namely, refrigeration, lighting, and HVAC systems.

Through this study, a comprehensive analysis study has been conducted to improve the energy performance of residential buildings in Morocco. An optimization technique associated with a detailed energy simulation program was used to evaluate the most cost-effective energy efficiency measures to be implemented to achieve optimal energy design for a residential building in the six climate zones of Morocco. A wide range of architectural designs and operation measures are considered, including the orientation, window-to-wall ratio, glazing type, wall and roof insulation levels, air leakage, type of lighting, appliances, temperature settings, and efficiency of the heating and cooling systems. Energy consumption can be reduced from 51% to 67% in Morocco’s various climate zones in a cost-effective manner thanks to the optimal designs, compared to the current design practices of residential buildings in Morocco. In addition, it can be found that the specific selection of optimal design features varies from one area to another, which shows the importance of our optimization study. The main findings of the analysis also show that energy saving and LCC reduction improvements obtained by the application of RTCM are far less significant than those provided by the optimization study. For different climate zones, Energy savings achieved through the application of RTCM varied from 8.6% to 41%, while for the optimum point, it was significantly higher, ranging between 51% and 66%. Our findings align with those of Abdou, Felimban, et al. [37,71], who also reported significant energy savings and demonstrated the feasibility and cost-effectiveness of achieving net-zero energy buildings. Likewise, in another study, Alaidroos and Krarti’s investigation into optimal energy savings for residential buildings across five sub-climate zones in KSA revealed significant potential, with savings ranging from 26% to 47.3% via implementing similar energy conservation measures [38]. Regarding the LCC, the reduction ranged between 0.17% and 16% following the RTCM’s application and varied between 18.7% and 25% regarding the optimal point. Following the optimization, it was also shown that the required LCC to obtain an NZEB increased only by 0.7%, 1.8%, 2.6%, 10%, and 5.2% for Agadir, Tangier, Ifrane, Marrakech, and Errachidia, respectively, compared to that of the reference building. On the other hand, for Fez, the LCC of the NZEB decreased by 0.7% compared to that of the reference building. Therefore, the Kingdom of Morocco should investigate programs centered on zero-energy and low-carbon buildings. It may be beneficial to develop these buildings through the introduction of a new national certification or label or demonstration projects across the country in order to increase the trust of owners and investors. On the other hand, alongside implementing new labels, certifications, and regulations, it is also imperative to improve energy consumption habits and lifestyles. In addition, we can never reach NZEB without the integration of renewable energies. Thus, Morocco should introduce a new building-integrated renewable energy policy framework. It is true that, in 2015, Morocco promulgated Law 58-15 relating to renewable energies, which authorizes the injection of low voltage into the national network, but this law remains insufficient without the publication of an implementing decree. In addition, while the technical feasibility of the proposed solutions is evident, their widespread adoption hinges on the economic capacity of users. Policy measures, such as subsidies, phased retrofitting approaches, and incentives for cost-effective solutions, are essential to overcome financial barriers and enable equitable access to energy-efficient housing. Finally, to promote building energy self-sufficiency, Morocco must also exempt solar thermal and photovoltaic systems from all taxes. By integrating these considerations, Morocco can achieve its energy transition goals in a manner that is both sustainable and inclusive.