Net Zero-Energy Building: A Case Study Using Ecotect Software Under Beirut Weather Conditions

Fadl Bdeir and Chadi Nasrallah
Department of Industrial Engineering, American University of Beirut, Beirut, Lebanon
Correspondence to: Chadi Nasrallah, chadinasrallah123@gmail.com

DOI: https://doi.org/10.70389/PJES.100016

Additional information

• Ethical approval: N/a
• Consent: N/a
• Funding: No industry funding
• Conflicts of interest: N/a
• Author contribution: Fadl Bdeir and Chadi Nasrallah  – Conceptualization, Writing – original draft, review and editing
• Guarantor: Chadi Nasrallah
• Provenance and peer-review:
  Unsolicited and externally peer-reviewed
• Data availability statement: N/a

Keywords: Net zero energy building, Ecotect software, Passive design strategies, Beirut weather conditions, Renewable energy systems.

Peer Review
Received: 24 January 2025
Accepted: 18 March 2025
Published: 28 March 2028

Introduction

There is rising concern about climate change and the increase in global average temperature, which are attributed to greenhouse emissions. These emissions are the result of human activity, such as the use of fossil fuels such as petroleum, natural gas, and coal.¹ The built environment is responsible for about 42% of annual global CO2 emissions. Of those total emissions, building operations are responsible for 27%, while the embodied carbon of just four building and infrastructure materials, namely cement, iron, steel, and aluminum, are responsible for an additional 15% annually.² Lebanon, a small country on the eastern side of the Mediterranean, is heavily reliant on fossil fuels. A recent UNDP report shows that Lebanon’s greenhouse gas (GHG) emissions are increasing at an average rate of 3.4% every year, which has led to a doubling of emissions since 1994. These emissions are mainly from the energy sector, which constituted 53–59% of the total emissions during this period alone.³

In response to the GHG emissions, sustainable approaches are becoming a priority. One of these approaches is the net-zero-energy building (NZEB), which means conceptually that the total energy used by the building on an annual basis is equal to the energy produced on-site. Since ancient times, man has found ways of using and converting natural resources to improve living conditions, and among these are houses and their construction techniques. Even if “energy efficiency” was not as common a term as it is nowadays, before the twentieth century, people have created, and transferred from one generation to another, the good practice codes of efficient energy practices.⁴ It is hard to locate a building that can be considered the first NZEB. However, a few publications appeared in the late 1970s and early 1980s, in which phrases such as “A zero energy home or an autonomous energy house” and an “energy-independent house” were used.⁵

The “House of Tomorrow” by George F. Keck and the “MIT Solar House I” by Hoyt C. Hottel, built in the 1930s, demonstrated the important heat gains from the sun.6 The two buildings pioneered the energy efficiency stream in buildings based on scientific methodologies of calculation, and strategies of design and construction. The oil crisis in 1973 amplified the interest in the energy efficiency of buildings. The concepts of building tightness, super insulation, heat recovery from ventilation systems, and passive technologies became widely known. Brenda and Robert Vale coined the terms “self-sufficient house,” “autonomous house,” and “greenhouse.”⁷ In the late 1980s, inspired by the energy-efficient houses of the 1970s, Wolfgang Feist, in collaboration with Bo Adamson, sketched the concept of “Passive House.” The Passive House concept outlined at the beginning of the 1990s integrated all the valuable theories and algorithms of design.⁸ The first energy-autonomous house designed and built by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany, was in 1992. Due to well-designed insulation and solar energy technologies, the house was able to cover its own needs without the help of external energy sources.⁹

Research studies have continued on sustainability and passive building strategies. Iqbal defined NZEB as the term used for a building that incorporates available renewable energy technologies commercially with energy efficiency construction methods where no fossil fuels are consumed.¹⁰ Kilkis defined NZEB as a building that has a total annual amount of zero energy transfer through the building during all-electric and other transfers that occur during a particular time span.¹¹ Laustsen gave the general definition for ZEB: zero-energy buildings do not use fossil fuels and rely entirely on solar and other renewable energy sources to meet their energy needs.¹² Noguchi defined NZEB as a house that consumes as much energy as it produces over a certain period of time.¹³ Similarly, Berardi discussed their methodologies for the design and evaluation of ZEB and NZEB.14 Furthermore, Ghaith Tibi et al.¹⁵ performed a case study using Ecotect software for a detached residence located in Lebanon’s inland region, where they applied passive design strategies that could save up to 78% of the annual heating and cooling electric energy consumption, taking into consideration geometry, envelope, orientation, natural ventilation with other factors.¹⁵ Shading devices were not taken into consideration.

Between 2014 and 2035, the global market for goods and services related to NZEB construction and renovation is expected to rise at a compound annual growth rate of 44.5%, surpassing $1.4 trillion last year. This is an indication that the concept of NZEB is getting popular. Caulfield discussed the exponential popularity growth of the NZEB for the next two decades.¹⁶ The concept of zero-energy buildings has enjoyed many definitions stemming from the above-described evolution and development. Some of these definitions might differ from each other, yet the main concept is that an NZEB is characterized by a significant reduction in its energy demands, which is achieved through efficiency measures. This enables the residual energy needs to be met through the use of renewable technologies.

The development of NZEBs is based on four principles. Based on the typology of the building and the climatic context, design teams must apply these four principles to find the most suitable measures.¹⁷ (1) Reducing the energy demand for all newly constructed buildings: About 40% of all energy consumed by buildings is used for space heating and cooling. This reduction can be applied by adopting passive design strategies. (2) Improving indoor environmental quality. (3) Applying a percentage of renewable energy demands to be covered by a renewable energy annual balance. (4) Reducing the overarching value for primary energy consumption and carbon emissions per year.

The basic concept behind the NZEB standard exacerbates the risk of overheating in homes under hotter weather conditions. Despite this, there is very little research and investigation regarding the issue and the potential of the widespread implementation of NZEB standards across Europe to compound the risk of overheating in buildings.¹⁷ Fundamental to the energy efficiency of these buildings, the following five principles are central to the Passive House design and construction: (1) super-insulated envelopes, (2) airtight construction, (3) high-performance glazing, (4) thermal-bridge-free detailing, and (5) heat recovery ventilation. All these key principles are linked to, and impact each other, in the design. To effectively create a Passive House building, the design should be looked at holistically to incorporate all five design principles. Passive design strategies are decided based on the climate of the region, mainly temperature and humidity. There is a wide range of passive design strategies, from passive heating to passive cooling and passive ventilation.

Research Methodology

The research will discuss passive strategies such as passive heating design to achieve NZEB and then will apply the NZEB concept on a 100 m2 house under Beirut weather conditions by using Ecotect software to study the effects of different variables such as orientation, building envelope, glazing, and shading, and then propose the optimal conditions for NZEBs under Beirut weather. After studying different alternatives and selecting the one that optimizes the energy needed, we will proceed with a renewable energy system calculation to cover the remaining needed load.

Passive Heating Design

In passive solar heating, the building envelope is composed of walls, floor, roof, and windows and is designed to collect, store, reflect, and distribute solar energy in the form of heat in winter and reject heat in summer. Energy from the sun is being used, or controlled, through the physical makeup of the spaces. Passive solar design depends on the location of the building, orientation, geometry, envelope, and other factors to achieve the target.

Orientation of the Building

The solar passive design technique puts forth light upon the orientation of the building as it affects solar radiation, daylight, and wind. In a hot and humid climate, the orientation of the buildings should be along the long axes in the east-west direction. This will eventually place the longest facade in the north and south direction, along with a short wall facing the east and west directions (Figure 1).

Building Geometry

The form of the building can affect solar access, wind exposure, rate of heat loss or heat gain through the external envelope of the structure, and airflow patterns around the structure, which will also affect ventilation. The compactness of the structure can be measured with the help of the ratio of surface area to the volume (S/V). The lowest S/V ratio is believed to be of circular geometry. Thus, the circular form of the building becomes the most energy-efficient in a hot and humid climate.

Envelope

The building envelope is what separates the interior of the building from the exterior; it consists of windows, outside walls, roofs, and floors.

Windows: To balance the amount of light admitted into the structure with the control of solar heat gain and conduction of energy. Up to 40% of a home’s heating energy can be lost, and up to 87% gained through glazing. Window performance is a combination of several factors. Thermal transmittance of the walls is the heat flow rate in a steady state divided by the area and the temperature difference between the surroundings on each side of a system. Solar heat gain coefficient (SHGC) represents the fraction of solar heat that enters the window and becomes heat; it includes both directly transmitted and absorbed solar radiation. The lower the SHGC, the less solar heat the window transmits through the glazing from the exterior to the interior, and the greater the shading capability. Visible transmittance (VT) of the glass VT (0–1): Percentage of the visible spectrum that is transmitted through the glazing. Light-to-solar-gain (LSG): The ratio SHGC/VT: LSG ratio is a gauge of the relative efficiency of different glass types in transmitting daylight while blocking heat gains.

It is important not only to make sure to specify high-performance windows but also to carefully consider how they are incorporated into the building design. Solar heat gain through appropriately placed windows can help offset the amount of heat a building needs during colder months. During the summer months, this needs to be counteracted with shading to prevent too much heat from the sun from getting into the building, causing overheating.

Walls: Walls consist of a major element in a building envelope. One of the characteristics is the thermal transmittance, which represents the heat flow rate in the steady state divided by area and the temperature difference between the surroundings on each side of a system. Thermal mass of the exterior surface that receives direct sunlight during the day and placement of insulation with respect to the building facade.

Roof: A roof of a high-performance building is especially important because it is a major area for heat transmission due to its generally large area and exposure to the sun. Using surfaces with high albedo (a measure of the reflectivity of solar radiation) for roofing can reduce the ambient air temperature so that the entire area is cooler, which helps reduce the thermal load on the building as well as the surrounding neighborhood.

The Solar Reflectance Index (SRI): It measures how hot materials in the sun are and is used to easily describe the amount of solar energy reflected by roofing materials. A building with light-colored shingles and an SRI of 54 would reflect 54% of incident solar energy and would be very cool relative to a building with conventional dark shingles.

Insulation and thermal bridges: Insulation is a critical element of the building envelope. Insulation acts as a barrier to heat flow and is essential for keeping the home warm in winter and cool in summer. Some types of insulation can also help with weatherproofing and soundproofing. Passive House makes the most of the envelope by super-insulating the building in order to minimize heat loss. The result is a significant increase in the thermal performance expected from the building envelope. When a material bypasses the insulation, it is known as a thermal bridge and can significantly reduce the effectiveness of insulation, especially if that material is very conductive, like metal. Minimizing repeating thermal bridges and aiming for continuous insulation where possible, helps make the most of the insulation within the building envelope.

Software Used

Ecotect software is an environmental analysis tool that allows architects and designers to simulate building performance right in the conceptual phase.18 It allows them to calculate a building’s energy consumption by simulating its context within the environment, especially when dealing with solar heat, natural daylighting, airflow for ventilation, and its energy consumption for man-made systems such as air conditioning and lighting.

Base Case Model Description, Parameters, and Performance

Beirut Weather Conditions

Lebanon, with a total area of 10,452 km², is located in the East Mediterranean and extends over some 210 km along the coast and 50 km inland. The climate in Lebanon is characterized in general by the existence of a cold winter season, a hot summer season, and two mild mid-seasons. The summer season extends from July to September, with August being the hottest month. Lebanon is divided into four regions based on temperature, relative humidity, and solar radiation, as per Table 1. These climatic parameters affect the heating and cooling requirements in buildings. Beirut, which is our case study, falls under Zone 1: Coastal, characterized by a warm and short winter and a hot and humid summer.

Table 1: General characteristics of climate zones and subzones.19
Climatic Zone	Climatic Subzone	Winter	Summer	Daily Gap
1. Coastal	1A Altitude < 400 m	Warm and short	Hot and humid	Small all year
	1B Altitude > 400 m	Cold and long increasing with altitude	Hot and humid with maximum daily temperatures differing slightly from 1A
2. Western Mid-Mountain	No subzone	Cold and long increasing with altitude	Cool and Moderate summer	More pronounced than the daily gap of Zone 1
3. Inland Plateau	No subzone	Colder and longer than the winter at same altitudes in Zones 1 and 2 (minimum temperatures lower than those in Zones 1 and 2)	Hot and dry summer, but cool at night. The minimum temperatures are lower than Zones 1 and 2 and the maximum temperatures are higher. Very low humidity.	In summer the daily gap is high and varies according to the year.
4. High Mountain	No subzone	Long and rigorous	Cool	Moderate to high in Eastern Mountain

Base Case Model Parameters

The house is a single-floor one, with a rectangular shape of 12.5 m × 8 m and a height of 3 m, with the long façades facing the east and west. The envelope has an infiltration rate of 0.5 air change per hour with a U-value of 4.021 w/m2·C. The external walls are composed of 1.5 cm plaster, 15 cm hollow block, and 1.5 cm plaster. Slabs are made from reinforced concrete without insulation, and the same is true for the roof. Windows are made from 6 mm single glass panes. Table 2 summarizes the U values of the base case model, while Figure 2 shows the building floor plan.

Table 2: Thermal characteristics of the building’s envelope.
Component	Description	U-Value (W/m2·k)
Roof	Plaster, reinforced concrete, sand, mortar, tiles	2.64
Walls	Plaster, hollow block, plaster	4.95
Windows	Aluminum frame single pan	5.41
Slabs	Reinforced concrete, sand, mortar, tiles	4.06

Note that the envelope thermal transmittance (U) is higher than the maximum value set by the local building code for the same region of 2.5 W/(m2·k).¹⁹ The house is divided into two zones. The first one is composed of bedrooms, and it is assumed that it is occupied only at night during sleeping hours, while the second one is the kitchen with a salon and living room, and it is assumed to be occupied during the day and in the evening. The zoning is used to design the operation, such as the number of people, which is equal to 3; the type of active system, which is mixed, that is used to provide for both heating and cooling for the house; and operating hours depending on each zone schedule. The weather file used to simulate Lebanon weather data for the Beirut area is the one of Rafic Hariri International Airport.²⁰ For this case study, we will adopt the following parameters: internal loads, including occupants, lighting, and appliances, are approximated to be 5 w/m2 of sensible load and 3 w/m2 of latent load. The thermal comfort band is set to be between 18°C and 26°C.

Energy Consumption in the Building Sector in Lebanon

Individual household energy consumption in Lebanon estimates vary from 0.45 to 2.2 MWh per household.²¹ Although no studies were found identifying per capita residential energy consumption, several values were obtained for total per capita energy consumption varying from 2.0 to 2.6 MWh per capita.^22–24 In 2007, final power consumption remained concentrated at 65% in the residential sector and the tertiary sector, then at 30% in the industrial sector, and finally at 5% in the other sectors (agricultural and administrative). In Lebanon, 67% of housing consists of flats in several-floor buildings. Among the housing units, 52% have 4–5 rooms. The average housing area in Lebanon is 129.3 m², with 21.8% of the housing units being power-heated, 25% using fuel oil, 27.3% using gas (LPG), and 17.6% using wood or coal (Figure 3).²⁵

Results

Base Case Model Results

The direct normal irradiation and the annual sun path analysis for the base case model are shown in Figures 4 and 5, respectively.

The simulation of the base case model showed that the annual cooling load is 27.25 kW/m2 with a peak of 3.95 kW on the 9th of July, while the annual heating load is 1.68 kW/m2 with a peak of 0.99 kW on the 6th of February. Table 3 summarizes the monthly cooling and heating loaded in Wh, while Figure 6 represents the combined heating and cooling loads during the year.

Table 3: Monthly heating and cooling loads in Wh.
Month	Heating (Wh)	Cooling (Wh)	Total (Wh)
Jan	84,241	–	84,241
Feb	40,856	–	40,856
Mar	16,761	–	16,761
Apr	–	–	–
May	–	21,807	21,807
Jun	–	323,900	323,900
Jul	–	701,805	701,805
Aug	–	851,132	851,132
Sep	–	623,371	623,371
Oct	–	186,048	186,048
Nov	11,326	17,559	28,884
Dec	15,614	–	15,614
Total	168,797	2,725,622	2,894,420

To learn how to interact with the model and what improvements need to be made, we will check the passive gains breakdown graph in Figure 7. In order to evaluate the passive design strategies that will be studied, different analysis functions were used, mainly the ones related to passive gains. The first function used is conduction loads through the fabric; these loads refer only to the gains due to differentials in air temperature between inside and outside the space. The second function used is Indirect solar loads through opaque objects, which refers to additional gains due to the effects of incident solar radiation on the external surface of exposed opaque objects.

The solar radiation acts to raise the external surface temperature, which in turn increases the conducted heat flow. Also, Direct solar gains through transparent objects is a function used to analyze the effectiveness of passive strategies; these loads refer to solar radiation entering the space through a window.

Optimized Model

Many fundamental parameters for the passive design concept will be studied to evaluate their function and role in different passive design strategies.

Orientation and Room Arrangement

The orientation of the house influences cooling and ventilation load. The natural ventilation flow rate is needed for passive cooling during the hot season, which constitutes 5 months of the year. A range of orientations has been modeled and tested using Ecotect weather tools to determine the best orientation of the house in terms of heating and cooling loads. Simulating the different orientations showed that the best orientation is to have the longest facade with more window/wall ratio facing north (192.5° angle), as in Figure 8, in order to minimize the solar gains during the hot season. Results are presented in Table 4.

Table 4 :Orientation performance summary.
Degrees	Heating Load (kWh/m2)	Cooling Load (kWh/m2)	Total Load (kWh/m2)
0	1.68	27.25	28.93
30	1.77	25.22	26.99
90	1.78	23.86	25.81
150	1.64	25.89	27.53
180	1.54	27.26	28.80

A study done in residential estate planning in 2013, in a climate similar to our base case conditions of Nanjing, that is, in Ma’anshan, belongs to a hot summer and cold winter region.¹⁸

Envelope

Different elements of the envelope were studied, such as walls, slabs, roofs, and glazing. Each had many alternatives, so using Ecotect software, we were able to identify the best option, resulting in the lowest cooling load. In our case, we will choose option W1 from Table 5 since materials are available in the market in order to achieve better load optimization.

Table 5: Envelope: wall performance.
Wall No.	Description	Heating Load (kWh/m2)	Cooling Load (kWh/m2)	Total Load (kWh/m2)
Base case W0	Hollow block 15 cm thick with 1.5 cm thick plaster both sides	1.68	27.25	28.93
W1	10 cm double walls with 4 cm air gap	1.54	26.21	27.75
W2	Double brick with solid plaster	1.68	27.22	28.90

The slab does not have much impact on the heating and cooling loads, so we will pick an alternative consisting of a 10 cm concrete floor on top of 1.5 m soil + parquet 5 cm, with a total load of 28.73 kWh/m2. A small improvement in the roof will lead to a high saving in cooling load since it is the most exposed to solar radiation and receives huge solar heat. We will adopt R2 from Table 6 since materials are available in the market and are considering better improvement in terms of cooling loads.

Table 6: Envelope: roof performance.
Roof No.	Description	Heating Load (kWh/m2)	Cooling Load (kWh/m2)	Total Load (kWh/m2)
Base case R0	15 cm concrete slab + 6 mm asphalt cover + plaster 1 cm	1.68	27.25	28.93
R1	15 cm concrete slab + 1 cm plastering	1.85	28.49	30.34
R2	15 cm concrete slab + PU rubber 5 cm + 1 cm plastering	1.28	23.93	25.21

Glazing and Shading

Glazing and shading are critical in passive design strategies since they have a high impact on both passive heating and passive cooling of the building. Double-glazing windows with different thicknesses of panels and air voids have been studied, and the output was very remarkable. Moreover, different shading element proportions have been modeled and tested to control direct solar gains during the hot season to avoid increasing thermal storage and undermining the effect of this setting is related to the wind speed and direction by a parameter defined as wind sensitivity used in the thermal simulation of natural ventilation that is used to passively cool the house. Option G1 will be adopted from Table 7 since the difference from other types is considerable and will help achieve our target related to load demand optimization.

Table 7: Window performance.
Window No.	Description	Heating load (kWh/m2)	Cooling Load (kWh/m2)	Total Load (kWh/m2)
G0	Single glazed, aluminum frame	1.68	27.25	28.93
G1	Double glazed with 6 mm air gap and low e-coat, timber frame	1.70	22.79	24.49
G2	Double glazed with 6 mm argon gap and low e-coat, timber frame	1.52	24.68	26.20

Adding shading elements as overhangs for west facade windows, which will receive the most solar direct + diffusion radiation, as shown in Figure 9, will help reduce the cooling needed from base case model 27.25 Wh/m2 to 23.73 Wh/m2 while heating load will almost remain the same at 1.61 Wh/m2.

Model Summary and Comments

Based on the alternatives simulated previously, we will combine the best options of each case to get the best model in terms of passively reducing energy consumption. A combination of best alternatives without shading devices will give a space load of 17.63 kWh/m2 (Table 8), representing a reduction of 39% from the base case model, which is remarkable.

Table 8: Best model space loads in Wh.
Month	Heating (Wh)	Cooling (Wh)	Total (Wh)
Jan	52,545	–	52,545
Feb	24,968	–	24,968
Mar	12,793	–	12,793
Apr	–	–	–
May	–	10,722	10,722
Jun	–	184,605	184,605
Jul	–	421,652	421,652
Aug	–	532,043	532,043
Sep	–	379,894	379,894
Oct	–	114,748	114,748
Nov	7866	14,303	22,169
Dec	7800	–	7800
Total	105,973	1,657,966	1,763,939

Adding the impact of shading devices will improve the reduction to 46.4%. Simulation results of the best model are shown in Figure 10, while the passive gain breakdown of the optimized model is presented in Figure 11.

Comparing the passive gains breakdown will show a reduction in the red color related to conduction and yellow color related to direct solar gains, which is logical due to the improvement applied to the envelope, including insulation, glazing with shading, and best orientation. As a percentage of total energy saving, as stated above, on average, 40% of all energy consumed by buildings worldwide is used for space heating and cooling, so we get: 0.464 × 0.4 = 0.185, meaning that about 18.5% of the total energy bill of a house. To calculate financial savings, assuming the cost of 1 kWh on average is $0.22,27 and the average annual electricity consumption per capita in Lebanon is 3,495.68 kWh,²⁸ and we have three habitants in the apartment, so we get: 3495.68 × 3 × 0.22 × 0.185 = $426 of total annual saving, which is remarkable.

Renewable Energy Application: Solar Photovoltaic Panels

After discussing different passive design strategies in order to achieve the maximum energy reduction needed for our base case model, we will focus on using a renewable energy system to cover the remaining energy needed, notably the solar photovoltaic panels system. Solar photovoltaic systems generally consist of six individual components: the solar PV array, a charge controller, a battery bank, an inverter, a utility meter, and an electric grid. The correct installation of all of these components determines how efficient the solar panels are. However, a charge controller and battery bank are optional. In order to determine the total electric power needed on an annual basis, we will consider whether the building uses efficient lighting appliances and electric equipment. The equipment and systems with their corresponding electric power consumption that are taken into consideration are shown in Table 9.

Table 9: Annual power consumption of base case model (kWh/Year).
S/N	Appliance	Quantity	Watts	Operation (Hours Per Day)	Watt × Hours	kWh/Year
1.	Lampe 1	3	10	6	180	65.7
2.	Lampe 2	6	15	4	360	131.4
3.	Television	2	40	5	400	146.0
4.	Refrigerator	1	230	14	3220	1175
5.	Freezer	1	100	16	1600	584.0
6.	Washing machine	1	600	3	1800	657.0
7.	Dryer/ironing	1	1650	1	1650	602.3
8.	Phone/laptop charger	2	15	4	120	43.8
9.	Wi-Fi router	1	10	24	240	87.6
10.	Pump	1	800	1	800	292.0
11.	Microwave or stove	1	1200	0.5	600	219.0
12.	Space cooling and heating					1512
						5516

To design the PV system in a way that covers all the building’s annual energy needs, we will use an average per day of: 5516/365 = 15.1 kWh/day. The average solar insolation of the building under study, 5.2 kWh/m2/day, is shown in Figure 12.

To estimate the electricity generated by a photovoltaic system, we will use the following formula:³⁰      

(1) Where: E = energy (kWh)
A = total area of solar panels (m2) r = solar panel yield (%)
H = annual average solar radiation on tilted panels PR = performance ratio, coefficient for losses

In our case, using 8 PV module Longi LR5-72HPH of 545 w, we have:

A = 2.2 × 1.1 = 2.42 m2; r = 21.3%; PR = 0.8;
Average daily solar radiation = 5.2 kWh/m2 We get
E = 8 × 2.42 × 0.213 × 5.2 × 0.8 = 17.15 kWh/day > 15.1 kWh/day.

So, we will use eight panels of Longi LR5-72HPH.

For the battery bank calculation, we will assume that we need a backup system for 24 hours, and we need the system to produce 4 A, so the total power needed will be: 4 × 24 × 220 = 21,120 Wh. Using loss factors of 80% for DOD and 60% for total discharge³¹ and using a system of 48 V, the size needed will be as follows:

(2) Applying the formula, we will get: so, we will use five batteries of 200 A each.

For the inverter size, since the system is 48 V and we have a system of 4360 w (8 × 545), we will choose an inverter of 5 kVA and 48 V. We are using a system of 8 × 545/20 = 19.1 A and 48 V, so the charge controller will be of 20 A and 48 V.

System cost: We will use the price from the Lebanese market to approximate the cost of the system.

Eight panels of 545 W are at 8 × 100 = $800. Five batteries of 200 A are at 5 × 180 = $900. Inverter 5 kVA and 48 V is at $350. The combiner box with a charge controller, wires, utility meter, chassis for panels, and workmanship will cost about $800. So the total cost of the system will be $2850.

Conclusion

The year-round fresh indoor air quality and stable temperature, the substantial reduction in energy use and operating costs, and the quiet atmosphere that the Passive House standard delivers are directly attributable to the NZEB principles and the way they are integrated into a Passive House building. Architects and designers should give full consideration to various ecological energy-saving methods in the concept design. Buildings must become more ecological, consume less energy, and ultimately create a better living environment. By building NZEBs instead of conventional ones, energy for buildings can be generated by the buildings themselves and can reduce the energy crisis and the country’s environmental emissions. This project explored how net-zero energy and passive design strategies can be implemented. A huge reduction has been noted in the required heating and cooling loads, from 28.94 kWh/m2 to 17.63 kWh/m2, consisting of 39% for a typical 100 m2 located in Beirut, by adopting simple passive design strategies, like upgrading the windows from single pane to double pane, applying insulation in roof and walls, orienting the building in correspondence to required passive heating or cooling reduction, and implementing shading devices to control solar exposure of the building.

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Cite this article as:
Bdeir F and Nasrallah C. Net-Zero-Energy Building: A Case Study Using Ecotect Software Under Beirut Weather Conditions. Premier Journal of Environmental Science 2025;3:100016

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