Comparison Regarding the Carbon Footprint of Various Sustainable Seismic Consolidation Solutions for Romanian Orthodox Churches

Abstract

In Romania, there are numerous Orthodox churches, many of which are historical monuments of great cultural value that have suffered multiple degradations over time due to various natural or man-made reasons. In a context that is currently increasingly focused on environmental protection, we aim to analyse the carbon footprint of several different consolidation proposals to an Orthodox church with structural deteriorations (and more) and the equivalent impact if a similar building were erected with new materials. The research is proposed to be a stepping stone for determining the sustainability of interventions for orthodox churches, as the existing literature is scarce when it comes to the emissions of these churches and there is no norm to prevent unsustainable interventions. The Orthodox Church “Sfintii Voievozi”, the subject of the analysis, is in the city of Tg. Jiu, Gorj County. The construction was documented to be between 1748 and 1764 and is a historical monument listed in the LMI GJ-II-m-A-09189 registry. The architectural solutions for the church and the structural elements that comprise the load-bearing system are presented. A detailed investigation was conducted to determine structural and non-structural degradations, specifying the main causes that have produced them. With regard to consolidation solutions, two options are presented and compared in this paper: Alternative I—minimal intervention and Alternative II—maximal intervention, both of which are reversible. The carbon footprint calculation was carried out for both options, determining the associated material consumption, and compared to the carbon footprint for the case of a new construction. In conclusion, the consolidation methods with a minimal degree of intervention is recommended as the “most environmentally friendly”, considering carbon emissions when comparing the options.

1. Introduction

In recent years, in Europe, more emphasis has been placed on maintaining and retrofitting its built inventory. With most European buildings built after the Second World War using industrial methods, most studies are addressing the structural and thermal performance of these mass-constructed, often concentrated districts [1]. The seismic behaviour of masonry buildings is a critical aspect of structural engineering, especially in regions prone to earthquakes. Masonry structures, such as piers and walls, exhibit unique characteristics that influence their ability to withstand seismic events. These materials are complex and behave differently under different types of load, making the analysis of their performance during seismic activity challenging. One of the key aspects of understanding the seismic behaviour of masonry is recognising the various failure modes that can occur. For example, flexural failure, also known as toe crushing or rocking, occurs when the compressive strength of the masonry is exceeded, resulting in vertical and horizontal cracks [2,3]. Diagonal shear failure is another common failure mode, which occurs when the tensile strength of the masonry is exceeded along the main tensile direction, leading to diagonal cracks through units or mortar joints. Sliding shear failure is less common but can occur under certain conditions, such as low compressive stress and high horizontal force, causing damage along a horizontal mortar joint [4]. Non-reversible structural interventions for seismic retrofitting [5,6,7] of reinforced concrete [8,9,10,11,12] are extensively investigated without considering the carbon footprint of these interventions [4,13]. The importance of this topic goes beyond academic study; it has direct implications for building safety and resilience in earthquake-prone areas, with risk assessment methods proposed by different researchers [14,15].

The retrofitting of masonry structures and the reduction of their carbon footprint involve various strategies, including the use of sustainable materials and methods that improve the energy efficiency and structural integrity of the building while preserving its heritage value [14]. By conserving existing masonry structures, the need for new construction is reduced, which saves resources and minimises the transport demand associated with moving materials for new buildings. Retrofitting interventions must be carefully planned to avoid damaging the heritage and architectural character of historic buildings and to respect the recommendations of ICOMOS and the Venice Charter [16,17,18]. This requires a multidisciplinary approach that involves structural and material engineers, architects, draughting specialists, sociologists, conservators, historians, and others.

The use of sustainable materials, such as wood, natural fibres, and recycled materials, can contribute to a lower carbon footprint. For example, the use of geopolymers in the form of a new fabric-reinforced cementitious matrix (FRCM) system combined with fly ash binder and expanded glass aggregate resulted in a 125% increase in shear strength and a 25% reduction in heat transfer. Fibre-reinforced mortar (FRM) systems, such as the FRCM technique, incorporate fibre-based meshes embedded in a cement or lime mortar coating, which can provide improved structural stability and energy efficiency [19]. Seismic activity can significantly affect historic buildings because they are not designed to withstand seismic events and can cause significant structural damage, including cracks, displacements, and even complete collapse [20,21,22,23]. In urban areas, seismic activity can exacerbate existing environmental issues, such as soil liquefaction, which can make post-earthquake recovery more difficult. Assessing the seismic vulnerability of historic urban centres is challenging, and several researchers have developed simplified methods [24,25].

In Romania, there are numerous Orthodox churches, many of which are historical monuments of great cultural value that have suffered over time from multiple deterioration for various reasons [26,27]. The most significant structural deteriorations are due to settlements and seismic actions [28,29]. In the current, increasingly important context of environmental protection, our aim is to analyse the carbon footprint in the specific case of an Orthodox church experiencing structural deteriorations (and more), comparing various consolidation proposals. In summary, the carbon footprint of a masonry structure retrofit can be significantly reduced by applying sustainable practices, including the use of efficient materials and designs that improve energy efficiency and structural resilience while preserving the historic and cultural value of the building.

2. Church Description

The Orthodox Church “Sfintii Voievozi”, the subject of the analysis, is located in the city of Tg. Jiu, Gorj County. The construction has been documented to the period between the years 1748 and 1764 and is a historical monument listed in the LMI GJ-II-m-A-09189; in Figure 1 the church is presented in the oldest photo available and in the current state. It was built on the old site of a wooden church dating back to 1523. The interior was painted in 1779 and suffered damage in the years 1793 and 1813.

Over time, the church underwent a series of interventions, starting in 1855 when the towers were heightened. Later in 1902 the ledges were covered with plaster, and between 1933 and 1940 the exterior painting dating from 1855 and the original dimensions of the towers were restored.

The church has a cross-shaped plan, characteristic of the old Greek style. Although it has undergone several instances of damage and interventions over time, the church has maintained its initial floor plan, as presented in Figure 2.

The church has two high levels with two towers and is irregular in shape with the structural walls, leading to an important dissymmetry in stiffness and load capacity in relation to the main directions of the building. It has a cross-shaped plan with apses at the altar; the nave has the maximum dimensions in the plan of 22.95 m in length and 10.90 m in width, and the maximum height is +20.80 m. The structural walls are arranged longitudinally and transversely and are made of solid brick masonry with lime, clay, and sand mortar. The wall thickness varies between 85 cm and 130 cm. The nave is separated from the narthex by two brick pillars. The narthex pillars are made of brick masonry and are connected by wooden ties and brick arches. The floors are made of brick vaults and domes, lacking rigidity in their planar actions. The towers transmit loads on arches supported by pillars and the perimeter load-bearing walls. The iconostasis is made of brick walls that bind as a bracing. The foundations are made of river stone masonry with lime sand mortar, with a width approximately equal to the width of the walls. The access staircase to the attic is within the thickness of the wall and is made of brick masonry.

3. Description of Degradations

The plaster is degraded due to the capillary rise of the rainwater shown in Figure 3. Several cracks from non-seismic structural damage have been identified, in the form of vertical cracks in the flanking walls caused by settlement of the foundation soil, in the area of the altar apse and narthex. There are cracks near the stone framing of the church entrance door, generated by settlements, shown in Figure 4. Cracks have been identified to the load-bearing structure due to seismic actions, in the form of horizontal sliding cracks in mortar joints between masonry panels. There are also horizontal cracks caused by torsion in the mortar joints between the masonry panels and vertical cracks in the window arches caused by vertical seismic forces (Figure 3). In the transverse arches and vault of the nave, there are cracks caused by the oscillation of the central tower (Figure 5). In the domes of the lateral apses, there are cracks parallel to the church’s axis, caused by seismic oscillation (Figure 5). In the longitudinal arches of the narthex, there are cracks in the key areas of the arches caused by the tower’s oscillations (Figure 6), and in the domes of the narthex there are cracks arranged at a 45-degree angle caused by the tower’s oscillations (Figure 7).

Cracks parallel to the church’s axis caused by seismic actions are present in the dome of the altar (Figure 4). There are also vertical cracks in the intersection area between the iconostasis wall and the perimeter walls that support the load, caused by seismic actions. The wood in the roof structure does not show significant deterioration. Local attacks by woodboring insects have been identified, along with some areas where roof elements have decayed.

No specific cracks generated by horizontal components of seismic forces, diagonal cracks in X, horizontal sliding cracks in mortar joints or bricks, or cracks generated by eccentric compression have been identified in the walls that hold the load at the ground level. All recorded degradations are taken from in situ investigations and from the available technical expertise of the church.

4. Consolidation Solutions

The consolidation methods were determined on the basis of static and dynamic spatial analysis. Following the proposed reversible consolidations, the load-bearing structure’s load-bearing capacity will increase without modifying its rigidity. Consolidation measures reduce the seismic vulnerability of the church, classifying it as seismic risk class III. Two consolidation options are proposed:

4.1. Minimal Intervention—Alternative I

To secure and consolidate the existing building, the following works are proposed:

• Removal of debris from the attic.
• Implementation of temporary wooden supports inside the church for walls, vaults, and arches.
• Construction of a reinforced concrete perimeter beam at the foundation level.
• Installation of a scaffolding system outside the church for consolidation works.
• Removal of plaster, sandblasting of brick walls, vaults, attics, and towers, and reining with hydraulic lime mortar.
• Restoration of the continuity of the brick wall in the area of the altar apse by inserting stainless steel helical bars into the mortar joints on the exterior surface of the wall (Figure 8). Biaxial basalt fibre meshes and microfibre stainless steel meshes will be installed on the exterior face of the apse wall, from elevation 0.00 up to the level of the galvanised unidirectional fabric belt.
• Restoration of the continuity of masonry in the contact area between the narthex and the porch, affected by differential settling of the foundations and seismic actions. The area will be reinforced with inclined stainless steel helical bars (Figure 8). Biaxial basalt fibre meshes and microfibre stainless steel meshes will be installed on the exterior face of the wall, from elevation 0.00 up to the level of the galvanised unidirectional fabric belt.
• Consolidation of the perimeter masonry in the contact area between the narthex and the nave, between axes 3 and 4. Biaxial basalt fibre meshes and microfibre stainless steel meshes will be installed on the exterior face of the wall, from elevation 0.00 up to the level of the galvanised unidirectional fabric belt.
• Construction of two external perimeter belts made of unidirectional galvanised fabric with a width of 15 cm each, with the aim of ensuring spatial collaboration of all load-bearing walls during seismic actions (Figure 8) and avoiding the appearance of localised failure blocks.
• Consolidation of vaults with fabrics made of galvanised steel fibres and hydraulic lime mortar. Consolidation will be carried out on the extrados of the vaults (Figure 9).
• Consolidation of the attics on the attic face, by placing stainless steel helical bars in the joints and a mesh made of basalt fibres and microfibre stainless steel. The mesh will be anchored to existing masonry with galvanised fabric connectors and hydraulic lime mortar.
• The masonry of the tower in the nave will be consolidated as follows.

  (a)

  Up to roof level, the masonry will be reinforced by introducing helical stainless steel bars into the horizontal joints on the exterior faces. Subsequently, the masonry will be strengthened with biaxial meshes with basalt fibres and stainless steel microfibres.

  (b)

  Above the roof level, the masonry piers delimited by windows will be reinforced with vertically arranged strips made of galvanised steel fibre fabric. The arches in the tower windows will be consolidated with inclined helical stainless steel bars (Figure 8).

  (c)

  In the upper part of the tower, on the exterior face, a band made of galvanised steel fibre fabric will be installed to serve as a belt (Figure 8).

• The masonry of the tower in the narthex area will be consolidated as follows.

  (a)

  Up to roof level, the masonry will be reinforced by introducing helical stainless steel bars into the horizontal joints on the exterior faces. Subsequently, the masonry will be strengthened with biaxial meshes with basalt fibres and stainless steel microfibres.

  (b)

  Above the roof level, the masonry piers delimited by windows will be reinforced with vertically arranged strips made of galvanised steel fibre fabric. The arches in the tower windows will be consolidated with inclined helical stainless steel bars (Figure 8).

  (c)

  In the upper part of the tower, on the exterior face, a band made of galvanised steel fibre fabric will be installed to serve as a belt (Figure 8).

  (d)

  On the interior faces of the tower walls, biaxial meshes with basalt fibres and stainless steel microfibres will be applied.

  (e)

  The tower dome will be strengthened by applying galvanised steel fibre fabric strips to the entrances of the masonry (Figure 9).

• Strengthening of the arches in the nave and narthex will be achieved by attaching strips made of high-strength galvanised steel fibre fabric to their reaches. These strips will not affect the cultural value of the surfaces as there is no painting on the eaves of the arches. Before the strips are applied to the intrados of the arches, inclined helical stainless steel bars will be inserted.
• Restoration of the connection between the altar brick wall (iconostasis) and the perimeter walls will be carried out by introducing zinc-coated bars with a diameter of 20 cm. The drilling will be done horizontally and will proceed from the altar towards the nave.
• Hydraulic lime-based mortars, specific for brick masonry, will be injected into all fissures.
• Rehabilitation of the access stairs to the attic by removing degraded bricks and replacing them with similar bricks.
• Roof elements will be consolidated or partially/fully replaced based on the level of degradation. Nodes and joints without contact between load-bearing elements will be strengthened.

4.2. Maximal Intervention—Alternative II

To secure and consolidate the existing building, the following works are proposed:

• Removal of debris from the attic.
• Installation of temporary wooden supports inside the church on walls, vaults, and arches.
• Construction of a reinforced concrete perimeter beam at the base level of the foundation, up to the sidewalk level.
• Construction of a working scaffolding structure outside the church for the implementation of reinforcements.
• Stripping of plaster, sandblasting of brick walls, arches, attics, and towers, and restoration of masonry joints with hydraulic lime.
• Restoration of the continuity of the brick wall in the area of the altar apse by introducing galvanised metal shims.
• Restoration of the continuity of the masonry in the contact zone between the narthex and the porch, affected by differential foundation settlement and seismic actions. The area will be reinforced with drilled metal rods on the walls.
• Construction of two exterior perimeter belts with metal profiles, 15 cm wide, to ensure spatial collaboration of all load-bearing elements during seismic actions.
• Strengthening of vaults with galvanised welded mesh and hydraulic lime mortar. The consolidation will be carried out in the attic on their extrados.
• Consolidation of the interior of the attics with welded meshes and hydraulic lime mortar. A 20 cm reinforced concrete belt will be created in the attics.
• Consolidation of the tower:

  (a)

  The masonry of the tower in the nave will be consolidated by cladding with galvanised welded meshes and hydraulic lime mortar up to the roof level. On the cornice, a belt made of flat metal bars will be installed.

  (b)

  The masonry of the tower in the narthex area will be consolidated by cladding with galvanised welded meshes and hydraulic lime mortar, mounted on the interior face of the tower. At the top of the tower, on the cornice, a metal belt made of flat bars will be installed on the exterior face.

  (c)

  A metal structure with a bracing function will be constructed in the attic of the church between the two towers. The metal structure will consist of horizontal metal beams fixed to the perimeter walls to ensure a rigid plate and transmission of horizontal forces between the exterior load-bearing walls. Two vertical bracing beams will be mounted on this metal structure, fixed at the ends to the masonry of the towers. These vertical beams aim to reduce the horizontal displacements of the towers and stiffen them.

• Strengthening of the arches in the nave and narthex will be achieved by fixing metal flat bars or profiles to their indices. Metal tie rods will be inserted into the birthplaces of the brick arch. The collaboration between metal flat bars or profiles and arches will be achieved through threaded metal rods inserted into the arch masonry and fixed with epoxy resins.
• Restoration of the connection between the altar brick wall (iconostasis) and the perimeter walls will be carried out by introducing zinc-coated bars with a diameter of 20 cm. The drilling will be done horizontally and will proceed from the altar towards the nave.
• Hydraulic lime-based mortars, specific to brick masonry, will be injected into all fissures.
• Rehabilitation of the access stairs to the attic by removing degraded bricks and replacing them with similar bricks.
• Roof elements will be consolidated or partially/fully replaced based on the level of degradation. Nodes and joints without contact between load-bearing elements will be strengthened.

5. Comparative Calculation of Carbon Emissions

In the case studied, according to technical expertise, two consolidation options are proposed: a minimal intervention option and a maximal intervention option. The carbon footprint resulting from each option was determined. For the complexity of the comparison, calculations were also be performed for the option of a new construction.

Thus, quantities of materials and the volume of activities were calculated for all three options. The determination was made by calculating the surface area, volume, and weight, considering the general characteristics of the materials. The densities are as follows: rubble 1500 kg/m³; soil 1500 kg/m³; timber 500 kg/m³; concrete 2200 kg/m³; mortar 1800 kg/m³; biaxial mesh with basalt fibres 200 g/m²; unidirectional mesh 2 kg/m². Consumption estimates were made using execution experience.

In

Table 1. Alternative I.

Intervention	Materials	Quantity	Weight [kg]
Installation of temporary wooden supports	Timber	15 m3	7500
Construction of a reinforced concrete beam around the foundation level	Concrete	16.5 m3	36,300
	Reinforcement		2025
	Anchoring mortar		100
Restoration of the continuity of the brick wall in the apse area of the altar	Biaxial mesh with basalt fabric	66 m2	13.2
	Structural mortar	1.4 m3	2520
	Stainless steel helical bars	10 m
	Structural mortar		30
Restoration of the continuity of the masonry in the contact area between the narthex and the porch	Drilled helical bars	12 m
	Biaxial mesh with basalt fabric	36 m2	7.2
	Structural mortar	0.8 m3	1440
Strengthening of the perimeter masonry in the contact area between the narthex and the nave	Biaxial mesh with basalt fabric	60 m2	12
	Structural mortar	1.2 m3	2160
Construction of two outer perimeter belts	Unidirectional mesh with steel fibre fabric	21 m2	42
	Structural mortar	0.4 m3	735
Strengthening of the vaults	Biaxial mesh with basalt fabric	90 m2	18
	Structural mortar	1.8 m3	3240
Strengthening of the attics	Unidirectional mesh with steel fibre fabric	10.5 m2	21
	Structural mortar	0.2 m3	360
Strengthening of the towers	Biaxial mesh with basalt fabric	26 m2	5.2
	Structural mortar	0.5 m3	936
	Helical stainless steel bars	20 m2
	Structural mortar	2.7 m3	50
	Unidirectional mesh with steel fibre fabric	30.8 m2	61.6
	Structural mortar	0.6 m3	1109
	Drilled helical bars	32 m
Strengthening of the arches in the nave and narthex	Unidirectional mesh with steel fibre fabric	17 m2	34
	Structural mortar	0.35 m3	630
	Drilled helical bars	7 m
Restoration of the collaboration between the brick wall of the altar (iconostasis) and the perimeter walls	Drilled helical bars	20 m
Injection of hydraulic lime mortar into all cracks	Crack mortar		500
Rehabilitation of the access stairs to the attic	Bricks	0.3 m3	420
Strengthening of the roof elements	Timber	0.5 m3	250

, the materials, quantities, and respective weights are presented for the first alternative of consolidation, which is the minimal intervention method proposed.

In

Table 2. Alternative II.

Intervention	Materials	Quantity	Weight [kg]
Installation of temporary wooden supports	Timber	15 m3	7500
Construction of a perimeter reinforced concrete beam	Concrete	34 m3	74,800
	Reinforcement		3400
	Anchoring mortar		200
Restoration of the continuity of the brick wall in the apse of the altar	Galvanised ties		100
Restoration of the continuity of the masonry in the contact area between the narthex and the porch	Steel profiles		2625
Construction of two external perimeter belts with metal profiles	Biaxial mesh with basalt fabric	60 m2	12
	Structural mortar	1.2 m3	2160
Strengthening of arches with galvanised welded mesh and hydraulic lime mortar	Galvanised welded mesh		780
	Structural mortar	5.4 m3	9720
Strengthening of the interior attics, with welded mesh and hydraulic lime mortar	Reinforcement		608
	Structural mortar	3.5 m3	6300
	Concrete	5.5 m3	12,100
Strengthening of the towers	Galvanised welded mesh		768
	Structural mortar	6.4 m3	11,520
	Steel band		332
	Steel profiles		1467
Strengthening of the arches in the nave and narthex	Steel band		100
Restoration of the connection between the brick wall of the altar (iconostasis) and the perimeter walls	Galvanised steel bars		100
Injection of lime mortar into all cracks	Crack mortar		500
Rehabilitation of the access stairs to the attic	Bricks	0.3 m3	420
Strengthening of the roof elements	Timber	0.5 m3	250

, the materials, quantities, and respective weights are presented for the second alternative of consolidation, which is the maximal intervention method proposed.

In

Table 3. Summary table.

Summary Table
Name	Alternative I		Alternative II
	Quantity	Weight	Quantity	Weight
Timber	15.5 m3	7750 kg	15.5 m3	7750 kg
Concrete	16.5 m3	36,300 kg	39.5 m3	86,900 kg
Reinforcement		2025 kg		4008 kg
Mortar	8 m3	13,710 kg	15.7 m3	28,240 kg
Biaxial mesh	259 m2	52 kg
Unidirectional mesh	174 m2	348 kg
Stainless steel helical bars	30 m
Drilled helical bars	71 m
Bricks	0.3 m3	420 kg	0.3 m3	420 kg
Galvanised welded mesh				1548 kg
Galvanised bars				280 kg
Steel profiles				4433 kg

the summary of the two consolidation methods is presented; it can be observed that in case of the maximal alternative the use of concrete, reinforcement, and mortar is much higher, while in the minimal alternative their attributes are taken by the biaxial and uniaxial mesh.

In case of a new construction built at today’s standards and using regular materials, the total quantities and weights are presented in

Table 4. New construction.

Intervention	Materials	Quantity	Weight [kg]
Foundation (width 1 m, depth 1.2 m)	Concrete	113 m3	282,500
	Reinforcement		9800
Column	Concrete	23.5 m3	282,500
	Reinforcement		2043
	Formwork	2.82 m3	1692
Reinforced concrete floor 15 cm	Concrete	30.45 m3	282,500
	Reinforcement		2000
Brick masonry 50 cm	Brick	446 m3	535,200
	Mortar	67 m3	120,600
Reinforced concrete arches, vaults, domes	Concrete	44
	Reinforcement		3826
	Formwork	9
Exterior and interior plaster	Mortar	36.8 m3	66,240
Roof	Sawn timber	26 m3	20,800
	Roof tiles	432 m2	82,944

; the calculation was done in order to determine the CO₂ emissions of constructing a new building as the authors are aware that demolition and reconstruction of an existing historical monument is not a real option.

For the calculation of the carbon footprint [CO₂ emissions], the unit values of construction materials were used from the database downloaded from [30].

Table 5. Total kg CO₂ emissions for the two alternatives.

	Alternative I			Alternative II
Name	Quantities kg	Carbon Footprint kg CO2 Equiv	Carbon Footprint CO2	Quantities	Carbon Footprint kg CO2 Equiv	Carbon Footprint CO2
Timber	7750	0.4525	3506.88	7750	0.4525	3506.88
Concrete	36,300	0.1209	4388.67	86,900	0.1209	10,506.21
Reinforcement	2025	1.99	4029.75	4008	1.99	7975.92
Mortar	13,710	0.1333	1827.55	28,240	0.1333	3764.39
Biaxial mesh	52	2.27	118.04
Unidirectional mesh	348	2.27	789.96
Stainless steel helical bars	6.66	6.29	41.89
Drilled helical bars	63.05	6.29	396.59
Bricks	420	0.213	89.46	420	0.213	89.46
Galvanised welded mesh				1548	2.76	4282.48
Galvanised bars				280	3.03	848.4
Steel profiles				4433	1.55	6871.15
	Total carbon footprint kg CO2		15,189	Total carbon footprint kg CO2		37,835

presents the total CO₂ emissions for the two alternatives and it can be seen that Alternative I has lower emissions by 40% compared to Alternative II. This is mainly due to the use of sustainable materials, such as basal-based uniaxial and biaxial mesh. In case of the emissions for a new construction presented in

Table 6. Total kg of CO₂ emissions for the new building.

	New Building
Name	Quantities kg	Carbon Footprint kg CO2 Equiv	Carbon Footprint CO2
Concrete	464,200	0.1209	56,121.78
Reinforcement	17,670	1.99	35,163.3
Bricks	669,000	0.213	142,497
Mortar	186,840	0.1333	24,849.72
Timber	18,900	0.4525	8552.25
Tiles	15,120	0.255	3855.6
	Total carbon footprint kg CO2		271,040

, these are seven times higher than those for Alternative II and 17 times higher compared to Alternative I.

6. Conclusions

From the calculations carried out, it is observed that in Alternative I of consolidation, we have 15.2 tons of CO₂, compared to Alternative II, where CO emissions are much higher, that is, 37.8 tons of CO₂. The higher values in Alternative II are mainly due to significantly larger quantities of concrete and steel (reinforcement, welded meshes, metal structure). The simple calculations of CO₂ emissions for these alternatives presented in the paper should open the discussion of sustainable retrofitting of the existing heritage of Romanian orthodox churches.

The amount of CO₂ emissions in the case of new construction will reach 271 tons of CO₂. Therefore, in Alternative I, the CO₂ emission value will be 5.6% compared to the new construction, while in Alternative II, the CO₂ emission value will be 13.9% compared to the new construction. In the present day in Romania, many new churches are being built next to the old existing ones that are left unattended or demolished. The approach is not sustainable and further research should be done to properly assess the complete image of sustainability when retrofitting or building new orthodox churches. Today, the only discussion is whether or not there is a budget to make the interventions or build a new one, with complete disregard in terms of the carbon footprint or the sustainability of the decisions.

Through consolidation methods with a minimal degree of intervention, a culturally valuable church can be preserved, allowing its use for a long time to come while ensuring the restoration of the construction’s safety.

In conclusion, considering carbon emissions, the minimalist Alternative I is recommended as the “most environmentally friendly” with minimal CO₂ emissions and minimal non-reversible structural interventions. However, the authors understand the limitations of the simple approach for calculating the CO₂ emissions used in the paper, which is why we recommend and intend to carry out further, more detailed and comprehensive studies regarding all modules of sustainability and include multiple churches for the studies.