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A research into the feasibility of green roof design in Russia: a case study of the Ryazan region

Introduction. The era of high technologies and economy disrupts interaction between man and nature, worsening the state of the environment and living conditions on Earth. In Russia, the construction industry follows a classical development model and applies stereotypical patterns of urban design. Finding problem solving methods means identification of problem triggers that help to clearly understand and develop rational problem tackling mechanisms. Green roofs suggest an advanced approach to architecture and urbanization whereby green spaces take the place of new buildings. Supplementary dynamic space is not reduced to its decorative and environmental functions. Materials and methods. We applied such research methods as analysis, the system approach, synthesis, deduction, and comparative analysis. The initial review of the state of affairs in the Ryazan region was performed with regard for the theoretical nature of this study; correlation and regression analysis were employed to assess territories and spaces. Results. The history of green roof systems is analyzed in the article. Systematization of the effective regulatory and technical framework enabled the co-authors to assess the widespread applicability of the green roof technology in Russia. Special attention is paid to the issues that are not covered by effective domestic regulations. The research work has shown that the first edition of GOST (All-Russian State Standard) 58875 is an attempt to consolidate previously issued manuals and recommendations. There is no information available about the seasonal efficiency of green roof solutions in different Russian regions. © Е.В. Сысоева, И.В. Морозов, 2021 Исследование вопроса возможности проектирования «зеленых» крыш в России на примере Рязанской области С. 24–54 25 ol. 1. Isue 1 8) Строельство: нука и обрование A number of issues remain unresolved. The “green roof” policy has not been developed. Conclusions. Russia is not ready for large-scale construction of green roofs. Further research into green construction should be carried out with regard for unstable climatic conditions in different regions of the country to confirm the feasibility of green roofing at the legislative level.


INTRODUCTION
Accelerating climate changes and shrinking natural resources, caused by growing population numbers, may soon make our planet reach a singular point in its development. Over the past 50 years, populations of vertebrates dropped by 58 %. Researchers believe that greenhouse gas emissions of anthropogenic origin will lead to an increase in the temperature of the Earth atmosphere by more than 2-60 °C in the coming decades [1,2].
Fast-paced life facilitates the development of innovative technologies whose operation entails the con-sumption of fuel, electricity, gas and other resources; therefore, it is difficult to unambiguously predict the occurrence of natural disasters, because future external and internal environmental impacts remain unclear [3].
The main sources of pollution include settlements and industry. Hence, one needs to concentrate on urban areas to take care of the biosphere. Industrial agglomerations, transport and its infrastructure are the main pollutants that have assumed the function of civilization destroyers [4]. The consequences are set forth by the Federal Service of State Statistics (Rosstat). If we consider the morbidity rate over the past 30 years (Fig. 1), we can track the predominance of respiratory diseases.
Multiplication of green roofs increases the size of landscaped area in megacities which can mitigate negative anthropogenic impacts on the environment, including those resulting from construction works, accompanied by shrinking vegetation areas in the urban environment. The positive effect can be direct and/or indirect. In the first case, vegetation and soil (substrate) will capture carbon dioxide (CO 2 ); in the second case, the availability of a system solution will reduce power consumption and minimize the use of fuel resources [5].
Experts, employed with the joint research center of the European Commission, believe that CO 2 emissions increased by 1.2 % in 2017 if compared with the previous year. Top largest emitter countries include the United States, China, 28 EU countries, India, Russia and Japan 1 [6]. The pace of CO 2 waste generation is shown in Fig. 2.
The concept of biosphere compatibility of cities and settlements, developed by the Russian Academy of Architecture and Construction Sciences under the leadership of academician V.A. Ilyichev is gaining relevance. It is focused on compliance with the criterion of progressive urban development (in terms of the state of the biosphere adjacent to urban territories and the level of human potential in urbanized territories) and reduction of destabilizing factors. This includes ingredient and parametric contamination of the natural environment and its components, expansion of the city into the natural environment by means of transport networks, engineering communications, etc., leading to the reduction in the size and integrity of natural frameworks, as well as the decrease in their stability and effectiveness of favorable impacts on the urban environment. The biosphere compatibility of cities is possible if nine conditions are met (Fig. 3) [7,8]. Green roofs will improve the ecological situation in megacities, helping to reduce the total amount of CO 2 emissions.

Historical background
The concept of vegetation on the roof was developed for various climatic conditions. Vegetation was used as a building element or a way to mitigate the effects of high temperatures in hot climates. This was mainly due to the insulating qualities of layers of soil (drainage) and plants in cold climates, they helped to retain heat in the building, and in warm climates, on the contrary, they served as heat protection devices 2 , 3 ,. 4 [9][10][11].
The cultural development of individual periods had a direct impact on structural and external design Science and Education of roofs [12]. In some cultures, the green roof demonstrated the social status of landlords. The green roof served as a place for socializing or enjoying the garden on an outdoor patio which was often unavailable to people with low incomes. Since the beginning of the 20th century, attempts have been made to find solutions to improve the lives of urban residents. Despite this approach and social beliefs, vegetation was still a core constituent of the well-being of residents. At the beginning of the 20th century, more focus was placed on people and society than the environment itself 5 [13][14][15][16][17][18].
The chronological sequence of development of green roofs is shown in Table. 1. Each historical period differs from the previous one due to the emergence of new engineering solutions whose composition was different from the previous ones.

MATERIALS AND METHODS
In the course of the work, the following methods of research were used: analysis, system approach, synthesis, deduction, and comparative analysis. The method of correlation and regression analysis based on multiple linear regression was used to determine factors of maximal influence on the total population of the Ryazan region.
Independent variables, used in the study, included the variable of demographic population growth (Х 1 ) and environmental parameters, such as the amount of emissions X 2 , air pollutants from fixed sources; contaminated wastewater discharges X 3 ; reforestation and landscap-ing of roofs X 4 ; artificial reforestation X 5 ; the number of dead forest plants Х 6 , including coniferous plants Х 7 ; the total area of urban land within the city limits Х 8 ; the total area of green spaces Х 9 ; removal of municipal solid waste Х 10 . Total population Y was a dependent variable.
To assess the significance of each regression coefficient, we used t-criterion. We took p = 0.05 in the research. The value of R 2 , the coefficient of determination,

The ancient world (BC))
Turf roofs (first stage) and prairies Truss structures, having the slope of 30°, had a framework made of wicker willow or hazel branches. Next, three layers of birch tree bark were laid, of which the final layer took the load applied to the turf. The turf was laid in two layers, the first (bottom) layer had the plant layer placed upside down, while the second one had the plant layer placed normally Hanging gardens of Babylon The garden had several terraces, one above the other, giving the impression of massive green steps. The upper level was 25 m above the ground level. The restored structure had cut stone, two rows of bricks and lead plates acting as waterproofing.
Reeds pre-soaked with bitumen rested on these slabs, and the top part was covered with vegetable soil 17th century Turf roofs (second stage) The roof had a framework made of cedar beams and rafters. Three layers of organic materials were laid on top: wild plum or chokeberry, wild grass, fine clay or gypsum. Turf was placed on top. The grass was to grow up on top, so that it continued to grow, restore its roots, generate the protective layer made of grass to prevent erosion

18th-19th centuries
Carl Rabitz's natural roofing with volcanic cement This flat roof was composed of cast concrete in wooden formwork and an insulation layer; bitumen cement, volcanic cement, which represents a mixture of Portland cement (burnt limestone + clay) and volcanic rock with gravel; soil; plants, trees, vegetables.
Most importantly, Karl Rabitz understood the essence of insulation. In 1867, the recommendations of the Berlin builder represented the right choice of the framework, insulation material, humus layer, an irrigation system, windshield, etc.

Science and Education
The first half of the 20th century General roofing from the 1940s to the 1960s Green roofs were particularly popular in the 20th century. In the first half of the 20th century, different materials were used, including the membrane protected with a sand-cement screed and a gravel drainage layer covered with quilted fiberglass, one layer of peat and the top layer of soil

Тhe second half of the 20th century
General roofing in the 1960s In the second half of the 20th century, the structure of green roofs had the following sequence of layers: traditional roofing represented a membrane covered with an extruded polystyrene insulation layer and a Leca drainage layer covered with geotextile and a modified top soil layer The early 21st century -present  Table 1 was taken into account to determine how close the data are to the selected regression line. The calculation was performed using MS Office Excel 2016. In the study, publicly available data extracted from state statistical reports and reports issued by the Ministry of natural resources of the Ryazan region for 2001-2019 were used in our calculations.

Regulatory and technical framework
Before the introduction of the All-Russian State Standard in Russia, the insufficiently complete regulatory framework, governing green roofs, was scattered across several legal acts.
The content of Construction regulations 17.13330.2017 "Roofs. Updated version of SNiP II-26-76" is reduced to one paragraph "green roofs", which provides general information about the sequence of layers, materials to be used and permitted loads. Structural roof solutions and technical characteristics of materials are specified in separate paragraphs of Appendix G. Elements of roof landscaping and other landscaping items are separately highlighted in Appendix D, that also sets the requirements applicable to the substrate, vegetation diversity and forms of landscaping 6 .
The "Recommendations for landscape design and improvement of roofs of residential and public buildings and other artificial frameworks" (JSC Mosproject, 2000) and "Manual for landscaping and improvement of roofs of residential and public buildings, underground and semi-underground garages, civil defense facilities and other structures" (JSC Mosproject, Moscow, 2001) describe in detail the features of used roofs; provide the values of acceptable supplementary loads on operated roofs that accommodate gardens resting on artificial frameworks; methods of wind and solar radiation protection; fire protection measures and lightning protection; architectural and construction details provided in the form of illustrative material, a selection of vegetation designated for "rooftop gardens". A separate paragraph contains the requirements applicable to "green" roofs: their use depending on the type of building, acceptable degrees of slope, functional purpose, methods of installation of "green" coatings, recommendations for the arrangement of rolled lawns.
The "Guide to the design and arrangement of roofs accommodating landscaped rooftop gardens using Technoelast-green, an enhanced protection material that prevents the growth of roots", manufactured by TECHNONICOL (CJSC TECHNONICOL, Moscow, 2004) has information on the features of materials; structural solutions; roof design with a detailed step-by-step description of individual installation features; on structural nodes to be studied to ensure the appropriate work performance; repairs; quality control (work acceptance rules); ways to ensure compliance with the safety requirements applicable to the installation of waterproofing; environmental protection.
The development of GOST R 58875-2020 took about five years; the document has eight main sections. The scope of its application is clear as of the first pages of this national standard. The document introduces general terms and definitions, which will further serve a professional dialogue between designers and customers focused on rooftop landscaping. The typology of "green" roofs is updated, now it has three varieties. Large-scale work was carried out to draft a section on environmental requirements applicable to the design of green roofs, it contains detailed information on the compatibility of materials and plants; their protection from harmful substances; requirements applicable to substrates, planting material, water and irrigation control systems. For example, the impossibility of using loam as a substrate or a substrate component of roof landscaping is now a publicly available item of information provided in the updated version of the national standard rather than a manual. The technical requirements section regulates design loads, structural design of "green" roofs, and general safety requirements. The final section is "quality control during the delivery of landscaping works", which is one of the most important ones in the national standard. The rules governing the work acceptance criteria can be characterized as instructions, which will minimize the likelihood of poor-quality work.
Paragraph 4.5.12 of effective Resolution No. 623-PP issued by the Moscow Government on August 6, 2002, including the revised version No. 497-PP issued on July 11, 2006, states that "rooftop and vertical gardening cannot be compensatory". As of the effective date of the national standard, the area of the "green" roof of any listed type must be considered as a landscaped area in the process of calculating the balance of the territory of a construction facility; it must be considered an integral part of the urban compensatory landscaping system, regardless of the vertical roof mark and the number of floors in buildings and structures 7 .
As a result, it is possible to graphically depict the hierarchy of Russian regulations, depending on the priority of implementing recommendations and rules applicable to the construction of "green" rooftops (Fig. 4).
A number of policy implementation tools were used to encourage the integration of "green" roofs Vol. 11. Issue 1 (38) Construction:

Science and Education
into new projects and boost the modernization of existing buildings [19][20][21][22][23][24][25]. Table 2 below shows some of the main mechanisms by virtue of which cities authorized or encouraged the construction of green roofs. The list is not exhaustive. Table 3 shows examples of the most effective approaches to the integration of "green" roofs into urban development in a number of foreign countries 8, 9 [24, 26-33].
In foreign countries, the construction of "green" roofs was regulated by several legal acts whose legal force was different, as well. Despite the voluntary and recommendatory nature of the regulatory and technical framework, incentives aimed at the installation of a system solution were used by a number of countries in the form of financial incentives, including discounts and subsidies. It is noteworthy that the issuance of regulatory documents was carried out in furtherance of reso-lutions. Foreign experience shows that the regulation of "green" construction was carried out with the active involvement of competent organizations and associations; individuals and legal entities are actively engaged in business activities in the field of building landscaping, especially "green" roofs. Associations support this issue as a means of sustainable construction, environmental protection and modernization of urban landscaping. Successful eco-construction results are achieved if associations become members of, for example, the European Federation of green roof and wall associations, as in the case of the Czech Republic. As a result, the information and experience are shared at thematic seminars and master classes for professionals and the general public, and expert publications are published. In most countries, cooperation on landscaped roofs is implemented through participation in international competitions.  This report is designed to provide information on sources of support for green roof and wall installation policies and programs in North America to corporate participants of "Green roofs for healthy cities". It is also designed as a resource for policy makers and supporters interested in creating or updating green roof and wall policies and programmes.
Toronto Building section, Toronto green roof technical Advisory group Toronto green roof construction standard It has green roof design requirements that comply with green roof construction standards, as well as the Ontario Building code. The standard was developed to facilitate design flexibility, so that each "green" roof could be designed to maximize its effect in each project. The guide provides construction professionals and others with a better understanding of the roof landscaping process Project "Green roofs of public buildings" (as part of a series of demonstrative energy programmes) The goal is to reduce annual energy consumption for heating and cooling floor under a green roof by at least 5 % compared to annual energy consumption before the introduction of green roofs. The project is aimed at sustainable development and it familiarizes citizens and users with the practice of "green" development in construction, which immediately improves both the environment of the building and the energy characteristics of the building. The construction, installation and maintenance standards are primarily designated for green roof designers, investors and contractors, but also provide a lot of important information to construction and insulation companies. No less important is the information about the special requirements that must be observed during installation, taking into account some flat roof designs and the material properties of products. The standard has a detailed description of functional layers of "green" roofs with an emphasis on the vegetation layer. The standards contain requirements for vegetation, listing the recommended set of plants. The publication also addresses the issue of temporary and permanent sustainability of larger plants on heavily landscaped roofs. It is completed with the conditions for obtaining readymade "green" roofs by the customer, maintenance requirements and recommended warranty conditions Developed within the framework of New green saving, a green roof subsidy programme; voluntary use; financial incentives

Czech Green Rooftop Association
Green roofs as a hope for the future -II The publication is the result of three years of systematic activities in 2013. Since 2014, the organization of a professional competition for green roof projects "Green roof of the year", thanks to which this publication can present two dozen highquality "green" roofs in the Czech Republic. Successful projects serve as a source of inspiration for all progressive investors, future and current homeowners, government officials and administrators Table 2 7 England Department of communities and local selfgovernment Fire-fighting characteristics of "green" roofs and walls

Continuation of the
This document provides an overview of existing guidance documents and illustrates the results of tests performed on green roofs and wall systems. It also provides guidance on fire safety aspects in the construction industry and maintenance of green roofs and walls "Living" roof policy; guidelines Green roof arrangement (GRO) Eco-friendly construction: a guide to the use of green roofs, green walls and additional elements of buildings The guide is designated for those who need independent advice on the planning, design, construction, and maintenance of green roofs, green walls, and other biological properties. In particular, the document aims to dispel myths and give designers the opportunity to maximize the benefits of design solutions.

GRO group of technical consultants
Green roof code of best practice for the UK, 2011 The GRO code aspires to be the code of best practice and as such it should be used to guide the behavior in terms of design, specification, installation and maintenance of a green roof The standard provides a method for calculating the wind resistance of plant roofing systems using glued roof membranes. It provides the minimum number of design and installation recommendations to those who design, define, and install plant-based roofing systems. It should be applied in conjunction with the installation specifications and manufacturer requirements in terms of specific products used in the plant roofing system, or be supplemented by them   Tax discounts applicable to green roofs The loan is provided against income tax and receipts. Since 2016, the loan reaches 50 % of all costs incurred in the process of construction of a "green" roof, up to $100,000 A discount program for "green" roofs (River Smart rooftops) The district of Columbia Department of energy and environment offers a discount of $ 10 (if the proposed "green" roof is located within the combined sewer system) or $ 15 (if it is located within the municipal storm sewer system per square foot of voluntary green roof installation Since the climatic conditions are different in different regions of Russia, this fact should be taken into account in the course of the roof design. Let's address the case of China, that develops additional standards that include features of installation of "green" roofs in the cities along with national (general) standards. Table 3 shows the financial incentive programs and strategies that can be applied in Russia. There are other strategies and programs that promote the construction and installation of the green infrastructure, such as the acceleration of the project approval if green roofs are part of the project plan and using green roofs for sustainable development plans to get higher scores. The US model is also relevant for Russia [34]: • funding (by means of a grant) the installation of certain types of "green" infrastructure. Applications must be submitted and approved before construction begins; • financing (by means of a discount): the installation of certain types of "green" infrastructure may cause the reimbursement of a portion of its cost (up to a certain amount); • financing (by means of a subsidy): property owners make payments in the amount of a portion of the contribution for the "green" infrastructure; • a mandate: effective regulations or rules require green roofs in specific circumstances; • housing management programmes: there are financial incentives and technical support to encourage property owners to voluntarily install and/or maintain green infrastructure and storm water management practices.

The analysis of the feasibility of installing "green" roofs in the Ryazan region
According to the Rosstat data, the population of the Ryazan region was a dependent variable Y in Science and Education the 2001-2020 period, the demographic situation is illustrated in Fig. 5. A correlation analysis of the table that has input values was performed to identify the factors that have the greatest impact. The automatically generated correlation matrix demonstrates a positive relationship between the demography of the Ryazan region and factors X 2 , X 4 , X 5 , X 6 , X 2 , X 8 , X 9 , X 10 , and its negative relationship with X 1 , X 3 . Further calculation of t-statistics excluded the possibility of adding factors to the model that do not affect the output value and worsen the model quality. A coefficient is considered significant if its absolute value exceeds the Student critical value. Having the total number of observations n = 21 with a significance level of 0.05, the critical value is 2.093. As a result of verification X 1 , X 3 , X 4 , X 6 , X 7 , X 10 factors were excluded. Their significance is minimal.
The regression analysis of the source data was performed using the "Data Analysis" package and independent variables that meet the significance condition, such as the amount of air pollutants X 2 , artificial reforestation X 5 , the total area of urban land in front of the city line X 8 , the total area of green spaces X 9 . The value of R, showing dependence of the value of dependent variable Y on the values of independent variables X, is equal to 0.802 > 0.8, which indicates satisfactory approximation accuracy (the model as a whole is adequate to the described phenomenon). The reliability based on the level of significance of the Fisher criterion (significance F) is much smaller, as it is equal to 0.05; therefore, the model is significant.
As a result, using the values in the "Coefficients" column, the following mathematical model of multiple regression was obtained in its natural form: where y  is the predicted value of the parameter, persons; x i are independent variables. As for the interpretation of equation parameters, if final statistical criteria are available, you can describe the mathematical model. The analysis has proven that in 80.1 % of cases, the final result depends on the factors included in the input data, and only in 19.9 % of cases the final result depends on disregarded factors. Given the results of another correlation, all four coefficients have an impact on dependent variable Y. Equation (1) shows that artificial reforestation and additional areas with green spaces can boost population numbers in a given region. "Green roofs" will perceive and regulate the negative consequences of human activities, in particular: • reduce the "heat island" effect; • prevent the greenhouse effect; • trigger a natural cooling and evaporation process; • reduce the percentage of chronic diseases. A positive coefficient, equal to 2.64, indicates that an increase in emissions of harmful substances will not have a negative effect on the rise of the demographic curve. If the averaged values of X 5 , X 8 , X 9 a are unchanged, its impact is minimal and it will be offset by factors of reforestation and landscaped areas. An increase in the area of urban land will decelerate population growth, as indicated by the coefficient equal to 15.21. This can be explained by the fact that when an additional territory is included into the total area, the share of the population whose growth decreases annually is also taken into account. Thus, the X 8 factor leads to the demographic decline.

CONCLUSION AND DISCUSS ION
The following conclusions were made based on the results of this study.
1. Each historical period was different from the previous one due to the emergence of new engineering solutions that had different component compositions. A combination of emerging issues, anticipated solutions and experience, trial and error served to design "green" roofs of modern times, which, in turn, differ due to the wide range of functional purposes. Consequences of the system solution in the domestic climate remain unknown. As it has turned out, the historical experience of using "green" roofs was not limited to one climatic zone. The charts have proven the feasibility of installation at low and high temperature conditions, it is important to consider the local natural features at the design stage.
2. The analysis of research works has identified the gaps in the "green" policy of Russia. Countries that have extensive experience in using the system solution enjoy support at the legislative level. In Russia, each climate zone requires dedicated technical guidelines for the planning, design and commissioning of green roofs, including, at least: • comparison of thermal designs for winter and summer seasons; • strength analysis with regard for snow and wind loads in winter; • identification of acceptable wind loads for different climatic regions and heights due to the presence of lifting forces to which the roof is exposed; • stability of the "green" structure in seismically active areas.
3. To date, there is no statistics on the operation of "green" roofs in different climatic zones, even at the theoretical level. In this case, construction companies cannot assume the risks of implementing the concept of landscaping in the future projects.
4. Financial incentives should be provided to promote the widespread use of green roofs.
5. Russia has no measures that help property owners and developers to go beyond the immediate financial scope to clearly understand long-term benefits and a relevant need for a sustainable urban environment.
6. "Green" construction is not considered in Russia as experimentally accumulated experience of installing "green" roofs on multi-storied buildings, which could be carried out as part of renovation processes to assess the results of the work. 7. Successful implementation of foreign projects, expert assessment of their effectiveness, focused on the primary aspects of green roofs are the main reasons for the development and introduction of the Russian standard GOST R 58875-2020, which is the first regulatory document that regulates walkable "green" roofs. The development of a national standard shows that the segment of landscaped flat roofs enjoys particular attention, and this means a focus on new developments in engineering and design solutions.
8. The hierarchy of regulatory documents clearly demonstrates the absence of a binding document governing the design of roofs to ensure the integration of landscaped areas in urban development. 9. Despite the fact that GOST R 58875 is not included in Resolution No. 1521, that has a list of mandatory regulatory documents, since June 1, 2020, the document has become a priority guideline for designers and architects working at roof landscaping projects. 10. Regulatory documents governing "green" construction in foreign countries were developed, on the one hand, as a way to solve the problem of emergence of an urban heat island, and on the other hand, to protect the environment in megacities. The imple-mentation of "green" roofs at the legislative level was unique in each country. In most cases, it was possible to increase the area of green areas by applying financial incentives.
11. Thus, Russia is still not ready for the largescale introduction of "green" roofs. In the future, it is necessary to conduct theoretical and practical experiments to study the efficiency of the system solution in different climatic regions of Russia.
12. The implementation of correlation and regression analysis made it possible to assess the dependencies and identify the factors that have the greatest impact on population numbers in the Ryazan region.
13. In the process of correlation and regression analysis, a multiple regression equation was obtained that reflects the average influence of each of the factors on the final result.
14. The use of factors and regression models made it possible to predict the effectiveness of "green" roofs as an option capable of reducing the negative impact to be produced on the ecological situation in the cities in the future, as well as to get the opportunity to reduce the population decline.