Carbon footprint: IPCC targets vs. building and social standards

. Residential buildings in Russia consume electricity, natural gas, thermal energy for home and water heating, as well as other resources from external suppliers. Such resource consumption results in direct and indirect carbon dioxide emissions that affect the environment. Sustainable development requires the humanity to fit the environmental carrying capacity, and measures against climate change require carbon emissions to reduce. This paper compares carbon footprint reduction target declared by UNCC Conference 2015 and the Paris Agreement, as well as targets offered by other environmental institutions, to carbon emissions arising from existing Russian building standards and social norms application, and actual data. Building standards set the amount of heat per square meter to be delivered to apartment buildings depending on its geographic location, while social norms set a minimal premises area per resident. Also social standards for electricity and natural gas consumption per person exist. Russian Government decrees regulate utility services parameters for apartment and residential buildings, setting hot water temperature and consumption standards per resident and for common household needs. These norms and standards permit the minimal carbon dioxide emissions per year per resident to assess and compare to the carbon footprint reduction target. This paper demonstrates that existing Russian building standards and norms result in carbon emissions per capita significantly exceeding the targets, and recommends standards and norms update to reduce carbon footprint, admitting at the same time that such update is only a step towards the Paris Agreement targets.


Introduction
Residential and apartment buildings in Russia consume electricity, natural gas (in gasified households), thermal energy for premises and water heating, and other resources from external suppliers. Such resource consumption results in ecological footprint [1,2], which is to be estimated in order to fit environmental limits. Natural gas consumption results in carbon dioxide emissions taking place at demand-side in terms of IPCC approach [3]; this is direct contribution to residential ecological footprint. Electricity and heat produced by utility services suppliers and delivered to the households from outside (supply-side) cause indirect carbon emissions, which also should be accounted to residential ecological footprint according to [3] as upstream emissions due to industrial processes and energy conversion, transmission and distribution.
This paper assesses residential ecological footprint basing on apartment buildings standards and norms for Moscow city as a typical example of middle latitudes' and northern regions' residential sector. Most of Moscow power plants and heat suppliers have been converted to natural gas from other types of fuel, in particular coal and fuel oil. Thus, carbon dioxide dominates among the emissions, and other types of pollutants (NO x , SO x etc.) were not taken into account. That permits making the assessment of residential carbon footprint to compare it directly to carbon footprint reduction targets declared by UNCC Conference 2015 and the Paris Agreement, as well as offered by other environmental institutions in order to fit the environmental carrying capacity and fight against climate change.
In order to meet the Paris Agreement goal of under 1.5°C rise by 2050, carbon dioxide average emissions per person should be around 2 tons/year by 2030 [4]. The Nature Conservancy [5] makes a note that actual average carbon footprint per person in the United States is 16 tons/year (one of the highest rates in the world), while actual global average is about 4 tons/year. To have the best chance of avoiding a 2°C rise in global temperatures, the average global carbon footprint needs to drop to under 2 tons/year by 2050 [5]. The Institute for European Environmental Policy [6] mentions 2.3 tons/year as a target to achieve by 2030. According to Global Footprint Network approach and assessment [7], current humanity activity and consumption rates create ecological footprint, which is far above the planetary carrying limits, so the goal to reduce carbon emissions is urgent indeed. This paper assesses typical Moscow resident carbon emissions arising from existing Russian building standards and social norms application. This is only a part of total carbon emissions per person as it does not include transport usage, shopping and recreation activities etc. But it can be compared to targets declared by [4][5][6][7], and can serve as a starting point towards it.

Materials and Methods
Russian Federation Government Decree [8] establishes the standard for residential gas consumption 8.3 m 3 per person per month in case gas meters in gasified buildings are not used. The carbon footprint resulted from the combustion of such amount of natural gas can be calculated using the formula (1): where k is specific indicator of carbon dioxide emissions per natural gas volume unit, kg/m 3 .
IPCC Guidelines [9] estimate CO 2 emissions as 1.90-1.94 kg of carbon dioxide per 1 m 3 of natural gas combusted, so average resident's carbon footprint due to gas stoves use is 0.2 tons/year. Natural gas is also used by Moscow centralized heat suppliers to prepare the heat agent to be delivered to apartment buildings. According to [10] when heat meters are not used the average amount of heat energy for residential spaces should not be less than 0.016 Gcal/m 2 (67 MJ/m 2 ) per month of heating season, which lasts at least 7 months in Moscow region. Moscow norm of premises space per person is not less than 18 m 2 [11], so minimal amount of heat per resident per year can be calculated using the formula (2): E 2 = 0.016 x 7 x 18 (2) which gives 2 Gcal (8440 MJ) per person per year. The gas consumption for heating the agent and delivery of such amount of heat to the apartment building can be determined by standard methodology [12] through lower calorific value of natural gas for domestic purposes, which is 31.8 MJ/m 3 , and about 90% efficiency factor for gas heaters. Thus, the carbon footprint resulted from the heat consumption can be calculated using the formula (3): which gives minimal resident's carbon footprint due to heat consumption of about 0.6 tons/year. In case the resident occupies larger space, the amount of heat energy consumed during the heating season will increase correspondingly. Thus, 50 m 2 premises space occupied with the only resident results in carbon footprint of 1.6 tons/year, while 100 m 2 space leads to 3.1 tons/year. Actual Russian Federation statistics of population housing conditions [13] estimate average premises space per capita in urban territories as 27.6 m 2 , so corresponding average carbon footprint is 0.9 tons/year.
In should be mentioned that many apartment buildings in Moscow are overheated during the most part of heating season, so actual carbon footprint per resident due to heat consumption can be significantly higher than mentioned above. Measurements taken with the heat meter for a particular Moscow multi-apartment building during several consecutive years (see Table 1) showed an overheating from 1.1 to 1.5 times above the heat consumption norms set by [10]. According to the total building space~10 000 m 2 , the amount of heat should be 1 120 Gcal for 7 month of heating season in sum. Each year of 2015-2021 the apartment building was overheated inevitably as it had no regulation system to prevent the excessive heat input from the resource supplier. It also should be mentioned that premises heating norms were established in 1994, while new construction methods and thermal insulation means have appeared since that time. New types of windows, as well as premises and balcony doors prevent heat leakages and make it possible to consume less thermal energy for space heating than norms [10] require.
Another source of carbon footprint is residential hot water consumption, as centralized suppliers use natural gas combustion to heat the water for domestic needs. Decree [14] establishes residential hot water consumption norm 4.745 m 3 /person/month when water meters are not used. Sanitary requirements [15] set hot water temperature to be at least 60°С and not higher than 75°С at hot water supply distribution point within the apartment building. Water entering the suppliers' place has a temperature of 6°С to 15°С depending on the time of year and other factors. Thus, the average water heating gradient is 57°C.
The amount of heat for annual domestic water consumption per person can be calculated through the same methodology [12] as mentioned above, having in mind water specific heat capacity 4.2 kJ/kg/°C and density 1000 kg/m 3 . The formula (4) gives 13.6 MJ of thermal energy spent per resident per year: E 3 = 4.745 x 12 x 1000 x 4.2 x 57 (4) Corresponding carbon footprint can be calculated using the formula (5): which gives 0.9 tons of CO 2 per resident per year as a result of hot water consumption. It should be mentioned that actual hot water consumption can be significantly less that residential norm 4.745 m 3 /person/month. That depends on how many apartment owners install and use water meters. Figure 1 demonstrates consistent decrease in hot water consumption from year to year as more and more users install hot water meters. Average hot water consumption for year 2022 is a bit less than 2.3 m 3 /person/month, and corresponds to carbon footprint 0.4 tons/year per resident. The graph asymptotically approaches to 2 m 3 /person/month, and that level seems to be achievable within several years. Lower consumption values are hardly to expect with the current way of life.
Another source of carbon footprint is electricity consumption formed by two components: 1) electricity consumed by residents, to be paid directly to the electricity supplier according to the individual meters data (installed in each apartment), 2) electricity consumed for general house needs, in particular for common areas lighting and elevators operation, to be paid collectively according to the common house meter data.
Current social norm of electricity consumption in Moscow (in case gas stoves are used) is 100 kWh/ person/ month [16]. That corresponds roughly to actual personal electricity consumption although individual electric meters data are not publicly available since it is transmitted directly to the resource supplier. It should be mentioned that Moscow Government planned to set the social norm 50 kWh/person/month; however, that project has been frozen since 2019, most probably because this norm does not correspond to the actual level of electricity consumption in the region and may cause disproportional financial effects.
Carbon footprint caused by 100 kWh/person/month electricity consumption can be calculated using the formula (6): M 4 CO2 = CEF x 100 x 12 (6) where CEF is Carbon Emission Factor, kg of CO 2 per kWh of electricity consumed. IPCC [9] estimates CEF for the natural gas as 0.491-0.891 kg of CO 2 per kWh depending on electricity generation technology used. The same source [9] and own authors' calculations [17] estimate CEF 0.59-0.8 kg/kWh for unknown electricity sources, averaged. The use of average CEF 0.7 kg/kWh gives carbon footprint more than 0.8 tons/year due to personal electricity consumption.
The electricity consumption for general household needs includes common areas lighting and elevators operation as well as power supply for antennas amplifiers, intercoms, pumps and other equipment within the building. Government Decree [18] of 2006 contains the norm of common household electricity consumption 14 kWh/resident/month for apartment buildings with elevators, when common building electric meter is not used. When applied this norm gives carbon footprint 0.12 tons/year.
Most of apartment buildings in urban territories are equipped with common building electric meters to measure actual electricity consumption for general household needs. Figure 2 shows actual data collected in particular Moscow multi-apartment building with 250 residents. Annual consumption 20-21 MWh have established in the apartment building since 2020 as a result of resource saving measures. That corresponds to electricity consumption for general household needs 82 kWh/resident/year (6.8 kWh/resident/month, more than twice lower comparing to the norm) and carbon footprint 0.06 tons/year. It should be noted that this value is much less than personal consumption and other components of residential ecological footprint.

Results and discussion
Building standards and sanitary norms requirements' and actual data analysis made it possible to assess residential carbon footprint per person and compare its components. Table 2 contains carbon footprint values estimated on the base of standard requirements and sanitary norms. As mentioned before, measurements taken with the heat meter for a particular Moscow multi-apartment building showed an overheating from 1.1 to 1.5 times above heat consumption norms. Residents are forced to keep windows open during the most part of heating season to get rid of excessive heat, and that definitely means unnecessary consumption. Table 3 contains carbon footprint values calculated basing on actual data (when available; marked in bold) instead of standards and norms.  Tables 2 and 3 comparison makes it clear that existing standards and norms do not correspond to actual consumption profile and are subjects to update.
Also tables demonstrate the potential for resource saving. First of all, overheating prevention can save at least 0.3 tons CO 2 per resident per year. Savings value can be even higher if new construction methods and thermal insulation means are taken into account.
The second opportunity is continuing (although with the speed slowing down) decrease in hot water consumption. Current hot water use of 2.3 m 3 /person/month instead of norm 4.745 m 3 /person/month has already saved 0.5 tons CO 2 per resident per year. Future consumption of 2 m 3 /person/month instead of current value would give additional saving of 0.05-0.06 tons CO 2 per resident per year.
Personal electricity consumption has certain potential for saving but that can take many years as household devices and equipment are very slowly changed to advanced, more economical models. Most of apartment owners have already changed incandescent lamps to LEDs and old refrigerators to newer ones, but it is hard to expect considerable personal electricity consumption decrease further, for example from 100 kWh/person/month to 50 kWh/person/month as previously mentioned Moscow Government project had planned before it was frozen.
The electricity consumption for common household needs can hardly improve actual saving of 0.06 tons CO 2 per resident per year as most of possible technical updates had already been deployed (lighting change, elevator models and controlling systems modification etc.). Also it should be noted that the electricity consumed for common household needs is itself the lowest of residential carbon footprint components, with the smallest potential for savings left.
Natural gas savings potential is hard to estimate as no gas meters are used in old gasified apartment buildings. Newer buildings and especially small cottages equipped with gas meters can provide some statistics but that is a subject for further study.

Conclusions
Residential Nevertheless, there are significant opportunities to reduce the residential carbon footprint. The first is preventing the premises overheating, which can decrease the carbon footprint for at least 0.3 tons/year per person to 2.36 tons/year. Newer buildings can have heating control system to regulate the amount of heat received from the supplier. Unfortunately, many old buildings have no such regulation systems and are unable to prevent excessive heat input. The supplier indeed can prevent it but not interested to, as the excessive amount is to be paid by the end user, and that increases the supplier's profit.
There are two ways to change it: technical and managerial, and both are under authorities' responsibility. Technical way requires old buildings to be renovated and equipped with regulation system. That can be done as a part of major overhaul, which requires considerable external funding and residents' resettlement until the renewal is finished. Managerial way requires the authorities to control the suppliers to prevent overheating, keeping the supplier from forcing of unnecessary services in terms of law.
As opposed to measures under authorities' responsibility, ones under building residents and operating companies' responsibility have already given the saving effect, specifically hot water and electricity for household needs consumption reduce. Individual meters stimulate savings effectively, and there is no necessity to change that order.
At the same time it is hard to expect further considerable reduce in these areas. Possible proceeding decrease in hot water consumption from 2.3 m 3 /person/month to 2 m 3 /person/month can save only 0.05-0.06 tons CO 2 per resident per year, lowering residential carbon footprint to 2.3 tons/year.
Although potential saving described above cannot drastically change the situation, it can be a step towards carbon footprint targets to contribute to the fight against climate change. The approach used in this paper can be adapted to other residential building types to calculate carbon footprint, to develop resource-saving measures and deploy it in order to minimize ecological footprint and fit the planetary carrying capacity.