Systematic Literature Review of Housing Policies in Carbon Emission Reduction: Reflection for Indonesia

. Housing cannot be separated from the discourse of carbon emissions in all building cycles: planning and design, material preparation, construction, operations, and demolition. Various countries have successfully reduced carbon emissions in the housing sector, one of which is by using policy instruments. However, reviewing the effectiveness of these policies has yet to be thoroughly explored. Using the systematic literature review method, this article aims to identify the policies implemented to reduce carbon emissions in housing and contextualize them for Indonesia. After careful identification of the relevant articles, 16 selected articles were reviewed. The study found that taxation, zero-carbonization, and strategies for retrofitting are the most enacted policies in many countries which address the more affluent subjects. Framework and policy for Indonesia were discussed for recommendations addressing all phases of the building cycles.


Introduction
Every stage of housing development cannot be separated from the carbon emissions caused to the environment. The design and planning process causes emissions of 370 kgCO2 (Shang & Geng, 2021). Preparing building materials produces carbon by 5% of the world's carbon emissions for cement (Hasanbeigi et al., 2012) and 0.488 tons CO2/hour -0.993 tons CO2/hour for transporting materials by ship (Utami & Puriningsih, 2014). Construction produces 50,553 kg CO2 or 139.95 kg CO2/m 2 (Pacheco-Torres et al., 2014). The operational process produces 374.21 kg CO2/year for electricity and 593.43 kg CO2/year for fuel oil (Kurdi, 2008).
Reducing carbon emissions in residential homes is proposed with various solutions. In design, carbon emissions in residential homes can be reduced using plants through the vertical garden method, which can expand the leaf contact area with the air to reduce carbon emissions (Kusminingrum, 2018). In energy utilization operations, efficient heating and cooling systems utilizing solar energy combined with heat pumps and steam injection can reduce carbon emissions by 12.1 tons per year and save 5 tons of coal (Fan et al., 2020). On a broader dimension, it can also be done through household activities that are wiser in dealing with cars, air traffic, and meat consumption, and the size of the house will reduce carbon emissions (Dubois et al., 2019). In addition, the zero-carbon homes policy can also reduce carbon emissions, as was done in the United Kingdom in 2016. However, many obstacles in practice remain, such as economic barriers, skills and knowledge, industry, legislature, and culture (Heffernan et al., 2015). The support of a clear and robust policy framework and solid industrial support is needed to overcome these obstacles (Forde et al., 2021).
In Indonesia's context, based on World Bank data, carbon emission per capita, as one of the critical environmental indicators, is still increasing. The situation is also challenging as other indicators need to be more supportive of improving the quality of the environment, such as the loss of forest land and low renewable energy initiatives (World Bank, 2023). Although some new housing development utilizes low-carbon emissions strategies, such as green building certification (Ministry of Public Works and Housing, Republic of Indonesia, 2023), the impact must be measured. It is still necessary to explore effective policies for Indonesia, where rapid urban development is present. Studying how other countries' policies respond to the carbon emission reduction program in housing is essential to determine the area of concern for further development of the guidelines in the future, especially for Indonesia contextualization. We are still dealing with large amounts of carbon emissions that cause the earth's temperature to increase, resulting in changes in rainfall patterns, sea level rise, and desert expansion (Sassi, 2006).

Methods
This study utilized the Systematic Literature Review method. This method is helpful before empirical research (Xiao & Watson, 2017). As an inclusion criterion, we included studies from disciplines related to architecture, engineering, and construction and excluded those considered far from it. We only included articles written in English. As the identification process, the search was carried out utilizing Harzing's Publish or Perish (PoP) application, which was connected to Scopus only. As the search procedure, we used the keywords "carbon emission," "housing," "house," and "policy." Scopus search settings were set as in the title and keywords. In keyword typing, we used the following technique: the carbon emission keyword is enclosed in quotation marks (") to become "carbon emission" so that the keyword search became specific, and then the keywords "housing," "house," and "policy" were added with the conjunction "AND" and "OR." Hence the search string was "carbon emission" AND house OR housing AND policy.
Initial screening on title search using keywords found only one related article. On the keyword search, we found 200 more articles (Harzing's Publish or Perish search limit was not more than 200 articles at once). As the second screening, we limited only the last five years of articles (2018-2022) and found 68 articles. Then the third screening eliminated the conference articles and found 56 articles. The fourth screening was by looking at the article's relevance to the studied topic through the abstract in the article. Our focus of the examination was to include only articles related directly to housing as the object of study. In this stage, we found 32 related articles. The last screening looked at the article's relevance to the investigated topic of policies and found 16 articles. Table 1 below shows the technical details of article screening. The analysis technique is by reviewing the results of the entire article and then collecting the study results on the same topic to categorize the policies. This analytical technique is a quantitative descriptive analysis focusing on systematically analyzing data to find percentages and trends (Hardani et al., 2017). The study results on the same topic are interrelated to form descriptive sentences. Conclusions are drawn from the essence of descriptive sentences.

Result and Discussion
Sixteen articles examine policies in various countries. Table 2 below shows the whole article.  (Giordano et al., 2021), most of the policy addresses design and planning aspects and operational aspects. The highest aspect given by the policy is the operational aspect of the household, including fuel consumption, use of electrical energy, number of vehicles, and use of renewable technology. Meanwhile, the design and planning aspects only cover the design of a zero-carbon home. In addition, aspects that address both include retrofit home technology and designs that adapt to low-carbon lifestyles.

Thematic Review of Policies
Several countries implement policies such as paying taxes, low-carbon housing policies, and residential retrofit policies. Australia, Switzerland, Japan, and Brazil use fuel and energy policies on carbon emission tax. Moreover, the United Kingdom and Australia use the zerocarbon home policy, and the United Kingdom uses the residential retrofit policy.  The carbon emission tax policy on fuel oil, although it reduces the use of fuel oil, also reduces the income of the rural area community and the poor due to the lack of public transportation (Vidyattama et al., 2021). Moreover, the tax value must be lowered compared to the initial policy framework (Malafry & Brinca, 2022). Alternative policies are to promote the use of fuelefficient equipment by the government, encourage people to consume foods with low processed carbon emissions (Jiang et al., 2020), and reduce dependence on private vehicles (Shigetomi et al., 2021). Another policy alternative is that the government can provide financial subsidies to increase the purchasing power of the poor (Zhang et al., 2021) but still focus on using clean energy, reducing energy consumption, and utilizing renewable energy sources (Keskin et al., 2020).
There needs to be more than a slight tax increase to trigger a change in the short term. On the other hand, significant changes may lead to more significant adaptation steps (Ott & Weber, 2022). However, it is necessary to pay attention to the form of policy coercion so that it is not excessive because it harms household acceptance of the policy. It is better if counseling through education and information on energy-saving measures is better than carbon taxes and consumption limits (Faure et al., 2022).
There are financial constraints to building a zero-carbon home due to the additional development costs when applying the zero-carbon home standard, which is also recognized by stakeholders (Li et al., 2022) and human resource and technical equipment capacity (Forde et al., 2021). In addition, the response received by a zero-carbon building is initially positive and then becomes negative (Edmondson et al., 2020). The approach is to hand over the construction of zero-carbon homes to the community with the support of financial subsidies and apply a physical framework (local land acquisition), conceptual (relationship between the house and its residents, and affective space (ease of access to administration in different responsible departments) (Lane et al., 2020) (Edmondson et al., 2020).
Retrofit development can use three new approaches: (1) retrofit technology disaggregation into three levels in a specific product, design choices, and technology systems; (2) the implementation experience of the homeowner to have a positive attitude towards retrofit innovation; (3) positive information that is orally distributed by the owner of the house to the surrounding community (Bobrova et al., 2021). Retrofit development targets people who owned buildings before 1990 and owners of detached or semi-detached houses (Trotta, 2018).

Discussion Policy Recommendations in Indonesia
Policies related to carbon emissions in Indonesia have problems related to carbon taxes and communication of carbon emission risks to society. The carbon tax implementation in Indonesia has been carried out since April 1, 2022, which has only touched electric steam power plants with a carbon trading scheme and carbon tax (Sutartib & Purwana, 2021). However, a carbon tax scheme that is still confidential makes it easier to legally reduce tax (tax avoidance) by taxpayer entities that produce carbon emissions (Lolo et al., 2022). In addition, implementing emission programs and policies in Indonesia is still a one-way risk communication. This risk communication only touches on the technical-administrative part and has not touched on two-way strategic concepts such as community involvement or emission reduction targets. As a result, messages about potential future environmental hazards due to carbon emissions have not touched the understanding, changes in attitudes, and people's behavior to reduce carbon emissions (Patrianti & Shabana, 2020). The applied solution consists of several strategies. The energy and transportation sectors can be managed with a carbon tax mechanism with a fuel approach if, in the future, there is an expansion of the sector subject to a carbon tax (Sutartib & Purwana, 2021). The principle used in the carbon tax should be tax transparency, as used by several other countries, so that the public can monitor the taxpayer entities that produce carbon emissions and reduce the fees paid by the community (Lolo et al., 2022). The carbon tax policy can be applied flexibly to archipelagic areas in Indonesia by focusing on areas with high population density (urban areas) with a focus on wealthy households. The carbon tax policy is more efficient because urban areas have better public transportation infrastructure. For carbon risk communication, it is possible to apply the involvement of private stakeholders who can synergize to provide mitigation messages to the community through various communication channels at this time. In addition, messaging development and fear factors are also needed in delivering the risk message (Patrianti & Shabana, 2020). This risk communication can also be in the form of policy counseling by utilizing the education system in urban areas, which will be more effective so as not to trigger a coercive policy reaction against the community.
Another alternative can be done by implementing a residential retrofit policy. Residential retrofit policies in the community will be easy to implement in urban areas, focusing on wealthy households due to technology and adequate financial capital.
The further prospect to pursue carbon emissions reduction in Indonesia are the mitigation in construction phases, alternative building materials, and renovation and demolition policies for Indonesia. Mitigation in the construction phases is one strategy to reduce the associated emission (Giesekam et al., 2018). The policies can develop the production of materials and components, transportation, and on-site construction phases (Han et al., 2022). For alternative building materials, the proposed regulations may consist of the policy of grouping materials: storing coal, that responsible for separating, transporting, and permanently storing CO2 to avoid its emission into the atmosphere (Budinis et al., 2018); material with cleaner production, which is responsible for promoting to use ecological materials through innovative technologies and manufacturing process (Ghisellini et al., 2018), and a group of material made from coal residues which consist of replacing raw materials by recycling materials. Sample of this material, like the use of fly ash (Sandanayake et al., 2018). Renovation and demolition policies are also relevant prospects for a new policy in Indonesia. Rapid development means more buildings to be built or changed to match the growing and dynamic business. At last, the policies may include waste management, management and prevention of waste on the site, and concrete recycling (Gálvez-Martos et al., 2018).

Conclusion
Several countries, in general, have used carbon emission tax policies, zero carbon homes policies, and community residential retrofit policies. The policy implementation problems include inequality between the poor and the rich, the financial community, and human resources capacity, which requires alternative approaches focusing more on the rich in urban areas. Policy implementation in Indonesia may use a carbon tax policy and a residential retrofit policy focusing on densely populated islands in urban areas and prosperous communities with a tax transparency system. Policy counseling can take advantage of relevant stakeholders and the education system. Policies can also be implemented by building ownership groups both for tax and zero carbon policies. From Indonesia's context, it predicted easy-to-control governmental buildings to simulate the effectiveness of the zero-emission strategy at the early phase of regulation implementation.