**1. Introduction**

The IPCC's sixth assessment report [1] has laid to rest any doubts about the genuine and very urgent impacts of climate change that our planet is facing. Global temperature change and changing precipitation patterns due to climate change have resulted in an increased frequency of extreme environmental events. Such devastating events have already taken up the form of large-scale forest and bush fires, hurricanes, increase in heat waves, droughts, water scarcity, and extreme storm conditions globally. According to the United Nations [2], climate and weather-related disasters have increased five-fold over the past 50 years. The impacts of this exponential increase have been clearly articulated by the World Meteorological Organization's Atlas of Morality: Economic losses from weather, climate, and water extremes (1970–2019) between 1970 and 2019, natural disasters have accounted for 50% of global disasters (11,000 in total) resulting in 45% reported deaths (91% in developing countries) and 74% reported economic losses globally (amounting to \$3.64 trillion) [3].

Interestingly, the WMO and the IPCC report have rightfully attributed the underlying cause for such widespread natural calamities to human doing. The WMO, after conducting a thorough review of the Bulletin of the American Meteorological Society concludes that within a time frame of 3 years (2015–2017) alone, a staggering 62 of the 77 disastrous natural events can be attributed to human influence. Sever heat waves impacts being the most apparent of these human impacts have even soared since 2015. The IPCC report further emphasizes the role of human doing attributing to global temperature rise and continued sea-level rise, which are seemingly irreversible over years to come. Human-made and natural wonders in the form of dense low-lying mega-cities, beautiful islands, delta regions as well as coastal regions are all now under-threat and are increasingly feeling the impact of climate change. The recent outcry from some such impacted countries for climate justice has been voiced in the recent COP 26 summit held in Glasgow.

Reducing current emissions by 45% is the new global challenge that must be attained to limit warming to the 1.5°C mark by 2100. This limitation is not surprising considering that most of the energy produced globally has been reliant on burning fossil fuels (primarily coal). A clear trend can be seen in the increase of atmospheric carbon dioxide concentration since the end of the eighteenth century and the beginning of the nineteenth century—this coincides with the time when coal came into everyday use [4]. The scientific principle behind the global warming trend is relatively simple to comprehend—burning fossil fuels, biofuels, and biomass release carbon that was otherwise sequestered, thus exponentially adding to the current stock of carbon globally. This burning process releases gases accompanied by tiny carbon particles (ranging from PM 10 to PM 2.5)—black carbon that tend to trap the sun's energy in the atmosphere (at a much higher rate than CO2), resulting in an increase in temperature. Forest fires, transportation, industries, buildings, electricity, and heat production are all black carbon and greenhouse gas (GHG) sources.

Fossil fuels and the associated use of coal and petroleum play a vital role in contributing greenhouse gasses (GHG) and black carbon and are fundamental to be discussed in the context of this chapter. However, industries, such as agriculture, including animals, chemical-intensive farming, clearing forests for agricultural land, etc., are among the highest contributors of GHGs to the atmosphere. For instance, according to the United States Environmental Protection Agency (EPA), methane gas, produced during combustion processes and anaerobic decomposition, has 28–36 times more potential to result in warming than CO2 [5]. Similarly, nitrous oxide, fluorinated gases, sulfur hexafluoride are all GHGs with higher potential to retain warmth in the atmosphere.

Within this context of climate change and the increasing responsibility on the shoulders of all citizens of planet earth, the building sector, coupled with the behavioral change we need to acquire toward the production, usage, and storage of energy, is of high importance for the future of our existence. According to the World Green Building Council's "Bringing Embodied Carbon Upfront" report [6], building and construction activities together account for 39% of energy-related CO2 emissions while they use 36% of final global energy. Besides this, the building also accounts for approximately one-third of black carbon emissions [7]. Of particular, importance within this emission is the 72.5% share belonging to the residential sector owing to its propensity for energy consumption—the third-largest energy consumer sector in the world. According to the IPCC's report, energy consumption-related indirect emissions in residential buildings have quintupled while it has quadrupled for the

#### *Energy-Efficient Retrofit Measures to Achieve Nearly Zero Energy Buildings DOI: http://dx.doi.org/10.5772/intechopen.101845*

commercial building sector (from 1970 to 2010). With a projected increase in the world population by half—almost 3.6 billion people toward the end of this century and a total of 11.6 billion people by the year 2100, the demand for housing and thus the increase in energy consumption and emission production could lead to disastrous climatic scenarios. Upfront carbon or the carbon emission released before the built asset/building is in-use is projected to constitute half of the carbon footprint of new constructions until 2050. The grave responsibility on the building sector thus revolves around addressing the tension between dwindling fossil fuel reserves and the ever-increasing energy demand. The Global Status Report 2017 published by UN Environment and the International Agency [8] further proposes that to address this complexity, the energy intensity per square meter of the global building sector needs to be improved by a minimum of 30% by 2030. Efforts to decarbonize the building sector or, in other words attaining a net-zero or nearly-zero building target is thus quintessential.

The chapter adheres to a hybrid methodology involving empirical research and simulation-driven design. A systematic review and data extraction from scientific journals, environmental organization websites, governmental regulatory bodies, and informational data specifically meant for the builder community are interfaced with a simulation-driven design for retrofitting an existing building. This interface was established to test theoretical and professional advice rendered through the study of literature and the actual impact of these propositions in the retrofitting of a common existing building typology. Section 2 of the chapter firstly reasons and establishes the need for retrofitting existing buildings. Once established, Section 3 systematically describes the concept of nearly-zero and situates the building industry within it. Section 3 emphasizes three essential components that need consideration while retrofitting existing buildings: Visual comfort (daylight-based zoning, shadings); thermal comfort and ventilation (Solar radiation-based zoning, openings, insulation, and window replacement); energy consumption (efficient lighting system and controllers, building material and HVAC system optimization, PV panels as the renewable energy sources). Section 3, while elaborating upon the technicalities involved in the three components, simultaneously presents the findings of the simulation-driven design as a proof of concept, thus elaborating upon the effectiveness of the promoted solutions. Section 4 serves as the conclusion of the chapter and future suggestions for developing a nearly-zero building future.
