# Measuring Carbon in Cities and Their Buildings through Reverse Engineering of Life Cycle Assessment
## 4 Discussion  
Several main questions related to (1) Carbon emissions Measurements (CEM), (2) Reverse Engineering (RE), and (3) Life Cycle Assessment (LCA), in this order, are discussed:  
1. Carbon emissions Measurements: 1.1 Real (in-situ, in real-time) carbon emissions measurement seems to be more accurate, and coherent to the approach of this paper, if derived from direct measurements, for target reductions, than the measures of KgCO\({}_{2}\)eq per m\({}^{2}\) that are used in this paper for reference. However, it is proven, through the previous studies aforementioned and this paper's results, the potential of the method to relate the GWP of the building and GHG, and the utility for building design choice, as the study is based on comparisons and abstract targets. This paper also provides measured raw data real Values of GWP and GHG, according to the data processing and modeling methods of this paper. With a different Data Base, raw data of GWP and GHG, a data set could be similarly related and modeled. The European reports that provide raw data on carbon emissions [2; 63], highlight in one of its sections the importance of the reduction of Carbon removal from the LULUCF sector, due to wood fires and wood extraction for construction and energy. Verbatim reproduction from the document, in order to show the sort of data (Raw Data literal exact transcription for Spain, full content in Supplementary Material, Figure S4) is as follows: \"Spain, 2021, ESP, 47486932, 8.609, 0.181, 233.650, 20.310, 9.520, 208.148, 19.870, 10.554, 4.383, 0.134, 4.920, 0.150, 18.575, 0.391, 705.016, 15100.203, 17219.338, 4858.969, 83.655, 1654.140, 2121.383, 7685.895, 112.529, 32708...\"
2. Likewise the variant Type 14 in the seven houses street hypothesis of this paper's Supplementary Material leads to reduction in carbon emissions, other system construction variants of the design of the house, could most probably, lead to greater reductions of Carbon emission. According to the results, a reduction of 19.64%, occurs when one of the seven houses of a block include biogenic solutions instead of conventional solutions, in the hypothetical case of a group of seven houses in a street. 3. In the fifteen houses hypothesis, if at least 53% of the houses of a block of 15 houses would choose a biogenic solution for the external layer of the facade walls (Types 8 to 15), the GHG of the emissions of the block (extendible to the city emissions) would be reduced greatly by design. Percentage to add to the 27.3% carbon emissions reduction from 1990 to 2021, or 21.7% change in total GHG emissions 1990-2017 in Europe and United Kingdom (EU-28), 29.5% for Denmark, values in Table 7.3 in [1]. Red%GWPS\({}^{\rm T}\) presents similar values. 2. Reverse Engineering and Models: According to previous studies related to the subject compiled in this paper's review, some researchers had concluded that the prediction model under multi-criteria evaluation shows better accuracy. However, for this study case, the third model, achieves high accuracy, probably because the model is structure-related [64] instead of energy related (contrary to the totality of the studies presented before in the References and Section 1 in this paper for multi-criteria modelization). 3. LCA 3.1. Design Process The shape of the building envelope, material selection, and other aspects of the design of a building, directly affect its carbon emissions: a house design of more than 78% wood biogenic solutions would reduce those Carbon emissions to 184 \(\text{KgCO}_{2}\text{eq}/\text{m}^{2}\)[65], therefore the cities, housing typology, low-carbon, approach seems adequate. LCA is typically studied separately, (once the design is defined), from the design process, rather than being integrated. The present study tries to show how to implement LCA within the design process as a fundamental issue that is necessary to be addressed to be able to promote a low impact built-environment. This approach has been taken to assess what the obstacles are that limit the use of LCA as an early-design tool.