Life Cycle Primary Energy Research Articles

Primary Energy and Carbon Impacts of Structural Frames with Equivalent Design Criteria: Influence of Different Materials and Levels of Prefabrication

This study aims to analyze the life-cycle primary energy and climate impacts of structural frames, paying particular attention to the design and prefabrication of different structural materials. The study considers an existing single-story office building with a composite concrete–steel structure and compares it with two functionally equivalent structures, i.e., a conventional reinforced concrete structure and a conventional steel structure. The existing building is located in San Felice sul Panaro, Italy. This study integrates dynamic structural analysis and life-cycle assessment (LCA). The study finds that the use of different materials can reduce the life-cycle primary energy use and CO2-eq emissions by up to 12%. Furthermore, the benefits derived from the recovery and recycling of materials can reduce the primary energy use and CO2-eq emissions by up to 47% and 36%, respectively. The prefabrication of structural elements can also reduce the primary energy use and CO2-eq emissions in the construction stage. A sensitivity analysis considers changes in the electricity supply system and shows that the primary energy and CO2-eq emissions due to prefabrication decrease when assuming marginal electricity based on renewable energies. This analysis supports the development of sustainable structural design to meet the standards concerning the whole-life-cycle carbon emissions of buildings.

Eco-Energetical analysis of circular economy and community-based virtual power plants (CE-cVPP): A systems engineering-engaged life cycle assessment (SE-LCA) method for sustainable renewable energy development

Amidst the escalating complexity of energy demands and climate concerns, natural calamities, and the Black Swan phenomenon have all presented formidable obstacles to the advancement and implementation of renewable energy sources. In light of the present backlog of studies in energy technology, the three primary issues identified and resolved in this study are inadequate analysis of the actual situation, absence of evidence of sustainable development, and flawed systematic methodology. This study proposes a novel renewable energy development initiative known as the circular economy and community-based virtual power plant (CE-cVPP). By integrating community participation and circular economy principles, this initiative aims to foster sustainable development and facilitate resilient progress. The principal focuses of the model are community renewable energy supply, energy demand, and community participation management. The sustainable framework is constructed upon the principles of circular economy theory. The systems engineering-based life cycle assessment (SE-LCA) method is proposed as an innovative approach to whole life cycle assessment that is grounded in systems engineering. Its purpose is to facilitate a systematic implementation and empirical evaluation of the sustainability of energy, the environment, and the economy. On the basis of disparities in renewable energy sources and a variety of spatiotemporal dimensions, CE-cVPP is categorised into four representative groups. We present a business community model for energy and environmental analysis that is based on a hospital in Harbin. The results suggest that the overall lifecycle primary energy conservation rate is 67.21%, which is an exceptional outcome that significantly promotes sustainable development in comparison to conventional methods. This improves environmental and human health protection as the full lifecycle emission reduction ratios for atmospheric pollutants are 53.50% (SO2-eq.), 51.69% (PM2.5-eq.), and 74.85% (CO2-eq.). Consideration is given to raw materials, equipment construction, equipment operation, tariffs on six pollutants, and material recycling when calculating the total cost. The annual total cost savings ratio for the full lifecycle is 54.21% when compared to the traditional system. This research possesses methodological and theoretical applicability to the energy and power sectors.

Reducing life cycle material, energy and emissions for liquid consumer products through printing

Packaging is either the largest or second-largest source of energy as well as multiple different environmental burdens across the lifecycle of many different beverages. Here we analyze the potential of a new approach to consuming beverages (and potentially other household liquids) with less energy and environmental burden. This involves printing the active ingredients on to a cup to which water is added just before consumption. When consumed with tap-water, beverages printed on PLA cups require 20%, 40% and 90% less packaging materials relative to Aluminum, plastic and glass-based packaging respectively. This yields a 23% – 48% reduction in lifecycle primary energy and 40% – 57% reduction in global warming potential (50% – 70% with biogenic carbon credit for landfilled-PLA). Sensitivity analyses suggest that the single greatest source of uncertainty in benefits of printed beverages is of a behavioral nature -whether one uses tap- or commercially bottled- water, which eliminates the benefits of printed beverages.

Life cycle assessment of a PEMFC-based distributed energy system for hotel application

Hydrogen fuel cell can not only generate electricity efficiently, but also provide a large amount of thermal energy by recovering the waste heat of the fuel cell stack. This study proposed a PEMFC-based distributed energy systems (PEMFC-DES) containing of input energy, PEMFC-based combined cooling, heating and power (PEMFC-CCHP) system and building loads. The performances of energy, environment, economics of the proposed system are investigated through life cycle assessment (LCA) under different hydrogen-electricity contribution rates (RH ), hydrogen production methods and hydrogen gas prices. The results show that the hydrogen production method has a greater impact on primary energy consumption and greenhouse gas emissions. At RH = 1.0, the greenhouse gas emission of coal-to-hydrogen is 2.1 times higher than that of the baseline system. The life cycle primary energy consumption and greenhouse gas emissions of the wind-to-hydrogen are the smallest at RH = 1, which are 85.14% and 87.64% lower than that of the baseline system respectively. Additionally, when the hydrogen price is lower than 20 CNY/kg, the total life cycle cost is lower than that of the baseline system.

Parametric life cycle assessment modeling of reusable and single-use restaurant food container systems

Single-use packaging generates millions of tonnes of plastic waste per year – a circular economy waste-reduction strategy is to implement reusable container systems for restaurant takeout. We developed a parametric life cycle assessment (LCA) and cost model and used scenario analysis to study customer behavior effects on greenhouse gas (GHG) emissions, primary energy, water use, and cost of a reusable container system in Ann Arbor, Michigan. Under our base case scenario, the primary reusable container has lower impacts across most metrics than comparable single use containers. Benefits are sensitive to excess customer transportation; if 5% of customers make trips solely to return used containers, the reusable system has higher life cycle GHG emissions and primary energy use than single-use. Additionally, if a large fraction (close to 100%) of customers practice excess at-home washing of containers, the life cycle primary energy impacts will be greater than those of most single-use containers.

Comparative life cycle assessment of a reinforced concrete residential building with equivalent cross laminated timber alternatives in China

With the development of mass timber, cross laminated timber (CLT) has gradually become a sustainable alternative to conventional building materials to alleviate the increasing energy consumption and carbon emissions by the building sector. This study aims to explore the life cycle greenhouse gas emissions (LCGHGE) and life cycle primary energy (LCPE) of three high-rise residential buildings in the cold region of China through a life cycle assessment approach. The three buildings are conventional reinforced concrete (RC), CLT and hybrid CLT buildings. The results show that CLT and hybrid CLT buildings produce 15.00% and 10.77% lower LCGHGE, respectively, compared to the RC building within a 50-year service life. A clear difference in greenhouse gas (GHG) emissions and primary energy (PE) in the product and construction stages is visible, with 46.52% and 37.24% of embodied GHG emissions reduced in CLT and hybrid CLT buildings, respectively, compared to the RC building. In the operational stage, RC building has lower PE and GHG emissions to CLT alternatives. The thermal mass effect has led to a 2.25% and 2.12% PE increase for space heating and cooling in CLT and hybrid CLT buildings, respectively, compared to the RC building. For the End-of-Life (EoL) stage, CLT demonstrates great recycling potential and biomass residues. The sensitivity analysis shows that the design of the low U-value of the building envelope and high-efficiency energy systems has a significant relationship with energy reduction during the operational phase of the three buildings, magnifying the impacts of the initial and EoL stages. • CLT and hybrid CLT buildings produce 15.00% and 10.77% less LCGHGE than RC buildings in Tianjin, China, respectively. • Mass timber construction shows great advantages over RC buildings in the P&C/EoL stage. • The operational GHG emissions and PE of CLT and hybrid CLT buildings were 12–13% higher than those of the RC building. • Energy-efficient methods can enhance the LCA performance of hybrid CLT building.

Life cycle energy and greenhouse gas emissions implications of polyamide 12 recycling from selective laser sintering for an injection‐molded automotive component

AbstractThe selective laser sintering (SLS) process generates waste polymer powders, which can be recycled as feedstock for producing injection‐molded components. Recycling this powder has implications on the life cycle modeling of the SLS product, as well as the subsequent injection‐molded component. This study investigates the life cycle primary energy demand (PED) and global warming potential (GWP) of an automotive fuel‐line clip produced with recycled polyamide 12 (PA12) from an SLS process in comparison to the conventional polyamide 66 (PA66) counterpart, based on real‐world industry data. In addition, the life cycle PED and GWP of an SLS part are examined, with and without recycling PA12 from the SLS process. The results indicate a strong dependence on the approach to evaluate the environmental burden of waste PA12 from the SLS process (cut‐off, mass‐based allocation, economic allocation, and substitution). Compared with the PA66 fuel‐line clip, the recycled PA12 (rPA12) clip reduces the life cycle GWP by up to 26% (cut‐off) or increases by up to 68% (mass‐based allocation). For the SLS part, recycling PA12 powder provides a 42% reduction to its life cycle GWP (mass‐based allocation). Finally, from an expanded two‐part system perspective, the recycling of PA12 from the SLS process provides an 8% reduction in life cycle GWP. Similar trends are shown for the life cycle PED profiles. This study demonstrates the importance of recycling additive manufacturing (AM) wastes within a broader cascading system to improve the environmental performance of AM and the circular economy across industrial systems.

Cost Optimized Building Energy Retrofit Measures and Primary Energy Savings under Different Retrofitting Materials, Economic Scenarios, and Energy Supply

We analyze conventional retrofit building materials, aluminum, rock, and glass wool materials and compared such materials with wood-based materials to understand the lifecycle primary energy implications of moving from non-renewable to wood-based materials. We calculate cost optimum retrofit measures for a multi-apartment building in a lifecycle perspective, and lifecycle primary energy savings of each optimized measure. The retrofit measures consist of the thermal improvement of windows with varied frame materials, as well as extra insulation of attic floor, basement walls, and external walls with varied insulation materials. The most renewable-based heat supply is from a bioenergy-based district heating (DH) system. We use the marginal cost difference method to calculate cost-optimized retrofit measures. The net present value of energy cost savings of each measure with a varied energy performance is calculated and then compared with the calculated retrofit cost to identify the cost optimum of each measure. In a sensitivity analysis, we analyze the cost optimum retrofit measures under different economic and DH supply scenarios. The retrofit costs and primary energy savings vary somewhat between non-renewable and wood-based retrofit measures but do not influence the cost optimum levels significantly, as the economic parameters do. The lifecycle primary use of wood fiber insulation is about 76% and 80% less than for glass wool and rock wool, respectively. A small-scale DH system gives higher primary energy and cost savings compared to larger DH systems. The optimum final energy savings, in one of the economic scenarios, are close to meeting the requirements in one of the Swedish passive house standards.

Water-energy-carbon nexus: A life cycle assessment of post-combustion carbon capture technology from power plant level

Carbon capture and storage (CCS) technology is widely regarded as an important strategy to limit CO2 emissions from point sources, especially for coal-fired power plants. However, current CO2 capture technologies are energy-intensive and require substantial cooling capacities. The extensive deployment of CCS technology increases the energy and water stress in power sectors. This study considers a plant level nexus approach to assess the relationship between water, energy consumption, and CO2 emissions of four types of available post-combustion carbon capture power plants from life cycle perspective. It is found that the integration of CCS translates into an increase in life cycle primary energy demand (PED) by 21–46% and water resources depletion by 59–95% compared with the reference power plant with wet cooling tower system, where the membrane-based system exhibits the best performance. However, the life cycle GHG reduction rate reduced to 65%–70% at 90% capture rate. The life cycle energy and water cost of GHG mitigation were quantified as 3.06–7.32 kJ/kg CO2-eq and 1.72–3.00 kg/CO2-eq, respectively, demonstrating the presence of sharp trade-offs between GHG reductions and energy demand as well as water consumptions for carbon capture technologies.

Implications of different modelling choices in primary energy and carbon emission analysis of buildings

In recent years, several comparative life cycle analyses have shown that increasing the use of wood in buildings can reduce the life cycle primary energy use and carbon emission of buildings. This study reviews the life cycle inventory methodology of primary energy use and carbon emissions, based on ecoinvent database, considering different modelling choices for (i) materials heating values; (ii) biogenic carbon; (iii) calcination and carbonation processes; (iv) electricity production scenarios; (v) impact distribution of multi-functional processes; (vi) post-use benefits. The analysis relates to the standards while the implication of different modelling choice is shown by comparing the primary energy use and carbon emission in the production and end-of-life stages of a multi-storey residential building with concrete, cross laminated timber and modular timber structures, respectively. The results highlight the displacement between different modelling choices in terms of primary energy use and carbon emissions. Such modelling options especially influence the LCA results in the product stage and beyond the end of life stage, and especially wood- and/or cement-based materials.

Advancing development of biochemicals through the comprehensive evaluation of bio-ethylene glycol

Biomass chemical industry potentially reduces fossil energy dependence and addresses climate change, however, reaching technical feasibility and economic competitiveness are still crucial challenges, especially in the conversion of lignocellulosic biomass. Herein, an early-stage analysis is conducted to evaluate technical, economic, and environmental benefits of ethylene glycol (EG) production from lignocellulose, which, for one representative demonstration, provides an insight into opportunities and constraints associating with the transition from lab testing to practical industrialization of biochemicals. With process design and modeling, techno-economic analysis, and life cycle assessment, the results reveal that lignocellulosic biomass-derived EG (bio-EG) is at present attractive in aspects of life cycle primary fossil energy depletion and greenhouse gas emissions, but the total production cost of bio-EG is 43% and 20% higher than that of coal-EG and petro-EG. To achieve the economic benefits of bio-EG, research strategies, such as raising the product yield, changing hydrogen sources, increasing feedstock collection efficiency, and lowing water consumption were explored and proved to be effective measures. In addition, a carbon tax of 184 and 598 CNY·t−1 CO2eq are the breakeven points to reach economic benefits of bio-EG compared to petro-EG and coal-EG, respectively. This work aims at conducting a comprehensive evaluation of bio-EG to promote its practical application, and also shedding light on bright prospects and general approaches to develop lignocellulosic biochemicals.

Life Cycle Primary Energy Demand and Greenhouse Gas Emission benefits of vehicle lightweighting with recycled carbon fibre

Recycled carbon fibre (rCF) is a potential material for sustainable vehicle lightweighting but its realistic environmental impacts are still unclear. In this study, a Life Cycle Assessment (LCA) investigates the primary energy demand (PED) and global warming potential (GWP) of using rCF reinforced Polyamide 66 (PA66) for a side-view mirror bracket, in comparison with its conventional cast aluminium counterpart. Results indicate that using rCF+PA66 with 40wt% rCF in the US can achieve around 13% and 34% reduction in the PED/GWP of the cradle-to-gate phases and the use phase, respectively. Scenario analysis is also carried out to understand the impact of geographical setting and fibre content in rCF+PA66. It shows that replacing aluminium with 40wt% rCF+PA66 in the EU saves 31.5% and 29.7% more cradle-to-gate PED and GWP, respectively, than in the US. A higher reduction of 43.4% and 41.2% in the cradle-to-grave PED and GWP compared to aluminium can be achieved by increasing fibre mass fraction.

Circular economy framework for automobiles: Closing energy and material loops

AbstractCorporations, including automotive manufacturers, are increasingly exploring extended circular economy strategies as a means to enhance the sustainability of their products. The circular economy paradigm focuses on reducing nonrenewable materials and energy, promoting renewable feedstocks and energy, and keeping products/materials in use across the life cycle of a system. As such, life cycle environmental burdens associated with vehicle manufacturing, use, and disposal could potentially be reduced through circular economy strategies; however, no such comprehensive circular economy framework currently exists for the automotive industry. We develop the first circular economy schematic of automobiles, derived from the Ellen MacArthur Foundation's framework. Further, we characterize the current automotive circular economy using metrics of renewable energy and recycled materials. Specifically, for current U.S. average sedans, we find that internal combustion engine vehicles (ICEVs) use ∼6% renewable life cycle primary energy and 27% recycled materials; for battery electric vehicles (BEVs), these measures are ∼8% and 21%, respectively. On a vehicle‐miles‐traveled basis, BEVs use ∼47% less nonrenewable life cycle primary energy than ICEVs, highlighting the importance of electrification as a strategy for automotive manufacturers to reduce environmental burdens. Our proposed circular economy framework is then applied to Ford Motor Company's sustainability programs and initiatives as an example. This schematic aims to provide a starting point for the automotive industry to operationalize circular economy strategies, the application of which could advance its overall sustainability performance.

Achieving net zero life cycle primary energy and greenhouse gas emissions apartment buildings in a Mediterranean climate

Achieving net zero life cycle energy and greenhouse gas emissions buildings is rare. This would entail not only covering operational energy use, but also embodied energy and displacing embodied greenhouse gas emissions in construction materials and renewable energy systems, across their supply chains.The aim of this paper is to evaluate the feasibility of achieving net zero life cycle primary energy and greenhouse gas emissions (NZLCPEGHG) buildings. We use a case study apartment building in Sehaileh, Lebanon and conduct a life cycle cost, energy and greenhouse gas emissions analysis over 50 years of a business-as-usual building and its NZLCPEGHG counterpart.Results show that a 6.5 kWp solar photovoltaic array, solar hot water, an improved operational energy efficiency, an all-electric operational energy demand, and a reduced embodied energy, can achieve a NZLCPEGHG apartment unit (154 m2, 4 occupants) in a four-storey building. Installing battery storage (or not) is critical regarding life cycle cost, swinging the net present value from −46 to +47 USD2020/(m2-of-gross-floor-area) over 50 years. The greenhouse gas emissions factor of the electricity grid is key to achieving a NZLCPEGHG building, with cleaner grids making it harder to displace embodied greenhouse gas emissions. We argue, inter alia, for a more transparent and comprehensive definition of NZLCPEGHG buildings, policy that subsidises this level of performance to cover additional capital costs, and reducing the initial embodied energy and greenhouse gas emissions that might never be paid-back or displaced. These measures will help address the current climate emergency.

Life cycle assessment approach for renewable multi-energy system: A comprehensive analysis

In response to the gradual degradation of natural sources, there is a growing interest in adopting renewable resources for various building energy supply. In this study, a comprehensive life cycle assessment approach is proposed for a renewable multi-energy system (MES) to evaluate its primary energy consumption, economy cost and carbon emission from cradle to grave. The MES, consisting of passive side and active side, is fully driven by renewable energy including solar, wind and biomass. On the passive side, building integrated photovoltaic, solar collector and wind turbines are adopted. On the active side, the biomass-fuelled combined cooling heating and power system (CCHP) serves as the primary energy supplier. The electric compression chiller and biomass boiler are adopted when the thermal energy from the CCHP system is not sufficient, while electricity is imported from the city power grid when the electricity demand is low. A representative office building in the United Kingdom and real-life inventory data is adopted to demonstrate the effectiveness of the proposed life cycle assessment approach. Through life cycle assessment, the advantages and disadvantages of the MES are compared with the reference CCHP system and conventional separate system in view of life cycle primary energy consumption, economy cost and carbon emission. Moreover, to gain an insight into the life cycle performance, the sensitivity analysis is conducted on the rated capacity of the power generation unit, climate zones, life span, recycle ratio and interest rate. The life cycle cost of MES is relatively higher than the conventional separate system mainly owing to the high construction cost of BIPV, wind turbine, solar collector and biomass feedstock. However, its life cycle primary energy consumption and carbon emission are much lower. It is believed that the proposed life cycle assessment approach can provide useful guidelines for government in policymaking and for building engineers in retrofitting works.

Retrofitting with different building materials: Life-cycle primary energy implications

The energy retrofitting of existing buildings reduces the energy use in the operation phase but the use of additional materials influence the energy use in other life cycle phases of retrofitted buildings. In this study, we analyse the life cycle primary energy implications of different material alternatives when retrofitting an existing building to meet high energy performance levels. We design retrofitting options assuming the highest and lowest value of final energy use, respectively, for passive house standards applicable in Sweden. The retrofitting options include the thermal improvement of the building envelope. We calculate the primary energy use in the operation phase (operation primary energy), as well as in production, maintenance and end-of-life phases (non-operation primary energy). Our results show that the non-operation primary energy use can vary significantly depending on the choice of materials for thermal insulation, cladding systems and windows. Although the operation energy use decreases by 63–78%, we find that the non-operation energy for building retrofitting accounts for up to 21% of the operation energy saving, depending on the passive house performance level and the material alternative. A careful selection of building materials can reduce the non-operation primary energy by up to 40%, especially when using wood-based materials.

Lifecycle Impacts of Structural Frame Materials for Multi-storey Building Systems

In this study the lifecycle primary energy and greenhouse gas (GHG) implications of multi-storeybuilding versions with different structural frame materials as well as construction systems are analysedconsidering flows from the production, operation and end-of-life phases and the full natural resourceschains. The analysed building versions include conventional and modern construction systems withlight-frame timber, reinforced concrete-frame, massive timber frame, beam-and-column timber frameor modular timber frame structural systems and are designed to the energy efficiency level of thepassive house criteria. The results show that the lifecycle primary energy use and GHG emissions forthe reinforced concrete building system are higher than those for the timber-based building systems,due primarily to the lower production primary energy use and GHG emissions as well as greater amountof biomass residues when using wood-based materials. The operation primary energy use and GHGemission for the buildings are lower when heated with cogenerated district heating compared to whenheated with electric-based heat pump, showing the significance of heat supply choice. The findingsemphasize the importance of structural frame material choice and system-wide lifecycle perspective inreducing primary energy use and GHG emissions in the built environment.

Life cycle analysis of a coal to hydrogen process based on ash agglomerating fluidized bed gasification

Abstract Developing coal to hydrogen is a crucial way to alleviate the conflict between demand and supply of hydrogen. A coal to hydrogen process based on ash agglomerating fluidized bed (AFB) gasification is carried out and simulated in this paper. Life cycle primary fossil energy consumption (PFEC) and greenhouse gas (GHG) emissions analysis are carried out to provide theoretical guidance for the development of the coal to hydrogen process. Two scenarios, the coal to hydrogen process with CO2 capture and storage (CCS) and without CCS, are analyzed. The results show that the PFEC of the scenario with CCS is 2.32% higher than the corresponding value of the scenario without CCS, whereas the GHG emissions of the scenario with CCS are 81.72% lower than the corresponding value of the scenario without CCS. Additionally, the sensitivity analysis shows that life cycle PFEC and GHG emissions are sensitive to the hydrogen transport mode and hydrogen transport distance. Suggestions are also proposed for the development of the coal to hydrogen process based on AFB gasification.

Energy demand and carbon footprint of cheddar cheese with energy recovery from cheese whey

This study evaluates the life cycle environmental sustainability of cheddar cheese with energy recovery from cheese whey via anaerobic digestion. Environmental hotspots and improvement opportunities along the supply chain are also identified. The cheddar cheese production process has been simulated by using Aspen Plus. The environmental impacts have been estimated through life cycle assessment (LCA) using the outputs from process simulation. The LCA data for the rest of the life cycle have been sourced from databases and literature. The results reveal that the total primary energy consumed in the whole life cycle of cheddar cheese is 347 MJ, with the carbon footprint equal to 14 kg CO2 eq. per kg of cheddar. Energy recovered from anaerobic digestion of whey reduces the total life cycle primary energy demand and the carbon footprint by only 2%. Much greater reductions could be achieved by targeting milk production and storage of cheese. However, anaerobic digestion of whey makes the cheese production process energy self-sufficient and reduces the production costs. It also makes the production process carbon negative, reducing its carbon footprint from 0.12 to -0.12 kg CO2 eq./kg due to the credits for electricity and heat produced from biogas.

Effects of end-of-life management options for materials on primary energy and greenhouse gas balances of building systems

In this study we have analysed the life cycle primary energy and greenhouse gas (GHG) balances of concrete-frame and timber-frame multi-storey building alternatives, designed to meet the current Swedish building code, considering different end-of-life scenarios. The scenarios include recycling of concrete and steel, cascading by recycling of wood into particle board and energy recovery at the end-of-life of the board, energy recovery of wood by combustion, and landfilling of wood with and without landfill gas (LFG) recovery. The energy recovered is assumed to replace fossil coal or gas. Our analysis accounts for energy and GHG flows in the production and end-of-life phases. We estimate the GHG emission changes achieved per unit of difference in finished wood in buildings or in harvest forest biomass between the timber buildings and the concrete building. The results show that the timber building systems give significantly lower life cycle primary energy balances than the concrete building system for all the end-of-life options. The concrete building system gives higher life cycle GHG balances than the timber alternatives for all the end-of-life options, except when wood is landfill without LFG recovery. The end-of-life primary energy and GHG benefit of wood materials is most significant for energy recovery while the benefit of cascading is low. However, replacing fossil gas instead of fossil coal significantly reduce the carbon benefits of the timber alternatives. The benefits of recycling steel and concrete are small. This study shows that end-of-life options for building materials can offer opportunities to reduce energy use and GHG emissions in the built environment.