Residential Units Research Articles

Evaluating the impact of flexible offices in coping with the uncertainty in future demand

The potential growth in working from home poses a large uncertainty in the future demand for office space. Flexible offices can help limit the negative effect of this uncertainty by allowing future changes in use. To ensure that the investment in flexibility is proportioned to the risk that it minimises, the real options methodology is used in this work for modelling the uncertainty in future demand for office space and estimating its effect on stakeholders in the long term. The methodology is tested on an example of a multistorey mixed-tenant office building in Zurich, Switzerland, for which ten designs are proposed and the triggering logic is modelled. The designs have various degrees of flexibility, and the triggering logic mimics the decision criteria of an owner. The results show that under the investigated circumstances, a flexible design with movable walls for enabling periodic conversion of the unrented office space into co-working spaces, and with parcelled technical elements to allow the conversion of long-unrented office space into residential units, is the optimal decision for all involved stakeholders over the building life. The authors draw conclusions about the strengths and limitations of the real options methodology in this context and envision future developments.

Residential Unit Design for Natural Ventilation in Tropical Multi-Family High-Rises With a Double-Loaded Corridor

This research investigates practical methods to improve the efficiency of natural ventilation in residential units of multi-family high-rises without additional areas. Typical studio- and one-bedroom-types of small units were redesigned using: 1) air post, 2) transom window, 3) buffer space with one corridor opening and 4) buffer space with two corridor openings. The simulation study using a CFD program to reveal that the indoor average air velocity coefficient (Cv ) in the best redesigned case (0.46) significantly improves from the base case (0.01). The paper demonstrates an example of application to an actual climate in Bangkok, Thailand. It was found that the proposed redesign using buffer spaces can considerably help upgrade the living conditions of the occupants in terms of both thermal comfort (24 hours vs. 0 hours in the comfort zone per day) and indoor air quality (24 hours vs. 8–17 hours that pass the minimum ventilation requirement per day) in the transitional month of February.

The green divide and heat exposure: urban transformation projects in istanbul

Extreme heat events are happening more frequently and with greater severity, causing significant negative consequences, especially for vulnerable urban populations around the globe. Heat stress is even more common in cities with dense and irregular planning and lacking urban blue-green infrastructures. This study investigates the greening and cooling effects of five selected urban transformation projects and their surrounding areas (within a 10-min walking distance) in Istanbul from 2013 to 2021, with a focus on environmental justice and climate adaptation planning perspectives. By employing temporal analysis of Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) values derived from Landsat data sets to detect changes in these five selected urban transformation projects in the megacity of Türkiye, Istanbul, this study finds that the distribution of green infrastructures (e.g., tree canopy) is only limited to project sites of long-running and state-supported urban transformation projects in Istanbul. Consequently, the unequal distribution of green infrastructures creates cooling effects only for the locals residing in the new residential projects. However, the surrounding areas have less urban green infrastructure and are exposed more to the urban heat over time. Urban development policies and planning highly contribute to increasing the climate vulnerabilities among those who do not benefit from the recently developed residential units in Istanbul. Such a trend can affect adaptive capacity of vulnerable communities and redress environmental injustices in urban planning in the megacity of Istanbul.

Modeling, optimization, and economic analysis of a comprehensive CCHP system with fuel cells, reverse osmosis, batteries, and hydrogen storage subsystems Powered by renewable energy sources

Renewable energy sources are gaining significant interest due to their potential to decrease pollution resulting from the utilization of fossil fuels for generating electricity that is environmentally friendly. In this study, an innovative combined cooling, heating, and power cycle that makes use of geothermal, solar, and wind energy was examined. The 100 residential units are investigated throughout the year by a number of different subsystems, including photovoltaic-thermal panel, Wind Turbine, Steam Turbines, Fuel Cells, Heat pumps, Reverse Osmosis, Electrolyzer, batteries, and a hydrogen storage tank. The model of six European cities "Marseille, Monaco, Montpellier, Naples, Perpignan and Rome" located in Italy and France was the subject of this research. Transient assessment and the response surface method were employed in this study's optimization in TRNSYS. With the help of design of experiments, a few simulation scenarios were created, and response surface method was then utilized to examine the outcomes. Based on the findings, the optimal system greatly decreased the yearly life cycle costs of the boiler, the thermal comfort rating, the overall cost of consuming electricity, and the cost of natural gas consumption. The results demonstrate that the suggested system efficiency is increased by the addition of hydrogen storage and battery, and that the employment of fuel cells and WTs stabilizes the system's power output at all times of the day and night. According to the findings, Montpellier was the best city in terms of electricity generation, cost, and natural gas usage. The total amount of energy generated by the urban system over the course of a year is 425690.937 kWh/year, of which 121217.314 kWh/year are sold to the grid and the remainder is used to power homes. The annual use of natural gas is 47547.706 m3/year, while the annual production of freshwater is 3756.07 m3/year. The findings of the optimization showed that Montpellier's system, which includes 185 solar panels and 6 wind turbines, performs better than other systems.

Exploring socio-ecological inequalities in heat by multiple and composite greenness metrics: A case study in Belfast, UK

In light of pressing environmental and social justice challenges, levels of interest in green infrastructure as a possible solution have increased markedly for reasons related to both climate change adaptation and enhancing quality living environments. This study explores how green infrastructure influences the urban heat island effects experienced by communities across the socio-economic strata found in Belfast. To avoid scale effects and obtain accurate results, we devise multiple and scale-composite greenness metrics to assess the distribution of green infrastructure based on each residential unit. The results indicate that despite widespread recognition that green infrastructure significantly contributes to the mitigation of heat island intensity, socio-economically deprived communities are exposed to greater urban heat. Further examinations identified the close correlations between green infrastructure distribution and socio-economic factors, which relate to two major spatial patterns: that the suburbs are better catered for than the inner city, and that south and east Belfast are better than west and north. Moreover, our findings identified a tendency that communities with higher proportions of female- and ageing- populations have greater greenness and are less exposed to heat, which suggests the distributional and environmental injustice in GI provision and related heat adaptation are driven by the underlying socio-economic dynamics and the vulnerable groups may change based on local context. Overall, we found that there is a need to incorporate and prioritise different types of green infrastructure in plans for heat adaptation and to integrate green infrastructure development with environmental justice in areas that suffer socio-ecological deprivation in mitigating urban heat island effects.

Supporting families with complex early parenting needs through a virtual residential parenting service: An investigation of outcomes, facilitators and barriers.

To investigate clients' perspectives about outcomes of a telehealth residential unit (RU) program for families experiencing complex early parenting issues, and to explore facilitators and barriers to positive client outcomes. Qualitative study using semi-structured interviews. Semi-structured interviews were conducted with mothers (n = 18) admitted to a telehealth RU program. Interview transcripts were analysed using thematic analysis. Mothers reported short-term improvements in their child's presenting issues (e.g. feeding to sleep, night-time waking, co-sleeping), increased confidence and increased partner involvement. According to participants, program outcomes were facilitated by a positive parent-clinician relationship, the accessibility of clinicians and being able to take part in the program from their own home. Barriers included difficulties with technical equipment and connecting with the clinician overnight, and challenges with implementing strategies in the longer term. This nurse-led telehealth program was viewed positively by parents and the study identified a number of areas for improvement. Telehealth early parenting programs provide an important way for parents to receive support with early child sleep, settling and feeding issues. Clinicians working in this area should focus on the development of positive parent-nurse relationships, enhancing communication and availability for parents during overnight periods and supporting parents to develop early parenting skills that will be applicable across the early childhood period. The study is the first to address client experiences of a telehealth RU program. Facilitators and barriers identified will inform service improvements to the program going forward, and similar telehealth programs for families; to ensure benefits and service outcomes are maximised for parents for such a crucial service. The Consolidated Criteria for Reporting Qualitative Research (COREQ) guidelines for qualitative research were followed.

Investigation of heating energy performance gap (EPG) in design and operation stages of residential buildings

The Energy Performance Gap (EPG) in buildings is a recognized phenomenon. However, its definition and underlying factors are extensive, necessitating a thorough investigation of the quantitative impact of each factor contributing to the EPG. In this research, a calibration-based approach is employed to identify and measure the contribution of these factors. Questionnaires, measurements, analyses, and calibrations are conducted on the energy performance of four residential units of an apartment block building in Iran as a case study. Subsequently, the impact rates of three key causes of the EPG, namely heating system efficiency, weather data in an EnergyPlus Weather (EPW) format file, and occupant behavior, are determined. By incorporating these causes into the model calibration process, the disparities between the design and operation stages are decreased. The study highlights the significance and quantifiable effects of accurate and measured boiler efficiency, utilizing a genuine EPW file rather than a convenient EPW file e.g., airport stations, and adopting precise and adaptable assumptions for occupant behavior modeling in bridging the EPG between the design and operation stages. There are a number of factors that impact the design stage gap, including boiler efficiency, occupant behavior, and a corrected EPW file, which contribute 43.9%, 26%, and 6.6%, respectively.

Techno-Econo-Enviro Assessment of Photovoltaic-Thermal (PV-T) System for Residential Use in Iran Based on Köppen Climate Classification

The reason for utilizing PV-T systems is their capability to generate both electricity and heat at the same time, which enhances energy efficiency and decreases the need for multiple energy sources. Considering the potential of solar energy and different climates in Iran, in this research, the feasibility, modeling, and comparison of the PV-T system to supply electricity and heat to residential units were investigated in 28 cities with 9 climates of Iran. A thorough evaluation of performance was conducted using the software Polysun 9.0 and PVsyst 6.6.8 for a duration of one year. The scientific novelty of this study relies on the simultaneous utilization of two analytical software, the thoroughness of the research, and taking into account the impact of climate on the findings. Investigations showed that the best performance of the designed system is related to Bandar Abbas and Zahedan, and the worst performance is related to Rasht and Sari. In general, according to the amount of electricity and heating produced by the PV-T system, it showed that Shiraz and Rasht stations have the highest and lowest production of energy. In terms of environmental effects, Birjand station will have the most and Rasht the least reduction in CO2 emissions. In terms of heating energy demand for the investigated building, Ardabil has the highest amount and Bandar Abbas has the lowest amount.

Financing Brownfield Redevelopment and Housing Market Dynamics: Evidence from Connecticut

Brownfield redevelopment projects are often perceived as more risky than greenfield investment, and financing opportunities may be more limited and expensive. Different financial support projects have been developed to support regeneration projects, and empirical evidence has shown that all buildings near the intervention area may benefit from an increase in prices once the brownfield project is complete. The article considers the Connecticut market and evaluates the characteristics of the brownfield projects that had access to a financial support program (loan or grant), the impact of the regeneration process on the liquidity of the housing market, and the gap between the price and the appraisal value of the residential unit. Target areas for this type of financing program are mainly characterized by low income, a high density of population, a high incidence of homeowners, and a high crime rate. Once completed, the brownfield requalification has an impact on the housing market because the brownfield recovery reduces the number of house sales due to the increase in the average price in the surrounding area and makes the selling price more consistent with the appraisal valuation. The empirical evidence provided may be useful for public institutions that are suffering from budget constraints and have to prioritize areas for financial support solutions.

Identifying bioclimatic techniques for sustainable low-rise high-density residential units: Comparative analysis on the ventilation performance of vernacular dwellings in China

Vernacular dwellings equipped with bioclimatic techniques, used to form low-rise high-density communities in most Asian regions, are of great value for the development of modern sustainable residential units. Natural ventilation is a major concern mainly because of its climate-related characteristics of improving indoor thermal comfort at extremely low ecological costs. Therefore, this study applies a comparative analysis coupled with field investigations and numerical simulations to the ventilation technologies of vernacular dwellings in different areas of China. Geometric prototypes of typical vernacular dwellings in six climate zones were generated based on field measurements. Computational Fluid Dynamic (CFD) simulations were conducted in OpenFOAM with the Reynolds Averaged Navier-Stokes (RANS) modeling approach and the RNG k-ε turbulence model. A correlation analysis of the building elements and climate factors was also performed to determine the relevant parameters affecting ventilation performance. The results revealed different emphases and verified strategies for wind environment regulation based on different local climates. Six physical parameters, namely wind projection angle, orientation, wind inclination angle, window-to-wall ratio, top-to-bottom ratio, and height-to-width ratio of the atrium, are considered to be closely related to ventilation efficiency. The findings from the current research provide quantitative evidence of the effectiveness of natural ventilation technologies of vernacular dwellings and contribute to comprehensive knowledge for designing sustainable low-rise high-density residential units with optimum ventilation functions.

Greenery, sun exposure and ventilation of public spaces in residential units in Tirana

When referring to residential units, well-ventilated and lit green spaces are considerable contributors to increasing the quality of life of its residents. This research aims to analyse the transformation of the spaces between the buildings in the context of Tirana, by simultaneously stressing the key distinctions between their original design and their current situation. A typical residential complex close to Tirana’s centre is used as a case study to further illustrate this topic. The research starts with a qualitative morphological analysis of greenery, lighting, and ventilation condition of public space between residential units. It expands with a quantitative-comparative analysis, based on questionnaires conducted with residents, as well as by-passers of the selected residential area. The apparent reduction of greenery in spaces between residential units was one of the study’s most obvious findings. Originally intended as green spaces, public spaces between residential units have since been used for a variety of purposes, including being occupied by extensions of buildings or open parking lots. These interventions have resulted in a shift of usage to the inner streets of the residential block, which are now used for vehicles and are no longer either quiet or exclusively dedicated to pedestrians. The overall value of this space has been transferred from a straightforward recreational area to an economic space. Consequently, designers and urban planners have a responsibility to re-evaluate the significance of green surfaces, in addition to the shape and orientation of the residential unit as a foundation of sustainable urban development.

Scale Model Studies of Different Ventilation Strategies for Tropical Public Housing in Surabaya

The present study explores applying different ventilation strategies for public housing in Surabaya through a scale physical model. Previous studies indicate that natural ventilation alone is insufficient for alleviating discomfort in warm-humid climates. Many studies have been carried out concerning this topic but rarely evaluated performance comparison among different strategies in the low-to-middle residential unit. The present study aimed to analyze the influence of varying ventilation strategies on the thermal condition of the internal space of public housing in Surabaya. Three strategies, i.e., naturally induced ventilation, fan-induced ventilation, and direct evaporative cooling, were included in the study. Thermal condition in the models was then recorded and analyzed. The study shows that fan-induced ventilation and direct evaporative cooling can reduce indoor air temperature. Regarding the detrimental impact of humidity on comfort, natural and fan-induced ventilation will be sufficient to promote a tolerable indoor environment.

Impact of model detail on daylighting metrics in residential buildings

Daylight metrics that shall guide performance-driven design must be applicable to models that reflect the limited knowledge at the time of planning decisions. In particular in residential buildings, the furnishing is beyond the control of such decisions and therefore unknown in the planning phase. The impact of model detail on illuminance- and luminance-based metrics is tested on a residential unit in Singapore. At two elevations, representing a work-plane and the eye level of a standing inhabitant, the metrics are computed from a) a detailed model incorporating furniture and shading devices, b) a model with only shading devices, and c) a minimalist model representing only the design decisions of the architect. As a potential approximation to the detailed model, d) a variant of the minimalist model with wall reflectance reduced to 0.20 is tested. The results for the three levels of detail are compared and indicate the significant impact of detail on all assessed daylight metrics.

Kajian Kes: Kebocoran Antara Tingkat di Bangunan Kediaman Bertingkat Malaysia

Building defects are a common issue in the construction industry. Defects of high-rise buildings, such as cracks and leaks, are often caused by poor workmanship, and insufficient and low-quality building materials. Other contributing factors to building defects are inadequate cooperation during construction, poor design and improper installation. Inter-floor leakage is a widespread matter in new homes, leaks are detected late and repeated leaks occur even after repairs have been carried out. Inter-floor leakage often occurs in new homes. Leaks are detected late and repeated ones occur even after repairs are carried out. This study aims to diagnose buildings with inter-floor leakage problems by using several diagnostic tools and techniques like visual, destructive and non-destructive tests. Experts use testing equipment to determine moisture and appropriate maintenance or repair. A case study is carried out on a residential unit with a leak in the ceiling due to a crack on the rooftop. The findings of the study can provide knowledge about building diagnosis to property owners and property managers, identifying the cause of leaks and enabling early detection of building defects and suggested repairs to prevent similar leaks from occurring. By utilizing diagnostic tools and techniques, owners and property managers can detect problems early, minimizing damage and expenses in the long run. Based on the study, existing cracks can be converted into expansion joints, white paint can be used on the walls to control heat, installed thermal insulation to control solar energy stress and waterproof membrane can be applied to prevent moisture penetration.

Sistem Pendukung Keputusan Pemilihan Apartemen Terbaik Menerapkan Metode TOPSIS dan Pembobotan ROC

An apartment is a residential unit or place to live in a high-rise building, usually consisting of several floors or levels. Choosing an apartment is very difficult because there are many factors that must be considered in choosing the apartment. In Jakarta Selatan City, there are many apartments, because each apartment has its own conditions and charm. There are problems with apartment buyers because of the variety of facilities available, so buyers are confused about choosing which apartment is most suitable for them. So by implementing a system that can help decisions and provide recommendations for apartments that are suitable for customers. This research has 5 criteria, namely: Price, Size, Cost, Facilities and Location. Therefore, by implementing a Decision Support System using the TOPSIS method and ROC weighting which can produce weight values and produce ranking values which can help in solving the problems in this research. So the one chosen in the selection of the best alternative apartment A5 was the Denpasar Residence with a value of 0.8396

Evaluation of an Existing Validated Emirati House versus a New Parametric Design Based on the Local Social Environment through the Application of Advanced Tools

Al Ain is the second-largest city in the Abu Dhabi Emirate, and the population of Al Ain has been growing rapidly for the last 50 years. The residential units in Al Ain are arranged using different concepts in relation to household social and economic behaviors. While Al Ain city has mostly low-rise and mid-rise residential buildings, the local population tends to live in traditional low-rise villas. The governmental statistics show a high ratio of energy consumption in the form of electricity for cooling loads, and it is estimated to increase with the rapid growth of the population. In this context, it is important to investigate different strategies to control the energy consumption of residential buildings. The purpose of this study was to assess the energy usage and demand of an existing villa in Al Ain and see how a newer design approach can help to reduce the annual energy consumption of households. The newer design option is based on a parametric (application of a parametric façade) approach whilst taking sustainable design approaches. The newer design options are compared to the existing villa and a traditional extension villa attached to the existing villa in terms of annual electricity consumption. The process of design and energy modeling of all cases used the Estidama baseline standards for technical and construction specifications. The process started with selecting an existing six-bedroom villa in Al Ain. Moreover, the selected villa had a planned extension to be constructed in the future. Then, an annual energy model of the existing villa was created in Rhinoceros 7.0 with the Grasshopper 3D plug-in. The energy results were validated against the real energy bills of the villa. Once the energy model was validated, the newer options of the design were modeled, and the projected energy consumption was compared with the base case results to see how energy-efficient the newer model would be. The research shows that it is possible to save up to 60% of electricity annually by carefully selecting a sustainable design in the early stages.

СУЧАСНА ТИПОЛОГІЯ ЖИТЛОВИХ БУДІВЕЛЬ

In modern design practice, the idea of housing as a hierarchically constructed system, stretching from the world of things in family life to the settlement as a whole, occupies a strong place. The approval of these ideas in real and futuristic projects, in theory and in buildings is a characteristic feature of the recent history of housing creation. Even in the 20s, many architects sought to push the boundaries of housing design to the development of furniture and equipment. Many projects of that and later times are known, in which social and household services are modeled in a residential building and outside it, zones of individual and social activity are marked. The urban planning aspect received an increasingly active expression in housing issues. Thus, the concept of "housing" was significantly expanded, and in the 1960s and 1970s, another more precise definition of this system as a residential environment became widespread. The modern typology of residential buildings is very diverse and has deep historical roots. It covers both the traditional experience in creating housing and the developments of recent years. Since residential construction is one of the most dynamic areas of architectural practice, the process of improvement and development of housing forms is continuous. The very concept of "type of residential building" has received a rather broad interpretation. This is reflected in various classifications of residential buildings found in the literature. The different properties of buildings serve as the basis for distinguishing types of residential buildings. However, the most stable and common signs for determining the type of house are considered to be: superficiality; type of communications providing access to residential units; connection with the ground level.

Transfer learning for occupancy-based HVAC control: A data-driven approach using unsupervised learning of occupancy profiles and deep reinforcement learning

Model-free heating, ventilation, and air conditioning (HVAC) control systems have demonstrated promising potential for adjusting indoor setpoint temperature based on dynamic occupancy patterns in smart buildings. Although these control systems offer the advantage of not needing building or occupancy models, the involved trial-and-error learning process can cause considerable thermal discomfort for occupants, particularly during the initial learning period. Given the critical importance of thermal comfort, this limitation is a major barrier to the practical implementation of such systems. To address this challenge, the present study proposes a framework to enhance the learning process of the model-free HVAC controllers. Specifically, a transfer learning (TL) technique is adopted based on a similarity analysis of occupancy patterns using an unsupervised learning of occupancy profiles. This control framework leverages a k-means clustering algorithm with dynamic time warping to match the most similar households in terms of occupancy patterns within 26 residential units. The results demonstrate that the proposed method significantly improves the performance of the HVAC control system. It enhances the jumpstart performance and total rewards by nearly 25% and 5%, respectively, compared to a conventional model-free controller. Furthermore, it reduces the deviation period and mean temperature deviation by approximately 4% and 68%, respectively. Overall, this framework presents a promising approach to enhancing the performance and practicality of model-free HVAC control systems by reducing the thermal discomfort during the learning process.

Embodied Carbon in Australian Residential Houses: A Preliminary Study

Embodied carbon is a buzzword in the construction industry. Australia is committed to achieving Net Zero 2050 targets, and minimizing embodied carbon (EC) is inevitable. Owing to the population growth, there will be a significant demand for residential construction. Therefore, the material consumption in residential construction should be evaluated and proper strategies should be in place to minimize EC. The aim of this research is to undertake a preliminary study of EC in the Australian residential sector, with an emphasis on new residential home construction. This research presents a preliminary study on EC in residential buildings in Australia. Three case study residential buildings were used in this study. All three case studies are single -story residential units, with a gross floor area between 200 and 240 m2. One Click LCA software was used to calculate the EC. The EC of three case study residential homes is between 193 and 233 kgCO2e/m2. Based on the findings of this study, ‘other structures and materials’ contribute to a large amount of EC in residential construction. Concrete and aluminum are considered significant contributors to EC. Therefore, it is vital to either introduce low-EC material to replace aluminum windows or introduce various design options to minimize the use of aluminum in windows. There are various sustainable concretes available with low EC. It is essential to explore these low-EC concretes in residential homes as well. This research identifies the importance of adopting strategies to reduce the carbon impact from other sources, including concrete. It is also essential to consider the EC through transportation related to construction and promote locally sourced building materials in residential construction. Therefore, the results of this research indicate the necessity of reducing raw material consumption in Australian residential construction by implementing approaches such as a circular economy in order to circulate building materials throughout the construction supply chain and reduce raw material extraction.

Contributions of residential traffic noise to depression and mental wellbeing in Hong Kong: A prospective cohort study

Prior studies on the association between traffic noise and mental health have been mostly conducted in settings with lower population densities. However, evidence is lacking in high population-density settings where traffic noise is more pervasive and varies by topography and the vertical elevation of the residential unit. This study aimed to assess the mental health impact of residential traffic noise in one of the world's most urbanised populations. Data were analysed from 13,401 participants aged ≥15 years in a prospective cohort in Hong Kong from 2009 to 2014. Residential traffic noise level was estimated using 3D-geocoding and validated models that accounted for sound propagation in a highly vertical landscape. The 24-h day-night exposure to traffic noise, denoted as Ldn, was estimated with a 10-dB(A) penalty for night hours. Probable depression and mental wellbeing were assessed using the Patient Health Questionnaire-9 and the Short Form Health Questionnaire SF-12v2, respectively. Mixed effect regressions with random intercepts were used to examine the association between traffic noise and mental health outcomes. Residential road traffic noise (for each increment of 10 A-weighted decibels [dB(A)] 24-h average exposure) was associated with probable depression (odds ratio (OR) = 1.17, 95% CI: 1.05, 1.31), and poorer mental wellbeing (mean difference = −0.19, 95% CI: 0.31, −0.06), adjusting for sociodemographics, smoking, body mass index, self-reported health, proximity to green space, and neighbourhood characteristics (average household income, population density, and Gini coefficient). The results were robust to further adjustment for air pollution. In stratified analyses, residential traffic noise was associated with probable depression and poorer mental wellbeing among students and individuals aged 15–34 years. Residential traffic noise was associated with probable depression and poorer mental wellbeing in a highly urbanised setting. As traffic noise is increasing in urban settings, the public health impact of noise pollution could be substantial.