How to Create a Sustainable Community in China: The Historical Building Retrofit of the Blackstone Apartment

Abstract

In the process of urban expansion, the sustainable renovation of existing buildings can be an important way to solve the environmental and resource issues in China. The aim of this research is to explore the feasibility of an old building renovation to achieve sustainability in the appearance and performance of the building. Blackstone Apartment, located in Shanghai’s typical old district, is used as an experiment to plan a building renovation. Based on the cultural characteristics, climate conditions, and construction status of the site, this paper discusses how to improve the environmental quality, building performance, and energy efficiency of the building.

Through a study of literature on green renovation technology and the study of retrofit project-related cases, the final project focuses on the design of a green roof on the structure, with the purpose of improving the urban landscape and the influence of the environment on the urban climate. A ground source heat pump system adapted to the Shanghai climate is designed for the old building to reduce the energy consumption requirements of the existing air conditioning. In addition, a music theme is incorporated into the design of the project, to bringing a unique artistic experience and cultural environment to the community residents.

Keywords: sustainable retrofit, historical building, green roof, heat pump

1. Introduction 

In China, retrofitting of existing buildings plays a critical role to achieve sustainable development. Shanghai is a city with a long history and culture. Most of the old buildings have reached a period of functional failure or degradation due to the technical level when they were constructed. The Blackstone is an example of such reuse. As the existing building retrofitting got the attention of the Chinese central government, the century-old historical neighborhood is gradually being renovated and transformed into a novel fashion block.

1.1  Location and Overview

The Blackstone Apartment is located in the center of Fuxing Middle Road in Shanghai’s Xuhui District. It is a six-story building across the street from the Shanghai Symphony Orchestra Hall. The building is the first purpose-built luxury apartment for expatriates in Shanghai.

1.2  Site History

The building was completed in 1924, named after the missionary who built it. It was served as private residences originally and only foreigners were allowed to live in the building.

In the 1940s, it was converted into the office for the United Nations Relief and Rehabilitation Administration, which came to China to help distribute relief after World War II. In the 1950s, the last foreigners left, and the Blackstone Apartment became completely for the Chinese. Now, it holds both commercial and residential functions with Bohemian. 

1.3  Architectural style

The Blackstone Apartment is a Baroque Art-deco building that was created from imported British concrete and stones. The exterior and interior walls were carved with roses, ribbons, and other soft patterns. Inside, the carved glass and the Mosaic parquet reveal the elegance in details. The whole building is steel reinforced concrete construction. You can see the eclecticism with the symmetrical elevation of the fun porch.

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1.4  The Government Renovation Strategy

In the late 2010s, the Blackstone Apartment was redeveloped as part of Xuhui’s plan to open its historical buildings to the public. The old building with the complex behind it, is now the Blackstone Music Comprehensive Park. 

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1.5  The Environmental Impact of Buildings and Scope of this Project

However, during the renovation process, designers often pay more attention to the spatial layout of the building to explore its commercial value, and ignore the environmental and energy sustainability.Building impacts on the environment include soil, energy, carbon dioxide emissions, materials, waste, water treatment, etc. Therefore, the sustainable transformation of the old building is also a complete system that leads to the envelope, vertical plants, drainage system, renewable energy utilization and so on.

The research focus on green roof systems and mechanical cooling and heating systems, and proposes a conceptual modification scheme within this scope.

2.  The Landscape Design of Green Roof

2.1  Research of the Green Roof System

2.1.1 Definition and Benefit 

Green roofs, also known as ‘vegetated roofs’ or ‘living roofs’, are ballasted roofs consisting of a waterproofing membrane, growing medium (soil), and vegetation (plants) overlying a traditional roof. Green roofs have the potential to address several of the environmental problems associated with urbanization such as insolation, energy efficiency, heat island reduction, stormwater runoff management, noise attenuation, and create habitats. It can also enhance the aesthetic value in urban environments and improve the life quality of residents by creating recreational activities. [6]

2.1.2 Three main types of green roof

There are three basic types of green roofing systems to consider when designing our project. It’s important to understand the slope and structure of the roof, as well as the future use and lifespan as we make choices. 

Intensive Green Roof: These roofs are designed with a considerable substrate depth-more than 15-20cm, and hold a heavyweight about 180-500 kg/ m². These consist of lawns, rooftop farms, shrubs, and trees. As a roof type that requires frequent maintenance, intensive systems can be thought of as gardens on a roof with a wide variety of plants. [8]

Extensive Green Roof: These green roofs typically have a shallower depth of substrate layer (less than 15cm) and have a lower weight in comparison to intensive ones. Normally they include vegetation that will make them low maintenance and self-sustaining. These roofs are usually very lightweight and useful, especially where no additional structural support is desired. [7,8]

Semi-Intensive Green Roof: 

This type of roof is normally used for retrofitting, instead of new roofing. It lies between the extensive and the intensive system, and usually includes a mix of plant types such as perennials, sedums, grasses, and shrubs. Instead of being a low-maintenance roof, this acts as a habitat. [7,9]

2.1.3 Typical load for a roof system

 Roof load is one of the most significant problems in the green roof renovation of existing buildings . Most resistance comes from the lack of load-carrying capacity of the old building structure. A feasibility study should be conducted on the existing structure to determine the load capacity of a building. 

Dead load: Loads imposed on a structure that are part of the permanent structure. 

Live load: Loads are imposed on a structure by people or items that are not permanently attached to the structure. [10]

Green roofs add both static and dynamic weight to a structure. When a green roof is added to an existing roof deck, it is imperative that a structural engineer evaluate the roof to determine what, if any, additional load the roof will bear. It also might be necessary to supplement the structure. Either way, the most important thing is that any structural alterations and upgrades should design without damaging historic features or altering their historic character.

 2.1.4 Case Study

Case 1 : Chicago City Hall, Chicago, IL

Chicago’s most famous rooftop garden sits atop City Hall. As a semi-intensive roof, it was initiated to reduce the urban heat island effect in the city and improve air quality. The green roof only covers half of the City Hall-county Building, allowing for comparative testing of the green roof and traditional roof.

*The relevant data[12]

Building Constructed: 1911

Roof type: Semi-intensive 

Size: 20,300 sqft

Year Installed: 2001

It is a combination of 20,000 herbaceous plants, 112 shrubs, and 2 trees were planted. Sedums and grasses are planted in the extensive areas, shrubs, and deeper-rooted plants in the semi-intensive areas, and the two trees in the deepest, intensive areas. The intensive areas are installed on cantilevered platforms over structural columns to support the additional weight. Portions of the roof that are not planted are used to collect rainwater for periods of drought which is stored in two 150-gallon cisterns.  

Initially, the city wanted to make the green roof accessible to building users. Despite the height of the building, the very low parapets meant any railing, if not set back from the parapet, would be highly visible as well as pose safety concerns. Currently, the green roof is only accessible for maintenance. 

Case 2 : The Green Cloud Project, Shenzhen, China

Shenzhen is a coastal city located in Southern China and it is a classic case of rapid urbanization. There are over 1000 urban villages in Shenzhen. Urban villages like Gangxia are especially vulnerable to floods, as the abundance of impermeable surfaces is unable to absorb rainwater. 

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The project utilizes three-dimensional light steel structures that are simple to construct and have the capacity to hold over 420 plant containers filled with plants mostly native to Southern China. The original concrete rooftop is transformed by vegetation, which is capable of absorbing and preserving rainwater, creating a nature-based stormwater management system for the residential building, achieving a 65% of run-off control rate.

This green roof not only improves the ecological environment of the urban village, but also connects the previously separate buildings and creates a friendly shared space for residents.

2.2  Research of the Water drainage system

2.2.1  Introduction

Green roofs can retain rainwater and naturally filters it before it is recycled or released into the ground. The drainage layer has an important role to play in the total system structure of a green roof. It buffers water and allows excess water to drain away, prevent flooding of basements and sewer systems. 

Planting trees, shrubs, and grasses on top of buildings offer a multitude of benefits. The soil soaks up excess water and slowly releases it back into the environment. During a dry period, the water stored can be reabsorbed by the vegetation layer above. Rainfall can also be saved and recycled by residents, offering a solution to water shortages in heatwaves and periods of low rainfall. Planting trees, shrubs, and grasses on top of buildings offer a multitude of benefits. The soil soaks up excess water and slowly releases it back into the environment. 

2.2.2  The Concept of Sponge City

As the earth’s climate crisis worsens, water management is integrated into the city design as a whole to change the living environment. Sponge City is considered a specific integrated urban water management. It indicates a particular type of city that absorbs the rainwater like a sponge, which is then naturally filtered by the soil and allowed to reach into the urban aquifers. This allows for the extraction of water from the ground through urban or peri-urban wells. In China, modern cities are made of concrete, glass, and steel. Entire natural water systems have been disregarded during the urban development process. The drainage system didn’t keep up with the above-ground urban development. Since extreme weather events have become more frequent with climate change, in 2015 the Chinese government launched the Sponge City pilot project in which thirty cities are taking part.  According to the government blueprint, 80% of urban areas should absorb and reuse at least 70% of rainwater by 2030. [15]

2.2.3  Case study

Case 1 : Rummelsburg, Berlin  

Rummelsburg is a good systems using a combination of green roofs, swales, and rain gardens that provide so much storage that they eliminated the need to construct additional stormwater pipes. The basic idea of a ‘Sponge City’ is to keep the rainwater in the city. Carlo Becker, the architect of Berlin’s Sponge City strategy said, the rainwater is a resource that shouldn’t be carried away but have to remain in the city.

The Sponge City Strategy aims to keep rainwater where it lands, to imitate the natural water cycle. Buildings are covered in green roofs and facades. Underneath there is a garage with a soil layer about 80 centimeters on it. It soaks the water during heavy rainfall. Then it is used by the plants and finally, it is evaporated. There is no storm sewer system in the whole area. Water-permeable surfaces are quite important, and from here it is infiltrating into the ground. 

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2.3  Research of the roof Safety

The benefits of green roofs are substantial.  As well as being aesthetically pleasing, they also can help reduce energy use, CO2 emissions, increase the cooling effect, and enhance biodiversity. However, roof safety practices can be easy to overlook. Safety regulations for green roofs in China are largely local policies, unlike other western countries that have uniform standards. To ensure people’s safety, developers should therefore carefully consider and manage some risk factors during design and construction:  

2.3.1 Access design 

According to the Shanghai greening Technical Specification (Test) (2008), roof greening should be equipped with independent entrances and exits and safety passages, and special evacuation stairs should be set up when necessary. However, many of the current rooftop gardens do not comply with the rules. The consideration for roof access and walking surfaces is essential for green roof applications when public rooftop access is permitted. The architectural design must adhere to the life safety code. Access must be restricted so that persons cannot accidentally walk near skylights, pipes, fixed machinery, equipment. [17]

2.3.2 Fall protection 

A physical barrier can be a guardrail. Guardrails or railing systems are used in green roof applications to reduce the hazard of falling from a rooftop. In China, any structure with a height of not less than 106.7cm shall have railings. Parapets and guardrails should be perpendicular to the ground to prevent children from climbing.

2.3.3 Windproof

Potted plants placed on railings, parapets should be fixed to prevent falling from high altitude. Windborne debris can be a concern in high wind areas, especially while a new roof is growing in. Material can be scoured from the roof and become a hazard to both the structure itself and surrounding areas. The use of modular systems or pre-established vegetation mats can reduce potential exposures to new roofs.

2.3.4 Fire Risk

Fire safety for green roofs should be focused on protecting the roof from exposure fires, limiting the ability for fire to travel on the roof; and ensuring the vegetative matter does not act as a fuel source. Consider a variety of factors when selecting your system: pebble or concrete paving, vegetation barriers around roof penetrations, routine maintenance to reduce the fire hazard, and try to make sure that green roof substrate does not contain a high volume of organic content. [18]

2.3.5 Water ingress risk

Leaks in the waterproofing system are most often caused by damage during the installation of the membrane or the protection course. Moisture penetration can also be a big problem due to a number of factors such as the roots of plants penetrating the waterproof membrane. Another cause is poor detailing/design at junctions, penetrations, and edges. Therefore, keep the roof design simple and regular maintenance is very important to mitigating the water ingress risk.

2.4  Diversity of Plants

The type of vegetation used will depend on the roof design and the climate in which it is installed. Selected plants should be suited for the growing environment and have root systems that survive well in horizontal growth conditions. There are some general principles: 

– Roof gardens should be generally selected with low wind resistance, shallow root system, drought resistance, cold resistance plant.

– Some plants with dry and cold resistance and low maintenance such as sedum often do not need to set up a separate irrigation system. 

– The maintenance problem of plants can be solved by natural precipitation. 

According to the climatic conditions of Shanghai, the plant species are recommended as follows:

2.5  The Design Proposal  

2.5.1  Roof Status

The Black Rock apartment has a flat roof with a reinforced concrete structure. There is a staircase that leads residents to the roof. Residents living on the top floor are allowed access to the roof for rest and activities, but it is currently closed to outsiders. Due to building height restrictions in the old city center, this six-story rooftop has excellent views of the surrounding old buildings, greenery, and the Shanghai Symphony Orchestra.

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2.5.2  Roof Structure Suggestion

Semi-intensive green roofing is normally used for retrofitting, instead of new roofing. It’s a little deeper than an extensive roof, but not as heavy as a full intensive roof. You have more plant options, as you can use closer to 10-inches of soil, and you still have the option of using trays or planting directly onto the roof. This creates a less heavy growing field, while still allowing for more customization.

Lightweight tray systems is another kind of new simple transformation scheme thatcould be considered. It can weigh as little as 17 pounds per square foot. It can give options for structures that cannot handle a heavier load.

The best solution for this project is to combine the Semi-intensive green roof and the lightweight tray systems. Semi-intensive green roof around the parameter of the building carried by columns which have the strong load-bearing capacity and can carry a small number of people for the building users. 

Since the roof has limited load capacity, it will not be a public access space. Some small party activities can be made by appointment to limit the flow of people. But it is not recommended to carry out a large number of tourists for sightseeing, large-scale gatherings, performance. 

2.5.3 Hand Sketch of the Green roof in Blackstone Apartment

According to this image, we can easily observe the roof structure. Along the column lines in the middle could form pedestrian passages; near the walkways, which is the weakest part of the roof can have a light tray system, so that plants aren’t planted directly on the roof.

Figure 2.16-2  The Green Roof Cross Section – step 2: Further sketch

The music concept is integrated into the design of the roof garden. Plants freely surround the platform and the sidewalks naturally meander through them. It presents the shapes of music notes and some hidden musical concepts from Bach’s music. The design idea fully reflects the richness of music elements and the flexibility of vegetation structure.

Considering the limited bearing capacity of the roof, the roof garden only open to the residents of the building and is will not available for the public. But on the west side, which is shown in Figure 2.17-1, a small stage is designed to hold private concerts for a small number of VIP members who make appointments to the concert. This design provides both the security of the roof and the privacy of the music club.

3．The Mechanical Heating and Cooling System 

1.Status of Blackstone Apartment

With the dramatic climate changes, the cooling demand has been increased and has led to the rapid growth of energy consumption, which causes traditional fossil fuel energy shortage and great damage to climate with the emissions of CO2 and harmful particles by extensive use of traditional fossil energy. Furthermore, with increasing public institution buildings “aging”, energy consumption increases year by year. Pipes are exposed to the facade of the building like in figure 3.1, which is very disadvantageous for energy-saving and safety.

Therefore, integration of renewable energies in historical buildings, including solar and geothermal energy, and the use of heat pumps and other high-efficiency heating ventilation and air conditioning systems is very important. 

2. How does the Ductless Mini-Split Heat Pumps works?

A heat pump is a device that “transports” heat energy from one place to another place. This is the basic feature of how heat pumps work. An air conditioner is a form of a heat pump. It “extracts” heat from indoors and pumps it to the outside. So on the indoor side, you have cool air blowing out of the vent, after passing through a heat exchanger. On the outdoor side, you have warm air blowing out of another heat exchanger. The heat exchanger on the indoor side is called an evaporator and the heat exchanger on the outdoor side is called a condenser.[18]

The main benefit of this method is in heating that most of the savings are realized. It can be an improvement on other heating methods which may use natural gas, heating oil, or electric heating. And also it has the benefit of maximum energy efficiency and improved comfort.

3. VRF Heat Pump System

VRF (Variable Refrigerant Flow) systems, also known as ductless systems, are typically all-electric systems that use heat pumps to provide space heating and cooling to building spaces. They allow one outdoor condensing unit to be connected to multiple indoor units. VRF gives each zone the power to control its temperature. Heating and cooling can occur simultaneously with a VRF system. [20]

VRF systems efficiently deliver refrigerant at variable rates and the exact amount to spaces that require it. It can not only eliminates energy waste from duct leakage and duct heat gain but also can save energy to the maximum because there is no need to waste energy on cooling and heating unoccupied zones of the building. Compared with air-to-air heat pumps, VRF offers energy savings due to better part-load efficiencies, heat recovery, smaller zones, and reduced duct losses.

3.4  Case Study

Boston’s Trinity Church

Trinity Church has been the beating heart of Boston’s Back Bay since its dedication in 1877. The congregation wanted to renew this treasured icon for the next century—giving new life to its role as a place for communal gathering and fellowship. 

They found the architects to be focused on producing an efficient and well-functioning building. A state-of-the-art geo-exchange heat pump system was designed and installed, providing energy-efficient heating and cooling to maintain an optimal environment.

Six new geothermal wells installed for heating and cooling, utilizing digital controls for further energy efficiency. Variable Frequency Drives implemented with an HVAC system, paired with CO2 sensors.

3.5  Proposals for The mechanical system  

3.5.1  Ground-Source VRF Heat Pumps 

A ground-source VRF heat pump system combines the advantages of both technologies into one system, making it one of the most efficient HVAC systems available for many applications. Therefore, this system will be very suitable for the Blackstone apartments.

3.5.2  Building Energy Dashboard with Sensor Music Player

It is also recommended to build an en energy dashboard with music sensor. The energy data collected by a building can be reflected on the dashboard, such as occupancy sensors, indoor air quality data like temperature and humidity, and alternative energy sources like solar panels that may be more interesting to occupants. The idea is that building occupants will see how much energy the building is consuming and be inspired to conserve.

Also, sensor Music Player(SMP) can be added into the project. It is not only a music player but connect with the energy data. If energy is lower than expected, it will play light music automatically. If energy is higher than expected, it will play sad music. Music as classical music that is played as background music on the first floor. Users can adjust their mood and behavior according to the music.

4 .  Conclusion

Retrofitting of existing buildings offers one of the main approaches to achieving sustainability in the built environment. It includes not only the design of building appearance but also includes certain approaches of building envelope improvement and mechanical systems improvement, while keeping the building indoor environment comfortable for humans.  

Generally, building retrofit measures are categorized into five major aspects: building envelope, equipment system, new technology updating (renewable energy sources), energy-conserving behaviors, energy management, and control system.

This paper conducts literature research on the renovation of existing buildings and takes the Black Stone Apartment in Shanghai as an example. Following by site visits and observation of the building, in view of the fact that the government plans to transform it into a music block but does not solve the practical problems of energy conservation, this paper puts forward design suggestions for it in two aspects: the green roof and the mechanical system.  

However, this paper only put forward the preliminary design scheme and did not do the concrete feasibility analysis and efficiency evaluation analysis. In future studies, other aspects of sustainable environmental modification also should be studied to explore efficient solutions to optimize the energy performance and help to extend the life of the historical buildings.

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