findings

Beijing

Shanghai

Shenzhen

     Technical Report
     Shading Study
     Train Study

Technical Recommendations for Shenzhen Wonderland

6/28/2000

Sephir. D. Hamilton, Brian. Dean

  Introduction to the Project

The conceptual design for the B1 and C1 sites on the Wonderland development in Shenzhen, China is complete.  From the site layout to the window details, architects and engineers manipulated the design to produce a sustainable housing development.  Designers considered the site, its surroundings, and the local climate to create the design, which works with nature to produce energy-efficient and comfortable apartments for the people of China.  This report details the overall technical considerations that guided the design.  Based on technical analysis using DOE-2 software, Phoenics CFD software, and sound engineering knowledge, the Building Technology team at the Massachusetts Institute of Technology makes several design recommendations in this report.  The submitted architectural design reflects many of the recommendations, while others need further attention during the design and construction process.  If all recommendations are implemented, we predict energy savings of up to ~2000 kWh (~60%) annually compared to the currently constructed apartments. First, this report presents a summary of recommendations in two tables.  The table ranks each recommendation with one, two, or three stars depending on its importance to the sustainability of the design.  Some items that have only one or two stars are still important, especially to occupant comfort during the hottest months, though they may not be essential to the annual energy use.

Next, the report demonstrates the possible energy savings of the recommendations.  It shows the effect of implementing all the three-star items, all the three and two-star items, and all the items together.

Finally, the report details the technical aspects of the design.  It explains the logic behind the building orientation and layout; it describes each side of the building façade (including the roof); it shows the possibilities of natural and fan-assisted ventilation; it reiterates the importance of reducing train noise; and then it discusses the programmable thermostat and air-conditioning units.

Summary of Recommendations

Apartments primarily facing North and South

Building Design Features

 

     Windows

North

Overhang: 10 % of window height;

Fin: 10% of window width;

Solar Heat Gain Coefficient < 0.8

Clear single-pane window; (vinyl frame if possible)

 

South

Overhang: 20% of window height;

Fin: 10 % of window width;

Solar Heat Gain Coefficient < 0.8

Clear single-pane window; (vinyl frame if possible)

 

Noise Control

Tightly sealed windows (double-pane, non-operable if possible) on walls adjacent to railroad.

 

 

     Walls

Insulation

Block wall plus 6 cm. (R=1.5 or greater) of insulation on west facing exterior walls.

*

Noise Control

Increase mass of walls adjacent to railroad by filling block wall cavities with dense concrete.

**

 

    Infiltration

Blower door test (Random sample units)

Less than 0.35 air changes per hour (fresh air by natural or mechanical ventilation).  All joints and cracks should be sealed well.

***

 

    Roof

Insulation

Have at least 14 cm. (R-3.67) of typical fiberglass insulation or comparable insulation rating inside weather barrier.  This will keep the top floor units from being too hot in the summer.

***

 

    Door

Noise Control

Exterior door adjacent to railroad should be heavy, such as metal with foam core or solid wood and should have gaskets and weather stripping to minimize infiltration of air or noise.

**

 

Building Equipment Features

 

     Cooling

Air Conditioning

3 COP minimum, plus 0.3 COP each time the upgrade costs less than 1500 yuan. (example: add 0.9 COP [3.9 COP total] if cost of upgrade is less than 4500 yuan; add 1.2 COP if < 6000 yuan)

HH

 

     Ventilation

Off peak ventilation

Closable through-wall exhaust fan (ensure that they are properly sealed to have minimal infiltration when ventilation is not in use).  For top floor units the exhaust fan should be placed near the roof.

HHH

 

     Thermostat

Programmable Digital Clock Thermostat

Install a programmable digital clock thermostat that controls the air-conditioner.  Install a thermostat that reads indoor and outdoor temperatures.

HHH

 

     Hot Water

Solar Collector

Significant energy can be collected from the sun to heat the water used for bathing and washing.

H

 

    HHH Essential for Sustainability        HHRecommended Feature         HAdditional Feature

Apartments primarily facing East and West

Building Design Features

 

     Windows

East and West with overhang

Overhang: 100 % of window height;

Fin: 0% of window width;

Solar Heat Gain Coefficient < 0.8

Clear single-pane window; (vinyl frame if possible)

***

East and West no overhang

Overhang: 0% of window height;

Fin: 0 % of window width;

Solar Heat Gain Coefficient < 0.4

See window specification sheet for window types.

Noise Control

Tightly sealed windows (double-pane, non-operable if possible) on walls adjacent to railroad.

**

 

     Walls

Insulation

Block wall plus 6 cm. (R=1.5 or greater) of insulation on west facing exterior walls.

*

Noise Control

Increase mass of walls adjacent to railroad by filling block wall cavities with dense concrete.

**

 

    Infiltration

Blower door test (Random sample units)

Less than 0.35 air changes per hour (fresh air by natural or mechanical ventilation).  All joints and cracks should be sealed well.

***

 

    Roof

Insulation

Have at least 14 cm. (R-3.67) of typical fiberglass insulation or comparable insulation rating inside weather barrier.  This will keep the top floor units from being too hot in the summer.

***

 

    Door

Noise Control

Exterior door adjacent to railroad should be heavy, such as metal with foam core or solid wood and should have gaskets and weather stripping to minimize infiltration of air or noise.

**

 

Building Equipment Features

 

     Cooling

Air Conditioning

3 COP minimum, plus 0.3 COP each time the upgrade costs less than 1500 yuan. (example: add 0.9 COP [3.9 COP total] if cost of upgrade is less than 4500 yuan; add 1.2 COP if < 6000 yuan)

**

 

     Ventilation

Off peak ventilation

Closable through-wall exhaust fan (ensure that they are properly sealed to have minimal infiltration when ventilation is not in use).  For top floor units the exhaust fan should be placed near the roof.

***

 

     Thermostat

Programmable Digital Clock Thermostat

Install a programmable digital clock thermostat that controls the air-conditioner.  Install a thermostat that reads indoor and outdoor temperatures.

***

 

     Hot Water

Solar Collector

Significant energy can be collected from the sun to heat the water used for bathing and washing.

*

 

    ***Essential for Sustainability        **Recommended Feature         *Additional Feature


Total Energy Savings

Compared with a “base-case,” the suggestions summarized above will save up to ~60% in annual energy use.

Building Component Description

Floor area

1 story, 6m x 12m

Orientation

Primarily north/south facing facades

Wall type

Concrete block, no insulation

Window type

Clear single pane, aluminum frame

Window area

40% window to wall area

Overhang type

None

Electric Air Conditioner

3 COP

Heating Setpoint

20 degrees Celcius

Cooling Setpoint

24 degrees Celcius

Ventilation

None

Base Case

Possible Savings

 

KWh (annually)

% savings

Base Case

4500 - 5200

--

3 Star Recommendations

~2700

40-50%


1, 2, & 3 Star

1500-1800

60-70%

 

 

Building Orientation and Layout

Buildings are oriented to minimize east/west exposure

 

Solar gain through windows accounts for approximately 40% of the total cooling energy load for a Base Case apartment in Shenzhen (“Base Case” is defined above).  Over a year, the energy from direct sunlight per area incident on all building surfaces (north, south, east, and west) totals nearly 2.53 MWh/m2.  Western and eastern facing windows each see 32% (64% combined) of the total annual solar energy per area.  Southern windows see 33% and northern windows see 3%.  Obviously, then, all energy-efficient designs in Shenzhen should try to minimize western and eastern exposures.

Northern row of buildings is continuous to block train noise

Trains produce approximately 90dBA of noise.  When people open windows, go onto balconies, or walk in courtyards they expect that noise is no greater than 45dBA.  The northern row of buildings cannot avoid the train sounds, but can block the rest of the site.  No openings should exist between the courtyard and the train tracks through the northern row of buildings.  Even small openings in the northern row of buildings, such as a narrow walkway, will greatly increase the noise levels in the courtyard.

Eastern side of the site is open to allow wind movement through the site

Wind should flow freely through courtyards, balconies, and apartment in order to keep people comfortable during hot months and to encourage natural ventilation.  The wind in Shenzhen comes mostly from the east (southeast and northeast), so it is important not to block the eastern side of the site.  Our site design leaves large openings to the east for the wind to enter.  However, the most recent plans for the site to the east show that several buildings block the wind from entering our site.  We encourage the designers to create openings in these buildings to allow the wind to pass into our site.

 

 

 

Western side of the site is partially open to allow air into the adjacent site

Our site should not block the wind from the future apartments to the west, so our design has several openings in the west side.  Ideally, for greater natural indoor ventilation, the western buildings would not have openings to the next site, but we must think of the future buildings.

Building Façades

Exterior color

The color of the exterior walls has minimal impact (<1%) on the annual energy use (comparing red brick with white paint).  Therefore, the aesthetics of the color scheme is more important than the energy.

nfiltration Infiltration accounts for approximately 15% of the total cooling energy load for a Base Case apartment (“Base Case” is defined above).  Construction and detailing techniques should ensure that infiltration is less than 0.35 air changes per hour in each apartment.  All joints (windows, doors, fans) and cracks should be sealed thoroughly to reduce leaks.  (Use blower door test on a random sample of apartments to ensure that they meet requirements).

Natural and fan-assisted ventilation will provide fresh air.  Providing ventilation at the proper times (when the outside air is cooler than the cooling set-point temperature) saves energy, rather than infiltration letting air in at all times.  To ensure good indoor air quality during the summertime (when air-conditioners are used and windows are closed) occupants should ventilate for a few minutes each morning using the exhaust fan.

Roof Must be insulated with at least R=3.67 K*m2/W (for example, 14cm of typical fiberglass or comparable insulation inside the weather barrier).  While providing only <100kWh (<3%) of energy savings over the year, this improvement will keep the top-level apartments more comfortable year-round.

Solar hot water collectors could provide domestic hot water to many apartments (if not all) while removing excess heat from the rooftop (thus making rooftop units more comfortable).  Solar hot water collectors, if used, should be integrated architecturally with the roof to avoid bad aesthetics.  The roof pitch in most designs has been set at 22° toward the south because this is the optimum incline to collect the sun throughout the entire year.  (To fully maximize the roof for solar hot water, designers could turn the roof into a single-slope facing south with a 22 inclination, instead of a double slope as it is currently with half sloping south and half sloping north.) Solar hot water heaters use direct sun radiation to collect heat and transfer it to water for use in the home.  Several designs exist ranging from glass plate collectors, to evacuated tube solar collectors.  They can be custom built and integrated into a roof structure or pre-made in a factory and installed on the roof after construction. The U.S. Department of Energy states that every 1m2 of solar collector area on a roof will heat roughly 40 liters of water/day throughout the year in a southern climate (average throughout the year).  We believe that solar hot water heaters installed on every roof would create a more sustainable building, although it may only supply a portion of the total hot water demand.  The solar water heaters also remove heat from the roof area, leaving top-floor apartments more comfortable.  We provide you with some contact and reference information on solar hot water heaters and ask that you fully investigate this option.

U.S. Department of Energy Gives an overview of solar hot water technology

www.eren.doe.gov/femp/techassist/solar_water.html

Tsinghua Solar Co.

Produces evacuated tube solar collectors in China

(background report ==> http://www.usembassy-china.org.cn/english/sandt/chihotwt.htm)

thesolar@public.bta.net.cn (Research and Development Division)

North Face Northern windows should have small overhangs and fins.  Although shading the northern window does not have a large impact on energy savings (<1% annually) it will greatly improve comfort during the summer months when the sun is to the north.  We recommend an overhang that has a depth equal to 10% of the window height and fins with depths equal to 10% of the window width.  This shading plan will block 100% of direct sunlight from August to April (obviously), 70% in May and September, and 50% in June.

The Solar Heat Gain Coefficient (SHGC) of the windows should be 0.8 or less (for example, 1/8” single pane, non-coated glass).  Windows should have vinyl (plastic) frames if possible to provide better heat insulation.

Windows adjacent to the railroad tracks should have tightly sealing gaskets.  If possible, these windows should be non-operable (to eliminate air gaps) and should have thick glass (at least 1/4” thick each pane).  The most important consideration is to eliminate air-gaps.  (For example, a one square meter window with a transmission loss of 30dB that has a 1mm x 1m air-gap now has a transmission loss of 26dB; a 1cm x 1m gap produces an equivalent T.L. of 19dB!)

Window Type

Transmission Loss (dB @ 500Hz)

Single pane (1/8” glass with gasket seal)

28

Single pane (1/4” glass with gasket seal)

31

Single pane (1/2” glass with gasket seal)

36

Exterior doors adjacent to the railroad tracks should be heavy (such as metal with foam core, or 100% solid wood), and should have gasket seals around the door and weather stripping at the bottom of the door.  This precaution will help reduce train noise inside.  Again, eliminating air-gaps is crucial.

Door Type

Transmission Loss (dB @ 500Hz)

Hollow-core metal (no gaskets)

16

Solid-core wood (no gaskets)

26

Solid-core wood (with foam gaskets)

30

Increase the mass of exterior walls for buildings adjacent to the railroad tracks to help reduce noise inside (e.g. fill concrete blocks with denser concrete)

South Face Southern windows should have overhangs and fins.  Shading the southern window has a large impact on energy savings.  We recommend an overhang that has a depth equal to 20% of the window height and fins with depths equal to 10% of the window width.  This shading plan will block 100% of direct sunlight from April through August, 60% in March and September, 40% in February and October, and 30% from November through January.

The Solar Heat Gain Coefficient (SHGC) of the windows should be 0.8 or less (for example, 1/8” single pane, non-coated glass).  Windows should have vinyl (plastic) frames if possible to provide better heat insulation.

East Face Western and eastern windows must be “self-shaded” to block late-day and early-morning sunlight.  Overhangs and fins are ineffective because of the sun angles are so low in the morning and afternoon. Therefore, the Solar Heat Gain Coefficient (SHGC) of the window itself must be less than 0.4.  (The total solar radiation transmitted and re-radiated by a window [q] equals the total solar radiation hitting the exterior of the window [E] times the SHGC), or:

 [Watts]

We propose two methods for achieving a SHGC of less than 0.4 on eastern and western windows.  The first method uses high-quality, double pane windows that do not obstruct the view from inside.  The second method uses an exterior screen (similar to an insect screen) mounted on a standard single-pane window.  The following details both methods:

Method 1 (Advanced Windows):

A double pane, low-emmitance (low-e) window can achieve a SHGC less than 0.4.  The e-value must be 0.05 or less.  A single pane tinted window may also achieve a SHGC less than 0.4.  Check with individual window manufacturers in China to find window performance.

Method 2 (Exterior Screens):

Exterior screens, such as the ones produced by Phifer Wire Products, Inc. in the U.S. and exported to World Choice Asia Limited in Hong Kong, combined with a single-pane window will produce a SHGC of less than 0.4.  Phifer’s “SunScreen” and “ShadeScreen” products are two that provide adequate sun protection.

Phifer Wire Products, Inc.

Produces the sun-screen products (just the fabric)

P.O. Box 1700

Tuscaloosa, AL 35403-1700

USA

Tel: 205-345-2120

www.phifer.com

World Choice Asia, Ltd.

Imports Phifer products and makes them into shading devices

Rm.1212, Metro Centre II

21 Lam Hing Street

Kowloon Bay

Kowloon West Face Should have R=1.5 K*m2/W or greater (for example, block wall with 6cm of glass fiber insulation inside the weather barrier).  This will help keep the western facing apartments cooler late in the day during summertime.  Although this increases the comfort of occupants late in the day during the warmest months, it does not save much energy over the entire year (<1%)?

Ventilation

>Proper ventilation during spring and fall can save up to 30% in annual energy usage if used at the correct times.

Wind driven ventilation alone will give between 0 and ~30 air changes per hour (ACH), depending on the apartment’s location and the direction of the wind, during spring and fall.

ACH for select apartments (East Wind- 3 m/s)

Apt. #

Delta P (Pa)

Q (m3/s)

ACH

1

0.0

0.00

<1

2

0.7

0.38

13

3

3.0

0.79

28

4

0.3

0.25

9

5

0.3

0.25

11

6

0.0

0.00

<1

7

2.0

0.65

23

8

0.7

0.38

10

9

1.0

0.46

16

10

0.7

0.38

14

11

0.3

0.25

11

12

0.0

0.0

0.0

13

0.0

0.0

0.0

14

0.0

0.0

0.0

Natural ventilation is an essential tool for an energy-efficient apartment.  Unfortunately, wind is often unreliable and adjacent buildings block some of the wind when it does blow.  Therefore, we suggest installing exhaust fans in each apartment to limit the need for air-conditioning when wind alone does not produce enough natural ventilation.

Large exhaust fans (similar to kitchen and bathroom fans, but larger) should be installed in each apartment to provide an average hourly air change rate of 36 (for a 100m2 x 3m apartment, that means 3m3/s through the fan).  The required flow rate is calculated for cooling a typical apartment (H2) with a total cooling load of 55.5 Watts/m2 to within 2°C of the outdoor air temperature.  The cooling load was calculated as an average for the six months of March – May and September – November.  Assumed ideal mixing where:

A typical exhaust fan must be about 0.5 – 0.7m in diameter to provide the required airflow rate for a pressure loss of 150Pa (20 Pa static pressure).  ACME Engineering and Manufacturing Corporation in the U.S. makes a large line of such fans.  We assume similar manufacturers and products exist in China and are readily available.

We suggest placing the exhaust fan in the kitchen of most apartments for aesthetic reasons.  On the northern row of buildings near the railroad tracks, however, avoid placing fans on the side exposed to the railroad because they will leak noise into the apartments.  For top floor apartments, we suggest placing the fan in the wall near the top of the cathedral ceiling to expel the hot air first.  In most installations, and for most apartments, the total static pressure loss is near 20Pa.

ACME Engineering & Manufacturing Corporation

P.O. Box 978

Muskogee, OK 74402

USA

Tel: 918-682-7791

Fax: 918-682-0134

www.acmefan.com

acmefan@acmefan.com

Noise

Noise is a noted concern for the comfort of occupants in apartments adjacent to the railroad tracks.  The northern row of apartments is shielding the rest of the site from noise, but it must also protect its own occupants from noise.  All exterior surfaces (at all heights) with an unobstructed view of the railroad tracks (including buildings at the northwest corner) should heed the following:

People expect noise privacy so that outside noise infiltration is less than 35dBA in bedrooms, less than 40dBA in living and dining rooms, and less than 45dBA in bathrooms and kitchens.

Trains produce ~90dBA of noise (most train noise is at low frequencies).  A traffic barrier will give up to 15dBA noise reduction, the distance away from the tracks (~20m) will give 6dBA reduction, proper window/wall/door combination (as discussed above) will give 20-40dB reduction when doors/windows are closed.  (Only 20dB reduction is possible if doors and windows have gasket seals, and up to 40dB reduction is possible if all noise recommendations are used.)

Acceptable indoor noise levels                                                Train noise spectrum

Thermostat It is extremely important for the occupants to be aware of the temperature and humidity indoors and out so they can operate the windows, fan, and air conditioner efficiently.  The user manual (attached at the end of this report) guides occupants on how to use natural ventilation, mechanical ventilation, and air-conditioning based on the temperature difference between indoors and outdoors.

All the apartments should have digital, programmable, clock-thermostats that monitor and display the indoor and outdoor temperature.

  Air Conditioner Occupants should be encouraged to buy efficient air conditioners.  The units should have a minimum COP of 3 (COP = Heat Extracted / Electricity Input).  Based on a ten year payback, it is economical (and efficient) for occupants to upgrade the unit by 0.3 COP each time the upgrade costs less than 1500 yuan.  (For example, they should buy a 3.9 COP unit if it costs up to 4500 yuan more than the 3.0 COP unit; buy a 4.2 COP unit if it costs up to 6000 yuan more than the 3.0 COP unit.)

Air conditioners that have too much capacity (Watts) run inefficiently.  Since these apartments are designed to use less energy than typical units in China, there is a risk that air conditioner sellers may oversize the air conditioner (meaning higher initial cost to the occupants, and more overall electricity use).  Energy calculations based on the above recommendations indicate that air conditioners should be sized at ~100W/m2.  (For example, a 100m2 apartment should have 10kW of total air conditioning capacity to meet peak summer demand.)


Shenzhen Residential User Manual

Building occupants should use this guide to control their apartment for comfort and energy-efficiency.  This is a first draft of the manual, and it may change depending on which energy-efficiency recommendations are implemented into the apartments.  The information here is a guide to obtain optimum energy-efficiency, but may be altered according to personal preference and habits.

Use of thermostat to minimize energy use

The programmable thermostat allows the user to come home or wake up in a comfortable home without conditioning it while sleeping or away from the home.  A thermostat, which monitors indoor and outdoor conditions, and controls the heating, cooling, and ventilation equipment for a home, can be used to turn the equipment off even when the user is not at home.  With the use of a programmable digital thermostat, we recommended using the following temperature settings throughout the year:

 

Cooling Season

Mixed Season

Heating Season

Early Morning

26°C (30 if away)

Off (fans on)

22°C (20 if away)

Mid Morning

30°C (27 if home)

30°C (27 if home)

20°C (22 if home)

Mid Day

30°C (27 if home)

30°C (27 if home)

20°C (22 if home)

Mid Afternoon

30°C (27 if home)

30°C (27 if home)

20°C (22 if home)

Evening

26°C (30 if away)

27°C (30 if away)

20°C (22 if home)

Late Evening

27°C (30 if away)

Off (fans on)

22°C (20 if away)

 You may alter these settings to suit your comfort level (noting that you may increase your energy use).  Sometimes, high humidity will force you to use air-conditioning even when the temperature outside dictates natural ventilation (this is perfectly understandable).

Use of temperature readings to control air conditioning and ventilation:

A user can optimize their air-conditioner and fan use by using this chart and the temperature readings from the indoor/outdoor thermostat:

Inside Temperature:

Outside Temperature:

User Action:

Above the cooling setpoint

At least 2°C below the cooling setpoint

Turn off A/C, use natural or mechanical ventilation.

Above the cooling setpoint

Above the cooling setpoint

Turn on A/C, turn off fan and close windows.

Below the cooling setpoint, above the heating setpoint

Below the cooling setpoint

Turn off A/C, use natural or mechanical ventilation.

Below the cooling setpoint, above the heating setpoint

Above the cooling setpoint

Turn off A/C and fan and close windows.

Below the heating setpoint

Below the heating setpoint

Turn off A/C and fan and close windows.

Below the heating setpoint

Above the heating setpoint

Turn off A/C, use natural or mechanical ventilation.

During the hottest months, when using the air-conditioner all day and not opening the windows (because it is too hot and humid outside), occupants should ventilate the apartment for 5 minutes every morning to ensure good indoor air quality.  Occupants may also choose to ventilate the apartment in the evening (before bedtime) for 5 minutes if the air seems stale.  To ventilate during these times, occupants should open all the windows and interior doors, then turn the exhaust fan on (full speed) for five full minutes.  After ventilating, occupants should close all windows and use the air conditioner to bring the indoor temperature back to the cooling set-point. Note: The above ventilating procedure is only necessary when the outdoor temperature/humidity is too high for natural ventilation (i.e. when the windows have been closed all day).

Use of shading devices to minimize heat gain from the Sun:

To minimize the heat gain from the sun, the residence should have the blinds or other shading devices covering the windows while the sunlight is in direct contact with the window.  Leaving the windows covered throughout the entire day while the resident is not home will make the home more comfortable toward the end of the day, as compared to allowing the sunlight to enter the residence.  Blinds or shades should even be used if the window is opened (sunlight can be blocked while still letting air in for natural ventilation).

Use of natural ventilation or mechanical ventilation to remove hot air:

You should open windows and interior doors so wind will move hot air out of the apartment and make your home comfortable.  During the spring and fall, you may be able to use natural ventilation all day without needing an air-conditioner.  During the warmer months, you may only be able to use ventilation during nighttime or morning hours (or not at all).  Use an indoor/outdoor thermostat (as described above) to determine when ventilation will make your apartment more comfortable. If it is uncomfortable inside, but the indoor/outdoor thermostat says you can use natural ventilation, then the wind may not be strong enough and you should turn the exhaust fan on.  When the fan is on, you should still have your windows and interior doors open to allow the air to pass through.

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Last modified on November 27, 2000 by china@juintow.com.
 
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