Technical Recommendations for Shenzhen Wonderland

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.

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.	*
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.

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.

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.

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.

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.

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).

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:

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.

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.

Produces the sun-screen products (just the fabric)

>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.

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.

Muskogee, OK 74402

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.

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

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.)

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.

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:

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).

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

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).

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).

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.

Cooling Setpoint

Exterior color

Produces the sun-screen products (just the fabric)

Muskogee, OK 74402