Environmental facades

Recent Building facades are expected to provide interior comfort, a feeling of openness, and in addition to saving energy. YKK AP is developing environmental facades, as a technology able to save energy, while delivering comfort by optimizing the interior environment, and cutting consumption.

In the development process towards a facade design integrated with the building, it is essential to consider how the shading and insulation performance of the openings impacts energy saving and comfort. We will now present four types of environmental facade.

Categories of environmental facades

Environmental facades

Recent Building facades are expected to provide interior comfort, a feeling of openness, and in addition to saving energy. YKK AP is developing environmental facades, as a technology able to save energy, while delivering comfort by optimizing the interior environment, and cutting consumption.

In the development process towards a facade design integrated with the building, it is essential to consider how the shading and insulation performance of the openings impacts energy saving and comfort. We will now present four types of environmental facade.

Categories of environmental facades

Environmental facades

Recent Building facades are expected to provide interior comfort, a feeling of openness, and in addition to saving energy. YKK AP is developing environmental facades, as a technology able to save energy, while delivering comfort by optimizing the interior environment, and cutting consumption.

In the development process towards a facade design integrated with the building, it is essential to consider how the shading and insulation performance of the openings impacts energy saving and comfort. We will now present four types of environmental facade.

Categories of environmental facades

Environmental facades

Recent Building facades are expected to provide interior comfort, a feeling of openness, and in addition to saving energy. YKK AP is developing environmental facades, as a technology able to save energy, while delivering comfort by optimizing the interior environment, and cutting consumption.

In the development process towards a facade design integrated with the building, it is essential to consider how the shading and insulation performance of the openings impacts energy saving and comfort. We will now present four types of environmental facade.

Categories of environmental facades

Low-E glass and internal blinds

• Blinds are located on the interior side
• The heat from solar gain is absorbed, reflected by blinds on the interior side, and is radiated from the room.
• Solar shading property is low.
• Thermal Insulative property is equal to the glazing.

Solar heat gain coefficient
η=0.30~0.55 η=approx.
Thermal transmittance
U=1.5 2.4 W/m2 K U=approx.
*Above values vary with the property of glass and blind

External blinds type

• Blinds are located on the exterior side
• The heat from solar gain is absorbed, reflected by blinds on the interior side, and is radiated from the room.
• Solar shading property is high.
• Thermal Insulative property is equal to the glazing.

Solar heat gain coefficient
η=0.05～0.10 η=approx.
Thermal transmittance
U=1.5 2.4 W/m2 K U=approx.
*Above values vary with the property of glass and blind

Mechanically ventilated type

• This type uses double-pane glass with blinds between the panes, and pass air from the room interior through the cavity by mechanical ventilation.
• The solar heat absorbed by blinds is removed by mechanical ventilation.
• Solar shading property is high.
• Thermal Insulative property is higher than double-pane glass, due to the airflow in the cavity between the panes. (Varies with the air flow rate)

Solar heat gain coefficient
η=0.15～0.25 η=approx.
(when mechanical ventilation is on.)
Thermal transmittance
U=0.5～1.0（W/m2・K） U=approx.
(when mechanical ventilation is on.)
＊Above values vary with the property of glass and blind and air flow rate

Naturally ventilated type

• This type uses double-pane glass with blinds between the panes, and pass air from outside through the cavity by stack effect.
• The solar heat absorbed by blinds is removed by ventilation.
• Solar shading property is high.
• Thermal Insulative property is higher than inner glazing.

Solar heat gain coefficient
η=0.10～0.20 η=approx.
Thermal transmittance
U=1.5～3.5（W/m2・K） U=approx.
＊Above values vary with the property of glass and blind

Thermal property of facade and thermal load of perimeter zone

The relation between solar shading/ thermal insulation property of facade and thermal load of perimeter zone can be described as below.

• Solar shading property is high = Low cooling load and high heating load[Figure 1-(A)]
• Thermal insulative property is high = High cooling load and low heating load[Figure 2-(C)]

In a warm area such as Tokyo, cooling loads account for the bulk of heating and cooling loads, the superior solar shading property of the facade is effective in reducing thermal loads all year round. It is vital to select the right facade system, with careful consideration of the balance between solar shading property and thermal insulation property, taking the region and orientation into account.

Thermal property of facade and interior comfort

For occupants of the building interior, comfort is important, not just energy saving. To secure comfort in the perimeter zone close to the facade, the temperature of the interior surface of the facade must be maintained at an appropriate level.

＜Summer and intermediate season＞

When the solar heat raise the temperature of the interior surface. → Room is maintained at an appropriate level but occupants around window feel hot.
＜Winter＞
When nighttime and cloudy weather fall the temperature of the interior surface. → Room is maintained at an appropriate level but occupants around window feel cold.
＊A facade with superior solar shading and thermal insulation property mitigates the impact of the changing exterior environment, reducing changing in the interior surface temperature of the facade to maintain comfort in the interior. Selection of the right facade system is also important for interior comfort as an assessment indicator.

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