Some info regarding passive/active system studies/outcomes
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.
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.
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)
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.
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.
Structural analysis
Besides a esthetic design and functionality as cladding, the curtain walls which form building facades require verification of structural performance values as the exterior walls of structure.
From the basic structure stage, we work through structural analysis simulations to realize the specifics of the facade design image, which is based on the architect’s design, and the performance requirements.
This process is a comprehensive verification of the form, strength and durability of the entire facade to the original components are conducted by our staff teams of design, manufacturing and construction sharing a common understanding.
Thermal analysis
Progress in construction and structural analysis techniques in recent years has dramatically expanded the range of expressive techniques available in the surface design of buildings, typified by all-glass facade design. With that progress, it has become important to take action to reduce CO2, against climate change, and reduce running costs at the facility maintenance stage, besides the obvious need to control the indoor thermal environment.
Optimize the indoor environment while minimizing energy consumption – YKK AP is pursuing the technical development of environment-conscious facades as a way to reconcile these conflicting demands.
Alongside design and construction, we also use high-precision thermal environment simulations to verify the development of insolation control, ventilation and other technologies.
Thermal performance from the development of Double-skin facade System, environment-friendly facades, and implementation of basic experiments.
In developing double skin systems, we have pursued system optimization through thermal analysis, fluid analysis, actual-size trials and performance assessment.
The building of simulation technology
 Trial in outdoor environment laboratory |  Indoor comfort evaluation using PMV |
Performance assessment of double-skin systems introduce thermodynamics and fluid mechanics.
The flow of air inside the central air layer, which varies with environmental and physical conditions are analyzed to find the temperature and heat flow of each component, and to predict and assess performance. This is a technology to predict results closer to reality, built through cross-referencing for consistency with data from the basic experimental research.
Development of peripheral technologies
The double skin system holds a large isobaric space, extending to the outside, so its behavior against weather differs from a normal window system.
The way the wind pressure is divided and borne by the internal and external glass panes when the window is exposed to wind is a major design issue which must be solved.
Beyond thermal performance, experiments on technical developments such as wind pressure and water resistance are also required to develop peripheral technologies.
see the cataloge here:
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