‘Airtight Envelope’ is one of the solutions to keep your building cool in hot climates
Our perception of comfort mostly depends on our activity, clothing and the properties of our thermal environment according to the scientist P.O. Fanger. The following are the main ways to achieve indoor comfort when it’s warm and possibly humid outside:
1. Encourage internal air circulation by keeping your building open
The commonly seen traditional design solution in hot and humid climate is to keep your building open to ensure that high volumes of air can flow throughout. These draughts help to keep your body cooler through the process of evaporative cooling on the skin. It is also suggested to use stack ventilation design for achieving better results.
In the recent times people are used to air-conditioned cars, shops and indoor public spaces. So, they are not willing to accept the thermal comfort conditions achieved by the traditional design approach because the traditional approach is highly dependent on the outdoor temperatures, humidity and wind speed. To address this, majority of the traditional buildings in hot climates are installed with air conditioning units, which is neither energy efficient nor particularly comfortable.
2. Isolate the interior space from the exterior space
The Passive House Standard suggests this approach to isolate the interior space from the exterior space when the exterior space is warmer and more humid than the acceptable indoor conditions. Isolating the interior from the exterior will help reduce the heat gains in the interior as well reducing the energy demand of the building. But, how is this possible?
Reducing / Limiting the heat gains
Any building requires to cool the unwanted heat gains in the space. In general, the heat gains are through the internal and external sources. The internal heat gain sources can be limited by selecting energy efficient appliances and electronic devices. In addition, highly efficient ventilation systems shall be selected and the utility systems like hot water systems and pipes shall be insulated properly to limit the unwanted heat from these systems to the interior space.
The external heat gains are the major contributor to the unwanted heat in the building. The external heat gains can be reduced by selecting sufficient insulation systems for the building envelope. The other primary source for the unwanted heat to enter the building is through the leakages in the building envelope.
is currently a major requirement that has to be addressed from design to construction of any building, mainly in the very hot and cold climates. Envelope airtightness can be ensured by conducting air leakage tests as per the ASTM or ISO standards. However, to ensure the integrity of the leakage tests; the tests shall be conducted by certified professionals from organisations like ATTMA, ABAA…etc. Also, to ensure the continuity of envelope insulation, thermographic tests can be carried out.
Passive Cooling Strategies
Based on the local climate profile, passive cooling strategies like window ventilation can be selected if the outdoor conditions are similar to the desired indoor conditions. Also, the designers can explore the feasibility of installing a geothermal heat exchanger system.
If Active Cooling is Needed
By deploying the above-mentioned strategies, the buildings can reduce the cooling load to become smaller than in conventional buildings. To address the remaining cooling demand, the designers can opt for energy efficient ventilation systems and other options like concrete core activation, which is especially good for bigger buildings and dry climates. All these options are currently being tested in the first Passive House in Dubai. In humid climates, additional dehumidification may be required.