With the ongoing pandemic and countrywide lockdown, the sanctity of our homes has become more important than ever. While “home” has always meant a place of comfort, today, the implications of it are even louder.

RETV or Residential Envelope Transmittance Value is simply the way to calculate the amount of heat gained by a residential building envelope (excluding the roof). The RETV value varies depending on the general climate zone the building is situated. Simpler to calculate than Energy Simulations, RETV has been recognized as a benchmark for home insulation across the globe. Talking of numbers, a RETV of less than 15 W/m2 is considered to be a compliant
value for residential engineering in several countries today.

What is RETV?

To understand RETV, we need to understand the constituents of building engineering and how they affect the heat loss/gain of the structure. With “green buildings” taking a step forward in the current decade, home insulation plays a vital role in not just energy savings but also the health of the residents. The first step to understanding REVT is your “Building Envelope”. It is any physical barrier that occurs between the indoor and outdoor environments. In simple terms, it is your building walls, roofs, windows, and doors. They act as the first barrier to the outdoor heat that enters your indoor space. The RETV value consequently incorporates the heat gain (could be positive or negative depending on the climate) from walls, glass (windows, skylight, etc) and shading (window sunshade, roof shading, etc). As easily understood, the walls form the major barrier here. For roofs, the average RETV is valued at