Journal article Open Access

Thermal Time Constant - TTC

Nowarski, Joseph

The design of a building's exterior walls has an important influence on energy consumption, building cost and thermal comfort. It influences also heating and cooling devices’ size.

Optimization of energy consumption of the building requires consideration of the building materials, their thickness and mass, type and thickness of insulation, and location of the insulation layer.

The correct way to optimize all the above parameters is a calculation of temperatures and energy consumption in a dynamic process, which means considering changes every few seconds. This may be done only with a computer program.

It is not easy to gain expertise in such programs. In addition, submission of input values to the program is time consuming and frustrating process, which many times ends with errors.

This work introduces the term “Thermal Time Constant” which may be applied to determine the thermal quality of the building as an alternative to the dynamic simulation program. The Thermal Time Constant method is much easier, simpler and faster than a computer dynamic simulation program.

Higher Thermal Time Constant (TTC) moderates the difference between day and night in the room, flattening the room temperature extremes caused by ambient temperature and solar energy.

Higher TTC is not necessary necessarily more expensive. To take advantage of high TTC is not so the question of additional investment, but the question of understanding the TTC concept.

In some cases consideration of TTC caused changes to the building's design and construction technique, bringing benefits to the contractor, the tenants and the national economy.

Disregarding TTC leads to wrong decisions, wrong design, waste of money on building construction and increased energy consumption.

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