DJHC Ltd

What is thermal analysis?

What is thermal analysis?

Using state of the art software such as IES™, DesignBuilder™ and Revit™, we can build a virtual model of any building, and analyse it across different conditions and dynamic weather scenarios to identify risk areas such as overheating, thermal bridging, and excessive energy consumption.

This process involves creating a 3D model of a building to inform the design decisions related to its form, materials, orientation, and environment.

The relative thermal performance of a building depends on a number of well-defined parameters. This article will introduce the concepts of these parameters and provide a step-by-step approach to explore the need for active cooling and heating.

We measure the thermal resistance of a structure which provides an accurate and reliable method for assessing the steady state heat flow. Even in winter, the building will be subjected to varying degrees of heat exposure so it’s important to consider this.

A reasonably accessible method for estimating the cycling flows of heat and the resulting need for cooling or heating was developed by BRE and adopted by CIBSE more than 40 years ago.

The admittance method is mainly used for determining determining the periodic steady-state thermal performance of a building. It assumes that the outside air temperature is constant over a repeating number of days. This method is especially useful for those designers who have limited experience in building modelling. It can help them gain an understanding of the various thermal properties of proposed designs.

The primary factors that affect the thermal properties of an opaque material are density, specific heat capacity, and thermal conductivity. These properties are generally measured in terms of thermal diffusivity. The thermal diffusivity of a material can vary widely depending on its depth.

The thermal inertia relationship can be used to evaluate the thermal properties of multi-layered structures. It can also be used to evaluate the storage capacity of materials. The amount of heat flow depends on the orientation of the air movements and the surface roughness of the material. The temperature difference between the air and the surface can also be calculated.

The coefficients are then used to provide the non-steady state factors that are necessary for the admittance method. It can be easily done for single layer structures, but it requires lengthy manipulation and is usually done in a spreadsheet.

This measure shows how much energy is passed through an element’s internal surface at a given time and the room temperature. It is often used to evaluate the energy efficiency of an element. The admittance time lead is a function that relates to the time delay between the arrival of the hot air and the cooling of the room.

The value of thermal admittance is mainly affected by the thickness of the wall closest to the room. As the wall gets thinner, the value of admittance approaches a constant value.

The thermal admittance factor is a non-linear factor that is used to evaluate the relative thermal performance of various components. It is typically used to evaluate the thermal bridging performance of various materials.

The time lag is how long it takes for heat to reach one side of a structure. It can also be calculated by taking into account the ‘decrement factor’, the term used to describe the amount by which conditions are moderated by any element of the structure. For instance, if the temperature rises to a certain level on the building’s outer surface, the amount of time it takes for the peak to reach the inner surface will reduce.

The final pair of factors to consider are the surface factor and the time factor. The time factor is a measure of the time delay that relates to the gain from localised sunshine. The Surface factor is the ratio of the heat flow from the inner surface of an element to the heat flow from the outer surface. This is referred to as the swing in heat flow. Generally, temperature and input material are the two main factors that determine the thermal admittance value.

Contact info@djhigginsconsulting.co.uk to find out more.

 

 

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