How Thermal Modeling Is Used to Design Energy Efficient Buildings

The two greatest benefits of increasing energy efficiency in the building sector are reducing building costs and limiting environmental degradation.  Common methods of increasing energy efficiency in buildings include improving building insulation, utilizing energy-efficient lighting solutions such as LEDs, and selecting proper ventilation and heating systems. These methods are overarching but can be further refined in accordance to the building’s surrounding environment.

However, this article proposes an accurate thermal behavior modeling technique to help guarantee energy efficiency. Read further to discover more about building thermal modeling solutions and how architects use them to design energy-efficient buildings.

How Can a Building be Designed to Reduce Energy Consumption?

Did you know that the building sector accounts for approximately 40% of all US primary energy and Associated Greenhouse Gas (GHG) emissions? Moreover, the building sector is responsible for 76% of electrical usage. Such figures have prompted the need for a reduction in energy consumption in buildings.

Generally, during a building’s design and development, architects, engineers, and contractors can apply comprehensive, integrated approaches to the processes, with the following as the bottom line.

• Reduction of cooling, heating, and lighting demands via passive strategies like conservation practices, daylighting, and climate-responsive design.
• Optimization of building performances by using thermal modeling during the design stage.
• Implementing renewable energy sources like solar heating for hot water, geothermal space heating, photovoltaics, groundwater cooling, etc.
• The specification of effective HVAC and lighting systems considering part-load conditions and utility interface needs.
• Integration of water-saving technologies to minimize the energy burden of availing portable water.
• Optimizing system control strategies by utilizing CO2 sensors, occupancy sensors, and other air quality alarms.

Thermal Modeling

Building thermal modeling is the representation of a building design in a computer simulation program to highlight and possibly—if not assuredly—predict how it will function thermally. The process involves testing different design elements uniquely, then depicting results as text or graphic output.

How Does Thermal Modeling Work?

Thermal modeling takes a digital twin of a facility and calculates the heat flow from the warm interiors to cold exteriors.

Such iterative mathematical analysis typically requires millions of calculation nodes to represent a real-life situation to the best. Ideally, it is also highly possible to create models and run them to analyze time-dependent temperature as well as water vapor flows.

A thermal model is a 3D computer simulation that predicts how temperatures in a building will vary from one space to another on a daily, monthly and seasonal basis. Thermal modeling can be used to improve your building’s thermal performance. 

Thermal Performance of Buildings

Generally, ‘thermal performance’ relates to the efficiency with which something retains or hinders the transfer of heat. In most cases, this relates to materials’ thermal conductivity or assembly. Materials regarded as having good thermal performance tend to be good insulators. Conversely, poor thermal performance materials are better heat conductors.

The thermal performance of a building is defined as the total energy expenditure per unit of the interior floor area required to heat or cool the building’s indoors to a minimum level of ‘thermal comfort.’

What Are the Factors Affecting a Building’s Thermal Performance?

• Temperature and seasonal changes
• Incoming and outgoing heat radiation
• Pressure difference
• Insulation
• Air movement
• Water/moisture absorption

Thermal performance is a fundamental consideration in the design phase of a building. The goal is to ensure compliance with building regulations relating to energy usage and efficiency.

Thermal Resistance

A building’s thermal resistance depends on the temperature differences across the used material’s thickness and conductivity—the greater the thickness, the lesser the heat flow. 

Construction layers with high thermal resistance, such as rock wool, are good insulators. On the other hand, those with low thermal resistance, like concrete, are poor insulators.

Comparing the relative performance of different material thicknesses means calculating their thermal resistance (units=m2K/W). You can calculate thermal resistance by dividing the material’s thickness by its thermal conductivity. Ideally, you will need to give an R-value specific to that thickness. As a general rule, the higher the thermal resistance, the better since there is greater resistance to heat transfer.

What are U Value and R-Value?

On the one hand, R-value is a measure of thermal resistance. It is also the ability of a material or object to resist heat flow. On the other hand, U-value is a thermal transmittance or heat loss via a structural element. While both are technically different, they are often used in the same context to rate building energy efficiency.

How Do You Find the Thermal Mass of a Building?

Thermal mass defines a material’s capacity to release, store, or absorb heat. The thermal performance of buildings differs across materials. Water and concrete have a high thermal mass since they possess a high capacity to store heat. In contrast, insulation foam has a low thermal mass since it has very limited heat storage capacity.

Thermal mass is also known as Volumetric Heat Capacity (VHC), which is calculated by multiplying a material’s density by the specific heat capacity. In this case, density is the weight per unit volume of a material. The specific heat capacity is the energy amount necessary to elevate the temperature of 1kg of material by 1°C. The higher the volumetric heat capacity, the higher the thermal mass.

How to Design Energy Efficient Buildings

Building Information Modeling (BIM) is an excellent tool for generating and managing digital representations of a structure’s physical and functional characteristics.

Using building thermal modeling software, designers and construction experts can contribute toward energy conservation in buildings. It is a critical aspect of comfort assessment regarding heat generation, storage, and disposal.

Thermal modeling is one of the prevalent benefits of Building Information Modeling (BIM). Contact the Maptelligent team to learn more.