Thermal Modelling for Comfort and Building Performance Assessment

We deliver thermal modelling for council thermal comfort compliance assessment, a parametric study of proposed improvements in an energy audit, and for NCC Performance Solutions. Thermal comfort, indoor conditions such as temperature and humidity, and heat flow are measured to evaluate the performance of the building.

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At Energy Compliance, we model any type of building and propose cost-effective improvements to improve thermal comfort and reduce energy costs.

At Energy Compliance, we model any type of building and propose cost-effective improvements to improve thermal comfort and reduce energy costs.

VURB JV3 DtS

Quality

We use realistic design assumptions to better resemble your building performance in our thermal modelling.
We utilize our expertise, our past experience and cost-effective measures to conduct the best solution possible.

VURB JV3 DtS

Quality

We use realistic design assumptions to better resemble your building performance in our thermal modelling.
We utilize our expertise, our past experience and cost-effective measures to conduct the best solution possible.

Service Guarantee

Our thermal modelling reports are council ready and we deliver on time. If we fail to deliver what we promised, and you decide not to use our report, you won’t have to pay the remainder of our invoice.

JV3 VURB DtS
JV3 VURB DtS

Service Guarantee

Our thermal modelling reports are council ready and we deliver on time. If we fail to deliver what we promised, and you decide not to use our report, you won’t have to pay the remainder of our invoice.

VURB JV3 DtS

Quick Turnaround

Quotations: Same business day of inquiry.
Thermal modelling reports: 4-7 business days (depending on the complexity of the project).

VURB JV3 DtS

Quick Turnaround

Quotations: Same business day of inquiry.
Thermal modelling reports: 4-7 business days (depending on the complexity of the project).

Obtain a quote

What is thermal modelling?

Thermal modelling involves using a computer program to create a 3D model of a building and simulate how the temperature and thermal comfort inside your building will change based on different factors like the weather, the building materials, and the building’s use. The goal is to see if the building will be comfortable for people to be in before it’s built. If it’s not, changes can be made to the model until the desired conditions are achieved.

What is the purpose of thermal modelling?

Thermal modelling can be used for all kinds of buildings to make sure a comfortable environment could be made for the occupants and to figure out how much it will cost to keep it that way. Some common reasons to use thermal modelling are:

  • Assess the thermal comfort of the occupants and desirable indoor conditions;
  • Investigate the contributing factors to the building’s heat loss or heat gain and ways to improve it;
  • Investigate the effectiveness of the mechanical or natural ventilation inside occupiable spaces;
  • Calculate annual heating and cooling loads and energy costs of a building;
  • Evaluate and compare different passive heating or cooling solutions for a better design;
  • Assess the feasibility of different energy source options, including renewables;
  • Impact of building design and design features on thermal loads and thermal comfort
  • Determine temperature setpoints and the need for humidity or CO2 control in special type applications; etc.
NCC energy efficiency thermal modelling daylight modelling performance solution jv3 VURB

Thermal modelling for a building depends on the following:

  • Location,
  • Adajcaent shading and light-reflecting structures
  • Building fabric
  • Glazing
  • Climate
  • Number of occupants inside at any time
  • Clothing
  • Activity level of occupants inside the building

Thermal modelling is a general term and applies to all efforts related to modelling a 3D version of a building using modelling software, to extract hourly indoor conditions and thermal loads. For instance, in Australia, when Deemed to Satisfy provisions are costly to achieve, or impossible to follow, Performance Solution pathways are suggested by The Australian National Construction Code (NCC) which mostly, requires thermal modelling using commercial software. For commercial buildings, a method is used called JV3 alternative solution to make sure the building uses energy efficiently. For residential dwellings, we use a method called Verification Using a Reference Building (VURB) to do the same thing.

Why do we undertake thermal modelling in Australia?

In Australia, thermal modelling is important for several reasons. It is used to check if a building’s design and mechanical systems can keep people comfortable indoors, and to see how much energy the building will use and cost. It can also help with selecting a feasible source of energy. Aside from this general purpose, thermal modelling is sometimes required to obtain a building permit:

Thermal comfort modelling
When a building has a lot of windows, lacks insulation, or has poor ventilation, thermal modelling is necessary to make sure the inside will be comfortable to be in. This is especially important for people who may be more sensitive to uncomfortable indoor conditions, like children or older adults.
Click here for more details on one of our thermal modelling projects.

Parametric study of Energy Conservation Measures (ECMs)
While performing an energy audit, it might seem obvious that lots of Energy Conservation Measures (ECMs) might reduce the running cost of the building, however, the main question remains how much? For instance, reducing the ceiling height of a community centre might help to reduce the running cost of the centre. However, it is critical to understand how cost-effective this ECM is. Thermal modelling can assist to model the existing building under different scenarios and quantify cost savings.
Click here for more details on one of our thermal comfort parametric studies projects.

Performance Solution
Where Deemed to Satisfy provisions are too expensive or impractical to follow, the architects and developers need to find a cost-effective solution to make sure the building meets the energy efficiency requirements of the code. This alternative method is called Performance Solution, and it is formulated in NCC where it requires thermal modelling using a computer program to show that the building will be energy efficient. There are different types of computer programs used depending on the type of building. These alternative solutions are Green Star, NABERS, or JV3 verification method for a commercial building, and VURB method for residential dwellings.
Click here for more details on one of our Performance Solution projects.

Daylight modelling
When a building has a complicated shape, is surrounded by features that block the sunlight, or daylight passes through a light court, daylight modelling may be required to make sure that a desired daylight level is achieved inside habitable spaces. In some Victorian councils, acceptable daylight access criteria are detailed in BESS and are required for ESD.
Click here for more details on one of our daylight modelling projects.

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What is thermal comfort? What impacts thermal comfort?

Thermal comfort is a comfortable feeling you get in a space with desirable thermal-related conditions. We might think that temperature is the only thing that makes us feel comfortable in a space, but sometimes a temperature of 22 degrees Celsius can feel hotter than 24 degrees Celsius if the humidity in that space is high or you are doing heavy work.

Thermal comfort mainly depends on:

  • Indoor temperature
  • Humidity
  • Air velocity
  • Area of cold/hot surfaces
  • Direct solar exposure
  • Activity level and clothing
  • Metabolic rate
  • CO2 ppm in space (and requirement for fresh air)

But how do you account for all that in space? Knowing each parameter could offset an “undesirable feeling” of the other factor.

Thermal comfort is achieved for a person when their internally generated heat can be transferred to the space and a balance is maintained between them so that the person feels comfortable. Your body produces (metabolic) heat based on your gender, age, activity level and clothing. Your body gets rid of the heat it produces by breathing, sweating, convection of air over your skin and radiative heat transfer to nearby surfaces. The rate of this heat transfer can be affected by what you’re wearing, how hot or cold the surroundings are, and how fast the air is moving around you. Humidity inside a room also affects the rate of transpiration.

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When we want to see how comfortable it is inside a room, we use the term Operative Temperature. This temperature is based on three things: how warm or cool the air is, how fast it’s moving around the room, and the average temperature of nearby surfaces (the latter is called Mean Radiant Temperature, MRT in short). Mean Radiant Temperature (MRT) could be defined as the surface temperature of an imaginary box that surrounds you and has the same temperature as the weighted-average temperature of all surfaces around you. If the heat coming from your body and towards this imaginary box, equals the heat going out of the box, you’ll feel comfortable and this is how thermal comfort is maintained inside a room. But if more heat is leaving your body and towards the box than going out of the box, you’ll feel cold.

ANSI/ASHRAE Standard 55 explains the mechanics of this heat transfer and the formulation from which those temperatures could be calculated alongside other formulas used to predict whether you are comfortable living or working in a room or not.

There are set of metrics used in a thermal modelling study to predict thermal comfort in a space, from which the most commonly used would be the Predicted Mean Vote (PMV).

What is PMV?

Predicted Mean Vote (PMV) is a metric to evaluate thermal comfort inside a space. It is developed as a quantitive measure to describe the indoor conditions and the feeling most people get while occupying a room. PMV calculation depends on six variables of air temperature, relative humidity, metabolic rate, air velocity, mean radiant temperature (MRT) and clothing insulation. To figure out how comfortable people are in different situations, researchers have done studies where they ask people how they feel in a room. They used a scale from -3 (feeling cold) to +3 (feeling hot). This helps them understand if people feel comfortable in different situations. PMV formula was developed based on those surveys.

According to ASHRAE Standard 55, an acceptable criterion for PMV is between -0.5 to +0.5 where 80% of people feel comfortable.
Building Code of Australia, NCC Vol 1.0 Section J, requires a thermal comfort level of between a PMV of -1 to +1 across not less than 95% of the floor area of all occupied zones for a duration of 98% of the annual hours of building occupation.
ISO 7730 defines the hard limit as ranging between -2 and +2, for existing buildings between -0.7 and +0.7, and new buildings ranging between -0.5 and +0.5 (reference).

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How to improve thermal comfort?

Thermal comfort is better to be assessed at the design stage through the thermal modelling procedure. Existing buildings could be improved to elevate thermal comfort levels but improving it would be costly and sometimes not possible.

  • Change heating/cooling set point

    Probably the most common solution to feeling comfortable is to set the right temperature indoors. However, if the services were designed to maintain a certain set point, you may need to increase the size of the heating/cooling source (e.g. heat pump or split system) for it to be able to deliver at desired set points. Thermal modelling helps to find the right indoor set points.

  • Maintain humidity

    Increasing humidity in a space helps to feel warmer and decreasing it feels colder. In a very hot and dry climate, utilizing an evaporative cooling system in summer and using a heating system with a humidifier in winter is probably a better idea than others; for humid climates, dehumidification in summer is essential for a comfortable environment.

  • Insulation

    Adequate insulation must be added to the building fabric to maintain the surface temperatures surrounding an individual occupying a space. Excessive insulation for a space with a high internal heat generation is also a bad idea as the heat transfer from inside to the outdoors gets difficult especially in hot climates.

  • Window area

    Although large windows make you feel luxurious and attached to the environment, they generally act purely in relation to thermal comfort. As a general rule of thumb, window areas of more than 10% of the floor area served, introduces excessive and unnecessary natural light into the space. Double-glazing is certainly preferred to single-glazing windows as it gets less cold in winter.

  • Window tint

    In hot climates, tinted windows (a window with a low SHGC) block the solar irradiation off the indoor space and contribute to feeling cooler and in cold climates, clear windows (a window with a low SHGC) let the solar irradiation in to heat the space and surfaces surrounding the occupants and reduce heating demand.

  • Sufficient openings

    In hot climates, sufficient openings help with the naturally-induced ventilation inside habitable spaces and on one hand, offset the cooling demand, and on the other hand, increase the convection heat transfer over the skin which cools down the body temperature. As a rule of thumb, the opening area should be 5% of the space area served.