How to use the heat loss calculator?

Please follow this short set of instructions on how to get your answer!

Start by selecting the material through which heat is being lost. Different materials have different thermal resistances. For most cases, we provide a default option for commonly used materials, but you can choose from a list of materials with their specific thermal resistance values. Click the button to see a drop-down menu of materials.
Pick the shape of the object or surface. You can choose from the following options:

Wall - Calculate the heat loss through a wall based on its area, thermal resistance, and the temperature difference.
Window - Calculate the heat loss through a window using the U-value, area, and temperature difference.
Roof - Similar to walls, but typically with different insulation values. You can input the area, insulation type, and temperature difference.
Floor - Similar calculation to walls and windows. This can vary based on material and insulation.
Other - If your shape doesn't fit into one of the standard categories, choose this option. You can enter custom dimensions and material details.

Depending on the shape, we will ask you to fill in some additional information to calculate the surface area or volume. For example, for a rectangular wall, we need the height and width to calculate the area, while for a cylindrical object, we will need the radius and height. If applicable, we may also ask for insulation values or other material-specific properties.

Provide the heat loss calculator with the temperature difference between the inside and outside. This value is crucial, as heat loss is driven by the difference in temperature across the material. We also include a default value for typical indoor/outdoor temperature differences, but feel free to adjust it according to your specific conditions.

How to calculate heat loss?

Although the heat loss calculator might seem complex at first, it is based on a simple formula. Calculating heat loss involves multiplying the surface area by the temperature difference and dividing by the thermal resistance (or multiplying by the U-value for windows). The basic formula is:

heat loss = area × temperature difference / thermal resistance

For windows, the formula is:

heat loss = area × U-value × temperature difference

In the case of the heat loss calculator, you also have the option to calculate the total heat loss for multiple units, so the final equation becomes:

total heat loss = area × temperature difference / thermal resistance × number of units

As you can see, the calculator works based on a few basic principles. The most complicated part might be determining the area or volume of irregular shapes, but don't worry! You can use our geometry calculators to find the area or volume of most shapes easily.

Example

Calculating Heat Loss

Heat loss through a material can be calculated by determining the temperature difference, the area of the material, and its thermal resistance. The general formula to calculate heat loss is:

\[ Q = \frac{A \times \Delta T}{R} \]

Where:

\( Q \) is the heat loss (in watts, W).
\( A \) is the area through which heat is being transferred (in square meters, m²).
\( \Delta T \) is the temperature difference (in degrees Celsius, °C).
\( R \) is the thermal resistance of the material (in m²·K/W).

Calculating Heat Loss through an Insulated Wall

If you have an insulated wall, you can calculate the heat loss by finding the area of the wall, the temperature difference, and the thermal resistance of the insulation. The formula for heat loss is:

\[ Q = \frac{A \times \Delta T}{R} \]

Example:

If the wall has dimensions: Length = 5 m, Height = 3 m, a temperature difference \( \Delta T = 20^\circ \text{C} \), and thermal resistance \( R = 2 \, \text{m}^2 \cdot \text{K}/\text{W} \), the heat loss can be calculated as follows:

Step 1: Calculate the area: \( A = 5 \, \text{m} \times 3 \, \text{m} = 15 \, \text{m}^2 \).
Step 2: Apply the formula: \( Q = \frac{15 \, \text{m}^2 \times 20^\circ \text{C}}{2 \, \text{m}^2 \cdot \text{K}/\text{W}} = 150 \, \text{W} \).

Calculating Heat Loss through a Window

If you have a window, the formula for heat loss is:

\[ Q = A \times U \times \Delta T \] where \( U \) is the U-value (thermal transmittance) of the window material.

Example:

If the window has dimensions: Width = 1.5 m, Height = 1.2 m, U-value = 1.5 W/m²·K, and temperature difference \( \Delta T = 15^\circ \text{C} \), the heat loss can be calculated as follows:

Step 1: Calculate the area: \( A = 1.5 \, \text{m} \times 1.2 \, \text{m} = 1.8 \, \text{m}^2 \).
Step 2: Apply the formula: \( Q = 1.8 \, \text{m}^2 \times 1.5 \, \text{W/m}^2\cdot\text{K} \times 15^\circ \text{C} = 40.5 \, \text{W} \).

Real-life Applications of Heat Loss Calculation

Calculating heat loss is important in several practical scenarios, such as:

Determining the energy efficiency of buildings and homes for insulation planning.
Estimating heating costs by calculating how much heat is lost through walls, windows, and roofs.
Designing HVAC systems that efficiently control temperature in buildings.

Common Operations with Heat Loss Calculation

Wall Heat Loss: \( Q = \frac{A \times \Delta T}{R} \)

Window Heat Loss: \( Q = A \times U \times \Delta T \)

Other Structures: For roofs, floors, and other materials, the heat loss is calculated similarly, depending on the material's thermal properties and the area exposed to temperature differences.

Heat Loss Calculation Examples Table
Object Type	Description	Steps to Calculate Heat Loss	Example
Insulated Wall	Calculating the heat loss through a wall by determining its area, insulation material, and temperature difference.	Calculate the surface area of the wall: \( A = \text{Length} \times \text{Height} \). Determine the thermal resistance of the wall material (\( R \)). Apply the formula: \( Q = \frac{A \times \Delta T}{R} \), where \( \Delta T \) is the temperature difference.	If the wall has dimensions Length = 5 m, Height = 3 m, a temperature difference \( \Delta T = 20^\circ \text{C} \), and thermal resistance \( R = 2 \, \text{m}^2 \cdot \text{K}/\text{W} \), the heat loss is \( Q = \frac{5 \times 3 \times 20}{2} = 150 \, \text{W} \).
Window	Calculating the heat loss through a window by considering its area, material, and temperature difference.	Calculate the surface area of the window: \( A = \text{Width} \times \text{Height} \). Find the U-value (thermal transmittance) of the window. Apply the formula: \( Q = A \times U \times \Delta T \), where \( \Delta T \) is the temperature difference.	If the window has dimensions Width = 1.5 m, Height = 1.2 m, U-value = 1.5 W/m²·K, and temperature difference \( \Delta T = 15^\circ \text{C} \), the heat loss is \( Q = 1.5 \times 1.2 \times 1.5 \times 15 = 40.5 \, \text{W} \).
Uninsulated Floor	Calculating the heat loss through an uninsulated floor by considering its area, material properties, and temperature difference.	Calculate the surface area of the floor: \( A = \text{Length} \times \text{Width} \). Determine the thermal conductivity of the floor material (\( k \)). Apply the formula: \( Q = \frac{k \times A \times \Delta T}{d} \), where \( d \) is the thickness of the material.	If the floor has dimensions Length = 4 m, Width = 5 m, thermal conductivity \( k = 0.7 \, \text{W/m·K} \), thickness \( d = 0.1 \, \text{m} \), and \( \Delta T = 18^\circ \text{C} \), the heat loss is \( Q = \frac{0.7 \times 4 \times 5 \times 18}{0.1} = 2520 \, \text{W} \).
Roof	Calculating the heat loss through a roof by using the roof area and the thermal resistance of the roofing material.	Calculate the area of the roof: \( A = \text{Length} \times \text{Width} \). Determine the thermal resistance (\( R \)) of the roof material. Apply the formula: \( Q = \frac{A \times \Delta T}{R} \), where \( \Delta T \) is the temperature difference.	If the roof has dimensions Length = 10 m, Width = 8 m, \( \Delta T = 25^\circ \text{C} \), and thermal resistance \( R = 3 \, \text{m}^2 \cdot \text{K}/\text{W} \), the heat loss is \( Q = \frac{10 \times 8 \times 25}{3} = 666.67 \, \text{W} \).