Infiltration heat loss calculation is a crucial aspect of building energy efficiency that often goes overlooked. Infiltration refers to the uncontrolled movement of air into and out of a building through cracks, gaps, and openings in the building envelope. This movement of air not only leads to discomfort for occupants but also results in energy loss and higher utility bills. Therefore, understanding how to calculate infiltration heat loss is essential for building designers and energy auditors.
The first step in calculating infiltration heat loss is to determine the air exchange rate of the building. The air exchange rate is the number of times that the air inside a building is replaced with outdoor air in one hour. This rate is influenced by factors such as wind speed, temperature differences between indoor and outdoor environments, the height of the building, and the tightness of the building envelope.
Once the air exchange rate is determined, the next step is to calculate the heat loss associated with infiltration. The formula for calculating infiltration heat loss is:
Q = A * ΔT * U
Where:
Q = Infiltration heat loss (in watts)
A = Area of the building envelope (in square meters)
ΔT = Temperature difference between indoor and outdoor environments (in degrees Celsius)
U = Infiltration heat transfer coefficient (in watts per square meter per degree Celsius)
The infiltration heat transfer coefficient (U) is a measure of the rate at which heat is lost due to infiltration through the building envelope. This coefficient depends on the tightness of the building envelope and the outdoor temperature. A tighter building envelope will have a lower infiltration heat transfer coefficient, resulting in lower heat loss.
To calculate the area of the building envelope, measure the length and height of each exterior wall of the building and multiply the two dimensions together. Add the areas of windows and doors to get the total area of the building envelope.
The temperature difference (ΔT) between the indoor and outdoor environments can be determined by measuring the indoor and outdoor temperatures using a thermometer. The larger the temperature difference, the higher the infiltration heat loss.
As an example, let’s calculate the infiltration heat loss for a building with a total envelope area of 200 square meters, a temperature difference of 10 degrees Celsius, and an infiltration heat transfer coefficient of 0.05 watts per square meter per degree Celsius.
Q = 200 * 10 * 0.05
Q = 100 watts
This means that the building is losing 100 watts of heat due to infiltration. To put this into perspective, if the building is heated using electricity, this would result in higher energy bills. By improving the building envelope’s tightness, the infiltration heat loss can be reduced, leading to energy savings and increased comfort for occupants.
Infiltration heat loss calculations are especially important for buildings with high ceilings, large windows, and old or poorly maintained building envelopes. These buildings are more prone to infiltration and can result in significant heat loss if not addressed.
To reduce infiltration heat loss, building designers and energy auditors can implement several strategies. One common strategy is to seal cracks and gaps in the building envelope using caulk or weatherstripping. Additionally, installing insulation in walls, ceilings, and floors can help reduce heat loss through the building envelope. Finally, upgrading windows and doors to be more airtight can also help minimize infiltration heat loss.
In conclusion, infiltration heat loss calculation is a critical aspect of building energy efficiency that should not be overlooked. By understanding how to calculate infiltration heat loss and implementing strategies to reduce it, building designers and energy auditors can improve energy efficiency, reduce utility bills, and enhance occupant comfort. Understanding the impact of infiltration on building energy consumption is essential for creating more sustainable and efficient buildings. infiltration heat loss calculation.