1. What is a Heat Loss Calculator (Stelrad)?

Definition: This calculator estimates the heat loss of a building element using the Stelrad method, which considers U-values, surface areas, temperature differences, and ventilation losses.

Purpose: It helps heating engineers and building professionals determine the heating requirements for a space.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total heat loss (Watts)
• \( U \) — U-value of the building element (W/m²K)
• \( A \) — Area of the element (m²)
• \( \Delta T \) — Temperature difference between inside and outside (Kelvin)
• \( \text{ventilation} \) — Additional ventilation heat loss (Watts)

Explanation: The calculator sums the conductive heat losses through building elements and adds any ventilation losses.

3. Importance of Heat Loss Calculation

Details: Accurate heat loss calculations ensure proper sizing of heating systems, energy efficiency, and occupant comfort.

4. Using the Calculator

Tips: Enter the U-value, surface area, temperature difference, and any ventilation losses. All values must be ≥ 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical U-value for walls?
A: Modern insulated walls typically have U-values between 0.15-0.30 W/m²K, while older walls may be 1.0-1.5 W/m²K.

Q2: How do I determine ΔT?
A: Subtract the outside design temperature from your desired indoor temperature (e.g., 20°C inside - (-5°C outside) = 25K.

Q3: What's included in ventilation losses?
A: This accounts for heat lost through air changes in the space. It can be calculated separately using air change rates.

Q4: Should I calculate each building element separately?
A: For accurate results, calculate walls, windows, roof, and floor separately then sum the results.

Q5: How does this relate to radiator sizing?
A: The total heat loss (Q) indicates the radiator output required to maintain the desired temperature.