Make Up Air Heating Gas Consumption Calculator

This calculator helps you estimate the gas consumption required to heat make-up air in HVAC systems. Understanding this calculation is crucial for energy efficiency and cost management in commercial and industrial buildings.

Introduction

Make-up air is the air supplied to a building to replace air that has been exhausted. In HVAC systems, this air often needs to be heated before being distributed. The gas consumption for heating make-up air depends on several factors including the volume of air, temperature difference, and the efficiency of the heating system.

Accurate estimation of make-up air heating gas consumption is essential for:

Energy cost budgeting
HVAC system sizing
Compliance with energy efficiency standards
Environmental impact assessment

How to Use This Calculator

To use this calculator, you'll need to know or estimate the following parameters:

Volume of make-up air (in cubic feet per hour)
Temperature difference between supply air and outside air (in degrees Fahrenheit)
Heating system efficiency (as a percentage)
Gas heating value (in BTU per cubic foot)

Enter these values into the calculator and click "Calculate" to get your results.

Formula

The gas consumption for heating make-up air can be calculated using the following formula:

Formula

Gas Consumption (cubic feet per hour) = (Volume of make-up air × Temperature difference × 0.68 × 1.08) / (Heating system efficiency × Gas heating value)

Where:

0.68 is the specific heat of air in BTU per cubic foot per degree Fahrenheit
1.08 is the conversion factor from BTU to cubic feet of natural gas

Worked Example

Let's calculate the gas consumption for a system with the following parameters:

Volume of make-up air: 10,000 CFH (cubic feet per hour)
Temperature difference: 40°F
Heating system efficiency: 85%
Gas heating value: 1,030 BTU per cubic foot

Using the formula:

Calculation

Gas Consumption = (10,000 × 40 × 0.68 × 1.08) / (0.85 × 1,030)

= (10,000 × 40 × 0.7344) / 877.1

= 293,760 / 877.1

= 335.7 cubic feet per hour

This means the system would consume approximately 335.7 cubic feet of natural gas per hour to heat the make-up air.

Interpreting Results

The calculator provides the gas consumption in cubic feet per hour. To understand the practical implications:

Convert to other units if needed (e.g., cubic meters per hour)
Compare with energy efficiency standards for your region
Consider the cost implications based on local gas prices
Evaluate the environmental impact of gas consumption

Note

These calculations provide estimates. Actual consumption may vary based on system conditions, maintenance, and other factors not accounted for in this simplified model.

FAQ

What factors affect make-up air heating gas consumption?: The primary factors are the volume of make-up air, the temperature difference, heating system efficiency, and the heating value of the gas used.
How accurate are the calculations from this calculator?: This calculator provides estimates based on standard formulas. For precise calculations, consult with HVAC professionals or use detailed system simulations.
Can I use this calculator for residential heating systems?: While the calculator can be used for any heating system, it's particularly designed for commercial and industrial HVAC systems with make-up air requirements.
What units should I use for the inputs?: Use cubic feet per hour for air volume, degrees Fahrenheit for temperature difference, percentage for efficiency, and BTU per cubic foot for gas heating value.
How can I reduce make-up air heating gas consumption?: Improving heating system efficiency, optimizing temperature settings, and implementing energy recovery systems can help reduce gas consumption.