AC and Heating
When temperatures drop on a jobsite, warehouse, industrial facility, or event tent, reliable heat becomes essential for productivity and safety. At Climate Control Solutions, we help contractors and facility managers size and select the right temporary heater for their application. Whether you’re using portable heaters or large indirect-fired systems from Flagro, proper sizing ensures consistent temperatures, lower fuel costs, and safer operation.
Accurate heater sizing depends on three core factors:
- BTU requirements
- Make-up air
- Insulation quality
Understanding these elements will help you choose the right heating solution for any temporary structure.
Why Proper Heater Sizing Matters
An undersized heater runs nonstop and still struggles to reach temperature. An oversized heater cycles inefficiently, wastes fuel, and heats unevenly.
Correct sizing ensures:
- Consistent heat across the space
- Lower fuel consumption
- Reduced moisture and condensation
- Safe operation in enclosed environments
Whether you’re heating a warehouse or an event tent, proper sizing is the foundation of an effective heating plan.
1. Understanding BTU Requirements
A BTU (British Thermal Unit) measures heat output per hour. To size a heater correctly, you need:
- Space dimensions (length × width × height)
- Required temperature rise
- The level of insulation
Basic Sizing Formula:
BTUs per hour = Cubic feet × Temperature rise × Insulation factor
Example:
40′ × 30′ × 12′ = 14,400 cubic ft
Temperature rise needed = 35°F
Insulation factor = 1.2 (poor insulation)
14,400 × 35 × 1.2 = 604,800 BTUs/hr required
In this scenario, you would select a heater—or a combination of heaters—capable of producing around 600,000 BTU/hr.
Climate Control Solutions offers multiple units in this range, including:
- Flagro FVO-400RC (390,000 BTU)
👉 https://climatecontrolsolutions.com/product/flagro-fvo-400rc/ - Full Indirect-Fired Heater Collection
👉 https://climatecontrolsolutions.com/indirect-fired-heaters-2/
2. The Role of Make-Up Air
Make-up air replaces air that escapes or is exhausted from the space. If warm air leaves the structure, cold air enters—and your heater must work harder.
Common causes of air loss include:
- Open doors
- High foot traffic
- Ventilation fans
- Dust control systems
- Leaky tent seams or temporary walls
Spaces with high air turnover often require larger heaters or multiple Flagro units to compensate for heat loss.
3. Insulation and Heat Retention
Insulation plays a major role in heater selection.
Well-Insulated Spaces
- Retain heat effectively
- Require fewer BTUs
Partially Insulated Structures
- Require additional heating capacity
- Heat loss varies with construction quality
Tents & Temporary Enclosures
- Lose heat rapidly
- Often require 1.5× to 2× the BTUs of permanent buildings
- Wind exposure increases heat loss
For tents and temporary structures, we commonly recommend high-output indirect-fired heaters such as:
- Flagro FVO-400RC Indirect Fired Heater (390,000 BTU)
👉 https://climatecontrolsolutions.com/product/flagro-fvo-400rc/
Choosing the Right Heater Type
Portable Heaters
Ideal for:
- Jobsite trailers
- Small enclosures
- Offices or break rooms
Indirect-Fired Air Heaters
Best for:
- Warehouses
- Construction sites
- Industrial buildings
- Large tents
These heaters deliver clean, ductable heat and are built for high airflow.
Climate Control Solutions carries the full line of commercial indirect-fired heaters, including:
- Flagro FVO-400RC (390,000 BTU)
- Flagro FVO-200RC (185,000 BTU)
- Flagro FVNP-200RC / FVNP-400RC
- Flagro THC-175DF / THC-355CDF Direct Fired
Full category link:
👉 https://climatecontrolsolutions.com/indirect-fired-heaters-2/
Common Sizing Mistakes to Avoid
- Ignoring ceiling height
- Underestimating air leaks
- Not factoring in make-up air
- Assuming BTU ratings tell the full performance story
- Relying on one large heater instead of zoning the heat
Practical Tips for Accurate Sizing
- Measure space volume—length × width × height
- Evaluate insulation honestly
- Consider door frequency and ventilation
- Oversize slightly when unsure
- Use multiple heaters for divided or irregular spaces
Final Thoughts
Temporary heater sizing is about more than selecting a unit with a high BTU rating. It’s about understanding the environment, insulation levels, airflow, and how heat escapes the structure.
At Climate Control Solutions, we supply the full line of Flagro commercial heaters, including indirect-fired heaters ideal for construction sites, industrial warehouses, restoration projects, and temporary structures.
