Experience Files

"I've lost the heat in a house I'm drying, and the dehumidifiers can't maintain temperatures over 70°, should I rent a heater?"  

Yes, absolutely. Supplemental heat is often essential to keep structural temperatures above 70°F, ensuring there's enough energy for efficient water evaporation from the wet materials. However, the choice of heating units is complex, with many factors and opinions to consider. Based on my 28+ years in the restoration business, here are some insights:

Indirect Fired Heaters (Oil or Propane): A Powerful First Choice

My first recommendation is an oil or propane indirect fired heater. These units can often significantly reduce, or even negate, the need for traditional dehumidifiers, especially during winter months. Cold outdoor air typically has very humidity (low grains per pound), and when combined with the heat associated with these units, the output can rival the drying power of a desiccant dehumidifier.

However, consider the following:

• Temperature Rise & Efficiency: You need to compensate for outside conditions. A 300,000 BTU/hr heater might only produce a 70°F temperature rise. If outdoor temperatures are near zero, such a unit won't effectively warm a cold or frozen structure.

• Security Concerns: These systems often require leaving a window or door open for ducting, which can create a security vulnerability.

Direct Fired Heaters: A Strict No-Go Indoors

Never use a direct fired heater system indoors or duct them into a house. Aside from the fact that combustion gases alone can be lethal to employees or unsuspecting homeowners, these units also introduce a significant amount of moisture related tot he combustion process into the air, counteracting your drying efforts.

Hydronic Heaters: A Restoration-Friendly Option

Hydronic heaters are an excellent fit for the restoration industry. They typically use a highly efficient outdoor boiler to heat a fluid, which then transfers heat to a series of fluid-to-air heat exchangers inside the structure. Since these indoor units recirculate internal air, they can rapidly raise indoor temperatures. While the hoses can be a minor nuisance, they're generally manageable, and the power requirements are usually no more demanding than a typical air mover.

Electric Restoration Heaters: Versatile and Effective

Electric restoration heaters, often around 20,000 BTU/hr, can effectively heat approximately 1000 sq ft (with 8' ceilings). Because these units continuously process indoor air, they can achieve impressive temperature rises. Many can operate off a dryer or range outlet, freeing up standard 110V outlets for fans and dehumidifiers.

You should avoid consumer-grade electric heaters at all costs. They typically lack the appropriate UL ratings for operation in a wet environment, posing significant safety risks.

Powering Up and Temperature Management

I recently discussed a project with insufficient electrical power (100 amp service, no 220V available). My suggestion was to rent a 20kW generator and two 20,000 BTU/hr electric heaters for supplemental heat, as opposed to a single 300,000 BTU indirect heater. The latter likely wouldn't heat the house effectively and might also overwhelm the available power for other drying equipment.

Finally, always be aware of critical temperature thresholds:

• Fire sprinkler heads can engage at temperatures around 155°F.

• Ceiling temperatures can be significantly higher than temperatures at the top of dehumidifiers or arm height when monitoring.

• Dehumidifiers typically begin to struggle with efficient water removal at temperatures over 90°F.

• Many building materials and appliances can start to fail at temperatures exceeding 100°F.

Understanding these heating options and their implications is vital for effective and safe structural drying.