Monetizing Open Drying Systems


Professional restorers have been trained on a method of drying which can sometimes lead to faster drying times and reduced costs for customers and insurance companies. However, this method is rarely documented or used in the real world. Why? Because we don’t get paid for using outside air. We would like to suggest there are ways to get paid for the knowledge of drying science which would allow the use of outside air.

This tool in the restorer’s toolbox is to use some outside air to assist drying. Open drying is a “system [which] introduces outdoor air without mechanical dehumidification” and combination drying is “use of outdoor air while dehumidification systems are deployed when conditions are appropriate.” See section 12.5 of the IICRC S500 standard for full definitions. In order to consider an open or combination drying system, the humidity ratio (GPP) must be lower outside than inside.  Additional considerations include changing weather conditions, building security, acceptability to the property owner, and access to the outside. A skilled restorer can use the outside air to dry structures more efficiently.

This is an airmover set to make negative pressure during winter. A common concern of using negative pressures to assist drying in winter is that the structure may become too cold. A solution is to power the airmover with a plug-in thermostat. Set the thermostat to whatever temperature you would like to maintain, the airmover will turn off if the affected area reaches your set point. When this picture was taken, the affected area was 73 gpp, while the outside air was 29 gpp. The airmover set on low was processing 500 cubic feet per minute, running approximately 50% of the time. Based on these numbers, over 150 pints of water would be removed daily, more than most LGRs.

Why doesn’t the restoration industry use open or combination drying systems more frequently?

  • There is no financial incentive for the restorer to use an open or combination system.  
  • We fail to measure and document the outside psychrometric conditions, so we don’t know if the conditions are conducive to drying.
  • Restorers default to installing mechanical dehumidification.
  • We make emotional decisions; it’s cold outside or it’s raining, without applying the psychrometric and science to the decision.

The billing model for water damage restoration involves a daily rental rate for equipment.  This system, even with the best intentions of the restoration contractor, is viewed with skepticism by both the customer and the insurance company.  The contractor in control of the job is not only responsible for the results; a clean, dry, safe structure, but also the bill.  Sometimes the bill is inflated by the contractor by poor job management or just pure greed. More often the insurance company and customer think the contractor is padding the bill with extra days or excess equipment on a legitimate scope of work, when in reality, the charges are accurate.  The IICRC S500 has gone to extraordinary lengths to quantify equipment with the air mover calculations, and the simple and detailed dehumidifier calculations.

With the current billing system, a competent restoration contractor using open or combination systems, when the conditions are right, is penalized for excellent performance and results when using the outside air.  Not using mechanical dehumidification is a financial disincentive. 

If we bring value to the job by using the outside air, we should be able to charge for it.  At the very least we should get credit for the ‘free’ contribution to the drying process.  We have come up with two systems to consider monetizing (get paid) for the use of open or combination systems.  We have excluded calculations for open drying systems using portable heat as the costs associated with renting portable furnaces fairly compensate the contractor.

Option 1:

Determine the open/combination system grain depression, then use the following formula for estimating the pints removed in a 24-hour period.

Grain Depression × Cubic Feet per Minute of the system ÷ 71 = Pints Per Day (PPD)

Divide the PPD by the 24-hour rental rate of your dehumidifier to establish a value (cost) per pint of water removal for that specific job.

To establish the value of the open portion of combination system, calculate grain depression between the inside and out. Determine the CFM of the open system (i.e. bath room exhaust fan 130 CFM). Use the formula above to estimate the pints removed per day.  Multiply the PPD X the dehumidifier’s values established above for the cost/value of the open portion of the combo system.  

Using the same calculation, you can establish a value for a wide-open system (without heat) or a burping or flushing system.  

Option 2:

This is a radical, but potential solution: replace the entire current method of charging for dehumidification. Instead of charging for numbers of            dehumidifiers by the day, simply charge for the cubic footage that is being dehumidified, regardless of how it is being dehumidified. Charges would be based on class of loss, more for class 3 and 4, less for class 1. 

To document that proper dehumidification was achieved, restorers would document the affected area temperature and humidity, and progress on wet materials. The IICRC S500 (section 12.5) discusses this as the reason for documenting dehumidification: “The primary indicators related to dehumidifier performance are the ongoing control of the drying environment and a resultant reduction of material moisture level.”

The general idea for monetizing an open system was proposed by an insurance adjuster in an ASD class once he realized the true value of an open drying system.  Suggesting that if the restorer could establish a value for the open system, some compensation should be given.  Of course, he suggested we discount the open system to establish a better value for the insurance company paying for something that is a bit intangible (results vs equipment).  At the very least, by providing the calculation you will get some good will and a negotiating tool for the balance of the bill.  

For a free copy of a formatted excel spread sheet with the above calculations, email:

If we focus on doing what is best for the customer, while still maintaining our margins, we will all benefit in the long run.  Do the right thing for the right reason at the right time and the money will follow.  Focusing on renting equipment to run the ticket is short term and short-term profits are just that, short and not sustainable. Long term success depends on providing value to customers who use our services again and again.

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David Oakes & Kevin Fisher

David Oakes, David has worked in the field of cleaning and restoration since 1973. He owned and operated a full-service cleaning and restoration firm for 42 years which provided fire and water damage restoration services. David has worked on both commercial and residential restorative drying jobs in all capacities. He also does consulting for both insurance companies and restoration contractors. David is admitted as an expert witness in State and Federal Court. David is an IICRC Certified Triple Master, IICRC Approved Instructor WRT, ASD, CCT, OCT, FSRT & TCST.

Kevin Fisher, Kevin has worked in the field of cleaning and restoration since 1999. He has worked and consulted on projects around the world while instructing WRT and ASD courses with the Restoration Sciences Academy. He is an IICRC Triple Master and Water Loss Specialist. He volunteers his time as the Restoration Division Chair of the IICRC.

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