Lew Harriman – Fellow ASHRAE – Damp Buildings, Human Health and HVAC Design

Air Date: 8-7-2020|Episode 595

This week we welcome Lew Harriman for a discussion about the new ASHRAE document “Damp Buildings, Human Health and HVAC Design”. The new document is intended to provide clear guidance for consultants, building owners/managers and others on measuring and managing moisture in buildings.

Lew Harriman was a contributor to the EPA guidance for Moisture Control in Buildings, the EPA’s Guidance for Air Cleaners and most recently the ASHRAE Special Publication titled: Damp Buildings, Human Health and HVAC Design. After college and a 5-yr stint in the US Air Force, Lew worked for a manufacturer of industrial dehumidification systems for 10 years, before beginning a second, 32-year career as a humidity control and building forensic consultant. He operated his one-person firm under the name Mason-Grant until 2018, when he retired from active consulting and took the tongue-in-cheek title of “Emeritus Director of Research” because he says likes the sound of it. Still, he seems unable to off-load his attachment to ASHRAE volunteer work, since he continues to serve as a humidity and filtration consultant to ASHRAE’s COVID-19 Epidemic Task Force.

This episode follows up our series we call the Moisture Mob Episodes. Check them all out at the links below.
Moisture Mob Episodes
Z-Man’g Blog:

Damp Buildings, Human Health and HVAC Design, Lew Harriman

During his show introduction, Radio Joe announced the dates for RIA’s 2020 Virtual Conference. October 6-7. The conference theme is “FRAGMENTED Industry, No More! For more information and to register https://2020.restorationindustry.org/

Lew Harriman retired after a 44-year career in HVAC and building science.After 5 years in the Air Force, he worked for 10 years for a manufacturer of industrial dehumidification equipment. After that, he began 34 years as an independent consultant for humidity control IAQ and building forensic investigation.

These days he spends his time:

  • Rehabbing of his woodworking shop (spoiling his grandchildren!!)
  • Providing occasional informal advice on building moisture and Humidity problems.
  • Volunteers as a consultant to the ASHRAE COVID-19 task force
  • Annual webinars for ASHRAE – Humidity control
  • Intermittent volunteer advisor to ASHRAE standards committees as they discuss implementation of new 60F dew point limit in cost-effective ways

Nuggets mined from today’s episode:

ASHRAE is not a typical organization. ASHRAE is all volunteer. Volunteers pay to: become members of the association, pay to attend conferences and then donate their time to update the 4-volume ASHRAE Handbook and updating ASHRAE Standards. According to Lew, it’s both fun and very rewarding to talk to association colleagues about problems, solutions and to reach consensus on best practices.

The US government does not fund ASHRAE.

In 2019 the ASHRAE website received 810K hits, Due to ASHRAE’s collection and organization of COVID19 info, the website received 550M hits during the first 4 months of 2020.

Damp Buildings Report

What it is, and what it is not?

  • The ASHRAE board of directors decided that the organization’s position statement on dampness called for better, more focused information, and a better definition of what level of moisture causes problems.
  • Established a multidisciplinary task group: Building owners, HVAC engineers, forensic investigators, public health officials, government epidemiologists.
  • Result of three years of collaboration and investigation: ASHRAE Special Publication published March 2020 titled “Damp Buildings, Human Health and HVAC Design.”
  • Clear understanding and discussion of the issues, with comprehensive bibliography, simple early warning measurements and suggestions for avoiding dampness problems (But it is not a Standard and is not written in code language)


  • Damp buildings do increase health risks, as documented by comprehensive investigation of peer-reviewed public health investigations (each referenced in the report).
  • Buildings in general are rather fault-tolerant of occasional water damage or high humidity. That’s a good thing because all are very likely to have moisture problems over their lifetime
  • Designers and owners can easily avoid problems through design and operation
  • The health-relevant problems begin to emerge when dampness is accepted as “normal for THIS building or “normal in THIS climate zone”.
  • Building dampness is NOT normal and should never be accepted as such by designers or owners.

Report’s advice

  • Understand that “persistent” dampness is the problem (not occasional water damage or intermittent high RH)
  • Persistent = The condition has become typical – it extends for days or weeks at a time rather than infrequent excursions of a few hours per week above the suggested early warning thresholds of “abnormal” conditions
  • Abnormal = conditions that may occur with some regularity, BUT, are NOT normally the basis of design for durable buildings and energy-efficient HVAC systems.
  • Early warning symptoms – Abnormal conditions suggestive of potential future problems
  • Persistent high equilibrium moisture content of materials (aW over 0.75)… AT THE SURFACE
  • Persistent Wood Moisture Equivalent above 15% in gypsum board or ceiling tile
  • Persistent high moisture content of concrete or masonry that must be in contact with moisture-sensitive materials (e.g.; paper-faced gypsum board, engineered wood products or water-based coatings.
  • Equilibrium Relative Humidity above 90% (ASTM test)
  • Capacitance (AKA impedance) measurement 3% and above (as measured by the popular Tramex meter, or a correspondingly high reading on a different meter)
  • Persistent high indoor dew point (above 60°F)

Getting the report? – PDF is free from ASHRAE for public benefit (printed version ±$30.00 at ASHRAE bookstore)

  • What has been the result of the report, if any?
  • Major change to 2019 revision of ASHRAE Std 62.1 – Ventilation Design (for commercial/institutional buildings)
  • Maximum 60F Dew Point Tempat ALL times, including unoccupied hours
  • Basically requires a Dehumidifier unit or component that keeps indoor humidity under control regardless of temperature set point or cooling load.

Does this apply to all buildings now?

  • ASHRAE standards represent the best advice available from ASHRAE rather than a legal (building code) requirement
  • Standard 62.1 is intended and worded in code language to support building codes: new buildings and major HVAC rehab.
  • Not all jurisdictions require compliance with ASHRAE standards


  • The new Standard 62.1 dew point maximum is IDEAL for owners and managers who want to specify HVAC that avoids persistent dampness and associated risks
  • Very easy to specify: “The HVAC design shall comply with provisions of ASHRAE 62.1-2019, section 5.10 so that the system is capable of maintaining a maximum indoor dew point of 60°F at all times, including unoccupied hours, whenever the outdoor dew point is above 60°F”
  • Since 75F, 50% RH is a 55F Dew Point, designing for max 60F DPT is (or should be) very easy and very cost-effective.
  • With dedicated Dehumidification component, there is no need to run AC when building is UN-occupied. Huge energy saving over current practice.

Personal observations (Lew makes it clear he does not speak for ASHRAE) COVID19 indoors: It’s reasonably clear that with COVID19 and people indoors:

  • wear masks indoors when in groups
  • restrict size and duration of indoor groups and meetings
  • AFTER those measures, consider HVAC improvements:

it’s a good idea to dilute the concentration of possible viruses indoors, using as much ventilation air or open windows as the HVAC system can handle without losing control of temp and humidity.

  • improve central system HVAC filtration to MERV 13 minimum
  • Add portable HEPA air cleaners to workstations, offices and conference rooms where people must gather
  • add upper air disinfection using wall-mountedUVC lamp fixtures and slow air circulation fans.

Lew’s comments on bi-polar ionization?:

  • Using bi-polar ionization to “get rid of viruses” has not been proven to work any faster than normal attenuation in the supposedly conclusive lab chamber testing that Lew has reviewed. In his view, using bi-polar ionization to save energy by increasing filtration effectiveness as a substitute for outdoor air ventilation isn’t a reliable solution. The technology sounds sexy, but has little or no documented effectiveness in the real world of buildings and free-flowing HVAC systems rather than in closed environmental chambers. Lew has not seen any credible documentation to suggest it reduces COVID-19 problem compared to the measures he described above.

Pete Consigli’s comments:

  • Pete loves Lew’s new bio and title:” Emeritus Director of Research”
  • Mickey Lee is a fellow woodworker
  • Mike McGuinness does school IEQ work in New Jersey and finds that schools never seem to adjust for the high humidity of summer, carpets are cleaned during summer which adds moisture and when HVAC is shut down to save energy triggers mold bloom.
  • During the winter, his grandmother put a metal Maxwell House Coffee can with water on the radiator to add moisture.

Z-man signing off


Name the 2 ASHRAE documents that provide key guidance on the ventilation requirements for healthcare facilities?


ASHRAE Standard 170-2017 alongside HVAC Design Manual for Hospitals and Clinics.