Air Date: 6-26-2015|Episode 374
This week IAQ Radio welcomes back Lew Harriman of Mason-Grant Consulting in Portsmouth, NH. Lew will be presenting at Healthy Buildings 2015 on Investigating and Avoiding Moisture-related Problems in Existing Buildings….
This week IAQ Radio welcomes back Lew Harriman of Mason-Grant Consulting in Portsmouth, NH. Lew will be presenting at Healthy Buildings 2015 on Investigating and Avoiding Moisture-related Problems in Existing Buildings. He was a contributor to the new EPA Moisture Control Guidance for Building Design, Construction and Maintenance and his presentation will include information from this important industry document. Lew Harriman began his career as an architecture student at Dartmouth, but after five years as an Air Force officer, he went to work for a manufacturer of dehumidification systems, and got permanently diverted into HVAC engineering, where he has spent the last 38 years.
In 1990, Lew was the lead author and project manager for the landmark second edition of Munters’ Dehumidification Handbook. Lew is also an ASHRAE Fellow and International Distinguished Lecturer. For ASHRAE, he wrote, designed, illustrated and managed the projects to create the ASHRAE Humidity Control Design Guide, and also the ASHRAE Guide for Buildings in Hot & Humid Climates. He currently serves as Vice Chair of ASHRAE Technical Committee 1.12 (Moisture Management in Buildings), and also as Chair of the Document Revision Committee for the 2013 ASHRAE Position Document titled: Limiting Indoor Mold and Dampness in Buildings.
Most recently Lew co-authored Measured Home Performance -Guide to Best Practices for Home Energy Retrofits in California with Rick Chitwood. Measured Home Performance is all about what’s working when you measure, a topic we have featured recently on IAQ Radio. LEARN MORE this week with Lew Harriman on IAQ Radio!
Moisture Go To Guy
Lew Harriman was today’s guest on IAQradio. Lew is Director of Research & Consulting at Mason-Grant in Portsmouth, New Hampshire.
Nuggets mined from today’s episode:
- The US Department of Defense stores stockpiles of valuable military equipment all over the world and has big corrosion problems. One of the most corrosive environments is Kuwait. Lew is among the team tasked with the responsibility of conducting a worldwide survey on what is being done, what is working and what isn’t?
- Seasonally occupied buildings (schools, etc.) get moldy when shut down over the summer. A cause of mold proliferation is intermittent cooling and its effect on moisture content of buildings and furnishings when the indoor air has a high dew point. When the HVAC system is not operating, these buildings fill with random amounts of humid outdoor air. Intermitted chilling of walls leads to moisture absorption and mold growth. While it’s a huge waste of energy to run cooling consistently, it makes a lot of sense to have a small dehumidification system to keep things dry whenever the main cooling is not needed for temperature control (nights, weekends and vacations). Unfortunately, few have schools have the available funding needed for the systems.
Some helpful and affordable measures include: improving system maintenance, filter changes, determining the needed ventilation intake airflow and installing dampers that also indicate air flow, so the systems won’t bring in excessive and arbitrary amounts of humid outdoor air.
- The EPA’s “Moisture Control Guidance for Building Design, Construction and Maintenance” has been one of the agency’s most popular downloads.
- Lew habla español. Lew, fluent in Spanish, is a peer reviewer on the Spanish translation of the “Moisture Control Guidance for Building Design, Construction and Maintenance” due out later this year. Many Spanish speakers in the construction trades will surely find the document useful.
- He is working with Terry Brennan on an ELearning professional development credit course for ASHRAE. As moisture and humidity is the biggest cause for architect and engineer E&O litigation, the AIA is very interested in the course.
- He is chairing an ASHRAE multidisciplinary task group (MTG) on building dampness. The goal is to describe a quantitative and measurable definition of a damp building or damp space that is likely to increase health risks, and outlining a protocol by which building owners can determine is a building is dry enough to reduce the risks of negative health effects.
- Inspired by the fieldwork of Richard Chitwood (an engineer and HVAC contractor in Shasta, CA) Lew coauthored the “Measured Home Performance Guide to Best Practices for Home Energy and Retrofits in California”. To date, the most effective home energy savings have been achieved by investing in instruments and training the workers to use them while they are doing their work (as opposed to paying consultants and raters to audit that work, after it’s too late to make a difference in the result).
- At this point, the only legal definition of excessive moisture is what a persuasive attorney dreams up in a courtroom. We need reliable, inspectable and quantitative definitions of “excessive dampness.”
- Relative humidity doesn’t tell you when you are in trouble and dew point does. An upper dew point limit of 55° F in a mechanically-cooled building provides a margin for error; an allowance for some moisture absorption by surfaces without leading to mold growth.
- Relative humidity isn’t useful for calculations while dew point is.
- Restoration contractors learn and know about grain depression, engineers learn and know about cooling.
- Restoration contractors focus on dehumidification, engineers focus on cooling.
- When concerned about dehumidification, thinking cooling and “sensible heat ratio” of cooling coils is unproductive; akin to “rating lightbulbs by the darkness they don’t provide.”
- Controlling indoor humidity by drying ventilation air is at the heart of every book he has ever written, and it’s certainly not a new idea. Willis Carrier controlled humidity in his famous Sackett-Williams printing plant installation in 1914, at the dawn of modern air conditioning, by drying the building’s ventilation and makeup air.
- ASHRAE has a project for developing a guide to dedicated outdoor air systems. (DOAS) If you control the amount and reduce the dew point of incoming ventilation air, won’t have a problem building. If you don’t, you are at a much higher risk of problems.
Tips for investigating moisture problems:
- “A consultant is a man sent in after the battle to bayonet the wounded.”
- Consultants don’t have the luxury to monitor building behavior and performance over time; even though behavior of HVAC systems over time and behavior of the building envelope during rainstorms is crucial to understanding any indoor moisture problem.
- Measure dew points and surface temperatures in suspect areas.
- Measure and limit the amount of intake air.
- Dry all the ventilation air, any time that incoming outdoor air is above a 55°F dew point.
- Dew point of >65°F is a high risk for condensation, because HVAC dusts and pipes are frequently well-below that temperature.
- Brick veneer can be problematic construction when a vapor barrier behind it is absent. Brick absorbs moisture. When sun dries the brick the water vapor is forced into the cooler building. No easy or inexpensive fix. Solutions requires disassembling either the exterior or interior of the building and designing/reconstructing properly.
When, Global Watchdog Pete Consigli asked Lew (whom he credited with introducing thermal cameras to the disaster restoration) to opine on their use in restoration, Lew opined that the DR field more than any other industry has embraced the use of thermal cameras and that a $250 attachment for smart phones was available.
Water activity is biologically available moisture, as such Lew is optimistic about the work that Decagon is doing developing water activity meters and sensors.
Todays Music: Nobody Wants To Be Moist- 07, by Simon Helberg YouTube
Trivia: The term grains of water is commonly used in psychrometrics, how many grains are in 1 pound of moisture?
Answer: 7,000 grains
Z-Man signing off