MOLD
This presentation provides an overview of how to manage moisture and reduce microbial risk in multifamily housing along with the benefits of using supplemental dehumidifiers specifically designengineered for apartments or multifamily dwellings.

According to the American Society of
Heating, Refrigerating, and Air-
Conditioning Engineers (ASHRAE), when humidity and moisture are not effectively controlled, persistent dampness can lead to:
• material damage
• corrosion
• structural decay, and
• microbial growth, including mold.
Source: “Limiting Indoor Mold and Dampness in Buildings.” ASHRAE Position Document. Approved by ASHRAE Board of Directors,
June 27, 2012. https://www.ashrae.org/about-ashrae/position-documents (accessed July 2015)

In addition to mold growth and potential health risks, long-term moisture accumulation or episodic water damage has negative, measurable consequences for the structural integrity of a building and its materials.
Keeping a building dry enhances a building’s:
• value
• durability
• sustainability
• indoor air quality
• occupant comfort, and
• energy efficiency.

Mike is the vice-president of and partner in
Martin Riley Associates-Architects, P.C. He is a registered architect with 33 years of experience in private practice. Martin Riley
Associates is an 20 person strong
Architectural firm based in Decatur GA that is active throughout the Southeast in a variety of building types primarily focused on housing and in particular affordable housing. Mr. Riley received his Bachelor of Science in
Architecture from Georgia Institute of
Technology in 1981. After graduation, Mike relocated to New Jersey to work in the sustainable development field but quickly returned to GA to work with Alan Salzman and
Jackie Martin in what now is Martin Riley
Associates.

Brian Smith, owner of WB Properties &
Construction, has built thousands of multi-family units throughout the
Southeast. As a general contractor, owner of a water/mold restoration company – Back To Normal, with a degree from UNC- Greensboro in
Biology, Brian was uniquely qualified to tackle the issues of humidity and mold in apartments. While partnering with longtime NC apartment developer, Tom
Honeycutt, their collaboration and experience led them to create an AIA award winning solution for preventing high humidity and mold in apartments.

Understanding the basic principles of water vapor is critical for anyone who is responsible for:
• designing
• building
• operating or
• inhabiting buildings.

Air is a mixture of gases and water vapor.
• Specific humidity (SH): the ratio of water vapor content to the mixture of the air content for a specific mass . Considered a true measure of the volume of water in one pound of air (7000 grains of moisture will make 1 lb of water).
• Relative humidity (RH): most commonly used term to indicate the moisture level of the air compared to the maximum moisture-holding capacity of air at saturation . RH is expressed in percent. RH should be maintained below 60% to prevent microbial growth
• Dew point : the temperature at which an air mixture (if cooled) would reach 100% relative humidity (RH) or saturation .
• Dry bulb temperature (DBT): usually referred to as the air temperature. (Most air-conditioners can only account for DBT)

• Accurate load calculations have a direct impact on
– energy efficiency
– occupant comfort
– indoor air quality
– building durability
• Oversizing the HVAC system is detrimental to
– energy use,
– comfort
– indoor air quality
– building and equipment durability

Heating and cooling load calculations are dependent on
• building location
• indoor design conditions
• orientation
• building construction
Cooling loads are made up of sensible and latent heat gains.
The mechanisms of heat gain are conduction, infiltration, ventilation, and radiation. The components of the cooling load calculation are covered in depth in ACCA MJ8.
US DOE Strategy Guideline: Accurate Heating and Cooling Load Calculations Arlan Burdick IBACOS,
Inc. June 2011

As building envelopes become more energy efficient, air conditioning (AC) systems are commonly required to run fewer cycles —this is good, energy use goes down.
However, if there is no active cooling there is no active dehumidification. Examples:
• Small Apartments (smallest conventional split HVAC system = 1.5 tons cooling)
• Resident Doesn’t Use A/C

• An oversized HVAC system will have both a higher initial cost and a higher cost of operation. The frequent starting and stopping of short cycling can lead to premature failure of the equipment.
• Short cycling limits the total amount of air circulating through each room, and can lead to rooms that do not receive adequate duration of airflow.
• In the cooling season in humid climates, cold clammy conditions can occur due to reduced dehumidification caused by the short cycling of the equipment.
• The system must run long enough for the coil to reach the temperature for condensation to occur and an oversized system that short cycles may not run long enough to sufficiently condense moisture from the air.
• Excess humidity in the conditioned air delivered to a space may lead to mold growth within the house.

As apartments and multifamily housing become more energy efficient through tighter construction, sensible cooling loads are reduced and more importantly, the sensibleto-latent-load ratio becomes reversed.
Factors contributing to lower sensible cooling loads include:
• high performance windows
• northern and southern exposures
• shaded exterior surfaces/walls, and
• living spaces/apartments at or below grade
(basement units).

Relying on HVAC systems alone to properly dehumidify tightly constructed multifamily housing sometimes requires air conditioners to “over-cool” the space in order to remove sufficient levels of moisture. Over-cooling wastes energy and results in uncomfortable living conditions.

Moisture control plans during the construction of a building are somewhat limited.
Protecting a building from excessive moisture accumulation during its construction phase requires the monitoring of:
• site drainage
• foundation construction
• wall construction
• roof and ceiling assembly construction, and
• mechanical and plumbing system installation.

The daily indoor living habits of occupants contribute to moisture gain year-round. These include, but are not limited to:
• bathing
• respiration/sweating
• cooking (boiling water/liquids)
• plants
• aquariums
• cleaning.

Multifamily housing is a complex and dynamic system, and its occupants are an integral and constantly changing component of that system.

ASHRAE maintains a residential ventilation standard that sets minimum ventilation requirements for buildings three stories and less (see table to right).
• ASHRAE 62.2-2010,
Ventilation and Acceptable
Indoor Air Quality in Low-
Rise Residential Buildings

Are energy recovery ventilators
(ERVs) the best solution for moisture management in multifamily housing? The short answer is, “no.”
On humid days, an ERV will introduce much more moisture into a space than it removes. An
ERV is not a dehumidifier. An
ERV has a very high sensible heat transfer and very low latent
(moisture) transfer; often estimated at 20% to 30%.

Lessons from looking at weather data.
1. Actual latent load can easily be greater than a design estimate.
2. Latent load is independent of sensible load.
IMPORTANT: Moisture removal is dependent on AC run time.
Statistically, most summer air will contain more moisture than desirable inside dwellings and additional dehumidification will be needed.*
Source: *Welklin , Dan. “Moisture Science 101.” http://www.acca.org/wp-content/uploads/2014/01/Welklin-Class-notes-
Moisture-Science-101.pdf
(last accessed July 2015)

In climates when the exterior air has a higher moisture content than that of the interior air, and whereby the effect of dilution ventilation only increases the interior moisture content, supplemental dehumidification may be required since AC systems cannot remove the moisture load without over-cooling the space.
Supplemental dehumidification units work to:
• ensure appropriate moisture removal independent of HVAC operation
• enhance comfort design or eliminate the need to over-cool in order to dehumidify
• address excess moisture introduced through mechanical ventilation, and
• be more efficient than an HVAC system during shoulder seasons when air conditioning is not required, e.g., 70 °F and 70% RH days.
oisture removal, supplemental to the cooling system, where there is no need for cooling.”

Traditional dehumidification options for use by single-family homes, apartments, or multifamily housing include portable units or whole-house units.
Portable dehumidifiers are typically freestanding units with wheels so they can be relocated or repositioned easily. Since they are designed for use in smaller spaces or single rooms, they are available in varying sizes. Proper use and maintenance of these units requires the homeowner or tenant to relocate the unit as necessary and empty the reservoir when manual draining is required. Portable units are often noisy and many residents don’t like the “ugly box” sitting in the middle of their floor space

Whole-house units are inefficient for apartments or multifamily housing since they are typically engineered for larger spaces, e.g., a single family home > 2000 ft 2 .
They are more expensive than portable units, require installation by a licensed
HVAC technician, and operate in conjunction with an existing HVAC system requiring air-handler operation. To work properly, whole-house units require the tenant to understand and adjust the wall-mounted controls as required. While these units will adequately remove excess moisture from apartments, common complaints include excessive noise and heat displacement .

A standalone dehumidifier specifically design engineered for apartments or multifamily units:
• places apartment humidity control directly in the hands of landlords—a tamperproof cover prevents tenants from gaining access to the humidistat
• operates independently of the existing
HVAC system to quietly (47 dbA or less) and efficiently remove excess moisture
• may be hardwired into existing electrical and piped into plumbing
• automatic re-start after a power interruption
• energy efficient (average rated power consumption is 285 watts)
Energy Star rated

A standalone dehumidifier specifically design-engineered for multifamily housing:
• may be installed inside an interior wall between existing studs or surface mounted using the optional surface mounting box
• can be used for new construction
(to prevent problems) or retrofit applications (correct existing moisture issues)

In their publication “Florida Homeowner’s Manual for
Energy Efficiency,” the Florida Solar Energy Center at
Cape Canaveral reports that you can cut air conditioning costs by about 8 percent for each degree you raise your thermostat.
Source: Parker, Danny. “Florida Homeowner’s Manual for Energy Efficiency.” Florida Solar Energy
Center/University of Central Florida,
June 1992. http://www.fsec.ucf.edu/en/publications/pdf/FSEC-EN-20-92.pdf
(last accessed July 2015)
“Supplemental dehumidification, in and of itself, does not save energy. Rather, it is justified by enabling the energy savings from dramatically reduced sensible cooling loads in high-performance homes in hothumid climates.”
Armin Rudd, Building Science Corporation

Occupants commonly raise the cool setting on a thermostat as a result of the apparent temperature effect, whereby human comfort is usually attained at a higher sensible temperature with a lower moisture concentration.
For example,
• 72°F at 70% RH feels the same as…
• 74°F at 50% RH

The graph below shows how the indoor relative humidity (RH) decreased in a onebedroom apartment (approximately 650 ft2) located in South Florida after a supplemental dehumidifier designed for apartments was installed. The 1.5 ton air conditioner was short-cycling, operating for durations between four to nine minutes
• Manual outside air (outdoor RH range: 70%–95%)
• Existing indoor RH range: 67%–78% (prior to installation of dehumidifier)
• Indoor RH range after installation of dehumidifier unit: 52%–56%

The data in these two graphs demonstrates how a new, well-insulated, tightlyconstructed apartment could not maintain acceptable relative humidity (RH%) levels using only a 1.5 ton split-system air conditioner. However, an identical apartment using a supplemental dehumidifier had no problem maintaining appropriate comfort levels and indoor air quality while eliminating the possibility for mold to grow.
Apartment with a supplemental dehumidifier
• Very steady temperature curve at 76 °F to 77°F
• RH range: 45% –47% (well below the 60% threshold to be at risk for mold growth)
• RH% should remain below 60% to prevent microbial growth.
Apartment without supplemental dehumidifier
• Erratic temperature curve 74 °F to 78°F as the air conditioner struggles to maintain a constant sensible temperature with additional latent moisture load
• RH range: 67% –71% above the threshold for microbial risk

• ACGIH. Bioaerosols: Assessment and Control . Cincinnati: American Conference of Governmental and Industrial Hygienists,
1999.
• AIHA. Recognition, Evaluation and Control of Indoor Mold. Prezant, Weekes and Miller, Eds. Fairfax: American Industrial
Hygiene Association, 2008.
•
American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), www.ashrae.org
(accessed July 2015)
“Limiting Indoor Mold and Dampness in Buildings.” ASHRAE Position Document. Approved by ASHRAE Board of Directors, June
27, 2012. https://www.ashrae.org/about-ashrae/position-documents (accessed July 2015).
ASHRAE. ASHRAE/ANSI Standard 1602009, “Criteria for Moisture-Control Design Analysis in Buildings.” Atlanta: ASHRAE,
2009a.
ASHRAE. “The Nature, Significance, and Control of Solar Driven Moisture Diffusion in Wall Systems.” Research Project 1235.
Atlanta: ASHRAE, 2009b.
ASHRAE. “Chapter 44: Building Envelopes.”
ASHRAE Handbook
—HVAC Applications.
Atlanta: ASHRAE, 2011a.
ASHRAE. “Indoor Air Quality Guide: The Best Practices for Design, Construction and Commissioning.” Atlanta: ASHRAE, 2011b.
• ASTM. Performance and Durability of the Window-Wall Interface: STP 1484. Hardman, Wagus and Weston, Eds. West
Conshohocken, PA: ASTM International, 2006.
• ASTM. Moisture Control in Buildings: The Key Factor in Mold Prevention . 2 nd Edition . Treschel and Bomberg, Eds. West
Conshohocken, PA: ASTM International, 2009.
• ASTM. “Standard Guide for Assessment of Fungal Growth in Buildings (D7338-10).” West Conshohocken, PA: ASTM
International, 2010.
• CMHC. “Survey of Building Envelope Failures in the Coastal Climate of British Columbia.” Report by Morrison-Hershfeld. Ottawa,
Canada: Canadian Mortgage and Housing Corporation, 1996.

• Dastur, Cyrus, et al. “Closed Crawl Spaces: An Introduction to Design, Construction, and Performance.” Advanced
Energy. Report to the U.S. Department of Energy under Contract No. DEFC26-00NT40995. DOE, 2005. www.advancedenergy.org
(accessed July 2015)
• Harriman, L., G. Brundrett, and R. Kittler. Humidity Control Design Guide. Atlanta: ASHRAE, 2006.
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• IICRC. IICRC/ANSI S5202008, “Standard and Reference Guide for Professional Mold Remediation.” 2 nd Edition.
Vancouver, Canada: Institute of Inspection, Cleaning, and Restoration, 2008.
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• Parker, Danny. “Florida Homeowner’s Manual for Energy Efficiency.” Florida Solar Energy Center/University of Central
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(accessed July 2015)
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• Welklin , Dan. “Moisture Science 101.” ACCA Building Performance Forum, October 2014.

Ron D. Revia
Innovative Dehumidifier Systems
6260 Ocean Hwy West,
Ocean Isle Beach, NC 28469
(910) 579-3348 www.HumidityHappens.com