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Building Symptoms and What Tenants Will Typically Do to Tolerate the Problem
This post by Don Snell is the third in a series of four examining the relation of moisture building assessments
and building science as a component to design, construction, and commissioning.
The tenant, in an attempt to achieve more comfortable space conditions, will typically lower the thermostat set-point, causing these spaces to cool further while the relative humidity remains high.
This increases conditions conducive to condensation and mold on cold surfaces in the space. The mold then gives off odors known as volatile organic compounds (VOCs), which cause the tenant to mask the damp odors with disinfectant.
At this point, the tenant recognizes that it is too damp in the space and attempts to clean the mold and also installs desiccants to help minimize the dampness. The symptoms continue until the tenant has had enough or the problem gets too big to control.
To be continued…
Click here to read our previous post on this topic.
Author Donald B. Snell, PE (Georgia, Virginia, and Pennsylvania), Certified Mechanical Contractor (Florida), and Senior Mechanical Consultant with Liberty Building Forensics Group, has provided moisture and IAQ-related forensic building investigations on more than 200 buildings. For more information, contact Donald B. Snell at d.snell@libertybuilding.com.
Understanding Where the Air Comes From, Where It Goes, and How It Impacts the Living Space
Figure 1
This post by Don Snell is the second in a series of four examining the relation of moisture building assessments and building science as a component to design, construction, and commissioning.
Air will take the path of least resistance. Infiltration and air leakage across the mechanical closet and air handling unit represent a path of least resistance.
This type of infiltration:
(1) depressurizes the mechanical closet,
(2) reduces the amount of return air from the living space, and
(3) results in a positively pressurized living space (as seen in Figure 1).
Normally, positively pressurized spaces are a best practice condition, but in this case, the air handling unit cooling coil is not sized for this amount of infiltration and becomes inadequate in dehumidifying the supply air being distributed.
This condition results in an elevation of relative humidity, which translates to the contact of warm, humid air with cold surfaces in the air handling unit. These are benchmarks conducive to elevated condensation.
To be continued…
Click here to read our previous post on this topic.
Author Donald B. Snell, PE (Georgia, Virginia, and Pennsylvania), Certified Mechanical Contractor (Florida), and Senior Mechanical Consultant with Liberty Building Forensics Group, has provided moisture and IAQ-related forensic building investigations on more than 200 buildings. For more information, contact Donald B. Snell at d.snell@libertybuilding.com.
Moisture Building Assessments: A Retrospective Look at Building Design and Operation
Figure 1
This post by Don Snell is the first in a series of four examining the relation of moisture building assessments and building science as a component to design, construction, and commissioning.
Many of the decisions made during the building design process can either create or lead to problematic situations with airflow – even when approved building codes are followed.
One such example can be seen when mechanical closets for air-handling units (AHUs) have outdoor accessibility. (See Figure 1.)
The AHUs located in these closets are intended to circulate air conditioning or heating to the living spaces which they serve. It’s assumed that the air will automatically circulate and go where it is intended.
This doesn’t always happen, however, because problematic building designs often don’t account for excessive air leakage; infiltration; and consequential moisture, mold, and odor problems.
Here are several important factors about airflow to consider:
- Excessive air leakage can occur when wall materials, assemblies, and whole wall systems do not meet the leakage rates in accordance with the American Society of Testing and Materials (ASTM).
- Excessive air leakage can also occur at air handling unit casings.
- Infiltration can be caused by unconditioned airflow due to wind pressure and mechanical effects.
- Warm, humid climate conditions tend to exacerbate the consequences of moisture problems within a space.
Imbalanced airflows, excessive air leakage, and infiltration are examples of air not going where it is intended. Although designs such as outdoor-accessible mechanical closets have benefits such as maximizing space and functionality, they lack best practices for moisture control. The consequences of moisture and mold problems are even greater when these mechanical room closets are designed as return air plenums. (See Figure 1.)
To be continued…
Author Donald B. Snell, PE (Georgia, Virginia, and Pennsylvania), Certified Mechanical Contractor (Florida), and Senior Mechanical Consultant with Liberty Building Forensics Group, has provided moisture and IAQ-related forensic building investigations on more than 200 buildings. For more information, contact Donald B. Snell at d.snell@libertybuilding.com.
Hidden Risks of Green Buildings
TIPS Fidelity & Surety Law Committee Members, This is a reminder to register for our upcoming live audio webinar taking place next Thursday, December 8, 2011 from 1:00 pm – 2:30 pm Eastern. Entitled Keys to Managing Green Construction Risks, Liability and Litigation,
Read more ...WPL Publishing Co., Inc., publisher of Construction Claims Advisor and Construction Advisor Today, announces a valuable new interactive webinar: The Hidden Risks of Green Building Wednesday, October 26, 2011 1:00 – 2:30 PM EDT Presented by: James K. Bidgood, Jr., Smith Currie & Hancock, LLP George H. DuBose Liberty Building Forensics Group FOR IMMEDIATE RELEASE [...]
Posted on June 2, 2011 by Chris Cheatham Ever since I read the D.C. Green Building Act and its “performance bond” requirement, I have been morbidly interested in the idea of LEED bonds. When Kristen Bradley, at SuretyBonds.com, offered to write an article on the topic, I couldn’t help but say yes. SuretyBonds.com, a nationwide surety bond [...]
Read more ...Codification
Someone recently asked me why I was baffled about the Department of Defense’s decision to use both LEED and a green building code. Here are two reasons:
1. The policy is a waste of taxpayer money.
2. The policy unnecessari…
Codification controversy abounds! The author of a blog recently published by Building Design + Construction points out the fact that there is a “bru-ha-ha” brewing among the newly formed AHPBC (American High-Performance Buildings Coalition) and the USGBC. The AHPBC says that LEED does not meet ANSI-type “consensus” standards. They are right. Adding to the challenge [...]
Check out Chris Cheatham’s latest blog post on LEED: It is not looking pretty for federal green building policy. Earlier in the year, I speculated that Congress might target green building certification as an unnecessary cost. Well, it happened. From the ASHRAE Government Affairs Update: House Passes National Defense… View the whole story: http://www.greenbuildinglawupdate.com/2011/07/articles/codes-and-regulations/federal/defense-department-leed-funding-to-be-eliminated/index.html
