Technical Updates

Posts Tagged ‘Liberty Building Forensics Group’

Best Practices for Design, Construction, and Commissioning

We are extremely excited to announce the release of ASHRAE’s new publication, Indoor Air Quality Guide – Best Practices for Design, Construction, and Commissioning. Our own Vice-President, George DuBose, was one of the contributing authors for this comprehensive guide, which you will definitely want for your reference library.

George DuBose – Contributor 

George DuBose’s experience in green building design, indoor air quality, and construction added a significant contribution along with many other experts whose combined efforts and combination of skills, knowledge, and talents are now available to you in this informative guide. 

Indoor Air Quality Guide

Written by experts in the field of indoor air quality (IAQ), the Indoor Air Quality Guide is the most comprehensive and practical resource ever developed on design and construction for enhanced IAQ.

For architects, engineers and building owners who want commercial and instructional buildings with high-quality indoor environments, this guide provides the strategies needed to achieve good IAQ using proven technologies and without significantly increasing costs.

Most building designs provide minimally acceptable indoor environments through compliance with requirements in building codes and standards. Enhancing IAQ can improve occupant health, comfort, and productivity while increasing building value and reducing risk for owners. As the industry moves toward high-performance green buildings, building professionals must become more knowledgeable about principles and methods for achieving enhanced IAQ.

This guide bridges the gap by focusing on the major IAQ issues: moisture management, ventilation, filtration and air cleaning, and source control. Equally important, it highlights how design and construction teams can work together to ensure that good IAQ strategies are incorporated from initial design through project completion.

The Indoor Air Quality Guide – Best Practices for Design, Construction, and Commissioning is a valuable resource which experts will be using as reference for years to come.  Make sure you have this guide available for your information and implementation as soon as possible.

Click here to order your copy of The Indoor Air Quality Guide.

Download summary here. Get more information about the guide here.

Obama’s new green requirements for federal buildings will likely catch on up in Canada in the near future, says a Canadian journalist in a recent article called “U.S. green wave is moving north”.

Ottawa-based Korky Koroluk advises fellow Canadians that those within their construction industry should be aware of an executive order signed by U.S. President Barack Obama last October “setting out numerous green requirements for the U.S. federal government and requiring various government agencies to meet a number of energy, water, and waste-reduction goals.”

Although for now, these requirements only apply to federal buildings, he argues that “government construction is a trend-setter” and that it is only a matter of time (once private sectors begin demanding what they see being successfully implemented at the federal sector) before the rest of the construction industry is impacted.

Some of the new ”green” requirements include:

• the need for a 26% improvement in water efficiency by 2020;
• a new emphasis placed on sustainability requirements;
• a net-zero-energy requirement for all federal building projects by 2030.

Koroluk asserts that “by encouraging the promotion of green public-private partnerships, the government is using a powerful lever on the way to sustainable buildings”… and says that “given the Canadian tendency to look southward for innovation, it seems likely that many of the things that are just beginning to happen in the U.S. will slowly find their way into Canadian practice.”

Click here to read the article in its entirety.

How a company makes the leap into “green” can either lead to great success and an increased presence in this environmentally conscious marketplace, or to additional problems and more liability.

We’d like to recommend an excellent article called How to Avoid Litigation Risks from Greening Your Products by Nexus, a project of the The Green Roundtable. (Article was originally printed in GreenBiz on May 5, 2010.)

The authors argue that “it is essential to understand what it means to green your product and consider the risks of going green up front in order to avoid ending up in the courtroom down the road.”  They explain the criteria by which one can determine that a product is green, and describe the legislative landscape for green product manufacturers.

Colorful green litigation could result from not probing and asking important questions ahead of time – questions like: Does marketing a product as green create a warranty? Can a manufacturer be liable for failure to warn or for providing a product claimed to provide certain benefits that does not live up to these representations? What if a manufacturer is selling its product for use in a green building and represents it will obtain a certain certification, but is unable to do so? These types of questions typically end up getting resolved in the courtroom.

Click here to read the article in its entirety.

HVAC systems can contribute to IAQ problems in at least three ways:

• Inadequate building pressurization and dehumidification
• Intrusion of high-moisture outside air
• Inside surfaces of equipment that promotes or permits microbial growth

The HVAC system complements the building envelope by properly conditioning the building’s interior, including the building envelope, and pressurizing the building with dehumidified air (called exfiltration). When negative building pressurization occurs in humid climates, multimillion-dollar moisture and mold problems can result from intrusion and condensation of moist outside air.

HVAC systems that positively pressurize a building space by supplying unconditioned or only partially conditioned outside air will avoid infiltration of outside air through the building envelope. However, this same situation can result in moisture loads inside the building that exceed the dehumidification capabilities of the HVAC system. One of the most significant causes of moisture accumulation in existing buildings in hot, humid climates is an overemphasis on ventilation at the expense of proper dehumidification.

AC equipment is typically more efficient in cooling air than in dehumidifying it. As a result, unconditioned outside air brought into a building is often cooled to the desired temperate before it is properly dehumidified, creating elevated RH levels and microbial growth inside the building. Furthermore, because AC equipment is typically controlled by temperature (thermostat) instead of by humidity (humidistat), the equipment never senses the elevated moisture level within the building space and therefore never fully removes it.

In any climate, the normal functioning of standard AC units can result in microbial growth. Just downstream of the cooling coils, the air is at or near 100 percent RH during the cooling season. The interior surfaces of the AC unit and ductwork immediately downstream of the cooling coils are often lined with insulation, generally for acoustical purposes. Dirt and fungal spores are often trapped in the lining. This environment is conducive to microbial growth and can lead to IAQ complaints because the conditioned air (and any microorganisms it carries) is distributed inside the building.

To be continued…

In hot, humid climates, one membrane can often act as the secondary weather barrier, air barrier, and vapor retarder. The most common of these membranes is “peel-and-stick” bituthene membrane (self-adhering composite membranes of rubberized asphalt bonded to polyethylene film) installed in masonry wall cavities or directly behind envelope finish materials, such as fiber-cement siding or stucco on lath.

In temperate climates, such condensation can easily occur in the winter, wetting the wall components. Even with low indoor RH levels, the wide temperature differential through the wall generally ensures that a first plane of condensation will be within the wall. Not only does condensation in such conditions cause mold growth, but the wetting of insulation reduces the wall’s thermal effectiveness.

Thus, the building envelope plays a vital role in minimizing uncontrolled moisture and air movement into a building and in preventing moisture entrapment within the wall. Although the building envelope contributes to moisture-related IAQ problems in hot, humid climates, infiltration of humid outside air and vapor diffusion through the envelope is not usually as great a factor in more temperate climates.

However, in temperate climates, the building envelope plays an important role in minimizing rainwater intrusion into the building, and in avoiding the subsequent mold growth that can result from such intrusion. In very cold climates, vapor diffusion or exfiltration of humid indoor air during colder months can also be a problem in wall cavities.

(To be continued…)

With the widespread use of mold-prone, porous sheathing materials (such as exterior gypsum sheathing), the selection of the waterproofing membrane in the drainage plane and its interface with the flashing requires more careful thought. Breaches in the waterproofing layer can easily result in wetting, degradation, and mold growth on the sheathing and other wall materials, including the interior drywall.

Failures of exterior insulation and finish systems (EIFS) installed in the 1980s and 1990s have been widely reported. The early uses of this European system in the United States often failed because they relied entirely on the primary weather barrier of the synthetic stucco. When this stucco failed, often where it joined other building components such as windows, water penetrating behind the insulation could not drain out. The porous sheathing materials (most likely gypsum or oriented strand board [OSB]) absorbed the water, degraded, and failed. Newer EIFS designs require drainage planes in the wall system, which reduce the likelihood of such water drainage problems.

To control air and moisture flow through the wall, any air barrier or vapor retarder must have the proper air resistance or moisture permeability and must be installed at the correct location within the walls. The presence of multiple vapor retarders within a wall system is a common problem, and many architects do not recognize that common construction materials act as effective barriers. For example, exterior grade plywood is a relatively low-permeability material that can function as a vapor retarder.

Condensation tends to occur where cool surfaces meet warm, moist air. If moisture-laden outside air is retarded before it meets the first cool surface inside the building envelope (often called the “first plane of condensation”), then few problems will result. If this moisture is allowed to further enter a wall system, it will condense. That is when moisture and microbial growth problems threaten. If the cool surfaces and moist air meet within the occupied space, then moisture problems can occur throughout the building, resulting in widespread mold odors and complaints from occupants.

To be continued…

Shortly after construction was completed, a seven-story, four-star hotel in Charleston, South Carolina, developed severe moisture and mold problems. The investigators attributed the problems to rainwater intrusion through the hotel’s exterior brick veneer. Following that diagnosis, the hotel owner spent more than $10 million on renovations, including a completely redesigned and reconstructed building envelope.

The summer after the renovations were completed, the moisture and mold problems returned. While focusing on the envelope leaks, the investigators had overlooked the significant secondary source of moisture: outside air infiltration.

In areas like South Carolina, where hot, humid conditions persist, IAQ problems are largely due to a combination of high ambient moisture, improper interaction between the building envelope and the HVAC system, and misapplication of design and operation principles.

1) High ambient moisture – Given the high ambient moisture levels in humid climates during the summer months and the dehumidification limitations of many AC systems, excessive moisture accumulation within buildings and the resulting microbial growth are understandably major problems. Microbial-related IAQ problems in buildings can also occur in temperate climates, although more serious errors in the design, construction, or operation of a building normally must occur for such problems to develop in these areas. Cold climates are just as susceptible to moisture problems as hot, humid climates, and building envelopes must be designed accordingly. Many microbial problems in temperate climates are more commonly a result of water intrusion (rainwater and subsurface water) through breaches in the building envelope system, including subsurface envelope systems.

In all climates, anything that elevates the indoor RH or results in damp materials (leaky pipes, for example) for an extended period can cause microbial IAQ problems. Landscape irrigation systems, indoor swimming pools, and building humidification systems can provide enough moisture to create microclimates and microbial growth problems, even in dry climates. Buildings in Boise, Idaho; Denver, Colorado; and Kona, Hawaii have all been hit with severe IAQ problems from microbial growth as a result of introduced moisture, despite the fact that they are considered arid climates.

To be continued…

Comparing the latent and sensible loads for several major cities in different geographic regions (Peart and Cook 1994) helps illustrate the new definition. A study was done showing the monthly average latent and sensible loads from outside air for Orlando, Florida; Atlanta, Georgia; and Columbus, Ohio. During the cooling season in Orlando, the latent load far exceeds the sensible load of outside air. The effect of these conditions, which occur for more than half a year, is that any outside air drawn into the building envelope or occupied space will likely cause moisture accumulation and microbial growth problems. Furthermore, because this outside air is used for ventilating the building’s occupied spaces, it presents a huge dehumidification challenge for the makeup air system. Clearly, under these conditions, Orlando is highly susceptible to moisture intrusion problems.

Atlanta was shown to be less susceptible to moisture intrusion problems than Orlando because, on average, the difference between sensible and latent load is small, particularly during the peak cooling months. Standard AC systems have a better chance of accounting for the latent load in Atlanta than in Orlando. Nevertheless, the latent load in Atlanta represents enough of a moisture accumulation risk that it belongs within the upper boundary of the humid zone. However, according to the ASHRAE-defined humid zone, Atlanta is outside the critical zone for humid conditions.

When looking at Columbus, the latent load from outside air is consistently less than the sensible load. The reversal of the load relationship explains why buildings in Columbus are not likely to develop moisture-related problems from outside air intrusion, because any outside air that infiltrates into buildings in Columbus will be adequately dehumidified before it is cooled.

The new definition also explains why, in certain areas of the country, building commissioning procedures are more critical than in others. For example, if the building exhaust systems are started before the AC and makeup air systems, as is typical, huge amounts of moisture may infiltrate the building, depending on the outdoor conditions.

In applying the new humid climate definition, however, two qualifications must be made:

• The definition is based on average climatological data. At certain times during the summer, the latent load of outside air can exceed the sensible load to a much greater extent than was reflected in the study. Such episodes of extreme high moisture entering the building can cause problems despite seemingly safe average conditions and must be considered in problem prevention.
• If the building envelope has an improperly located vapor retarder, moisture accumulation problems can occur, even if a favorable sensible/latent load relationship exists. Condensed moisture behind the vapor retarder will never reach the AC system for proper dehumidification but will accumulate in the wall system. Thus, architectural aspects of the building work in conjunction with outside conditions to create problems.

To be continued…

The inevitable is about to happen and most people don’t even know it is coming — green buildings are going to become, by codification, the law of the land. For some firms, this will just mean business as usual. For other firms, this change will be cataclysmic.

ASHRAE produces standards that are adopted by most model building codes, and the ASHRAE Draft Standard 189.1P is the new “Standard for the Design of High Performance Green Buildings Except Low-Rise Residential Buildings.”

This new ASHRAE Standard (currently in its final draft) is written in code language and will have the impact of mandating that all new buildings will be green buildings, thus eliminating the option of constructing anything less robust. Even if this standard is not adopted by all model codes, it will become the de facto standard of care. On the surface this sounds like a very good thing — mandating better-performing, more energy-efficient buildings – and it certainly has many redeeming aspects.

Here’s the downside:

• Lack of Experience Will Increase Design and Construction Deficiencies – Many of the optional aspects of the current USGBC LEED® guidelines will now be mandatory for designers and contractors. This means that, even if your designer or contractor doesn’t fully understand the key technical issues (e.g., envelope air barriers), they will still be required to use them. This practice of forcing designers and contractors to implement building features that they don’t fully understand creates a dilemma in the industry: either represent yourself as technically savvy, or face certain extinction. Given these as choices, building failures becomes more likely as firms design and construct buildings with components that they do not understand in an effort to keep the work coming in.

• Standard of Care Will Be Elevated – These new code requirements will automatically raise the required standard of care for the design and construction industry. This will increase the risk profile of their projects and may (at least initially) trigger some exclusion clauses in their current insurance policies. What are now considered “best practices” will soon be considered the minimum standard of care.  

• Regional Issues Not Addressed – The new standard mandates national green building requirements throughout the country with very little regard of the unique regions of the country where certain concepts may not be appropriate. This is almost always a problem when national standards are uniformly imposed on climates with unique requirements (e.g., hot and humid, very cold, or very rainy climates).

The inevitable result is that everyone will quickly morph into a green practitioner and the true marketplace differentiators (those with experience and unique technical expertise) will become difficult to discern. While codes can dictate that the industry follows certain standards, it cannot mandate that they get correctly implemented — with an increase in design and construction deficiencies and lawsuits being the inevitable result.   

Recognizing that this new standard (due to be issued in final form in 2010) could be a game-changer in the building marketplace, what’s the path forward?

• Review a copy of the current draft version of ASHRAE 189.1P and begin to understand the impact of the new requirements on your firm’s business, insurance, risk management, and technical expertise. (Note: This is available on line from www.ASHRAE.org)
•  Identify what requisite skills and knowledge your firm will need once this new standard is implemented.
• As this draft standard is finalized, expect more updates from Liberty Building Forensics Group with our analysis on its impact.