DA07 Criteria for Moisture Control Design Analysis in Buildings
DA07 Criteria for Moisture Control Design Analysis in Buildings is a new Design Application (DA) manual in AIRAH’s collection of technical resources.
|
How can this DA manual help?
The purpose of this guide is to specify performance-based design criteria for predicting, mitigating, or reducing moisture damage to the building envelope, materials, components, systems, and furnishings, depending on climate, construction type, and HVAC system operation. These criteria include the following:
-
Criteria for selecting analytic procedures
- Criteria for inputs
- Criteria for evaluation and use of outputs
|
Released in August 2020, DA07 covers:
- Criteria for design parameters
- Moisture performance evaluation criteria
- Building reporting
- And more.
DA07 is designed for:
As the definitive guide for moisture control in Australia, this manual is designed for engineers, architects and contractors, as well as equipment owners, operators and specifiers.
|
DA07 release schedule
- August 3 – Digital release
- August 7 – Hard copy release
- August 27 – AIRAH Webinar Streamline (click here to watch the recording)
Pricing
| |
Digital access |
Hard copy
|
AIRAH Members
|
FREE |
$79 |
Non-members
|
N/A |
$229 |
GST included
Access the digital version | Order a hard copy
For more information about downloading DA Manuals on Adobe Digital Editions, please click here.
About DA07
This AIRAH technical guide is adapted from ASHRAE 160, which is an American voluntary consensus standard developed under the auspices of ASHRAE.
Although the majority of new buildings are safe, comfortable, and designed to provide effective protection against moisture-related problems, there are a certain number of buildings built each year that do experience moisture or mould problems. Whether this number is now increasing and whether the increase is due to the greater emphasis on energy-efficiency measures today is a widely debated topic. The purpose of this guide is not to answer either of these questions but rather to provide guidance on how to best design buildings with adequate moisture control features.
This guide formulates design assumptions for moisture design analysis and criteria for acceptable performance. Ideally, a design analysis involves the determination of the probability of failure and treats all design parameters and loads as stochastic variables. However, sufficient data is often not available to make a full statistical treatment practical. Instead, where only limited data exist, a moisture design protocol must be based on a combination of statistical data and professional judgment.
Another judgment involves the choice of an acceptable probability of the occurrence of damage. Although it is common to impose very stringent criteria for structural design because of safety concerns, moisture damage usually occurs over a long period of time and usually has less catastrophic, although sometimes costly, consequences. An international consensus has emerged that the analysis should be predicated on loads that will not be exceeded 90 per cent of the time.
This guide adopts this approach. In a moisture analysis for building envelope design, the choice of indoor environmental conditions is extremely important, especially for buildings in cold climates. This guide opts for a design indoor climate definition that is based on engineering principles, is independent of construction, and reflects the influence of ventilation and air conditioning equipment and controls that may or may not be part of the building design. In buildings where indoor humidity and temperature are explicitly controlled, the building envelope performance should be evaluated with the intended indoor design conditions.
In residential buildings, indoor humidity is rarely explicitly controlled, so default design assumptions are needed for these buildings. In general, the methodology outlined in this guide encourages designers to use their own design parameter values if they are known and part of the design. If they are unknown or not included in the design, the methodology outlined in this guide provides default values for those loads and parameters. This guide does not address design details that deal with rainwater intrusion, plumbing leaks, ground water, and water damage caused by natural disasters such as floods and cyclones.
Although proper design for these issues is extremely important, and damage from such events involves a large percentage of moisture damage in buildings, they can be more effectively addressed by codes, training of the trades, and specific design guidelines (see Annex B, “Commentary”).
This guide assumes that appropriate measures were taken to limit bulk water entry into the building and building envelope. It does not intend to replace the judgment of the design professional. Rather, it provides a framework for the design professional to identify and consider factors that are important to the durability and serviceability of the building. In addition, many items in this guide are based on incomplete information and are, therefore, partially based on the best professional judgment of the development committee at the time of writing.
The development of this guide has pointed to many unanswered questions – questions that hopefully will be addressed and answered by research in the near future. Since the original ASHRAE 160 parent document was published in 2009, ASHRAE Standard 160 has incorporated several addenda focused on:
-
Simplifying the conditions necessary to minimise mould growth by eliminating two criteria
- Limiting indoor relative humidity to 70 per cent or less in the design analysis and revising the residential design moisture generation rates
- Simplifying the calculation procedure for wind-driven rain without significantly impacting the accuracy of results
- Updating references, and
- Replacing the simplified mould growth criterion with a mould index that predicts risk, which is more consistent with assembly performance observed in the field.
This guide formulated by a modified AIRAH Adoption of revised ASHRAE standard 160 reflects the current state of knowledge about mould growth while providing less stringent criterion.
