Tags: Jan Luistermans

17 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: GUIDELINES FOR DELIVERING EFFECTIVE AIR BARRIER SYSTEMS-INTRODUCTION

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INTRODUCTION

Inadequate control of airflow through the building envelope is often a primary factor contributing to premature building envelope failures. If moisture-laden air is permitted to travel through the building envelope, the moisture may, under certain environmental conditions, condense within the walls of the structure. In above-freezing conditions, this may cause corrosion or rotting of the structural components, staining of the interior and/or exterior facade, and may stimulate the growth of mold and mildew. In cold climates, accumulated moisture may experience numerous freeze-thaw cycles, which can precipitate spalling and the formation of icicles on the exterior facade.

Air leakage is also a concern in areas where interior temperatures differ greatly from exterior temperatures, such as the Prairie Provinces, which can experience periods of extreme cold during the winter and extreme heat during the summer. The excessive heating and cooling loads placed upon buildings in this type of climate leads not only to an increase in space conditioning costs to the owner, but also has a negative impact upon the environment through increased energy consumption and the emission of greenhouse gases. In fact, studies conducted on high-rise residential and commercial buildings in cold climates have shown that anywhere from 20 to 50 percent of heat loss can be attributed to air leakage.

In Canada, building rehabilitation for roofing and wall system repairs and replacement cost an estimated $7.5 billion annually. A conservative estimate of the premature failure rate is 3 to 5 percent, or $225 to $375 million per year, with premature failure defined as any performance condition requiring repair or replacement of the system before the benchmark date. The building envelope has been identified as being particularly vulnerable to durability problems.
It is the growing global awareness of these air leakage-related problems that is driving the federal governments in Canada and the United States to introduce more stringent codes and regulations to govern building air permeance. In order to improve occupant health and safety, revisions were made to the National Building Code of Canada (NBCC) in 1995 designed to reduce air leakage in buildings, including those buildings classified within Part 3 of the Code1. Public Works Canada also recently revised their National Master Specification to include air barrier inspection and testing. In the United States, Persily’s Envelope Design Guidelines for Federal Office Buildings: Thermal Integrity and Airtightness (1993) also documents the requirements as outlined in the NBCC. In addition, State Energy Codes are being adopted and/or revised, making air barriers a mandatory requirement in new construction and retrofits. ASHRAE/IENSA Energy Standard for Buildings Except Low-Rise Residential Buildings (90.1-1999) also governs building envelope sealing.
Recently, air barrier trade associations have formed in Canada and the United States with the objective to improve the quality of air barrier system installations by providing education and training for the workforce. For an installer to become ‘certified’ through the association, an applicant must possess the required knowledge of air barrier material and system theory, and demonstrate sufficient skills in practical applications. In addition, through the associations’ quality assurance programs, documented self-testing and on-site third party audits are performed to verify the quality of the installation, and confirm the certified installers’ ability to build to expected standards.

While there are numerous ASTM (American Society for Testing and Materials) methods, says Jan Luistermans, for testing air barrier systems and/or components, there is no generic regimen for the application of these techniques being utilized on a widespread basis. The need for a complete design, inspection and testing protocol for air barrier systems cannot be understated. A recent study concluded that even routine testing can have a significant impact upon the airtightness of a building. Where air leakage testing was conducted, there was an overall reduction in air leakage for the system, a significant decrease in heating and cooling loads, a reduction in greenhouse gas emissions, and an increase in the life cycle of the building envelope.
With the growing use of inaccessible air barrier systems (such as bituminous membranes), on-site inspection and testing during installation is necessary to identify problems before the system is covered with finishing materials. The cost to repair an air barrier system after it has been covered can be conservatively estimated to be 50-60 times the cost of a correct first-time installation. Hence, the need for inspection and testing is obvious.

5 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: IDP — How is IDP Different? — Collaborative, Holistic or systemic thinking, Whole-building budget setting…

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Collaborative

One of the principal differences of the process is that the architect is not simply the form-giver, but an active participant in exploring alternative ideas within a broader team of experts who play active roles earlier in the process. In particular, there is joint problem-solving and joint decision-making rather than team members simply taking their assignments away to work on and bringing them back to be re-integrated. It has been proposed by some that IDP could be equally called integrated decision-making.

Holistic or systemic thinking

The old Zen saying that everything is connected to everything else is never truer than when designing for sustainability. The goal is to optimize the building’s performance by considering all of the building components and subsystems together and their interactions, to achieve synergies. When this is done right, you get something where the whole is greater than the sum of the parts, and it may even be cheaper. The example at the end of this section illustrates a common way this is achieved.

Whole-building budget setting

As design professionals, we are pretty good at knowing what our piece of the design “should” cost. We carry these rules of thumb around but they are usually not based on whole building optimization. They also tend to be the basis for valueengineering individual components.
This is not the best way to get the least cost building overall. As Amory Lovins has pointed out, “Optimizing components in isolation tends to pessimize the whole system—and hence the bottom line”.
A green building design based on holistic thinking will not likely cost more overall, but the costs may be distributed differently than costs based on a traditional design approach. Costs get transferred from some components to others. Budgeting must be done in a way that allows the movement of money to where it does the most good when a holistic solution is found. This flexibility should also extend to the determination of the professional’s fee structure, which will be discussed later.

Iterative

The traditional phases of the building design process, pre-design, schematic design and development, don’t disappear in IDP. What does change however is how the work gets done in each phase and how team moves from one phase to the next.
The IEA Task 23 guideline document describes these intermediate workflows as “iterative loops,”. The team repeatedly reviews and refines ideas to resolve problems at whatever scale is appropriate, at each phase of design. A key aspect is to allow new information to inform or refine previous decisions.
It is also important to follow through on the iterations in the IDP process by explicitly identifying subsequent IDP tasks and group meetings, interwoven with the overall project schedule. If this is not done upfront, it is too easy for the design team to revert to familiar, business-as-usual, linear design processes after the excitement and energy of the initial kickoff charrette begins to wane. An explicit IDP process schedule is a key tool to managing the IDP process. Reviewed by Jan Luistermans.

5 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: IDP — How is IDP Different? — Goal-driven

Author: admin

The big-picture goal is incorporating sustainability into the project, but it is necessary to set explicit subsidiary goals, objectives and targets as a means of breaking the goal into manageable pieces.
These are best framed in performance; not prescriptive, terms and will then form the basis for strategies to achieve them. These goals are set with the entire project team involved and must include the client. The idea is to get commitment, not compliance, from everyone involved. People support what they help create. The first goal is a review of the project brief against the list of client needs. Is this the best location from an environmental point of view? Is a new building actually required or would a major renovation be more appropriate?
Remember, because you started this process really early on, you get to ask these questions. In some cases, the best answer for your client might not result in a new building project this time, but the added value to your client by doing the right thing enhances the relationship, your reputation and will likely result in repeat business. From there the team moves on to specific environmental goals. These can be derived from rating system categories, but they should include fixed targets for:

Reduced site impacts;
Reduced off-site impacts, such as stormwater runoff, greenhouse gases or other emissions;
Reduced energy and water consumption;
Improved indoor environmental quality and thermal comfort, contributing to human health;
Increased construction waste diversion and recycling, material reuse and recycled content;
Improved durability, longevity and maintainability.

IDP, because of its inclusionary nature, is also a useful way to develop goals for social values, although there is little consensus in the building industry generally on how to deal with social issues at a project level, unless they are an explicit part of the program.
These goals and targets need to be clearly articulated, written down and kept front and centre as the design progresses. They serve as reference points as the detailed design develops or if conflict arises between goals. Reviewed by Jan Luistermans.

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