Strike a Winning Balance
Building a truly sustainable building requires the deft touch of a racecar crew chief. To ensure his vehicle is competitive, the chief oversees a variety of disparate but integrated efforts-finely-tuning the engine, tinkering with the suspension, maximizing tire wear, analyzing track conditions and applying aerodynamic principles to determine the final set-up. And to cross the finish line, these and countless other key factors-like the skill of the driver-must strike the proper balance.
So, too, the creation of a winning structure, one that blends moisture management, energy efficiency, indoor air quality and countless other factors to result in a champagne cork-popping building.
But ours has typically been an industry of independents (designers, builders, manufacturers) that are experts in their own field but not necessarily accustomed to working as a team to achieve the most sustainable building possible. How do we guarantee in this demanding era of environmental acronyms-with LEED in the lead-that we work with pit-crew precision throughout the design and construction process?
Clearly, we must continue to build our buildings and homes to be increasingly more energy efficient. This requires superior moisture management, durability, and indoor air quality strategies to make certain that buildings perform well into the future. But in doing so, the challenges are many-and they must be addressed in order to orchestrate a balance when designing, constructing and maintaining sustainable buildings.
Let’s consider a common but rarely considered moisture management conundrum: can you actually over-protect your building?
Tight SpotsWith improvements in construction practices, building envelopes have become “tight,” meaning builders are doing a much better job of preventing moisture and air from infiltrating a building. But what happens when it does, say through a leaky window, an improper flashing detail, or a misplaced vapor retarder? The same system that works to prevent moisture from accumulating in the wall can serve to keep moisture from getting out, thus actually increasing the likelihood of moisture- and mold-related damage.
Conversely, the misconception that buildings should “breathe” can mean there is little control over the infiltration of air and moisture being brought into the building. If this happens in a well-insulated wall (chances are we won’t ever see less-insulated walls), moisture can accumulate. Does anyone really want to live in the drafty, leaky log cabins of our ancestors? Although they certainly were able to dry out quickly after a storm and didn’t grow mold, they were not very comfortable.
Properly installed and secured vapor retarders and air barriers are currently the tools used in reducing the likelihood that moisture can enter a wall assembly. But several factors should be addressed before choosing what grade and where to install vapor retarders, including the climate zone and the building’s use and tenants.
Of course, the reputation-enhancing rewards for getting it done right can be substantial. Even though moisture control is referenced either directly or indirectly in Energy Efficiency, Resource and Materials, and Indoor Environmental Quality sections in virtually every green building code, standard and program, there are many ways to make mistakes that actually make things worse
The point is-there are multiple paths and trade-offs to ensure moisture control is addressed. It is important to look at the climate zone, the building orientation and landscaping, the architecture-and shape of the roof and building, the windows and doors, the day lighting, the HVAC system and how it is sized, and the material choices that have been made before making a final determination.
Finding the right path that strikes a balance for that particular structure and its long-term performance means that you-and your building-will land in Victory Lane.
Q&A On Energy Efficiency1. Is striking the perfect balance with regard to increased energy efficiency, durability, improved indoor air quality and overall moisture management in a building envelope truly possible? Does it change as the weather or seasons change?
While achieving this coveted balance is challenging, many tools and training are now in the market place to make doing so much easier. Building and remodeling for increased energy efficiency is not going away - in fact, it will be required like never before. To achieve the balance goal, builders will need to address the whole building, including the HVAC and ventilation systems, to optimize performance for moisture management, durability, and indoor air quality.
It is a well-known fact that buildings that can effectively dry out will outperform buildings that don’t. Wet buildings will deteriorate faster and can contribute to other moisture related problems like mold. Air-tight, energy efficient buildings also need outdoor air ventilation to help ensure good indoor air quality. This is one of the challenges of striking the perfect balance … to be able to bring in outdoor air, treat it for temperature and humidity while lowering the building’s energy consumption, the latter due to the advanced building enclosure and HVAC strategies in place.
Naturally, there are seasonal and weather considerations as outdoor temperature swings and high humidity levels will always challenge the “perfect balance.” At any locale, moisture entering the building through either ventilation or the building enclosure must be addressed.
2. Is there a hierarchy of importance? Does the hierarchy change depending on the region of the country?
The main objective of green building codes and programs is to increase the energy efficiency of new homes and buildings. But for buildings to be comfortable, long-lasting, and healthy, they need also have supporting moisture management, durability, and indoor air quality strategies to support the energy efficiency strategies. This system ideal is universal; how it is done will differ by climate zone to address the unique circumstances in each.
3. Are any of the components more overlooked or underappreciated than others?
High-performance wallboard is often overlooked and underappreciated. Wallboard is typically valued only for its recycled content and regional materials contribution, but not for its capacity to work in conjunction with the other components in the wall assembly for optimum performance in the balance we previously discussed. High-performance wallboard should be appreciated for how it deals with job-site moisture and long term moisture impacts over the life of the building.
For example, with energy efficient wall assemblies, a lot goes into achieving a high R value and an air tight building enclosure. But what if water gets into the wall for whatever reason? That wall will be incredibly slow to dry. A high-performance wallboard designed to resist water has the ability to stay wet longer, without deteriorating or growing mold as the wall dries out. These products don’t fix moisture problems, but they can help keep a moisture or water problem from becoming something more detrimental.
4. Is one of the components over-rated?
There is not too much emphasis put on any one component, but there may be some misunderstanding. One example involves window and opaque wall ratios and how they can impact the real R value of a wall assembly. An exterior wall with a lot of windows will have a different energy efficient performance level compared to a well insulated wall without windows.
5. Is it possible for a contractor or even an architect to strike the perfect balance?
It’s becoming easier for contractors and design professionals as there are now a lot of energy and moisture management modeling tools and training opportunities available that allow for simple product and systems planning. In addition, there is vast knowledge on the topic of achieving the most balanced and efficient building envelope now; much of it in response to mistakes made in the past! The DOE’s EERE Web site (www.eere.energy.gov) and the EPA’s EnergyStar Web site (www.energystar.gov) are good places to get started.
6. How does a building owner or architect know that the envelope specialist is qualified? Are there credentials required?
The qualifications-and needs-depend on the level of the building project. For example, in a high-rise building, the entity that would be best qualified to know how to achieve a perfect balance within the structure would be someone aligned to the engineering and building commissioning field, the building’s HVAC system and can work with others members of the design team. A good example would be engineering experts like Morrison Hershfield, an engineering and management firm that has offices across the country. If you are building a single-family, residential home, you can get that knowledge from local green building experts like the EarthCraft Home program based here in Atlanta which works with both builders and homeowners.
Credentials may not be required, but it is good to look for an experienced and trained company or individual, and ask about their certification and background in the areas important to the project team.