Picture this: you’ve been tagged to design the building envelope for the next national institution. Maybe it’s an addition to the Smithsonian, or a presidential library. In any case, you are building for posterity, and this thing has got to last. What do you do?
The challenges are great for building envelopes, which must keep the water, air, vapor, and heat of the surroundings from affecting the interior space. But despite all the possible combinations of climate to be found in North America, there is one basic design that works from sea to shining sea.
Water, air, and vapor are harder to quantify than heat which is why the code spends less time discussing them. But if your wall fails to control them, all the insulation in the world won’t help.
Sometimes called the “perfect wall,” this design puts all the control layers (for temperature, moisture, air, and water vapor) on the outside of the wall, thereby protecting the structure. The only variable for this design is the thickness of the exterior continuous insulation.
Designing a resilient building envelope can seem intimidating, especially with all the building and energy code requirements. And while there is no getting around the complexity of the interactions between a building’s interior, its walls, and the surrounding environment, things make more sense when you take the time to look at the fundamental physics at work.
The hardest part of building a resilient wall is managing moisture. If water gets inside the wall, all sorts of problems arise, including mold, rust, and structural degradation, depending on the materials used.
Many owners, architects, engineers and builders can be confused by the complicated and interrelated science involved in the important layers protecting the building from temperature changes, not to mention the complex factors that affect insulation performance.
Continuous insulation (ci) and cavity insulation products are both sold with R-value ratings, but the way these two products are used in wall construction means they do not have the same effectiveness.
Four state legislatures recently took action on measures that would have a significantly negative impact on the adoption of progressive energy code provisions.
The following is a summary of code change proposals to the 2018 International Building Code (IBC) which have been submitted by various foam plastic insulation associations, including the FSC, XPSA, PIMA, and CPI.
At the recent 2018 RESNET Building Performance Conference, Jay Crandell (ARES Consulting) and Amy Schmidt (Dow Building and Construction) gave a presentation titled “Stranger Things – The Energy Code Myths that Haunt Us”.
The Applied Building Technology Group has developed a new tool to aid and simplify the design of code compliant steel stud walls.
In the January 2018 issue of RCI’s Interface technical journal, Applied Building Technology Group’s Tim Ahrenholz provides in-depth analysis on how to design the “perfect wall” in cold climates.
Moisture vapor transmission and water resistive barriers are complicated topics. Below is a classic sketch of what can happen when sound science is not applied with respect to building construction and code compliance.
A misguided reliance on “breathing” or drying potential as the primary means to make a building’s wall work, without proper consideration of variations in conditions of use, can lead to the problem of wetting potential being too high when conditions of use change.