April 2016

The Beauty Of Building Science

Frank Fuller and Pat Grotlisch

You know that airflow and moisture can wreak havoc on your buildings, but do you know how and why? A little knowledge of building science can prevent these issues in future projects as well as diagnose and correct them in renovations.

The drafty structures of yesteryear were created with more hygric buffer capacity — the ability of airflow to move through, soaking up moisture that travels on the air and then releasing it over time. By contrast, we tightly seal today’s buildings to prevent heat loss. That prevents any wet materials from drying as quickly and leads to problems, like mold and mildew, that can wreak havoc.

To help, building scientists have identified the control layers that should make up a wall (and ultimately a building envelope) to manage the flow of moisture, air and heat. In descending order of what to address and manage first, they are:

  • Rain control layer – to keep water out of the building;
  • Air control layer – to seal air leaks and keep humidity out of the wall systems; and
  • Vapor control layer – to control diffusion and prevent or allow vapor diffusion through materials, depending on the situation. Together, these first three components make up the weather-resistant barrier (WRB).
  • Thermal control layer – to manage insulation and air sealing, thus reducing the space-conditioning load by preventing heat loss (in cold climates) and heat gain (in hot climates).

Continuity between all the layers, along with the building structure, is key. For example, there are transitions, such as between a wall and a slab or roof. They require transition components like flashing or sealants to address the enclosure assembly so the layers work together cohesively, like a well-oiled machine. If something is missing from one layer of the assembly, it will push the problem onto the next layer, resulting in a domino effect gone awry.

Air and moisture flow (moving from warm to cold, moist to dry, and areas of higher pressure to lower pressure) as well as condensation and dew point (moist air carried into a wall cavity by air leakage will condense on the first hard surface it encounters that is colder than its dew point) will greatly affect the projects you are designing and building. If you strategize your control layers, you can prevent any problems from arising. You can do this by selecting and placing the right insulation to manage the temperature in the stud cavity; designing and placing a proper vapor retarder to manage the amount of water vapor migrating into the wall; and creating an optimal WRB layer.

Yes, you can do it all, and we can help you. We can provide more than enough excellent ammo to help you fight the good fight and build a better — or rather, the best — wall and assembly. Keep these products in your arsenal, and you are well on your way to building an ideal continuous building envelope:

Gold Bond® brand eXP® Interior Extreme® Gypsum Panels
Gold Bond® brand eXP® Sheathing
Gold Bond® brand eXP® Shaftliner
DEXcell® brand Glass Mat Roof Board
DEXcell® brand FA Glass Mat Roof Board
DEXcell® brand Cement Roof Board

Building science is a complex subject, and we want to help ensure that you are checking all the right boxes and your building envelopes are meeting all the appropriate standards. Call us today, and we can talk with you more about this. As always, we are here to help you design and build better.

"For years the EPA has focused attention on improving the quality of the exterior environment. However, individuals spend approximately 70 percent of their time indoors. LEED recognized the importance of the quality of indoor air to the productivity and health of building occupants by including it as one of the major categories. Through awareness of building science, we know that air transfers between the exterior and interior of buildings creating opportunities for problems with mold and moisture. National Gypsum’s fiberglass-faced gypsum board is GREENGUARD certified and contributes to good indoor environmental quality by protecting against mold, moisture and exposure for wall and roof applications."
- Pat Grotlisch

"It is quite evident from the ICC and the 2015 IBC that owners, architects, general contractors and manufacturers need to be thinking in terms of systems to achieve the standards outlined. Here is the IBC mission statement: The IBC provides minimum standards to ensure the public safety, health and welfare insofar as they are affected by building construction and to secure safety for life and property from all hazards incident to the occupancy of buildings, structures or premises. In regards to the building envelope itself, we are talking about the roof to foundation as a continuous system that addresses thermal requirements, air infiltration resistance and moisture management. Addressing transitions, intersections and material compatibility with all the proper parts and pieces creates a continuous system that improves energy performance and provides savings. So roofing products, rigid insulation, air barriers, sheathing and flashing products should work together to build a continuous system. For the past several years, owners, architects and general contractors have been hiring consultants to ensure that the building envelope meets these standards. RCI and the Building Enclosure Council (BEC) are just two associations that are making sure that roof and envelope consultants are up to speed on 2015 IBC and ASTM standards that confirm compliance. LEED v4 even refers to building commissioning (the whole building blower door test) as an option to
achieve points."
- Frank Fuller

Product Overview

DEXcell® Works Well For All Your Roofing Systems

Our high-performance DEXcell® Roof Boards resist mold and provide a fire barrier for commercial structures.

DEXcell® brand Glass Mat Roof Board is ideally suited for mechanically fastened roof systems, while DEXcell® brand FA Glass Mat Roof Board is designed for fully adhered roof systems. These glass mat roof boards both feature coated fiberglass facers and an enhanced gypsum core, making them mold-resistant. Made of Portland cement, lightweight aggregate and glass mesh, DEXcell® brand Cement Roof Board is lightweight and moisture- and mold-resistant; it provides a hard,
durable surface.

Project Profile

World-Class Casino Resort In National Harbor

MGM Casino National Harbor
Under construction and committed to build to LEED Gold Standard

Slated to open later this year, this destination gaming resort is located in National Harbor, a waterfront development just south of Washington, D.C. The 1-million-square-foot, $925 million MGM National Harbor Resort will include a 300-room luxury hotel, an expansive casino, a 1,200-seat theater, high-end retail, and 35,000 square feet of meeting space and specialty restaurants. Among the quality products used to construct it: 2.8 million square feet of Gold Bond® brand XP® Fire-Shield® Gypsum Board; 500,000 square feet of Gold Bond® brand eXP® Sheathing; and 250,000 square feet of Gold Bond® brand eXP® Shaftliner.

Read More About The Project

Continuing Education

When April showers happen, buckle down and complete some CEUs. This month, we recommend:

Advantages of Using Cover Boards in Low-Slope Roofing Assemblies
High-Performance Gypsum: Protect against Mold, Moisture and Exposure


How To Handle Fire Safety

Watch how we put our products to the fire test (for ASTM E119).

Watch Video


Amy Hockett
National Marketing Manager, Architectural Services & Sustainability

Pat Grotlisch

Frank Fuller

Alan Zeedyk
Gulf / Southeast

Thad Goodman
Central / Midwest

Scott Hughes
Northeast / Atlantic

Trang Schwartz
Architectural Specialist