Other programs that also address the make-up of materials and products include the well-known GREENGUARD program, with different levels of certification for different applications, such as for schools (i.e., indoor environments for children) or other settings. The Living Futures Institute has also developed the “Declare” program as part of the Living Building Challenge. This program allows manufacturers to reveal what is in their products and to specifically address whether or not they contain any harmful elements or compounds identified on the Declare “Red List” of things to avoid.

Photo courtesy of Georgia-Pacific Building Products

The Texas Children’s Hospital in Houston, Texas, specified building products resistant to mold and moisture, challenges never welcome in a healthcare environment.

MOISTURE CONTROL

Attention to the choice of materials and the design standards for healthcare facilities is important. But, there is another significant point: ensuring that those materials, systems, and people won’t be adversely impacted by moisture. Water and moisture-related issues in buildings are often among the most cited risks and problems that are encountered during the operation of a facility. For example, the Chubb Insurance Group cites the top five sources of interior water damage loss in buildings as roofs (15%), toilets (15%), sprinklers (14%), water heaters (11%), and HVAC (8%). They also note other sources such as vacancies, boilers/machinery, sewer backups, water storage tanks, and water mains (https://www.chubb.com/us-en/businesses/resources/10-most-common-sources-of-commercial-water-damage.html). The good news is that a lot of those potential problems can be addressed through the proper design, specification, and construction of different parts of the building, such as roofs, walls, and interiors.

One approach to tackle water and moisture issues head-on is to develop a moisture control strategy that incorporates the “four D’s” of design.

Deflect: The first, most fundamental approach, is to deflect water away from sensitive areas in the building construction. This includes rainwater, water from snow melt, water from internal operations, excess water from HVAC systems, or any other source of water. By first deflecting it away, the potential for problems is greatly reduced.

Drain: Water will always follow gravity to flow downhill and drain to a lower point. This is the basis for most building plumbing and roof drainage systems. Areas that are prone to have water present should have adequate drainage properly built in. In addition, exterior wall assemblies need to be designed so that they can drain away any water that penetrates, rather than allowing it to build up and sit inside the assembly. Rainscreen systems are being used to accomplish this purpose.

Dry: It is reasonable to expect that most building construction assemblies will find water or moisture inside of them at some point. The issues often arise only if that water is not able to dry or evaporate so that it no longer poses a threat to the integrity of the assembly or other nearby construction. Therefore, allowing for assemblies to “breathe” to remove any moisture can be very important. Strategies for achieving this will vary depending on the building, type, location, and risk of level.

Durability: A backstop approach to supplement the strategies of deflect, drain, and dry is to use materials and assemblies in construction that are durable enough to withstand the potential effects of water and moisture. This typically means specifying materials that won’t be harmed either on the surface or by the penetration of water. It can also mean adding materials to protect the primary surface material so it can be more durable against weather or heavy usage.

One of the key reasons to focus on a moisture control strategy in a healthcare setting is to prevent harm to the building while also protecting the people. Moisture is a key ingredient needed for the creation of mold and mildew which has been shown on numerous occasions to have negative health impacts. Moist environments can also lead to the growth of bacteria which can be detrimental or even deadly to people whose health is already compromised from other conditions.

A further strategy to help prevent such growth in buildings is to use materials that simply don’t support their growth. That means specifying materials that are non-organic, either on the surface, their interior make-up, or both. In that way, even if water is present and the temperature is favorable, there is nothing to feed the mold spores, so they will either die or simply be dissipated by the drainage or drying aspects of the assembly.

With all of these things in mind, we turn our attention in the following sections to three main areas of consideration for the design and construction of all healthcare facilities, namely, the roof, the exterior walls, and interior walls.

Image courtesy of Georgia-Pacific Building Products

A cover board, also known as a protection board or rigid board, is installed in a roof assembly to enhance the resiliency and durability of the roofing system.

ROOF PROTECTION

On most healthcare buildings, roofing is a big investment whether at the time of first construction or when it is time for it to be replaced. A common benchmark used by roofing consultants is that roofing typically represents five percent of the initial building costs but up to 77 percent of the capital expenditures during building operations—not to mention approximately 50 percent of the construction litigation cases. That’s why the durability of the roof is so important—it contributes to a lower likelihood of problems arising and a longer lifespan for a lower total cost of ownership. For commercial buildings, including most healthcare buildings, the roofing is usually a membrane system (e.g., EPDM, TPO, PVC, Modified Bitumen) installed over rigid foam insulation that is secured or anchored to a roof deck (e.g., steel, concrete, wood). The membrane durability will depend, in large part, on the type and thickness of the roofing membrane selected and attention to what is installed beneath it.

A durable, well-designed roof can also make a difference in terms of how the roof protects the building construction and its occupants under normal and severe weather conditions. Once bulk water or even air-borne moisture penetrates a building’s roof and works its way into the occupied portions, the damage can be both extensive and very noticeable but unfortunately, the damage typically starts long before detection. If moisture accumulates in the roofing system, it can break down water-soluble adhesives, delaminate roofing materials, and corrode metal components, collectively shortening the lifespan of the entire roofing assembly. It can also lead to embedded water in the roof system which may become ideal breeding grounds for mold, mildew, or bacteria.

How best to guard against these roofing issues and risks to the operation of a facility? The answer lies in understanding that there are essentially three potential sources of moisture intrusion in a roofing system.

Construction Activity:First, it can be introduced during construction. Since roof construction is completed outdoors, and the weather conditions can’t be controlled, a contractor may need to work under damp conditions to satisfy construction schedules or to protect the building’s interior. In these instances, rain and dew may become trapped and retained in roofing materials.

Membrane Punctures: The second potential source of water in a roof is from a puncture of the roofing membrane, thus causing a roof leak, whether during construction or after it is complete. Even the smallest penetration in a roof membrane allows water to enter the roof assembly. Punctures can result from both man-made causes and environmental, including foot traffic, and hail or windblown objects that can pierce the roofing membrane. When a puncture exists and a storm hits, gravity or the building’s diaphragm draws the moisture into the roofing assembly. In addition, nearly 70 percent of commercial roofs tend to house HVAC systems and other mechanical equipment that require routine maintenance, which puts stress on the membrane and makes it prone to perforations. The increasing use of roof-mounted solar panels also creates an added concern about maintaining the integrity of the roofing if additional intentional penetrations or maintenance are needed.

Of particular note regarding roof puncture protection is the well-documented rise in the frequency of severe storm disasters between 1980 and 2022. The NOAA National Centers for Environmental Information indicates that the frequency of severe storm disasters is increasing faster than any other disaster type, with 70 percent of their average property losses attributable specifically to hail damage. Property losses are documented by insurance companies who report that in 2022, insured losses related to hailstorms exceeded $10 billion in the U.S. for the 15th consecutive year.

Just as significant, FM Global (formerly known as Factory Mutual), a world-leading property insurance company, has identified hail zones classified by the size of hail commonly reported in an area. Moderate Hail Zones (defined as hail measured up to 1.75 inches in diameter) are common west of the Rocky Mountains, along the East Coast, and around the Great Lakes. Severe Hail Zones (with hail 1.75-2.0 inches in diameter) have grown to reach a large part of the United States, including the South and parts of the Midwest. Very Severe Hail (VSH) Zones (starting at 2 inches but may exceed 4 inches in diameter) carve a path through the center of the country affecting 14 of the 48 contiguous states. As hailstones increase in size, they pick up speed such that hailstones in VSH Zones can fall at over 100 miles per hour. When hundreds or even thousands of large stones fall, it is easy to see how building damage can occur, particularly by puncturing the roofs of healthcare buildings.

Vapor Drive: The third moisture source is vapor drive. Roofing products get wet from the outside (i.e., from rain and leaks in the membrane) and from moisture originating inside the building. When high-humidity indoor air meets the cooler underside of the roof membrane, the water vapor can reach the dew point and condense into liquid water. Hence, vapor drive occurs when there is a significant temperature discrepancy between the inside and outside of a building. The laws of physics dictate that moisture flows in specific ways to find equilibrium. It migrates from warm areas to cooler ones, from areas where it is dense to areas where it is sparse, and from areas of high pressure to low-pressure zones. As a result, frigid temperatures outside buildings located in cold-weather regions will create a vapor drive that causes the accumulated warmth and humidity inside to move up into the roofing assembly where—depending on the amount of insulation included in the assembly—it condenses into liquid water and causes damage. Conversely, if the building is located in a hot, humid climate, the moisture outside the building will attempt to make its way inside, where it will condense on the cold side of the roofing assembly. Rigid insulation is typically installed on roofs in layers with offset seams to reduce the vapor drive that can pass through the assembly.

By addressing all three of these areas with proper roofing design and materials, all following the strategy of the four D’s, the risk of water and moisture entering the roof assembly can be lessened.