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New Course: Danger in the Damp
Enjoy this snippet from our new, fully narrated course: Danger in the Damp.
Approved for credit in Alaska, Georgia, Kentucky, Michigan, Oregon, and Rhode Island.
Or take the course without credit from any state to expand your knowledge!
"Moisture Damage to Buildings
In addition to causing health problems, moisture will damage building materials and components. That facility damage occurs at multiple levels. Since water and food are what most organisms need to thrive, prolonged exposure to moisture encourages infestation within and on, organic building materials and HVAC system components. Molds, bacteria and wood-decaying pests, like termites and carpenter ants, will suddenly feel right at home. Water interacts chemically with building components to cause structural fasteners, wiring, metal roofing and conditioning coils to corrode. It makes wood rot and causes adhesives used in flooring, sheathing and roofing to fail. Wood will also swell or warp when it becomes wet. Water-soluble building materials like drywall can essentially dissolve. Masonry can be damaged when water enters cracks and then expands into ice during freeze-thaw cycles. The integrity of concrete can be destroyed by sub-surface salt deposits, carried there by moisture intrusion. Paints and varnishes can be damaged and become clouded. When wet, the thermal resistance of insulation is greatly reduced.
Monetary Loss Due to Moisture Problems
Fixing any of these problems will generate significant price tags, especially in buildings exposed for prolonged periods to moisture.
One set of price tags involves health issues arising when air contamination becomes dangerous. The direct cost of medical problems, associated costs of treatment and ancillary losses of productivity must be borne by someone. Annual medical costs of just asthma-related illnesses, attributed to exposure to dampness and mold, have been estimated at $3.5 billion in the U.S. alone. Money is lost when employees are absent due to illnesses like asthma. Even when employees remain present, reduced productivity can be expected when there are pervasive moisture-related health and comfort problems. There are additional health problems related to mold and each problem carries its own annual medical price tag. Those are generally passed on as higher insurance premiums to everyone.
Damage to the building also creates huge expenses. A significant proportion of these costs is borne by tenants and building owners. There is obviously expense associated with repair and replacement of corroded structural fasteners, wiring and damaged moisture-sensitive materials. Increased insurance premiums will result from excessive claims for repair, especially if a water intrusion problem was known but left remedied for a length of time. Loss of use of building space after damage and during renovations will make it necessary to rent additional space for a time. There will be repair and replacement costs for damaged furniture, products and supplies. Damaged records that cannot be salvaged will create more problems down the road, requiring plenty of unscheduled time spent by personnel to figure out and resolve issues caused by now-missing data.
General Moisture Intrusion
When examining how to reduce financial loss from excess water, understand that moisture in buildings or building envelopes is likely coming from one of the following sources. When materials in the building, from acoustic ceiling tiles to carpets and rugs, absorb and hold that moisture, they will continually release it into the air in the building until they have been dried or removed.
In general, moisture enters enclosures in the following ways.
- Moisture is literally absorbed straight through external envelope materials.
- Precipitation or melting snow drains inside through cracks and holes.
- Moisture like melting snow can be sucked inside through available openings when air pressure inside is less than that externally. Basically, anywhere air can enter, water can follow.
- Moisture enters the building through construction flaws, poor selection of materials, poor installation methods used during construction or adjacent selected materials being incompatible with each other.
- More moisture enters from humid outside air flowing in than the building’s HVAC system can eliminate.
- Moisture enters in an event that floods a building, like a plumbing leak, a spill, a leak in the fire suppression system or an actual natural disaster affecting the integrity of the building envelope.
- One other significant way in which water enters is the introduction of excess moisture into the building by occupants. This is via poorly vented exhaust fans in kitchens and baths, from water spills, from water used in housekeeping tasks, humidity introduced in the breath of inhabitants, the uncontrolled entry of humidity from the exterior when doors or windows are opened, and plumbing fixtures are being allowed to run or drip.
Unwanted moisture will find its way into buildings. This fact is attested to by a proliferation of service companies who each contract to provide moisture abatement services for flooded structures. In this case, as in most others, solutions came into existence because of need.
It is easy to find sources of excess water when materials near the leak are saturated. Leaks or burst pipes are immediately apparent. Not so easy is when the source of intrusion is hidden from view, such as wet insulation in walls or water entering through the foundation. Totally frustrating is when a leak occurs in one location, but the water uses wires, ducts, etc., to travel some distance before dropping and making its presence known. It becomes evident, just nowhere near its actual point of entry.
There are straightforward steps that can be taken to reduce the chance of water intrusion. Specifying and using building materials that neither accept nor hold moisture is one practical solution. For example, rigid insulation will not hold moisture, whereas cellulose insulation will absorb the same. Metal siding will repel water, but wood siding becomes saturated unless protected. Single ply membrane roofing offers no lapped joints wherein moisture can reside, but that is not true of asphalt shingle roofing. Sandwich panels containing insulation faced with steel or aluminum sheeting are another prime example of materials which by their nature, repel moisture.
Construction detailing using forethought before construction begins can deny water entry. It is primary based on a good imagination and an understanding of water behavior. Since precipitation tends to flow downhill, flashings below copings, below windows, above door and window openings and above breaks in the continuity of the building envelope where water should lap down over the next shield in the water barrier, will keep water from entering. If wind striking a building face has potential to drive water up under flashing, then caulking should be specified, or other barriers put in place to prevent that. Capillary breaks can prevent water from bridging gaps. If there is a cavity into which moisture can enter and collect, weep holes should be provided to let that collected water drain from that cavity, back to the exterior. The devil is in the details, but unwanted moisture intrusion can be in the lack of them.
The above-mentioned material specification and detailing decisions should be choices made during the design process. The idea is to create a continuous envelope of materials that repel water and will not allow moisture to get through them and into the interior.
Another useful tool is ongoing efforts to find and eliminate any newly created gaps in the envelope through which moisture can get inside. Inspection during construction is the best time to do this, but it is also part of ongoing maintenance efforts. Indoor sources of moisture (other than the breath of inhabitants) can be found and fixed or eliminated. Uncontrolled air movement that pulls humid air in from the exterior can be controlled with airlocks or other known design devices.
By far, the best approach to indoor air pollution by mold is to do whatever it takes to just keep moisture from getting inside. Because once it gets a foothold, the growth of mold can follow."
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