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Chances Are
(risk assessment tool)
Are you doing all you can do to reduce your risk of developing a mold problem in your current home? |
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The heating ventilation, and air conditioning system is designed to provide comfort and improved air quality throughout the year, particularly in summer and winter months. If your contractor correctly sized your unit by following guidelines in Manual J, you will more likely not have air quality or moisture problems.
ASHRAE.org
Bigger is not necessarily better when it comes to HVAC units. While most people know that the primary use of AC is to cool a building, its secondary use, moisture removal is just as valuable. It might seem logical that a bigger unit which runs for less time would save more energy than a small unit that runs longer. This is not necessarily true. The HVAC system must be small enough to run long enough to reduce both temperature and humidity. Humidity should reach 65% or less. Relative humidity above 70% promotes airborne bacteria and mold growth and causes other problems as well. Oversized equipment cost more to buy and more to operate.
ASHRAE.org
Builders and HVAC contractors use a form developed by the Air Conditioning Contractors of America called Manual J. This form assists in calculating the correct size of air conditioning and heating systems. The form takes into account many aspects of the home including house orientation; window size, type, shading, and location; and square footage.
Proper maintenance can lower bills and extend life of the equipment.
Proper maintenance by a qualified HVAC technician involves checking all parts of the system including fan, duct work, condensate drip pan, heat exchange, energy connections, filters, etc.
You have taken a step that will reduce your risk of having a water “episode” in your home. By keeping the condensate pan drain and the emergency drain clean you have allowed the collected moisture to be removed safely from your home.
The condensate drip pan collects the moisture that is removed from the air as it circulates over the cooling coils. If you live in a dry climate, the condensate likely evaporates. However, if you live in a humid climate, the condensate flows from the pan into the sewer system. This drain as well as an emergency overflow drain pipe must be kept clear of algae in order for the condensate to be disposed of. You can keep the drain lines clear by adding ½ cup chlorine bleach to the drain on a monthly basis during the air conditioning season.
Whether your hot water heater is located in a closet or utility room in the house, the attic, or your garage, you have reduced your risk of having water damage by planning for a leaking or failing water heater.
Most water heaters do not last more than 10–15 years. In some locations, 7 years may be maximum. Because water heaters are usually out of sight, most people do not check or maintain them. Ideally we would routinely check and repair faucet or pipe connection leaks. To guard against water damage from a leaking heater, a drain pan with an emergency drain pipe connecting to the sewer or outside the home, can carry the water out safely.
Not only are you controlling moisture inside the home, you are not wasting water and money. TVWD.org
Plumbing leaks can usually be identified by a musty smell. Start your search for leaks by checking the most likely areas; hot water heater, under sinks, mixer valves on tubs and showers, toilets, etc. If you suspect a leak inside a wall, under a shower pan, or under the house, you may need to consult a professional repair person (depending on your repair skills).
See TVWD.org
By keeping standing water away from the foundation of the house, you reduce the likelihood of water penetrating the wall cavity. It also discourages termites.
Maintain slope away from building, carry roof load of water at least three feet away from building, and make sure that irrigation is directed away from the building.
If you home has a crawl space that has ventilation, you should have the floor of the house air sealed. A rigid sheating material should be attached to the underside of the floor joists, with the joints between sheets sealed with taped or mastic and fiberglass mesh.
See buildingscience.com
Air ducts or air handlers should not be located in an unconditioned crawl space.
Ground moisture must be controlled to prevent moisture migration from the ground into the house. This means a vapor barrier ground cover or a thin concrete slab.
Ground around the foundation should slope away from the building a minimum of 5% for the first 10 feet.
Air from the crawlspace migrates into the floor above unless that floor is well sealed. Building construction experts recommend a conditioned crawlspace which is like a mini basement. It should not be ventilated, should be dry, and receive conditioned air from the air handler. For further details see “Crawlspace Design” at buildingscience.com
Exhaust fans that are vented to the outside will take out excess moisture from the bathroom, dryer, and kitchen. This can help you maintain the relative humidity in your home in the recommended 40%–60% range.
The recommended relative humidity level to maintain is 40%–60%. When moisture is created inside the home and is not exhausted, it potentially can raise the relative humidity level above 60%. If you live in a very dry climate, you may simply need to use a fan to remove the moisture from the bath. In very cold climates, RH inside the home needs to be no greater than 30%.
Exhaust fans vented to the outside should be used to help maintain a recommended RH level in your home.
Depending on you how much humidity you and/or your family create, you can raise the humidity level in your home to levels that are conducive to mold growth. By exhausting the moisture to the outside, you can maintain the relative humidity at recommended levels.
Good for you. Normal household activities such as cooking, cleaning, bathing, washing clothes and dishes, drying clothes, breathing and perspiring can raise the humidity level too high. It has been estimated that the typical family of four converts three gallons of water into water vapor per day. It takes only four to six pints of water to raise the relative humidity of a 1,000 square foot house from 15 to 60 percent. To avoid the problems of excess moisture it is necessary to limit or control the amount of water vapor in the house. This can be accomplished by modifying lifestyle habits and by using mechanical means such as exhaust fans, dehumidifier, and air-to-air heat exchanger.
FCS.UGA.EDU
Generally, occupants of households are comfortable when the temperature and relative humidity are maintained 68 to 72oF and 25 to 50 percent relative humidity. Normally, mildew is a problem at a maintained relative humidity level above 60 percent, and static electricity is noticeable in cold weather at levels of 20 percent or lower. By using a hygrometer to monitor the humidity level, you can determine whether you need to exhaust humidity or add moisture.
MSUCARES.com
As you inspect your attic, you will be able to detect a roof leak early before major damage occurs.
Check rafters and roof decking for water stains. These leaks are sometimes hard to pinpoint. A bright flashlight will help focus on nooks and crannies in the framing structure.
These problem areas may account for as much as 90% of the roof leak problems.
Anywhere there is an extrusion through the roof, there is the potential for a leak. It is critical that these areas be sealed with caulk or flashing so water or moisture can not get in. Some experts suggest that as much as 90% of the leaks on a roof are a result of flashing problems. Additionally, shingles need to be checked after storms for damage that would allow leaking.
Exterior caulking is used primarily to prevent rain from entering the wall from the outside. Caulking on the outside of a window should be done only after interior sealing is complete. If the exterior is caulked first, it can trap warm, moist air in the wall, which can, in time, damage the wall.
WARNING: Do not use exterior caulking products indoors as they may give off harmful fumes.
A window should be sealed under the exterior siding material. Caulking or backer rod should be used to complete the seal on the window. The window trim then covers the window flashing. If you suspect a leak around the window, a moisture meter may be needed to find the location of the highest moisture concentration.
New double-pane windows with high-performance glass (e.g., low-e or spectrally selective) are available on the market. In colder climates, windows that are gas filled with low-emissivity (low-e) coatings on the glass help to reduce heat loss. In warmer climates, windows with spectrally selective coatings will reduce heat gain. See EEERE.Energy.gov
When the temperature is 70o F inside and 0o F outside, condensation will occur on the interior surface of a single-glazed window when the indoor relative humidity level is only 15%; on a double-glazed window at 42%; and on a low-emissivity window at 65%. By increasing the energy efficiency of the window, condensation is less likely because the interior glass surface does not get as cold.
If your home has single-pane windows, as almost half of U.S. homes do, consider replacing them. New double-pane windows with high-performance glass (e.g., low-e or spectrally selective) are available on the market. In colder climates, select windows that are gas filled with low-emissivity (low-e) coatings on the glass to reduce heat loss. In warmer climates, select windows with spectrally selective coatings to reduce heat gain. In the average home, moisture condensation appears first on the glass in windows and doors, because these are usually the coolest surfaces in the house. If you cannot replace your windows, condensation can be reduced or eliminated by installing storm window units. The air space separating the storm unit from the regular window becomes an insulator. This space allows the temperature of the storm window unit to approach the temperature of the cold outside air, while the temperature of the inside window unit can be much warmer without causing condensation. The relative humidity inside the home needs to be 30% to 40% to reduce condensation. See cecommerce.uwex.edu.
Water your landscape conservatively. Use a moisture sensor in your yard to determine is the sprinklers need to run or not. You are watering your plants, not your house.
Landscape watering that hits on the side of your house can create moisture problems what ever the siding. (brick, wood, stucco, etc.) See buildingscience.com.
If you need to wash the siding, it is best to use a bucket of water and a rag. See buildingscience.com.
By using a high pressure nozzle to wash wood trim or siding, you can force moisture into the wall cavity. This can create a full range of problems: corrosion, mold, odors, or staining.
There are so many areas in the house where moisture can create a problem, it is wise to have as many scouts on the look-out for the problem as possible.
The rules governing water movement are:
- Water runs downhill due to gravity
- Air carrying water vapor goes from areas of higher air pressure to areas of lower air pressure
- Water in the vapor form diffuses from more to less
- Water in the vapor form diffuses from warm to cold
- Water in a porous material can move upwards as it is absorbed or sideways
Access doors or panels allow you to check the mixer valves as well as the pipes inside the wall for leaks.
Access doors or panels allow you to check the mixer valves and pipes inside the wall for leaks. Some cities have codes that require these access panels. These access doors also allow for wood destroying insect inspections.
For the past 75 years, copper tubing has been the most reliable and cost-effective option for distributing water to and through our homes for various applications.
In older homes, the plumbing does not last forever. Depending on water quality, copper pipes usually survive for 30-40 years. Without proper grounding of copper pipes, leaks caused by electrolysis may occur much quicker. This will be much more common in a pier and beam house or even in a slab when some types of pvc or plastic is used though the soil and metal pipes are only used above ground. http://stephenville.tamu.edu/~clee/bmold.html
Homeowner’s insurance generally covers household water damage if the damage is sudden and accidental, such as damage caused by burst pipes. It does not cover damage of the sort covered by flood insurance, i.e., rising water from outside; or damage caused over time by lack of maintenance.
Inspect around your water heater, washer, dishwasher, sinks, lavatories and refrigerator icemaker. If hoses indicate wear, replace them. Consider replacing hoses to major appliances such as your washer and dishwasher every two to five years. Steel, so-called "no burst" hoses have been shown to have a longer lifespan than other models.
By leaving the bathroom door open after hot, steamy showers or baths, you are allowing the moist air that was not exhausted through your vent to dissipate throughout the house.
If you close the bathroom door after a hot, steamy bath or shower, you may increase the relative humidity level in the bathroom to a level where mold will likely grow. Use your vent fan, monitor the RH (< 60%), and leave the bathroom door open to allow the remaining moisture to dissipate throughout the house.
By cleaning regularly and thoroughly, you are removing some of the potential food sources for mold to feed on.
Dust, pet dander, pollen, and dead insects are ideal nutrient sources for mold. When moisture is added or the RH is above 90% - 60%, mold will likely grow.
You have prevented moisture from entering your home by maintaining the flashing and caulking.
Flashing is metal or composition strips used to seal junctions between roofing and other surfaces, or in the valleys between different slopes. These areas must be sealed to prevent water or moisture from entry into the house.
You have reduced the risk of flowing water from the roof entering the wall cavity by having an overhang to divert the water out and away from the opening.
Windows and doors are openings in the building envelope where moisture can easily enter if they are not protected and sealed. Since water flows downward with gravity, an overhang that carries the water out over the door or window reduces the risk associated with the opening.
Flat roofs must be thoroughly sealed and guttered in order for the falling rain to escape the roof.
A flat roof must be sealed, sloped and have a way for falling rain to escape.
Why are flat roofs more problematic than sloped ones? Though they seem simpler than the ornate slate, shingle, or metal roofs, flat roofs manifest a number of problems. Most flat roofing materials, such as asphalt or tarpaper, have a relatively short life span of 10 to 12 years. Asphalt shingles can last 35 years and many well-made slate or metal roofs can last 100 to 150 years.
Although they seem uncomplicated, flat roofs require a high level of craft, particularly at the edges, where they join walls. The metal detail in this area, called flashing, requires careful execution. Joints sealed with roofing tar or cement usually indicate poor craftsmanship and will not last long, since the cement quickly becomes brittle and cracked.
Ultimately, the problem with flat roofs is that they are? flat. Deteriorated asphalt shingle roofs continue to shed water, although many of the shingles are peeled or missing, because the slope of the roof and the overlapping layers of shingles keep the water flowing down and off the roof. Even a small hole in a flat or gently sloped roof has the opportunity to cause a leak, particularly if water forms puddles on the roof.
Next: Other Links
- Controlling Moisture to Control Mold Mini-Course
- Begin Course
- Getting Wet (introduction)
- Looking for Moisture in All the Right Places (locating moisture)
- Bulk Moisture
- Air Transport
- Air Vapor
- Capillary Action
- Waltz Around Mold (steps to avoid moisture and mold)
- Construction/Design Techniques
- Maintenance/Repair
- Behaviors
- Chances Are (risk assessment tool)
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Controlling Moisture to Control Mold Mini-Course developed by Janie L. Harris, M.Ed., CRS, Extension Housing and Environment Specialist, Texas AgriLife Extension Service, Texas A&M System, College Station, Texas.
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Last updated: 26 July, 2010
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