Bathroom ventilation systems are designed to exhaust odors and moist air to the home's exterior. Typical systems consist of a ceiling fan unit connected to a duct that terminates at the roof.
 
Fan Function  
 
 The fan may be controlled in one of several ways:

• Most are controlled by a conventional wall switch.
• A timer switch may be mounted on the wall.
• A wall-mounted humidistat can be pre-set to turn the fan on and off based on different levels of relative humidity.

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• and also force the exhaust fan to work harder;
• be insulated, especially in cooler climates. Cold ducts encourage condensation;
• protrude at least several inches from the roof;
• be equipped with a roof termination cap that protects the duct from the elements; and 
• be installed according to the manufacturer's recommendations.

The following tips are helpful, although not required. Ventilation ducts should:

• be made from inflexible metal, PVC, or other rigid material. Unlike dryer exhaust vents, they should not droop; and 
• have smooth interiors. Ridges will encourage vapor to condense, allowing water to back-flow into the exhaust fan or leak through joints onto vulnerable surfaces.

Above all else, a bathroom ventilation fan should be connected to a duct capable of venting water vapor and odors into the outdoors. Mold growth within the bathroom or attic is a clear indication of improper ventilation that must be corrected in order to avoid structural decay and respiratory health issues.

 Winterization is the process of preparing a home for the harsh conditions of winter. It is usually performed in the fall before snow and excessive cold have arrived. Winterization protects against damage due to bursting water pipes, and from heat loss due to openings in the building envelope. Inspectors should know how winterization works and be able to pass this information on to their clients

Leaky window frames, door frames, and electrical outlets can allow warm air to escape into the outdoors.

• Windows that leak will allow cold air into the home. Feeling for drafts with a hand or watching for horizontal smoke from an incense stick are a few easy ways to inspect for leaks. They can be repaired with tape or caulk. 
• On a breezy day, a homeowner can walk through the house and find far more leaks than they knew existed. Leaks are most likely in areas where a seam exists between two or more building materials.

• Patio furniture should be covered.
• If there is a deck, it might need an extra coat of sealer. 

Adequate winterization is especially crucial for homes that are left unoccupied during the winter. This sometimes happens when homeowners who own multiple properties leave one home vacant for months at a time while they occupy their summer homes. Foreclosed homes are sometimes left unoccupied, as well. The heat may be shut off in vacant homes in order to save money. Such homes must be winterized in order to prevent catastrophic building damage.
 
In addition to the information above, InterNACHI advises the following measures to prepare an unoccupied home for the winter:

• Winterize toilets by emptying them completely. Antifreeze can be poured into toilets and other plumbing fixtures.   
• Winterize faucets by opening them and leaving them open.
• Water tanks and pumps need to be drained completely.
• Drain all water from indoor and outdoor plumbing.
• Unplug all non-essential electrical appliances, especially the refrigerator. If no electrical appliances are needed, electricity can be shut off at the main breaker.  

 
In summary, home winterization is a collection of preventative measures designed to protect homes against damage caused by cold temperatures. These measures should be performed in the fall, before it gets cold enough for damage to occur. Indoor plumbing is probably the most critical area to consider when preparing a home for winter, although other systems should not be ignored.

Moisture intrusion can be the cause of building defects, as well as health ailments for the building's occupants. Inspectors should have at least a basic understanding of how moisture may enter a building, and where problem areas commonly occur.

 Some common moisture-related problems include:

• structural wood decay; 
• high indoor humidity and resulting condensation;
• expansive soil, which may crack the foundation through changes in volume, or softened soil, which may lose its ability to support an overlying structure;
• undermined foundations;
• metal corrosion;
• ice dams; and
• mold growth.  Mold can only grow in the presence of high levels of moisture. People who suffer from the following conditions can be seriously (even fatally) harmed if exposed to elevated levels of airborne mold spores:
  • asthma;
  • allergies;
  • lung disease; and/or
  • compromised immune systems.​

Note:  People who do not suffer from these ailments may still be harmed by elevated levels of airborne mold spores.

How does moisture get into the house?

Moisture or water vapor moves into a house in the following ways:

• air infiltration. Air movement accounts for more than 98% of all water vapor movement in building cavities. Air naturally moves from high-pressure areas to lower ones by the easiest path possible, such as a hole or crack in the building envelope. Moisture transfer by air currents is very fast (in the range of several hundred cubic feet of air per minute). Replacement air will infiltrate through the building envelope unless unintended air paths are carefully and permanently sealed;
• by diffusion through building material. Most building materials slow moisture diffusion, to a large degree, although they never stop it completely;
• leaks from roof;
• plumbing leaks; 
• flooding, which can be caused by seepage from runoff or rising groundwater; it may be seasonal or catastrophic; and
• human activities, including bathing, cooking, dishwashing and washing clothes. Indoor plants, too, may be a significant source of high levels of humidity.

Climate Zones
 
In the northern U.S., moisture vapor problems are driven primarily by high indoor relative humidity levels, combined with low outdoor temperatures during the winter. In the southern U.S. (especially the southeast), the problem is largely driven by high outdoor humidity and low indoor temperatures during summer months. Mixed climates are exposed to both conditions and can experience both types of problems. Humid climates, in general, will be more of a problem than dry climates. Wind-driven rain is the main cause of leaks through the building envelope.
 Inspectors can check for moisture intrusion in the following areas:

Roofs
A roof leak may lead to the growth of visible mold colonies in the attic that can grow unnoticed. Roof penetrations increase the likelihood of water leaks due to failed gaskets, sealants and flashing. The number of roof penetrations may be reduced by a variety of technologies and strategies, including: 

• consolidation of vent stacks below the roof;
• exhaust fan caps routed through walls instead of the roof;
• high-efficiency combustion appliances, which can be sidewall-vented;
• electrically powered HVAC equipment and hot water heaters that do not require flue; and
• adequate flashing. Oftentimes, inspectors discover missing, incorrectly installed or corroded flashing pipes.

​Plumbing

• Distribution pipes and plumbing fixtures can be the source of large amounts of moisture intrusion. If the wall is moist and/or discolored, then moisture damage is already in progress. Most plumbing is hidden in the walls, so serious problems can begin unnoticed.
• One of the most important means of moisture management in the bathroom is the exhaust fan. A non-functioning exhaust fan overloads the bathroom with damp air. If the exhaust fan doesn’t turn on automatically when the bathroom is in use, consider recommending switching the wiring or switch. The lack of an exhaust fan should be called out in the inspection report. The fan should vent into the exterior, not into the attic.
• The bathroom sink, in particular, is a common source of moisture intrusion and damage. Although overflow drains can prevent the spillage of water onto the floor, they can become corroded and allow water to enter the cabinet.  
• Use a moisture meter to check for elevated moisture levels in the sub-floor around the toilet and tub.
• Bathroom windows need to perform properly in a wide range of humidity and temperature conditions. Check to see if there are any obvious breaks in the weatherstripping and seals. Are there are stains or flaking on the painted surfaces?
• Check showers and bathtubs. Is the caulking is cracked, stiff or loose in spots? Are there cracked tiles or missing grout that may channel water to vulnerable areas? If some water remains in the bathtub after draining, it may be a warning sign of possible structural weakening and settlement in the floor beneath the tub.

Utility Room

• The water heater tank should be clean and rust-free.
• The area around the water softener tank should be clean and dry.
• Check that all through-the-wall penetrations for fuel lines, ducts, and electrical systems of heating system are well-sealed. All ducts should be clean and dust-free. Inspect the air supply registers in the house for dust accumulation.   
• Filters, supply lines, exterior wall penetrations, vents, ductwork and drainage of the cooling system must all be in good working order to avoid moisture problems.  

Attic

• Look for stains or discolorations at all roof penetrations. Chimneys, plumbing vents and skylight wells are common places where moisture may pass through the roof. Any such locations must be inspected for wetness, a musty smell and/or visible signs of mold.
• Are there areas of the insulation that appear unusually thin?
• Rust or corrosion around recessed lights are signs of a potential electrical hazard.

Foundations

Model building codes typically require damp-proofing of foundation walls. The damp-proofing shall be applied from the top of the footing to the finished grade. Parging of foundation walls should be damp-proofed in one of the following ways:

• bituminous coating;
• 3 pounds per square yard of acrylic modified cement;
• 1/8-inch coat of surface-bonding cement; or
• any material permitted for water-proofing.

In summary, moisture can enter a building in a number of different ways. High levels of moisture can cause building defects and health ailments. 

• NM and NMC conductors are composed of two or more insulated conductors contained in a non-metallic sheath. The coating on NMC cable is non-conducting, flame-resistant and moisture-resistant. Unlike other cables commonly found in homes, they are permitted in damp environments, such as basements. 
  
  
• Underground feeder conductors appear similar to NM and NMC cables except that UF cables contain a solid plastic core and cannot be “rolled” between fingers.

 
The following NEC regulations apply to Romex conductors:

• They are not permitted in residential construction higher than three stories, or in any commercial construction. 
  
  
• They must be protected, secured and clamped to device boxes, junction boxes and fixtures. 
  
  
• Support devices that may damage the cables, such as bent nails and overdriven staples, are not permitted. 
  
  
• NM and NMC cables should be secured at intervals that do not exceed 4½ feet, and they should be secured within 12 inches of junction boxes and panels to which they are attached. Cables that do not comply with this rule can sag and are vulnerable to damage. 
  
  
• They are intended as permanent wiring in homes and should not be used as a substitute for appliance wiring or extension cords.

Note:  Some communities have never allowed the use of Romex wiring in residential construction. Armored cable is typically used in these communities. 

Armored Cables (AC)
 
Armored cable (AC), also known as BX, was developed in the early 1900s by Edwin Greenfield. It was first called “BX” to abbreviate “product B – Experimental,” although AC is far more commonly used today. Like Romex cables, they cannot be used in residences higher than three stories, and the rules for protection and support of AC wiring are essentially the same as the rules for Romex. Unlike Romex, however, AC wiring has a flexible metallic sheathing that allows for extra protection. Some major manufacturers of armored cable are General Cable, AFC Cable Systems, and United Copper Systems.

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• The dissipated heat from knob-and-tube wiring can pose a fire hazard if the wires are enveloped in building insulation. A possible exception is fiberglass insulation, which is fire-resistant, although even this type of insulation should not cover knob-and-tube wiring. The homeowner or an electrician should carefully remove any insulation that is found surrounding KT wires. 
  
  
• Knob-and-tube wiring is more vulnerable to damage than modern wiring because it is insulated with fiber materials and varnish, which can become brittle. 
  
  
• Some insurance companies refuse to write fire insurance for houses with this type of wiring, although this may be remedied if an electrician can verify that the system is safe. 
  
  
• Disregarding any inherent inadequacies, existing KT cable systems are likely to be unsafe because they are almost guaranteed to be at least 50 years old.

In summary, inspectors should understand the different types of conductors that are commonly found in homes. 

Taking air samples during a air quality inspection is crucial for several reasons. Mold spores are not visible to the naked eye, and the types of mold present in a home can often be determined through a laboratory analysis. Having the air samples analyzed can also help provide evidence of the scope and severity of a mold issue, a well as help in assessing human exposure. 

Samples are generally best taken if visual, non-invasive examination reveals apparent mold growth or conditions that could lead to growth, such as moisture intrusion or water damage.  Musty odors can also be a sign of mold growth.  If no sign of mold or potential for mold is apparent, one or two indoor air samples can still be taken, at the discretion of the inspector and client, in the most lived-in room of the house and at the HVAC unit.  

Outdoor air samples are also typically taken as a control for comparison to indoor samples.  Two samples -- one from the windward side and one from the leeward side of the house -- will help provide a more complete picture of what is in the air that may be entering the house through windows and doors at times when they are open.  It is best to take the outdoor samples as close together in time as possible to the indoor samples that they will be compared with.

InsideOut inspectors should avoid taking samples if a resident of the house is under a physician’s care for mold exposure, if there is litigation in progress related to mold on the premises, or if the inspector’s health or safety could be compromised in obtaining the sample.  Residential home inspectors also should not take samples in a commercial or public building

Buying a home?
The process can be stressful. A home inspection is supposed to give you peace of mind but, depending on the findings, it may have the opposite effect. You will be asked to absorb a lot of information over a short period of time.  Your inspection will entail a written report, including checklists and photos, and what the inspector tells you during the inspection. All of this combined with the seller's disclosure and what you notice yourself can make the experience overwhelming. What should you do?

Relax.
Home inspectors are professionals, and if yours is a member of InterNACHI, then you can trust that he is among the most highly trained in the industry. Most of your inspection will be related to maintenance recommendations and minor imperfections. These are good to know about.
However, the issues that really matter will fall into four categories:

1. major defects, such as a structural failure;
2. conditions that can lead to major defects, such as a roof leak;
3. issues that may hinder your ability to finance, legally occupy, or insure the home if not rectified immediately; and
4. safety hazards, such as an exposed, live buss bar at the electrical panel

Anything in these categories should be addressed as soon as possible. Often, a serious problem can be corrected inexpensively to protect both life and property (especially in categories 2 and 4).
Most sellers are honest and are often surprised to learn of defects uncovered during an inspection. It’s important to realize that a seller is under no obligation to repair everything mentioned in your inspection report. No house is perfect. Keep things in perspective.
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And remember that homeownership is both a joyful experience and an important responsibility, so be sure to call on your InterNACHI Certified Professional Inspector® to help you devise an annual maintenance plan that will keep your family safe and your home in top condition for years to come.