Introduction Home inspectors who use more advanced (and costly) tool often do so under a separate inspection agreement and charge additional fees for the services. Some jurisdictions that license home inspectors specify certain minimum tool and specify when they must be used. Some jurisdictions prohibit home inspectors from performing certain services or require additional licenses or certifications to perform the services.
Moisture Meter A moisture meter detects and measures water within materials. There are two types of moisture meters. The pin-type measures the resistance between pins inserted into the material being tested. Resistance decreases as the moisture content of the material in-creases. The pinless-type uses radio frequency to measure the moisture in the material. Some moisture meters combine both types. Each meter type has advantages and disadvantages.
Pin-type meters are limited to measuring about as deep as the pins are long (about 5/16 inch). Some pin-type meters have long pins that can be inserted deep into the material. These meters are often used for EIFS moisture intrusion inspections. Pin-type meters leave holes in the material where the pins are inserted. This can be a problem when measuring finish materials.
Pinless meters measure moisture to a depth of between one-half and one inch. Moisture deeper than this may not be detected. Pinless meters are best when measuring moisture under hard materials that cannot be penetrated by pins, and under finish materials where damage by the pins would be objectionable.
Most moisture meters are calibrated to measure moisture in wood. Some have adjustments that can recalibrate for measuring other materials. Both types of meters can produce inaccurate results if not properly calibrated and used.
Moisture meters should not be used as an inspection tool, meaning that they should not be routinely used where water infiltration is not suspected. Use of moisture meters as an inspection tool takes the inspection beyond a visual inspection. The home inspector might be held responsible for water intrusion problems that were not detected.
Moisture meters are better used as a confirming tool, meaning that they may be used to confirm or deny the presence of water where evidence is observed, for example, stains, and where water intrusion is suspected. They are good when used to measure differences in moisture between different areas.
Use of a moisture meter is not required by SoPs. Their use by home inspectors is common in most markets.
Infrared (Laser) Thermometer and Infrared Camera An infrared thermometer and an infrared camera measure the infrared radiation emitted from the surface of the object being measured. They cannot see though objects and cannot determine the condition inside the object unless the condition affects the infrared radiation emitted from the surface of the object.
An infrared thermometer and infrared camera convert the infrared radiation measurement into a temperature readout. A camera provides an image of the object, the colors of which correspond to the temperature of the object. Typical uses of an infrared thermometer involve determining the temperature of air around HVAC supply registers and return grilles, circuit breaker temperature, and hot water temperature. Typical uses of an infrared camera involve detecting moisture intrusion, absent or improperly installed insulation, circuit breaker temperature, and air leaks.
Temperature measurements using an infrared thermometer and an infrared camera are subject to error; the error can be significant. Infrared thermometers display the average temperature over an area. The size of the area increases with the distance from the thermometer, so the temperature measurement error is usually larger when the thermometer is further away from the object. The size of the area is usually a function of the price of the infrared thermometer. Less expensive models measure a larger area compared to more expensive models.
Infrared thermometer and infrared camera temperature readings are affected by the emissivity of the object being measured. Emissivity may be simply defined as the ability of the object to emit infrared radiation. Lower emissivity means a greater chance that the measured temperature will be incorrect. Shiny metal usually has a lower emissivity than oxidized or dull metal, but most metal has a relatively low emissivity unless it has been covered with a dark, dull material. Most non-metal objects usually have a relatively high emissivity.
Use of infrared thermometers is not required by SoPs. Their use by home inspectors is common in most markets. They may be used as an inspection tool when used properly. A probe-type thermometer is usually more accurate and should be used instead of an infrared thermometer when possible.
Use of infrared cameras is not required by SoPs. An infrared camera should not be used as an inspection tool for the same reason as a moisture meter. It may be used as a confirming tool or as an added inspection service using an inspection agreement written for an infrared camera inspection.
Combustible Gas Detector A combustible gas detector detects gas such as methane (natural gas) and propane. Typical use involves testing gas fittings for leaks. All but the least expensive models will detect other combustible gasses, but these gasses are uncommon in houses. Less expensive models provide an audible tone that varies with the amount of gas detected. More expensive models also provide a visual indication of the gas amount detected.
Use of a combustible gas detector is not required by SoPs. Their use by home inspectors is uncommon in many markets. Their use is common practice in some markets and their use may be prudent in markets where using a combustible gas detector is the local standard of care. In most markets, a combustible gas detector may be used as a confirming tool but should not be used as an inspection tool. The home inspector should not report the use of a combustible gas detector unless a leak is confirmed. In this case, the home inspector should recommend evaluation of the fuel gas supply system as recommended by a qualified specialist.
A few home inspectors attempt to detect a cracked heat exchanger by using a combustible gas detector or a carbon monoxide detector to test the heated air leaving a fuel-fired furnace. These instruments are not designed for this use and the results are unreliable. This is not a recommended procedure.