About Infrared and How Infrared Cameras Work

Infrared is an energy which can be described as light we can't see. The thermal imaging camera sees the light as heat and can show this in the infrared picture, each pixel is allocated a colour based on it's temperature resulting in the infrared photo. Each photo will have a colour scale as an indication of the colour and temperature range. Moisture takes longer to heat up and cool down compared with the surrounding objects in a scene causing a hot or cold temperature difference, which the infrared camera can see as heat. All materials whose surface temperature is above absolute zero (-273°C) emits infrared (heat).

Far infrared waves are thermal. Objects at temperatures found in buildings radiate heat almost entirely in the far infrared range. The infrared information is then passed to a signal processor which translates the infrared data into an image that can be viewed and the infrared images along with normal digital images can be stored for later documentation in the cameras reporting software.

Don't get a home or building pre-purchase inspection until you have read this!

Often when I get booked to do a thermal imaging pre-purchase inspections I find that there has been a number of other (valuation or structural type) inspections already completed. I don't recommend they be done first as experience has shown me that when moisture issues are discovered often due to the difficulty and costs associated with the repairs the sale is not completed. It still amazes me how many homes have moisture related issues that the owners are unaware of and unfortunately some where the owners have been aware of moisture issues and had repairs done but don't disclose this information. Nine out of ten of vendors say they are not aware of any leaks when asked prior to doing a building moisture inspection and yet nine out of ten homes we inspect we find moisture leaks. Not many people will knowingly purchase a leaky home as most repairs require building permits and can take months to be completed, not to mention at what cost. As a result a lot of perspective home purchasers have had to pay for two or sometimes three building inspections plus my inspection costs for a property that they don't end up buying. So if you want my advise get an Thermal Imaging Infrared Moisture Inspection done first.

With our inspections we can also conduct cladding inspections and comment on maintenance issues, which are also two important issues that often are not given enough importance or reported on. A number of inspection companies advertise that they will also check for moisture but you should read the fine print and question the amount of time that will be devoted solely to moisture testing. I have been doing this for a while now and find it takes about two hours to properly moisture test an average size home using an infrared camera (without an infrared camera would take considerably longer) and a non-invasive moisture meter. I would be concerned about companies that advertise that they can do both structural and moisture inspections in less time.

How does an Infrared Inspection compare to other types of inspections?

Whether it's your home or business from your buildings foundation to its roof, infrared provides you by far with the most thorough non-invasive building inspection and best dollar value for a visual inspection of your property. A Thermographer can look at large areas quickly and more thoroughly compared to other types of investigation methods. By analysing Thermal Images of your buildings, water, air and heat leaks, only the faulty areas need to be repaired, sometimes saving thousands of dollars. When Maintenance checks are also conducted often leaks are found that without the aid of Infrared are not visible and would go undetected or in the case of some water leaks until substantial damage has occurred. Thermal Imaging works particularly well for example on finding leaks in membrane roofs and plaster cladding which in the past have been almost impossible to locate.

The standard practice if you are unsure of the cause to completely replace the item in question, roof or cladding even when in some cases the roof or cladding is still in good condition, because the exact location of water entry has not be found. As a result when moisture testing reclad houses I am still finding leaks. Infrared Inspections help avoid costly random destructive testing by pinpointing the exact location of problem areas. To find a leak in a home can be like looking for a needle in a hay stack without a Thermal Imaging Infrared camera. A Thermal Imaging camera is not a magic wand, cannot see through walls and will not expose all defects. A Thermal Imaging camera is only an inspection tool, like all tools there are limitations, that's why we predominantly use moisture meters also during inspections. With our experience, other inspection techniques and inspection tools, we can provide a broader more comprehensive assessment of the condition of the inspected items.

How to use a moisture meter for moisture inspections in NZ?


I have been using non-invasive moisture meters for moisture inspections for a number of years now and have found that there are a number of traps for beginners. It is important to know the moisture readings you are getting are accurate and not false readings caused by the material being tested or the inspectors inexperience. The main problem is the people selling moisture meters generally don't use them every day and are often not aware of some of the problems and therefore the information is not passed on. One of the most important things to remember before you start is to check the exterior and evaluate the risk of the area you are checking, for potential leaks, has not leaked in the past or been repaired as a repaired area could give normal moisture readings.

Damaged or rotten timber will often give low or normal readings as the timber may no longer hold moisture or may have rotted away altogether. Repaired areas can give normal moisture readings if they are no longer getting wet, but still could have unseen damage. Check for visible moisture damage on the internal wall. Often with rotten timber framing damage the wall will become soft and I notice the sound the bulb on the meter makes as you touch it on the wall changes tone if the wall is soft or wet. Generally if the leak is still active it will spread by capillary action and readings around the damaged area will still be high. To correctly set the Trotec-T650 you must hold the meter the same way you intend to use it, away from any objects, stand still when turning it on and be in the area you will be testing. If you hold it at the end to set it and further up when taking readings, then the readings will be too high and vise versa. Make sure the moisture meter bulb is not dirty, contaminated or wet.

You should always have a strong magnet on you when moisture testing as metal strapping and nails give false high readings. Metal strapping is typically fitted each side of doorways. Older homes can have foil backed Gib fitted as an early form of insulation. Gib bracing sheets cause two problems the material itself increases the readings and they have metal strapping and a lot more nail fixings fitted with washers. You can often confirm Gib bracing sheets with the magnet due to the closer fixing of the nails and by checking the house plans also. Concrete can give high readings and still be normal. Readings on Gib walls that are strapped onto concrete will give higher than normal readings also.

Base readings should always be taken for direct comparison. As I always use an Infrared camera for my inspections the Infrared camera is used to find the anomaly and the moisture meter is used to confirm my findings. The IR photos will often be clear enough to identify nails and strapping to confirm false readings also. The inspector will consider all of these variables before concluding whether a moisture reading taken is considered to be normal, damp or wet.

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