Tooling up for Home Performance: Part 3 of 3: Optional/Advanced Testing Equipment
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This article is the final installment in a three part series where we discuss the types of diagnostic equipment necessary for Home Performance work.
In the first installment we covered the 5 national standards governing much of the home performance work in the US (www.bit.ly/hp-standards) as well as an overview of pressure measurements. The second installment delved into the products used in combustion testing.
This final segment will cover the optional and more advanced diagnostic test equipment used in home performance testing.
I’ve Got A Temperature
The three key modes of energy gain or loss in a home are air leakage, solar (gain only) and conductive. Thermal imagers can detect areas of “thermal difference” or changes in the temperature of surfaces. This can lead to spotting and correcting these areas of thermal gain and loss, thus improving the home’s performance.
One of the basic principles of thermography is that all materials above absolute Zero (–273.15°C or –459.67°F) radiate infrared (IR) energy. That means every thing in our world has “got a temperature.” Thermal imagers (or thermal cameras or IR cameras) have a special lens, which focuses IR energy on sensor array. The array detects this energy pattern and turns it into an image on an LCD screen, essentially painting pixels of color to represent temperature levels (ala’ The movie Predator). The colors on a thermal imager screen represent the surface temperature that are in the field of view of the lens.
You are likely familiar with point-and-shoot IR “guns” which give you a spot temperature. Well, those guns have one pixel each. A thermal imager has thousands (sometimes tens of thousands) of pixels in order to paint the thermal picture on the LCD screen.
There is a generally recognized minimum spec for thermal imagers used in home performance diagnostics. They need to have at least a 120×160 pixel sensor array. Or the equivalent of 19,200 point-and-shoot IR Guns all duct-taped together!
Another key technical detail for a thermal imager is the Noise Equivalent Temperature Difference (NETD), which is a measurement of thermal resolution or sensitivity. The recognized threshold for home performance is that the NETD must be less than or equal to 0.10°C at 30°C (0.18°F at 86°F). This allows the user to be able to see the important details of temperature differences.
It recommended that users invest about 20% of their thermal imager camera budget for training in thermography. There many factors to be aware of when using a thermal camera, too many to list in this article, but there are two areas of particular importance.
First, a thermal imager does not “see through” materials. It can only detect IR energy coming off of a surface. For example if you can see the pattern of internal wall studs when viewing a wall, you are simply seeing the thermal difference on the wall surface due to the heat being conducted to or from the wall surface by the studs. Additionally, you cannot see the air temperature at a grille, but you can detect the surface temperature of the grille, which should be close to the air temperature if it is given a chance to stabilize with the temperature of the air.
The second critical property to understand is emissivity. That is the tendency of a surface to emit (1.00 emissivity) or absorb (0.00 emissivity) IR energy. Basically it tells you how much of a thermal mirror is the surface you “see” in the thermal imager. The more of a mirror it is to IR energy (lower emissivity number) the more it will reflect any ambient IR energy or IR energy form other surfaces, thus throwing off the temperature measurement of the surface. For example copper pipe has an emissivity of 0.24, making it hard to directly measure pipe temperature. However, the addition of a strip of black tape to the pipe will allow a temperature reading to be made.
During a home performance check up, a thermal imager is typically used in conjunction with a blower door, to spot the areas where air is infiltrating or “thermal bridges” are present. Test set up is important, as solar gain, wind, duration of blower door test, and air temperature difference from inside to outside all impact the ability of a thermal imager to create a pronounced visual difference of the temperature. This pronounced visual difference will help target the areas that need to be addressed to improve the home’s thermal performance.
Wet and not so wild
Moisture meters come in 2 basic types: contact and non-contact. Contact meters actually measure the difference in electrical resistance in a material between 2 pin probes that are pushed into the surface of a material. Non-contact moisture meters the principle of electrical impedance to detect moisture from ¾ to 1” below the surface.
Some moisture meters are available with both contact and noncontact sensors, and most recently, they can come with a basic thermal imager built in to look for the presence of water due to the thermal changes from the evaporative cooling effect as moisture leaves as material.
Using standard scales, moisture meters allow a home performance evaluator to see if excess moisture is present, or even traces of past water presence, which may be indicative of water leakage or condensation issues that came impact Indoor Air Quality, material durability and even safety (slips and falls).
It’s a gas
Radon is a naturally occurring radioactive gas and is the number one cause of lung cancer among non-smokers, according to EPA estimates. Overall, radon is the second leading cause of lung cancer. Radon creeps up from the ground into a home or building and can concentrate to unsafe levels.
Performing a radon test is the only way to know the level of exposure that a resident has. Radon testing takes time, at least 48 hours, and there is no way around that.
Recently some new, lower cost detectors have become available (see www.bit.ly/TT-radon) and while they are not suitable for formal real estate evaluation, they do give fairly accurate long term results and present as a form of screening for more in depth evaluation.
Watts next
Home performance evaluation/work may also delve into electrical consumption. Luckily there are many devices available to look at plug load usage as well as well as total home (panel or sub panel) monitoring. Some of the devices are intended for temporary use, while others may be installed to monitor and either datalog or log and continuously monitor and report data via wireless connections and/or web portals. Some devices actually calculate KW and KWH which provides the rich information necessary to compare to bills and budgets and help influence desired changes in electrical consumption.
Like any trade, good home performance work comes from the proper use of diagnostics tools coupled with training and field experience. Some of the tests and diagnostic products mentioned in this series may require certification or training for use. It is not recommended that untrained individuals try to perform many of these tests as serious injury or property damage may result; call a professional.
I hope you enjoyed and got something out of this series of articles. Remember, TruTech Tools, LTD (www.TruTechTools.com/Resources) has more free technical reference materials and videos available as well the diagnostic products mentioned.
Posted In: Building Performance, Residential Buildings
