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Old 1/21/19, 12:54 PM
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dandersen dandersen is offline
Retired Member
Join Date: Jun 2005
Location: Nashville, TN
Posts: 10,633
Default Re: Tell Me What You See!

William, I think you made a great assessment with the available information provided, which is insufficient to make a determination of anything one way or the other. I especially like your statement "So, the logical approach would be to employ a process of elimination."! We should spend more time on "what it is not" than "what it seems to be".

ie. there is information about flashing and roof issues that were not addressed because of existing weather conditions. Is there not access to the underside of the roof in these locations?

I see discoloration in the digital pics: however, this does not verify actual roof/flashing leakage.

1. We are looking at scans in a room that frequently experiences 100% rh during use. Any slight heat loss in the building envelope will result in condensation.

2. Cooler Sheetrock promotes condensation of water vapor. So what is causing cooler temps? Well we must consider the three methods of heat transfer; conduction, convection and radiation. As the top of the ceiling or walls are not exposed to the sky, we can "eliminate" radiational cooling. Will a lack of proper insulation allow air movement and subsequent heat loss. Yes it would, but we may not be able to assess this visually without invasive inspection. Does the density of materials use to construct this building envelope cause some areas to conduct heat at different rates?

There are two other considerations. Can we use our IR Building Science training to determine "Apparent R-Value" of the cooler spots of the wall/ceilings? Or we can just assume that there is no insulation there based on the knowledge of construction practices were insulation is not used in particular areas. Second, we can use psychometrics to determine what temperature we should be expecting from wet evaporating objects subject to the ambient air. For example if the thermal exception is colder than the calculated wet bulb temperature, we are not looking at just evaporative cooling. This leads to the possibility that this is not a roof leak. We can not exclude this from being water, but that it could be water due to adverse conditions such as air leakage and/or inadequate insulation.

My next step would be to apply a convective heat source to the anomaly and record the reaction. This is the the only method to detect moisture over air leakage and insulation issues.

3. Thermal assessment: how do the thermal anomalies represent the occurring heat transfer? There are numerous targets in each thermal scan. How do each of these target areas represent the heat transfer? Did you tune your scans for each and every target represented in the scan? If not, the Delta T data will be significantly in error.

Without accessing the raw data in these scans, and reliant on the limited data provided, I can eliminate 99% of the thermal exceptions based on what I know about how buildings are constructed in my area, and how they fail to function as intended. I would conclude that "if" this were a moisture issue (Leakage), it could be a condition where past leakage had occurred but has significantly evaporated over a substantial period of time. My next act would be to cause the leak to occur and document it as it happened.

4. "If" what I see in digital pics is in fact water staining, taking moisture meter readings is insignificant information. Sticking the wall/ceiling with a moisture meter may or may not record moisture. Thermal scans indicate that if this is moisture, it is an inndiract measurement of conditions deep inside the wall (likely beyond the functional ability of a commonly used moisture meter). Either way, the information is irrelevant because the current condition depicted by IR indicates evaporated moisture (if anything). You will not get usable data using a moisture meter in this state.

If you don't go find more data, this inspection is inconclusive as to the "source" of this condition. Even if you can say it's wet, you can not determine the source of why it is wet. Subsequently you can not fix the problem. This leads to the people that call me and tell me they have spent thousands to fix the problem, but it's still there and they have no idea what to do about it.

David A. Andersen & Associates
Clarksville - Nashville Home Inspector Lic#40 (Retired)
ITC Level III Thermographer Cert#1958
Building Science Thermographer Cert#33784
HVAC Certification EPA Cert#2046620
BPI# 5015804