Moisture in Insulation

Alan C Grubb · 09-01-2011, 04:08 PM

Recently ran across this in an attic of brick home . Photo shows some RMax Poly Board in the attic,the bubbles caught my eye and when I put a moisture meter to it went thru theroof (no pun intended). All woodstructure around it was normal. Any theories as to what might have happened and how would you write it up?

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**Jerry Peck** · 09-01-2011, 04:20 PM

Originally Posted by Alan C Grubb

when I put a moisture meter to it went thru theroof (no pun intended).

The moisture meter likely went off scale due to the fact that you were trying to read through the foil ... foil will set moisture meters off, kind of like wetting your fingers and touching the moisture meter, it will go off real high.

Did you poke a hole in the bubble and see what happened? May have just been from hot air (literally, it is in the attic, hot air expands, adhesives fail, air bubbles form, air in the air bubbles expands as it heats up), you could say that the bubbles may have just been "full of hot air".

Alan C Grubb · 09-01-2011, 05:17 PM

Thanks Jerry never thought of that, but it makes perfect since. I did stick a bubble but just air that is what had me confused. Just one of those "duh" moments. Thanks again.

**John Dirks Jr** · 09-01-2011, 06:37 PM

Alan, also be careful when using moisture meters wherever there can be metal under the drywall. Corner pieces on drywall, flashings under windows, etc. Those materials will make the moisture meter read positive when the material is actually dry..

Terry Clayton · 09-01-2011, 09:12 PM

Originally Posted by John Dirks Jr

Alan, also be careful when using moisture meters wherever there can be metal under the drywall. Corner pieces on drywall, flashings under windows, etc. Those materials will make the moisture meter read positive when the material is actually dry..

Metal studs play havoc with the meters, I knew they were there and found them easily, but I was not expecting there to pieces left in the stud space and found several that crossed the stud space at different levels and thought there was moisture present, fortunately I found a small area opening I was able to fit my camera into and took some pictures and found no moisture.

**Eric Barker** · 09-02-2011, 07:59 AM

Good thread. Understanding your equipment is vital. I recently bought Tramex's roof and wall meter - Good Lord is that thing sensitive. All kinds of non-moisture stuff can set it off and if I don't use it wisely I'll come up with some pretty far off base conclusions.

**Scott Patterson** · 09-02-2011, 08:23 AM

Moisture meter class 101!
Everyone that uses a moisture meter (and that should be anyone that claims to be a home inspector) must know what can cause a false positive in a home. The following are some common and semi common items in a typical home that will cause a false positive:

1. Drywall corner beads
2. Plaster walls/ceilings with metal lath
3. Drywall screws/nails
4. Foil backing on various substrates and insulation boards
5. Mylar backing on various substrates and insulation boards
6. Mylar used as a wind barrier behind the drywall
7. Cast iron pipe in the walls
8. Some specialized or special effect wall paints
9. Carpet tack strips
10. Ceramic tiles with a metallic finish or look.

**Rich Goeken** · 09-03-2011, 04:03 AM

Originally Posted by Scott Patterson

Moisture meter class 101!
Everyone that uses a moisture meter (and that should be anyone that claims to be a home inspector) must know what can cause a false positive in a home. The following are some common and semi common items in a typical home that will cause a false positive:

1. Drywall corner beads
2. Plaster walls/ceilings with metal lath
3. Drywall screws/nails
4. Foil backing on various substrates and insulation boards
5. Mylar backing on various substrates and insulation boards
6. Mylar used as a wind barrier behind the drywall
7. Cast iron pipe in the walls
8. Some specialized or special effect wall paints
9. Carpet tack strips
10. Ceramic tiles with a metallic finish or look.

Scott, Sounds like you have found All of them through the years!

**Gene South** · 09-03-2011, 04:32 AM

The meters can also give false positives on the dried residue of previously spilled liquids. The salts in dried urine around a toilet floor will set the meter off, even when you cannot see the residue. Also found some floor cleaners, etc that had been spot-used on floors can give false signals. Just my observation.

**Scott Patterson** · 09-03-2011, 07:55 AM

Originally Posted by Rich Goeken

Scott, Sounds like you have found All of them through the years!

Yep! Experience is the best teacher and I have been a good student!

**Michael Thomas** · 09-03-2011, 10:03 AM

Originally Posted by Scott Patterson

Moisture meter class 101!
Everyone that uses a moisture meter (and that should be anyone that claims to be a home inspector) must know what can cause a false positive in a home. The following are some common and semi common items in a typical home that will cause a false positive:

1. Drywall corner beads...

Also, metallic ducts behind finished wall and ceiling surfaces.