I’m starting this course today, Thanks InterNACHI for its availability. I dont have any questions or input at this time, but thanks for the other feedback you other Inspectors are sending in. All information is appreciated.
I Just completed the insulation and vetilation course, and I have some questions. Well I also recently completed the Radon testing course. I noticed that in Radon mitigation requirements, when using 6 mil plastic, seams should be lapped 12" and sealed and in the ventilation section when 6 mil is being used its only requiring a 6" lapped seam and to be sealed. Being in a Zone 1 area, for Radon, why wouldn’t I expect all 6 mil plastic to be lapped 12" ?. Could I make this my standard ?. I know the two purposes are different but they both aid in minimizing adverse effects. How can this 12" lap be standardized for 6 mil applications in crawlspaces and basements be executed? Am I over thinking it ?.
Good question. In my inspection reports, I’d refer to “best practices” or “standards.” I’d pick one of them to refer to, including the IRC. And don’t use the “code” word. However, in reference to “lap,” I was never that specific in my report recommendations. It’s up to the contractor and possibly the AHJ for best installation practices. Not me (as a home inspector).
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Interior
starting this course now
On this page it notes a way of determining R value by multiplying the number times the thickness of the given insulation. Typically this would be assumed to be the thickness in inches, but perhaps it might be good to note that here for folks that aren’t as savvy.
http://education.nachi.org/show.php?element_id=1826&course_id=68
Ja’nette
Ja’nette
starting the course
Last course left…
Starting
Just finished up the exterior course and now it’s time for the interior course. Look forward to adding some more vital information and becoming all the more knowledgeable in becoming a top notch inspector!
starting interior inspections
[FONT=Garamond][size=3]“Repeat after me “don’t ever, ever put a layer of sand
between a plastic vapor barrier and a concrete slab –
don’t even think about it.””
This is a quote from Joseph Lstiburek in an article he wrote for Building Science (www.buildingscience.com) entitled Concrete Floor Problems (*http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?topic=resources/flooring-probs](http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?topic=resources/flooring-probs)) .* There are many great articles at the site that help bring together what we are learning here.
I noticed in the illustration of the basement foundation wall in the section titled Exterior Foundation Insulation there was an optional layer of sand between the vapor retarder and the concrete slab, and then I came across the article which explains why this is not a good idea.
My sister had some severe moisture problems with her slab and I think this may have been part of the very costly problem which was solved using the dimpled membrane between the slab surface and the floor covering.
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"Sometimes, a sand layer is installed on top of the vapor diffusion retarder, which is an incorrect installation and will create problems. "
I just found this under the section ‘Vapor Retarder and Capillary Break’ in this course.
Vapor barrier vs vapor diffusion retarder
“This “retarder” stuff drives me crazy. At the very beginnings of the history of vapor diffusion control—Ruddick (1914), Rowley (1941), Hutcheon (1954)—the term used was “vapor barrier.” The “vapor retarder” thing only started because of a lawsuit in Pennsylvania where the court found the term “vapor barrier” to be a misnomer and this led the weak-kneed cowards at ASTM to adopt the word “retarder” in place of “barrier” rather than telling the court to mind its own business. Reese Achenbach will verify that this story is not an urban legend but true—and you all thought that building science was uninteresting.” http://www.buildingscience.com/documents/insights/bsi-024-vocabulary/?searchterm=vapor barrier vs vapor diffusion retarder
According to the Lstiburek (this guy is good!) quote above and the two definitions below from this course they sound the like the same thing:
A vapor barrier, as defined by the International Building Code (IBC), is classified as 1 perm or less.
The 2006 International Residential Code (IRC) defines a vapor diffusion retarder as a material, membrane or covering, such as foil, plastic sheeting or insulation facing, having a rating of 1 perm or less.
The only thing that is still confusing is how there can be Classes (3,4) with greater than 1 perm for something that is defined by being 1 perm or less. I think this fact causes most of the confusion or am I misunderstanting something?
Three Classes of Vapor Retarders.
They are shown and described here.
http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers/:)
Retarder vs. Barrier
Defined at http://education.nachi.org/show.php?element_id=1878&course_id=68 and
Compared at http://education.nachi.org/show.php?course_id=68&element_id=1879
Thanks for the help Marcel and Ben.
Yep.
And if you ever think that a part of a course could use some improvements or more information, feel free to contact me.
We love it when members help make our courses get better and better.
Starting today.
Codes in Florida require the handrail to run past the top and bottom of the stairs 6’’. Has California not updated their handrail code ?