Re: Re: Attic insulation and Barriers

[Guest guest]

Sam,

See also my reply to Barb.

The vapor barriers I was describing were for dirt crawl spaces not

attics, because that was the original question.

Vapor barriers in attics are a very different beast and are more

climate dependant than for crawlspaces. Think back to the

discussion Barb and others had recently about sealed attics with

conditioned air vs open attics with outside air.

The key to vapor barriers in general is found in their permeance

rating, or perm rating for short. It is a rating for how much

moisture can pass through the material. A perm of less than 1 is

considered a barrier. Higher than one are retarders because they

don't stop all the moisture.

Most materials will have a perm rating in their technical

specifications. An excellent description of permeance and more

is by the Univ of Mass at:

http://bct.nrc.umass.edu/index.php/publications/by-

title/housewraps-felt-paper-and-weather-penetration-barriers/

Perm is at the bottom of page 3 under the heading " How Much is

Enough? " Immediately before that is " Apples to Oranges, " an

excellent description of how not all is equal because of how the

test is set up and conducted. You'll find the problems very familiar

to those for mold testing.

Others I've encountered is a perm rating for a barrier that was

over 200. They use the same name but a different method. For

composites like wall paper the perm may be 1 for vinyl but the

backing material is 30 (more like tissue paper). You need the

rating for the entire assembly but good luck finding it.

For example, I've been working with a client for over a year on a

series of many products. I never, and I mean never, got an

explanation that made any sense whatsoever for one wallpaper.

They had their own system which only compared one of their

products to another of their own. They had no measurment

comparing to another product even though they called it a " perm

rating. "

So the short answer to you question about which material is look

for the perm rating and then verify what they mean by perm

rating. Is it the objective standard or their own made up stuff?

Carl Grimes

Healthy Habitats LLC

-----

Carl,

Would the same hold true for vapor barriers in dirt crawl spaces as you

are saying could happen with vapor barrier in an attic?

Is the material for the vapor barrier the same? What is the right

material?

Thanks very much,

Sam

Carl/: When you say a vapor barrier on the ground, you mean right

on the dirt, not on a cement floor, correct?

Can paint on concrete be an effective vapor barrier?

<

[Guest guest]

Thanks very much Carl for all this information. At some point we will have to

address this with our crawl space. Really appreciate it. It is frustrating that

there seem to be no real standard. Is there a company that makes a 1 rated vapor

barrier that you trust from prior experience with your clients? 

One other question--- is there ever problems with these vapor barriers

off-gassing into the house above? We had a pitch from a remediation company that

wanted to use one of those crawl space encapsulation set-ups. It stunk like a

bad pool liner smell.

Thanks again as always,Sam

So the short

answer to you question about which material is look 

for the perm rating and then verify what they mean by perm

rating. Is it the objective standard or their own made up stuff?

[Guest guest]

Sam,

You can Google " vapor barriers " and get a long list. Each should

have their technical specifications page where you can see their

perm rating. A specific one which I'm more familiar with is

VaporBlock by Raven Industries. Main web site is at:

http://www.ravenefd.com/CF/VR/index.php

Technical specifications are at:

http://www.ravenefd.com/pdf/VB6-10-15.pdf

As you can see its Perm is less than 1. In fact, it is 0.1 or below.

The 10 mil thick if fairly puncture resistant but the 15 mil is even

better. Depends on what is under the barrier and how often

someone will be walking or crawling over it. Either one is much

better than the 6 mil routine material for radon barriers.

I have specified this barrier in hundreds of houses including those

with MCS. Only one rejected the material due to off gassing.

Other manufacturers material may be better tolerated if this one

is a problem.

A couple of other details: This is too heavy to be simply taped to

the wall. Heavy caulk won't work for long either. It should be

installed with a long U shaped piece of metal along the perimeter

which is then ramset to the foundation. Between the foundation

and the U channel should be an adhesive thick enough to fill in

pores and irregularties of the concrete. The combination of thick

adhesive and the mechanical pressure from the U channel seals

the edges so no moisture, radon, odor or other materials well get

out. Which means air from above won't get in. Therefore, no

mold underneath it. Even if there was mold and bacteria and

other filthe already there, it won't get through or around the edges

of the barrier.

Carl Grimes

Healthy Habitats LLC

-----

Thanks very much Carl for all this information. At some point we will

have to address this with our crawl space. Really appreciate it. It is

frustrating that there seem to be no real standard. Is there a company

that makes a 1 rated vapor barrier that you trust from prior experience

with your clients?

One other question--- is there ever problems with these vapor barriers

off-gassing into the house above? We had a pitch from a remediation

company that wanted to use one of those crawl space encapsulation set-

ups. It stunk like a bad pool liner smell.

Thanks again as always,Sam

So

the short answer to you question about which material is look

for the perm rating and then verify what they mean by perm

rating. Is it the objective standard or their own made up stuff?

[Guest guest]

Sam, our crawl space is clean dry and no odor at all. We have about 3

layers of 7ml heavy plastic down, and about 3/4 of the way up the walls. All

around the edge is a heavy layer of pea gravel. The plastic was layered a few

times alternating over seams and on the top are some cotton bags of gravel.

We even have a flood alarm right under the bathroom area in case of a

leak. No odor to the plastic which is the semi transparent type.

>>

Thanks very much Carl for all this information. At some point we will have

to address this with our crawl space. Really appreciate it. It is

frustrating that there seem to be no real standard. Is there a company that

makes a

1 rated vapor barrier that you trust from prior experience with your

clients?

One other question--- is there ever problems with these vapor barriers

off-gassing into the house above? We had a pitch from a remediation company

that wanted to use one of those crawl space encapsulation set-ups. It stunk

like a bad pool liner smell.

Thanks again as always,Sam

[Guest guest]

Flood and water leak alarms! Should be emphasized and mentioned often.

Carl Grimes

Healthy Habitats LLC

(fm my Blackberry)

Re: [] Re: Attic insulation and Barriers

Sam, our crawl space is clean dry and no odor at all. We have about 3

layers of 7ml heavy plastic down, and about 3/4 of the way up the walls. All

around the edge is a heavy layer of pea gravel. The plastic was layered a few

times alternating over seams and on the top are some cotton bags of gravel.

We even have a flood alarm right under the bathroom area in case of a

leak. No odor to the plastic which is the semi transparent type.

>>

Thanks very much Carl for all this information. At some point we will have

to address this with our crawl space. Really appreciate it. It is

frustrating that there seem to be no real standard. Is there a company that

makes a

1 rated vapor barrier that you trust from prior experience with your

clients?

One other question--- is there ever problems with these vapor barriers

off-gassing into the house above? We had a pitch from a remediation company

that wanted to use one of those crawl space encapsulation set-ups. It stunk

like a bad pool liner smell.

Thanks again as always,Sam

[Guest guest]

I know this is a very old post but we do have a flood alarm in our crawl

space. Good for plumbing and other.

Flood and water leak alarms! Should be emphasized and mentioned often.