So we see it more and more, "Zero Perm crawl space vapor barrier". Articles are written about it, professionals recommend it and resellers give it their own special name. For some reason companies in the crawl space industry, either just getting in it or have been in it for some time, feel they need a magical product in order to sell the job. Seems few are really concerned about results, but rather how much can they make.

The Truth
What is the most important characteristic of a crawl space vapor barrier? I will give you a hint- It's not the perm rating. It is the quality and durability of the material you use. The codes (both IRC and NCDOI no longer site a minimum "perm rating" as they once did. Today the requirement is minimum 6 Mil.

North Carolina Department Of Insurance-
R409.2.1 Ground vapor retarder. A minimum 6-mil (0.15 mm) polyethylene vapor retarder or equivalent shall be installed and secured...

So you see not much focus on the famous "perm rating". I will tell you why. The perm rating of an actual 6 Mil (not home center "visqueen" that product is an actual 4 mil) is between 0.1 and 0.06, of course the exact perm will depend on the quality of the polyethylene. In a 1200 sq ft crawl space with 3' high walls the amount of moisture that will pass through that 6 Mil plastic is 0.59 pints of water in 24 hours. Now that is just the plastic, not the tape or untaped seams. Simply put- if the barrier could be put in the crawl space as one piece and there were no obstacles, .59 pints of water is all the plastic would let into the crawl space each day (pressure, temperature and other factors will affect these results but unnoticeable so).
So what's all the "hub bub" about perm ratings? The perm rating is important, its important that it is less than 0.1 perms, past that it's just a bonus. That same crawl space with a 0.1 perm would increase your pints per day from 0.59 to nearly 2.0, that is four cups of water in 1200 square foot. The truth behind the BUZZ about perm ratings is well marketing, what else?

The Untruth
Like the "Antimicrobial" trick, the perm rating campaign is meant to prey on the ones that really don't understand the technical side of this business. Two of the most common deceptions are:
Zero Perm & Dividing the results
1. Zero Perm-This marketing scam is the most intentionally deceptive. Just from reading this article you have some kind of idea how perm ratings are presented. They are in whole numbers or in fractions of a number displayed as a decimal. So, for example the popular house wrap Tyvek™ has a perm rating of 48.0, while the 12 Mil DrySpace™ crawl space vapor barrier has a perm rating of 0.053.
Here's their scam- They display only whole numbers as their perm rating. While the honest guys show 0.053 perms, the dishonest guys show their 60 Mil crawl space vapor barrier as zero perm by doing this 0.103 instead of showing you this 0.103.
They do this because most consumers know with perm ratings, lower is better. Once they have you convinced their product is "Better" they charge you handsomely for the result of their deception. The also state 99% aluminum and that's not true either, but I will write about that next time.

2.Dividing The Results-This one is a bit harder to catch.
It makes me cringe each someone asks me for the perm rating of our DrySpace™ vapor barrier. Not because I'm ashamed of the performance, but because I know the person asking has no idea what they are asking for. Perm ratings are given in grains of water that pass thru a square foot of material per inch of mercury every 24hrs.
Here's their Scam-If your perm rating was 0.053 they will divid that number by 24 (hours in the day) and POOF the new perm rating is 0.0022. Who has the lower perm rating now? Of course they don't tell you they did that, mostly because you didn't ask. Two other scam that go with this is companies use the WVTR as their perm rating, while others use the metric perms (which is lower than US perms).

What do you do? The answer to this question is ALWAYS going to be- Do your homework and buy from a reputable company. Currently there are no "Plastic Police" so its a bit of a free for all.

I hope this helps in your search.....

If you get a minute drop us a line, we would love to hear from you!

Matt

Relative Humidity (RH) is the byproduct of two conditions in the atmosphere, temperature and dew point. To control or alter the RH you must manipulate either dew point or temperature.

Dew point temperature is the absolute measure of how much water vapor is in the air- Source The dew point is always less than the air temperature. The closer the dew point temperature is to the air temperature the closer the RH gets to 100%. Example- Dew point temperature 70F and air temperature 70F = 100% RH

If the home has an encapsulated crawl space then the dew point inside the house will be different than that of outside the house. Air temperature will actually dictate what the RH is at any given dew point temperature. Inside the home we keep the air temperature at a comfortable level, say 70 degrees (which I am assuming is this case). A crawl space that has been sealed and encapsulated will maintain an air temperature similar to inside the living area. With that said, similar air temperature means about 5 degrees cooler than the living area. This is due to the consistent temperature of the earth under the vapor barrier, a geothermal effect. This is good in many ways for the home, because the air temperature will remain between 60F - 68F degrees most all of the time. Back to our RH problem, so the house (assuming ) is 70F degrees (air temperature) puts our crawl space at (again assuming but will be close) 65F degrees (air temperature). In this scenario I will need to know either the dew point or RH to figure out the rest of the equation. In your email it states the RH levels so I will use them to find the dew point. Once I know the dew point I can show you what is going on in the crawl space and why it's happening.

The assumptions-

House air temperature: 70F/49% RH
Crawl air temperature: 65F (house temperature minus 5 degrees)
Crawl RH:Unknown
Dew point temperature in the living area- 50F degrees

Using a dew point calculator to figure out RH in the crawl space with this information-

Crawl air temperature (assumption): 65F
Dew point temperature inside the home: 50F (also the dew point in the crawl)
Crawl Space RH is 60%

So you can see there is an 11% difference in RH levels between the home and the crawl space. The only difference is the air temperature between the two spaces. If you raise the air temperature in the crawl space to 70F, same as the living area, you will have the same RH 49%. Setting the dehumidifier at 49-51% means it is trying to lower the dew point temperature in order to achieve a lower RH. To successfully lower the dew point temperature in the crawl space you must lower it for the entire house. This is quiet a task for any dehumidifier when you consider the traffic in and out of the house, the amount of showers taken, moisture from cooking, moisture in the wood inside the home and the natural moisture loss from each person living in the home. It will cause the dehumidifier to run more then 5 min an hour. If you wish to accomplish a shorter run time for the dehumidifier, then you can raise the air temperature in the crawl space. This can be done by conditioning the crawl space with air from the home, helping to deliver access heat to the coldest places- the crawl space. Of course when you raise the temperature to control RH, you make the RH level much more critical in the Mold growth equation (explained better in the next paragraph). The other option is to set the controls on the dehumidifier to a higher setting, maybe 58-60% (based on 65F degree air temperature).

There are several factors in Mold growth; dew point temperature is only one of them (amount of moisture in the air), the other being air temperature. RH is simplified as a mixture of dew point temperature and air temperature. This simplification does not allow for any absolute rules, for example Mold will grow once RH reaches 55%. As a convenience to avoid teaching in depth classes on dew point temperature and air temperature each time a dehumidifier is sized and installed it is widely expressed- 'to avoid mold growth, a safe RH is below 55%'. But, once RH is really understood that statement does not hold enough information. Last week, here in Michigan, our outside RH was 85% but the temperature was 31F degrees. Mold growth is not imminent in this equation because the air temperature is far to cold, but under the understanding of "less than 55%" it would be widely considered a mold growth threat. Just like RH is tweaked using air temperature, so is Mold growth. In a crawl space that has an air temperature below 70F will not generally be threatened by Mold growth until the RH rises past 67%. Keeping an encapsulated crawl space that has an air temperature of 67F and an RH of 58-60% will produce excellent results in the battle against wood rot, odor, Mold and mildew growth and a high electric bill caused by the dehumidifier. Of course the owner if the house has to add the crawl space to the list of maintenance duties required by the home, bi-annual crawl space inspections are strongly recommend.

Link: http://cureforthecommoncrawl.com/

There are a few kinds of insulation that you should use in a crawl space and a few kinds you should not. One of the kinds you should not is polyurethane closed/open cell spray foam insulation. The spray foam guys will tell you different and they will tell you their foam will seal all air penetrations in the foundation and sill plate. Take a look at this link, it discusses spray foam vs. rigid from a walking freezer point of view- http://www.squidoo.com/cooler-insulation

What the spray guys won’t tell you is:

Solving the mystery odor

Crawl space encapsulation is gaining ground in popularity across the United States and Canada. Even with its new popularity some people have shown caution by waiting to see if this new technology really works before investing into the thousands of dollars it takes to complete this home improvement. The good news is most of the bumps have been ironed out. We have yet to find a way to stop price gouging and contractors installing it improperly, but everything else is improving.

One of the bumps that has been fixed, most recently, is a mystery odor that appears after the encapsulation, somewhere between 30 to 60 days after. It was a mystery for obvious reasons, the encapsulation was suppose to stop the odor problems. So when it turned out that it seemed to create a new one, well customers nationwide were a bit more than upset. This problem first hit my desk in the spring of 2009 and the call was coming from Memphis TN. One of our contractors there was having a problem with an odor in a crawl space he encapsulated with the DrySpace™ brand vapor barrier. This house was a new home and the new owners were not accepting this odor.

Here’s what happened-

I get a call from Walter complaining that our DrySpace™ vapor barrier seemed to be causing an odor. He said it was hard to describe the smell, kind of like cat pee, it was terrible. My first reaction was the DrySpace™ vapor barrier is completely inert and there is no off gassing or smell to the plastic. Walter was quick to accept this explanation as he also believed it was not coming from the DrySpace™. As I understand, Walter relayed this information back to the contractor that built the house and they continued their attempt to figure out this problem.

I heard nothing more until October of 2009 when Walter called again, this time with much more frustration. As it turns out the contractor required him to remove the 20 Mil DrySpace™ (because he was convinced that was causing the odor) and install a 6 Mil clear plastic from the local hardware store. Within days of installing the 6 Mil, the odor was far worse than before and the contractor had Walter remove it. Believe it or not, the contractor then had Walter install the 20 Mil DrySpace™ again. With the second install the odor receded to the original complaint level which in turn caused Walter’s second phone call to me. At this point Walter, the contractor and the homeowner were desperate for a solution.

Upon further investigation I found out this was a new house but built on an old foundation. To be more exact, the foundation was a basement but the home’s contractor filled it in to make a crawl space. I know, I don’t get it either. Once I found this out I quizzed Walter on where the dirt came from. Of course he didn’t know but he was off to find out.

Walter called me a few days later with information, the contractor would not tell him where the dirt came from. To make a long story short, after several attempts at trying to find out where the dirt came from, I made a reasonable guess that it was not acquired through standard channels. My guess was that it came from a farm or a field somewhere. Since I knew the odor was not coming from the barrier and there was no fiberglass insulation in the crawl space, it seemed it could be coming from only one area; under the DrySpace™. It also seemed the dirt was the odd man out in this situation by being the unknown.

The Solution-

If it was coming from under the barrier then I thought maybe it was a gas like methane. I told Walter to mitigate the air under the barrier as if the crawl space had a Radon Gas problem. He and I both understood this was not Radon because Radon does not have an odor, but the process would remove any soil gas that was under there causing an odor. After a quick run down on how to set up the piping and a collection point he was off to put it place.

I called Walter after about a week to find out the outcome of my theory. Turns out the odor was gone the day following his installation of the mitigation system. Ahh, music to my ears.

Good story, but is that enough to call it a solution to every mystery odor found in a crawl space? I think not.

In the fall of 2010 I received a phone call from another DrySpace™ installer complaining of the same thing, also from TN but from Knoxville this time. Gary had three “stinky” crawl spaces with three upset customers. It seemed he tried everything, but taking out the DrySpace™ to remedy these problems. I told him the story about Walter and that he should try the same solution.

At about the same time I got two more phone calls about this problem, both from North Carolina. One of them was yet another installer out of Greensboro and the other was an customer of Moisture Loc in Charlotte. The installer had five “stinky” crawl spaces and his customers were complaining that they could not sleep at night the smell was so bad. The homeowner had everyone from indoor air quality professionals to HVAC contractors to the company that installed the barrier at his house trying to figure out where the smell was coming from.

Like Walter and Gary, I told Greg (the contractor from Greensboro) and Bill the homeowner from Charlotte the story about Walter and that they should use the same method to fix their problem. Gary, Greg and Bill each did and it solved their problem as well. That’s 10 crawl spaces with 100% success, now I’m thinking it’s the solution to every mystery odor in a crawl space. *Note- not all “vapor barriers” sold for crawl space encapsulation are odor free; even additives can cause off gas odors. It is very important to know what products are being installed in your home. Ask for the DrySpace™ brand crawl space vapor barrier by name, its guaranteed not to cause odor.

If you have any questions on how this process is done please feel free to contact us at 248.960.8870 or on the web http://crawlspaceinfo.com

For the last 2 or 3 years I have notice more and more plastic hit the market as a "cheap" crawl space vapor barrier. If the homeowner wants a cheap plastic in the crawl space that's fine, it's their home. What bothers me is the companies that are selling the cheap plastic offer it as quality and sell it for a premium. There isn't much I can do about it except complain AND do my best to make sure people know about the DrySpace vapor barrier. So.....

To insure there is no confusion on what you are buying we have changed the look of the DrySpace vapor barrier. Now all you have to do is look at the back of the barrier and you will know you have a quality crawl space vapor barrier made by an American company that will last a life time without falling apart. We changed the look of the DrySpace vapor barrier, the back is now SILVER and is known as the SilverBack DrySpace. We made a few other changes to make it easier for you to identify our products by looking at them. The width is now 13' 4" wide instead of 12'. This helps meet the needs of crawl spaces that have supports 12-13' from the foundation wall, which is most crawl spaces. By making our product wider it leaves the installer more options on how to best install the DrySpace with the fewest seams which strengthens the integrity of the installation.

The second change we made was to offer different three sizes; 13'4" x 100", 13'4" x 60" and 6'7.5" x 100". This also allows the installer to make the best choices for an install with the fewest seams, allowing less waste and limiting over bought material.

The third change we make was to the reinforcement. It is still as strong but now it has a new pattern to help identify the DrySpace vapor barrier from the rest of the pack.

All of these changes were made to help protect the customer, contractor and the DrySpace brand. Our vapor barrier products are made in the USA and we try very hard to source all of our products in the USA when possible. Products made in the USA are more expensive but are better made and have consistent quality. You will never have a problem with our products like the construction industry is having with the "Chinese drywall". That link is worth looking at!

In short, CrawlSpace Concepts is an honest company offering a quality product line that we are proud of . We are an accredited member of the Better Business Bureau with no complaints, ever and a member of 7 different Chamber of Commerce! It is very important to us to keep this reputation and we will continue to be leaders in the market.