Posts Tagged ‘moisture’

Condensation in a manufactured home crawlspace with “ventilation”

April 27, 2011

So, your brand new home was built with a crawlspace that has the vents installed according to code requirements. Further, the crawlspace has a proper vapor barrier covering the floor. You should have absolutely NO concerns about moisture in the crawlspace, right? Well, maybe.

Here is one case where I found out in a rather uncomfortable way that a crawlspace built with proper ventilation and a moisture barrier (of sorts) can indeed get lots of moisture.

One spring day last year, I left a meeting in Columbus around noon and headed toward Wilmington to do an FHA inspection on a new manufactured home installation. This home was built on a crawlspace with a poured concrete slab floor. The home’s air conditioning was not operating because it had not yet been fully installed. Wilmington had received light rain the morning of the inspection. The home reportedly has had drainage problems at one end; but the crawlspace was dry. By the time I got to the home, we were experiencing our usual humid weather our springs and summers bring.

Let’s get into the photo (fun) part of the story.


This photo shows a front view of the home on the day of the inspection. Note the right crawlspace perimeter wall.



This photo shows a closer view of the right perimeter wall area, which was still having some drainage problems on the day of the inspection.



When I went to enter the crawlspace, this view greeted me. Note the water droplets hanging on pretty much every surface in the crawlspace; but the slab is totally dry. BTW, that metal bar angling from the slab to the home’s frame is a lateral brace—part of the home’s anchoring system.



In a view down the crawlspace, water droplets can be seen on pretty much all surfaces.



And since I have a lot of pictures, here is yet another view of the water droplets on surfaces. The lateral brace in the photo is the second of the pair of braces used in the anchoring system. Note all of the droplets on the bottom board (the membrane along the bottom of the home.



This photo shows a closer view of water droplets on bottom board—and by this time on my camera lens.



Yep, a lot of water was present. And every time I raked any of these surfaces, I got a shower of cold water—not a pleasant experience.



This photos shows that the crawlspace vents were wide-open. Interestingly, no surfaces near the vent has water on them.


Where am I going with this story? All of the water droplets seen in these photos are due to condensation. The prior night, the area where the home was installed had colder temperatures and, since the home was not heated, the crawlspace temperatures were also on the chilly side. The next day, as is common in our area, outdoor temperatures climbed rapidly, as did the humidity levels, fueled in part by recent rain. The crawlspace surface temperatures remained below the condensation point of the air, causing water droplets to form on pretty much every surfaces inside the crawlspace, except those near the vents where the surfaces apparently warmed more rapidly.

I believe that this case is proof that even properly ventilated and moisture protected crawlspaces can get water in them. The condensed water may have come from water vapor coming up through the slab. However, the open vents provide a more open path to water vapor in the outside air.

Even if water vapor had come up through the slab, this case shows that the water vapor can be converted back into water droplets that can be absorbed by the crawlspace materials exposed to the water. Thankfully, the intact bottom board of this manufactured home prevented moisture from reaching the insulation above the bottom board. Otherwise, the insulation could sop up the water like a sponge and hold it long enough to possibly cause more serious issues.

However, this case shows that water can get inside a crawlspace without liquid water entering the crawlspace. If surfaces inside the crawlspace are below the dewpoint of air entering the crawlspace, condensation will occur. Having vents in the crawlspace open it up to outside air which can supply the moist air. Open vents can also allow heat in the crawlspace to escape, allowing surfaces in the crawlspace to cool to below the dewpoint temperature of air that may enter the crawlspace later.

Now, if the crawlspace does not have a vapor barrier, moisture issues could be much worse. I am looking forward to the time when I enter a crawlspace that actually has fog—and I have been in some that were close.

Oh, one other lesson I learned is that if you are going to enter a crawlspace with condensation on the surfaces, you will get wet. In this case, I was soaked to my underwear by the time I left the crawlspace. Very unpleasant.

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Want Proof That Termites Are (Misplaced) Evil?

April 15, 2011

I recently had a structural inspection that showed (once again) how much damage a gang of termites can do to a home. This damage was located in the rim joists and sole plates of a home with brick veneer. However, these termites had incentive to invade the wood due to the rim joists and sole plates being apparently exposed to excess water coming from behind the brick veneer.

Some background is needed before getting into the termite business. The sole plates are the boards that sit atop the foundation, upon which the first floor joists rest. Rim joists, also known as band joists, are the boards that box in the floor joists. The ends of all floor joists resting on the sole plate but up against rim joists. Rim joists also help stabilize the joists and help keep them from angling or twisting.

In a properly designed brick veneer wall, a gap is supposed to be installed between the brick veneer and the exterior wall sheathing. The exterior sheathing is the material that covers the outside face of the wall framing. Sheathing can be boards (in older construction), or plywood or oriented strand board (OSB) panels, although in some construction Styrofoam panels may be installed between the plywood or OSB panels. The gap between the exterior sheathing and brick veneer is supposed to serve as a drainage plain to provide water that gets past the brick veneer a drainage path to the base of the wall. And, believe me; water can get past the brick veneer, particularly if the brick is especially porous. Drainage holes (in combination with flashing) in the brick veneer just above the foundation in the brick veneer are supposed to provide a path for water to flow out of the drainage plain. Brick veneer installed on concrete block construction, more commonly used for commercial construction, is also supposed to have a drainage plain with weep holes.

Full brick exterior walls, such as those on many old buildings in Cincinnati, do not need weep holes because the water supposedly travels fully through the brick into the interior wall surface or back out to the exterior surface. Another brick construction that was usually not built with drainage holes was concrete block on a concrete foundation with brick veneer installed in front of the block. Unlike the previously described brick veneer/concrete block wall, the first floor framing in this construction was built on the block and the upper floor framing was built above that. The brick veneer in this construction extended from the concrete foundation and up the exterior wall. This last construction, as used for a crawlspace construction, is the subject of this blog post.

Let’s start with a photo of the foundation construction from inside the crawlspace, shown below:


This photo shows the concrete foundation with the concrete block above it. On the exterior side of the foundation, the soil level would be to the top of the first row of concrete block above the foundation. Now, take note of the dark streaks on the facing concrete foundation. Those streaks are due to water drainage through openings in the block mortar. The question is from where is that water coming. For sure, water can migrate from the soil through the block. But, the darkened block in the area in the corner area and along the foundation to the left that extends the full height of the block hints at another source—the drainage gap behind the brick veneer. Darkening of the block indicates that they are water-saturated. Further support for the drainage gap being a water source is evident from the darkened sole plate wood sitting on top of the darkened concrete block.

Let’s take a closer look at part of the area along the facing foundation. Note the copper water pipe in the photo above. This pipe is the same as the one shown to the left in the photo below. In this photo, the darkened woods of the sole plate and rim joist above the water-saturated concrete block is visible. However, also visible are darkened areas in the subfloor boards on top of the joists. The material that looks like resin or droplets is water droplets on the wood surfaces. The pattern of the water stains on the subfloor indicates that the water source is the exterior wall, and more particularly the drainage gap behind the brick veneer. Areas like these were found all along the exterior walls of this crawlspace foundation.


So, what do these findings have to do with termites—as it turns out, a lot. Termites are one of Nature’s maintenance creatures. They reduce wood back into a form that is useful to plants, microflora and soil. The trouble is that they cannot distinguish between the dead wood of a tree in the forest and the lumber we use in our buildings. The subterranean termites we have in the Cincinnati area also require water to live. In fact, they build mud and frass tubes in areas where they would be exposed to air to conserve water and will carry water from the soil into the tubes to keep them damp enough. In the photo below, the dark streaks on the foundation are the remains of such tubes between the ground and the sole plate. Note that the distance between the ground and the sole plate in the photo is about 5 feet. Termites can be very determined to find a food source.


If termites can find wet wood, their job gets much easier because they do not have to bring as much (if any) water up from the ground. So, in the case of this home, they found it in the wet sole plate and rim joist woods. And once they set up their work area in them, they went to town. The following photos show some of the visible damage. Note in all of these photos that the wood is darkened due to water exposure.




I want to emphasize the words “some of the visible damage.” The exact extent of the damage generally would only be known when the damaged wood is removed and inspected. An ice pick or awl can be used to probe the wood and somewhat determine the extent of damage. If the damage is on the other side of solid wood, though, this method would not find it. Also, termites form multiple tunnels in the wood, which means that unless the wood has been greatly degraded by the tunnels, as in the photos, a lot of probing would be needed to fully determine the damage. More sophisticated and expensive methods to determine the extent of damage exist, such as injecting chilled or heated air into the termite tunnels in the wood and viewing the wood using a thermal camera. In theory, the air would follow the tunnels and provide a temperature difference within the wood that is visible to the camera. The common method, however, is using a probe.

The damaged wood in this home will need to be removed, which will be expensive due to where it is located. The repair will also not be as ideal as new construction. Even worse, as wood is removed, more damaged wood that is not readily visible might be found, making the project much more expensive.

But, a question still exists as to why the sole plate and rim joist wood is getting wet when the wood is at least 16 inches above outside grade. Additionally, the drainage plain behind the brick should extend below the wood to the concrete foundation level. I believe that a couple of possibilities exist. The brick might not have a proper drainage plain, in that the brick veneer is right up against the exterior sheathing. I hope not because that likely means the exterior sheathing and upper floor framing could have moisture and/or termite damage. Another possibility is that the rim joists and/or sill plates block the drainage plain. Then again, water from the upper drainage plain may be filling up the concrete block and/or the gap between the brick and block to the level of the wood. Overall, though, the fact that the subfloor appears to be getting wet indicates that a drainage plain issue is present. When the wood is replaced, the real water source might be evident.

What are the morals of this story? Here are a few:

  • Damp crawlspaces or basements can be an invitation for termites to move in.
  • Properly designed and installed drainage plains behind exterior finishes, whether brick veneer or siding, can help prevent expensive repairs.
  • A great amount of water can penetrate through brick.
  • Trick observation—the crawlspace floor was muddy apparently due to water flowing into it. Since no vapor barrier was present, water from the wet soil can evaporate and enter the home where it can cause mold growth in those dark and quiescent locations where mold likes to hang. Then again, even a vapor barrier might not help if too much water is getting into the crawlspace.

Unfortunately, like most projects of this kind, I will not know the outcome due to the nature of these kinds of projects. Be assured that if I hear anything, you will be the first to know.

Shingle Overlays—Just Say No Way

March 11, 2011

Eventually, each owner will need to replace the shingles on his/her residence. At that time, the owner will need to decide whether to install new shingles over the existing shingles, known as overlaying, or to strip all of the shingles off to the roof deck before installing the new shingles. For the former, the existing flashings are also normally kept or supplemented. For the latter, flashings are normally replaced, as well as the underlayment. I will state up front that my firm, Criterium-Cincinnati Engineers, does not support overlaying and this blog lays out our reasons.

Building owners usually only give one reason FOR overlaying shingles and that is the cost is less than fully replacing the existing roof components. On the other hand, roofing professionals and engineers have a number of reasons NOT to overlay. These reasons include the following:

  • Total removal of all of the old roof materials allows inspection of the roof deck, valleys, joints between the roof and walls or chimneys, and areas around roof penetrations, such as sanitary or roof vents. This inspection could discover rotted wood, insects, holes and a number of other issues that could compromise the roof. Some might argue that these issues are visible from within the attic. Having been in more than a few attics, I can assure that these issues are not always visible. For some residences, the attic cannot even be entered and in others no attic exists, such as in residences with cathedral ceilings. We believe that a residence’s first roof replacement should particularly not be an overlayment because of the poor quality of some builders.
  • Total removal of the old shingles can assure that an underlayment is installed. Underlayments perform two main functions: an additional water barrier against leaks in the shingles and separation membrane between the shingles and the roof deck. Shingles installed directly on the roof deck sometimes melt or stick to the deck. But, shingles expand and contract on the roof deck as they heat up and cool down. Shingles stuck to the deck are restricted in their movement, which could result in the shingles buckling or tearing, shortening their life or creating leaks.
  • One of the most vulnerable parts of the roofing system is valleys. Valley flashings can fail and more than a few of these flashings have also been installed incorrectly. Poorer quality builders may not have installed valley flashings at all, trusting that the underlayment will protect the valley. Instead, shingles are weaved across the valley. (By the way, Criterium-Cincinnati Engineers does not support weaving shingles over valleys because of the increased chance for leaks.) Replacement, rather than reuse, of the valley flashings helps assure that valleys will be adequately protected. If the roof is older, new techniques have been implemented since the old roof was installed that adds better protection. One such technique used by better quality roofers is to install an elastomeric membrane beneath the flashing. Not only does the membrane protect against rain leaks, it protects against leaks due to ice dams.
  • In some areas of the country, roof areas above eaves are another area that may need extra protection because they are where ice dams tend to develop. These areas are also vulnerable to shingle lifting due to wind. Better quality roofers install an elastomeric membrane as underlayment over this area in addition to the underlayment used on the rest of the roof. Most original roofs do not have this degree of protection.
  • Rakes, the roof area over the gable, are other areas that are exposed to potential lifting. During overlayments, another layer of shingles are laid along the rake, which raises the edge of the shingles where they are better exposed to the wind and lifting.
  • Roof penetrations, such as vent pipes, also need to be flashed to prevent water leaking through the gap between the roof deck and penetrating object. But, these flashings can also fail and are sometimes damaged by high winds. When a roof is overlaid, these flashings are usually not replaced. So, what happens if these flashings fails before the second (or third) roof is replaced? Removal of the flashing could damage the roof shingles. The usual patch is to smear the flashing seams with tar or roof caulk. Tar or caulk does not normally last as long as the roof shingles and will have to be periodically inspected and repaired. If a leak develops in the tar or caulk, the usual (wrong) solution is to apply more tar or caulk, and the new material commonly fails quicker than the previous material. Even if the flashing is replaced, the best place for it is in the first layer of shingles, which is virtually impossible when more than one layer of shingles is installed.
  • Many two-story homes have second-story exterior walls that meet first story roofs. Flashing is supposed to be installed between the wall and the roof to prevent water entering through the gap between the roof deck and wall sheathing. As other internet posters on the subject of overlayments point out, roofers installing overlayments try to reuse the installed flashing by bending and weaving it with the new shingles. Alternatively, they may also pry out the siding, shove new flashing up under the siding and weave that flashing with the new shingles, leaving the old flashing in place. We have also seen where a roofer installed a continuous flashing up under the siding and ran a bead of roofing caulk between that flashing and the new shingles. And we have also seen where new flashing was not installed at all, but the roofer relied on roofing tar to stick the edge of the new shingles to the old ones. None of these alternatives are acceptable, especially if the old flashing leaks.
  • The addition of a new layer of shingles adds considerable weight to the roof structure. A new layer of shingles weighs about 2 pounds per square foot. Although that amount of weight does not seem like a lot, think in terms of 200 pounds for ONE layer of shingles for a 10 foot X 10 foot area (one square). Add the weight of the original layer of shingles and the total weight of the shingles is now at least 400 pounds per square. Over time, this weight can cause rafters to bow or the roof to sag, particularly for roofs with long rafter spans (distances between supports), rafters that lack ties between opposing rafters, or homes with balloon framing. Likewise, some builders use the maximum spacing between rafters with the minimum thickness of roof sheathing allowed by codes. The result is that the deck sags between the rafters causing the waviness sometimes seen in some roofs. If the roof has developed sags between rafters with only one layer of shingles, what do you think the roof will do with two or more layers? Add an abnormal snow load and the roof could collapse, as some folks found out during the 2010-11 winter.
  • As stated, shingles expand and contract as they heat and cool. The degree of shingle expansion and contraction with change in temperature further varies with thickness, material composition, manufacturing method, lot and a number of other factors. If one layer of shingles is expanding and contracting differently than the second layer of shingles, shear stresses can set up in the layer that expands or contracts less, which eventually will cause tears in the shingle. If these tears are exposed to weathering, the shingles life can be shortened. We have observed that many builders install thinner, cheaper shingles as the original roof on many homes. Homeowners, on the other hand, tend to install thicker sculptured shingles as the overlayment because homeowners believe they will get longer life from them. Guess what that usually means? Yep, two different types of shingles with likely different expansion and contraction properties that are also were likely not even made by the same manufacturer. Since the lower layer of shingles are thinner, they can expand and contract more than the overlayment shingles, which results in tears in the overlayment shingles.
  • Multiple layers of shingles add insulation to the roof, which leads to a hotter attic. In turn, a hotter attic leads to the shingles getting hotter. Heat is a major factor in breaking down shingle materials. Further, a hotter attic means greater expansion and movement of the shingles. The result is a shorter shingle life. A hotter attic also means that a homeowner could be paying more for cooling in the summer when the attic heat is transferred into the living space.
  • We have noted many cases of vertical stacking installation of the shingles. Vertical stacking is where the shingles are installed in eave to peak columns rather than installing them diagonally starting at one of the corners over and eave. Although shingles on properly installed roofs can start curling over time, particularly in overly hot attics, the shingles along the sides of the columns of vertically stacked shingles begin to curl more often and quicker than other shingles. The curled shingles make an uneven base for the new shingles, which creates uneven pressure on the new shingles. In turn, the uneven surface can cause tears in the new shingles exposing the inner part of the shingles to weathering, leading to shortened life.
  • Overlayment shingles are very often not aligned horizontally with lower layers. This misalignment results in the mid-area of upper shingles arching over the tab ends of lower shingles—again with the uneven base thing, causing the tears, weathering, etc.
  • Many shingle manufacturers offer a guarantee. However, that guarantee may not apply to overlays.
  • Dark streaking on roofs is usually caused by a very, very hardy blue-green algae. What happens when these shingles are overlaid with new shingles? That question has not been answered; but, the possibility exists for the algae to spread from the old shingles to the new ones.
  • Shingles that are failing begin to hold moisture. One sign of excess moisture is moss growing on the roof. When new shingles are laid over shingles that are holding moisture, that moisture has to go somewhere. If a moisture barrier exists below the roof deck, such as closed cell foam and insulation with a vapor barrier, the moisture could become trapped between the moisture barrier and the shingles, potentially creating a wood rot condition. Speaking of the moss, how sure are you that the roofer has bully removed the moss before installing new shingles? Exactly what happens to the organic matter trapped under the new shingles? Organic matter is also going to be in the old shingles from the moss rhizoids (root-like structures) that have grown into and between the shingles.

Most roofers estimate that useful life of overlayment shingles can be as much as 25% less than their claimed life, which means that overlayment may not cost less in the long run. For sure, if the roof leaks, the cost of repairing the roof and damaged interior finishes could also vaporize any cost savings from overlayment. The bottom line is shingles overlays just might not be worth the expected savings.

Sump Pump Systems Revisited

November 21, 2010

I recently came across a sump pump installation during a home inspection that caught me by surprise–and that takes some doing.  Below is a picture of the pit.  So, what was wrong with this sump pump pit installation in the following photo:

A sump pump pit in a home that I was inspecting.  What is wrong with this installation?

Hopefully, your answer is that the pit was constructed of cardboard.  More accurately, the pit was constructed using a concrete form tube, such as Sonoco’s Sonotube brand (http://www.sonotube.com/sonotube.html) or Quikrete’s Quik-Tube brand (http://www.quikrete.com/productlines/QuikTubeBuildingForm.asp).  For those unfamiliar with form tubes, they are thick-walled, multi-layered cardboard tubes that are used for rapidly constructing concrete forms primarily for column piers or foundations.  They have been a boon for structural construction in that, when a pier is needed, say to support a deck column, the installer only needs to dig a hole large enough for the form tube, (hopefully) install a footing or compacted base material, place the tube in the hole with rebar if needed, and pour concrete into the tube.  (I have also heard that form tubes make a wicked impromptu drum.)

For the installation in the photo, the form tube was used as a sump pump pit.  It appeared to have been installed a number of years after the home was built.  The basement in which the pit was installed had apparent moisture intrusion issues, which I concluded were  partially due to the water drainage for several adjacent properties being run within 20 feet of the basement.  The installation indicated that a hole had been made in the basement’s concrete floor and the sub-slab soil removed to a couple of feet.  Then, gravel appeared to have been put in the bottom of the hole and the form tube installed and concreted in place.  As the photo shows, a drain line is run through the side of the form tube, although from where it came could not be determined.

So what is wrong with using a cardboard tube for the pit.  The darker tube area deeper in the pit is the clue.  This part of the tube is saturated with moisture, even though a number of weeks had passed since the area received measurable rain.  I was able to stick a screwdriver blade through the darkened area of the tube, verifying that it was wet and degrading.  Over time, the cardboard will likely completely degrade.  As that happens, soil around the pit will erode into the pit decreasing the pit’s depth.  Erosion of the soil will also create a void under the slab and quite possibly under the nearby foundation.  And then, the home has great risk of structural issues that will be expensive to fix.

But, degradation of the pit and potential structural issues are not the only problems.  Water flowing into the pit is also likely not contained within the pit.  Instead, it is flowing out of the pit into the soil under the basement slab.   The lower part of the tube still being wet despite no rain for awhile shows that the soil at that level is also wet, which was verified by the mud on the screwdriver blade when I withdrew it.  Water in the soil below the slab will wick throughout the soil up to the slab.  If an adequate vapor barrier was not installed below the slab, water vapor from the soil can flow through the slab and into the home, causing moisture issues inside the home. Even if the sump pump removes the loose water under the slab, as the cardboard shows, the soil will still hold water because that is what soil does.  This moisture will eventually evaporate to water vapor, which could flow into the home through the slab if an adequate vapor barrier is not present.

And what happens if a LOT of water is flowing into the sump pit through the drain line in the photo?  In this home, cracks in the slab had been sealed, which may have been precautionary.  On the other hand, water could have percolated up through the slab already.  A large volume of water flowing into the sump pit and under the slab could lead to water flowing up through cracks in the slab, even if a vapor barrier were present.  Water could flow out of cracks in the slab without coming out of the sump–water seeks its own level and the top of the slab around the cracks could be lower than the top of the slab around the sump pit.  If this drain line is carrying water from around the exterior of the basement foundation, there could be a LOT of water, especially if water from nearby properties is being channeled near that basement wall.

Water flowing into the sump pit will also be carrying small soil particles.  Although soil particles being present in groundwater is normal, if that water is flowing from an area prone to soil erosion, the amount of soil particles could be greater than normal.  These soil particles are sucked into the sump pump with the water.  In turn, these soil particles erode the pump’s impeller, the part of the pump that moves the water .  Erosion of a pump’s impeller shortens the pump’s life, meaning that the pump would need replacing more often than normal.  (Note that for most pumps, replacement is cheaper than trying to rebuild them.)  Erosion of other materials inside the pump likely also occurs, decreasing the pump’s efficiency.  That is, the same amount of electricity is being used to run the pump; but the pump is not moving as much water for the amount of electricity used.  You pay the same amount for the electricity, but get less for it.  BTW, if you have not priced a sump pump lately,  they start at about $125 just for the pump–plumbers, if needed, are much more expensive.

For the sump pump system in the photo, it will need replacing.  Hopefully, a proper durable sump pit and pump will be used.  I also hope that the person who installed this sump pump system is not the one hired for the replacement job.  The homeowner assured me that person will NOT be the one they hire.  I just hope that no one else has hired him/her for their plumbing work.  Sump pump systems seem like such simple things, and they are to an extent.  However, they are very important systems for keeping a home high and dry.  They should be given the priority they deserve.

Central vs. Portable Humidification Systems

November 14, 2010

In previous posts, I discussed how humidification systems work and how effective a central humidification system might be.  In that post, I hinted at differences between central (whole house) humidification systems and portable (local) humidification systems.  In this post, I want to discuss more about the differences between the two systems.

If you have not realized yet from previous posts, I am biased–I am not a fan of central humidification systems.  I see them often in the homes I inspect; but I suspect that most do not work as intended.  Yet, there they are.  I have to wonder if the installation company actually analyzed the need for a humidification system or was just selling a product that is quite profitable for the company.  Simply asking the homeowner whether he and/or she wanted a humidification system is not the analysis about which I am talking, by the way.

Following are the reasons that I believe a PHS is better than a central humidification system.  For simplification, CHS is used for central humidification system, while PHS is used for PHS.

First is the big picture.  Why try to humidify a whole home when all of the home occupants are not in all of the home’s areas at once?  Let me put is bluntly, injecting a gallon of water into a room is going to be more effective at raising the humidity than injecting a gallon of water into the whole home.

Second is effectiveness.  I believe that a portable humidification system providing spot moisture would likely work better than a CHS.  With a PHS, moisture from a judicially placed unit can be directed into the air around a person’s head (the area that industrial hygienist types call the breathing zone or when they really want to be cool—the BZ).  Even if the PHS cannot be aimed to direct moisture into the occupant’s breathing zone, it can be located close enough to elevate the moisture in the air people are breathing.  If the room can be closed up, such as a bedroom, humidification will likely be more successful than trying to humidify an entire home.  In fact, in the previous blog where I discussed virus and humidification, a portable humidifier was used in that research.  As my previous blog post showed,, CHSs are probably not effective at significantly elevating humidity levels in some homes, particularly air leaky homes.

Home leakiness leads to the third reason portable is better than CHSs—losses.  Moisture in the air is in the form of water vapor, which behaves like the other gases in air.  As such, if the amount of airborne moisture in one area is greater than in another area, moisture in the first area will travel to the second area as long as the two areas are connected.  On cold winter days, the amount of moisture in the outdoor air is usually lower than the amount in indoor air (a subject for another post).  In air leaky homes, indoor moisture will likely move outdoors, even if outdoor air is moving in the opposite direction.  So, most of the water a CHS is putting into the air could be traveling directly outdoors, barely elevating the indoor humidity levels.  Over an entire home, the total area of the air leaks is less than those in a single room.  Therefore, the amount of moisture being lost from one area will be less than throughout all areas.  If a PHS is supplying more moisture to a given area than the central system is supplying to the entire home area, moisture levels in the area with the PHS will be greater.  Even if the moisture from the PHS is also traveling outdoors, it has a better chance of being effective as it travels through people’s breathing zones on it trip outdoors.

A fourth reason is condensation areas.  Most homes have cold surfaces in the winter where condensation can occur.  The chances that condensation surfaces are in the same room with a PHS are less than the chances of moisture from a CHS seeing a condensation surface.

A fifth reason is better humidity control.  Some PHSs now come with their own humidistats.  Basically, the portable unit is sensing the humidity right in the space where the person is.  CHS humidistats are installed in the return air duct in an effort to sense the “average” humidity in the home.  What happens if the return air system is pulling more air from some areas of the home than others, meaning that it is not sensing the true average humidity levels?  That issue is more common than you might think.  Some central system humidistats are placed on a wall in the home; but those also have the same issues as far as sensing the “average” humidity levels.

A sixth reason is operation.  CHSs, if they are working right, only humidify air when the air handling system is working.  During the rest of the time, the CHS is at the mercy of the thermostat.  The central humidification control system has to wait until the thermostat calls for heat before it can work.  Just in case someone is thinking that the CHS can be set to operate without the furnace, remember that the CHS needs air moving through it to work.  Someone is likely also thinking that the thermostat can be set to ON so that the fan is operating all the time.  Then, if the humidistat calls for humidification, air will be flowing through the CHS.  It could; but, the reason air downstream of the furnace is passed through the CHS is because heated air can hold more moisture than cooler air. So, more water will be lost with the CHS if unheated air is passed through it than heated air.  With PHSs, the unit is always injecting moisture into the air without the need for moving air to transport the moisture.

A seventh reason is maintenance.  If a valve on the CHS sticks open, water will be dumped right down the drain when air is not moving through it.  In some cases, the CHS drain is plugged up, and water is dumped into the air handler and then ultimately onto the floor outside the unit.  If that water travels to nearby furnished areas, moisture-related damage can occur.  Sometimes, the damage is extensive, such as shown in the photos below.  The fact is that CHSs are usually not inspected very often and problems may not found until a serious malfunction occurs.  If a PHS malfunctions, it is usually right in the same room with the home’s occupants, who can then see that a problem is occurring.  Maintenance of a PHS is usually so easy that the home owner can do it.  For most homeowners, a HVAC technician is needed to service the CHS.  Remember too, that the more debris that collects on the media inside a CHS, the less air can get through the CHS and the less effective it will be.  The PHS, on the other hand, can be kept clean of debris.

 

Water damage caused by a malfunctioning CHS

 

 

An eighth is bioaerosols.  One of the more well-known cases with PHSs is humidifier fever caused by a PHS that was not properly cleaned and reservoir water was allowed to sit in the unit and grow yuck.  When the unit was operated, the yuck was injected into the air that people were breathing.  But, CHSs are not without the same problems.  In fact, they are essentially operating as a back-up filter to air handler filter.  The debris collected on the media inside the CHS stays there until the media is replaced and that debris contains bioaerosols that may find the conditions inside the CHS a very nice place to grow.  Nowadays, most PHSs are made so that the owner can readily clean the unit and all of them recommend using fresh water every time the unit is operated.

A ninth reason is cost.  A homeowner can buy a lot of PHSs for the cost of one CHS.  For sure, the initial cost of a CHS is much more than a PHS.  But, consider also that if you are not happy with the operation of the humidification system, replacing a PHS is a lot cheaper than replacing a CHS.  I have found cases where homes had unused or disabled CHSs along with PHSs that were being used.

A tenth and final reason is choice.  For residences, homeowners are mainly stuck with one option—the wetted media CHS.  Although residential steam injection CHSs are available, they are even more expensive than the wetted media CHSs.  With PHSs, the owner has not only choice of the method of humidification, as explained in a previous post, a number of manufacturers produce the various types of PHSs.  Having a range of options also means more competition with PHSs than with CHSs, which further means price and feature competition.  I have seen several CHSs and they appear to be amazingly similar, while I have seen a range of PHS designs and those designs continue to evolve.

I guess I could be faulted in this post for not finding more advantages of CHSs over PHSs.  The truth is, none comes to my mind other than the fact that water is supplied to the CHS, while the owner has to carry water to the PHS.  Even though that difference could be considered an advantage of a CHS over a PHS, I think it can also be considered a disadvantage because when changing water, the owner actually is inspecting the PHS and likely keeping it clean.

If you have another opinion, let me know.

How effective are central humidification systems?

October 19, 2010

I am currently working on a post discussing central versus portable humidification systems.  In the midst of it, I realized that I was discussing a lot of issues that might be too much to take in one post.  In other words, it was getting kinda long.  So, I decided to break out part of it for this post.  Well, that and the fact I am beginning to get brain fog in composing the post.

So, for this post, I am going to discuss just how effective a central humidification system might be.  Warning to those who glaze at the use of calculations, they are in here.  If you cannot dig through it, just go to the conclusions.

So, you have a central humidification system that is dumping moisture into the air.  Just how effective is that humidification system at raising the humidity level of the air flowing through the air handler?  Consider this point—to raise the humidity 1% will require about 0.00004 gallons of water for every cubic foot of air (assuming I did my psychrometrics right).  That doesn’t seem like a lot, right?  But, a typical air handler fan pushes around 1200 cubic feet of air per minute.  That means 0.046 gallons (or about 0.7 pints) of water is needed every minute just to raise the humidity in the air flowing through a typical furnace 1%.  Want to try to raise that humidity from 10 to 50%?  That would be nearly 2 gallons of water per minute.  Do you think your humidifier can do that?

Now, consider this point.  Most central humidification systems work by evaporating water into the air passing through the humidification system.  That evaporation process is not 100%.  If you want proof and have one of these systems, check for water coming out of the overfill tube when the system is operating.  Now, the water flowing through the humidification system is not pure–it contains minerals.  As the water evaporates, it leaves those minerals behind to coat the media, as shown in the photo below.  As the media becomes coating, it is less able to absorb the moisture and the surface area of the media that is available for evaporation decreases.  Water that is not evaporated into the air passes through the humidification system to the overfill tube and is wasted.  Whether the water goes into the air or down the drain, you are paying for it.

 

Mineral encrustation on a wetable media inside a central humidification system.

Mineral encrustations on the humidification system as shown in the photo can also channel water down through only part of the media.  That further decreases the wetted area of the media from which moisture can evaporate.  Less areas from which water can evaporate means lower efficiency.

One more issue I would like to mention.  As the temperature of the water being supplied to the humidification system drops, less water evaporates into the air.  Basically, some of the water flowing over the media is absorbing heat without evaporating into the air.  That means that less water is entering the air.  I don’t know about your water system, but mine sure seems colder in the winter than the summer.  Per my previous post, the water valve supplying water to the humidification system only allows one flow rate.  During the winter, if you water supply temperature is colder, not only is water potentially being wasted, it could also be carrying some of the heat you are supplying to the air down the drain.

In my next (or maybe the one after that or after that or . . . ) post, I am going to get more into central versus portable humidification systems.  I promise.  Stay tuned.

What is the purpose of humidifying air?

October 11, 2010

In the last post, I said my next post would be to compare central to portable humidification systems.  Well, I got well into writing that post–which will be more than one post, as I found out–when the thought came to me that maybe I should explain some of the reason I have heard for humidifying our homes.  That last post indicated one reason based on more recent research and that is to control virus. We shall see if future research supports the findings.

Another common reason I heard is to protect the wood in a home.  I am not so convinced, at least for more modern homes that use a lot of manufactured wood products rather than the real McCoy (do people still use that phrase?).  All wood expands and contracts as the wood’s moisture content changes, and the content does change with the amount of moisture in the air.  Cracks form in the wood when it is constrained from moving either by the way it is installed or by its own natural structure.

 

Based on a little research (and note I said a LITTLE research) I believe that most wood in homes expands less than 1/4″ and more likely the amount is around 1/8″.  In a short article published on-line (http://www.forestry.uga.edu/outreach/pubs/pdf/FOR93-034.pdf), The University of Georgia Cooperative Extension Agency published results of a little study on the amount of moisture in wood in 20 homes or offices for oak and maple.  The authors found that the average maple moisture content 7.9 to 10.3% and for oak the average was 6.3 to 8.1%.  In another article published on-line  (http://www.thisiscarpentry.com/2010/09/03/moisture-content-wood-movement/), Mr. Carl Hagstrom gives this rule of thumb:  for every 4% increase in wood moisture content, the wood expands 1% (for “flat gain material”).  (Mr. Hagstrom also very nicely provides a link to an on-line shrinkage calculator at http://www.woodweb.com/cgi-bin/calculators/calc.pl?calculator=shrinkage.)  Putting these two bits of information together, wood inside homes will likely expand about 1% during a typical change in winter conditions.

Mr. Hagstrom further states that wider boards expand more than narrower boards, as you would expect based on his rule of thumb.  However, not a lot of wider boards are used in new construction.  Not that many old big trees are still around these days, and those that are usually are used for veneers.   But, craftsman builders know how to account for wood expansion–both back then and now.   Having inspected a large number of older homes, I have not seen a lot of cracks in finish wood.  I have seen plenty in structural wood, although not many I would consider bad enough to be structural issues.  At that, I have to wonder if the cracks were not caused by the wood not being adequately dried or being exposed to the more extreme variations in moisture and temperature of outdoor air.

I also do not hear many homeowners saying that they humidify because of concerns about the wood.  Instead, the issues are usually that pesky static shocks from walking across carpets in dry environments and physiological issues such as stuffy head and dry skin.  WikiHow has a list of things a homeowner can do to reduce static shock (http://www.wikihow.com/Remove-Static-Electricity).  Apparently, some carpets are also now manufactured to reduce shock.

I have my own theories about the physiological effects of dry air.  I believe that the dry air dries out the mucous membranes of the nasal system.   To prevent drying, the the mucous membranes swell to increase humidification of the air going into our lungs.  Swelling of the membranes causes little fissures in the mucous membranes that cause slight bleeding, which some people see when they blow their nose during this time.  The nasal stuffiness causes some people to use decongestant sprays that can also irritate the mucous membranes and some have rebound effects that make the stuffiness worse.  Decongestants , particularly the ones combined with antihistamines, can also cause a drying effect of the membranes.  Moisturizing sprays can help relieve the drying effects; but, the effect, for me at least, is relatively short-term.

I have one other alternative to help reduce the physiological effects of dry air that most people will not find attractive.  That is, reduce the air temperature of the home.  Doing so will effectively increase the relative humidity of the air.  I confess that during the winter, I keep my home at around 65 degrees.  Even though this temperature is noticeably lower than the 75 to 85 degrees most people keep their homes at during the winter.  I have found over the years, that our bodies are amazingly adaptive.  One other lesson I have learned is that I can always put on more clothes and putting a heating pad under my butt during the coldest days can go a far way toward keeping me warm enough.

Water that foundation

September 18, 2010

Well, I don’t mean literally.  Actually, I mean that sometimes homeowners need to water the soil around the foundation.  Here in the Cincinnati area, as with many other areas, we experienced a very wet spring.  Then, Mom Nature, apparently fearing that she might mess up the averages, pretty much completely shut off the valve.  We are now nearly 6 inches below average on rain–and our clayey soil is rock-hard dry.

One of the characteristics of clay soil is that it shrinks significantly when it dries.  You might have noticed such shrinkage in the gap that has opened between your foundation and the soil.  Keeping the soil evenly moist around the foundation helps prevent or even prevent shrinkage.  However, when watering the soil, don’t just water a narrow band of soil.  I normally recommend watering a band of about 6 feet.  Now, 6 feet is not a magical width; I just mean to water a wide enough band.  If you water too narrow a band or soil, the surrounding ground will suck up the water rapidly, essentially countering your good intentions.  You should also not spray water directly on the foundation, which is never a good practice.

How much to water depends on the soil composition, type and conditions.  Checking the soil using the old finger probe similar to the way you would check the soil in a planted pot is possible.  You just push your finger into the soil to a depth of about an inch and, if the soil feels damp to your finger, it is probably wet enough.  Then again, not being able to push your finger into the soil probably also tells you that the soil is too dry.  You can also use the simple plant moisture meters available in many stores for use on potted house plants.  If you want to get real sophisticated, soil moisture sensors that actuate an irrigation system are also available.  You can find these by Googling “irrigation soil moisture sensors”.  Creative homeowners who don’t want or can’t have an irrigation system installed around their foundations should be able to make up a system using soaker hose, the moisture sensor and control system and an irrigation valve.

So, what is the big deal about the soil being too dry around the foundation.  (Truth is, maybe I should not even be telling you this preventive measure because in the past, we have had a lot of jobs from homeowners because of this issue.  But, that is not our way.)  First and foremost, the foundation can settle and develop cracks and some of these cracks can be severe.  The most common reason for cracks is that the foundation settles unevenly, which is a particular problem with the type of foundation that everyone wants nowadays–the walk-out basement.  Heck, I like ’em too, even though I don’t have one.  With these types of foundations, the soil may be dry to the same depth all around the foundation; but the soil around one part of the foundation may be dry to below the depth of the footing while the soil around another part of the foundation is not.  Dry soil shrinks; so some of the soil around the foundation shrinks while it doesn’t around the other parts.  This condition results in part of the foundation moving while part of it doesn’t.  And that difference in movement can result in cracks.

Besides walk-out basement foundations, stair-step and concrete block foundations (both of which may also be a walk-out basement foundations) are especially prone to developing cracks under uneven soil drying conditions.  Another susceptible foundation construction, which is VERY common, is the crawlspace, stem wall or porch foundation that is poured continuous with, but which is much shallower than, a basement foundation.   The same logic can be used to explain why cracks could develop.  The shallower foundation settles while the basement foundation doesn’t.  Basement foundations that are not walk-out types, stem wall and crawlspace foundations aren’t totally immune from developing cracks either.  The conditions dictate the development.

Slab on grade foundations are also susceptible to developing cracks in the slab, depending on the slab construction.  In the case of these slabs, the soil around the outer edges of the slab could dry while the soil farther under the slab dries slower.  In this case, the soil around the perimeter of the slab shrinks while the soil farther under the slab doesn’t.  The perimeter of the slab settles, while the parts farther under the slab do not.  In this case, the slab might develop cracks as well as heave.

The second reason is that what does down might need to come back up.  Just as clayey soils shrink when they dry, they re-expand when they moisten.  If the foundation settles due to dry, shrinking soil, the foundation might not move back the same way when the soil moistens and re-expands.  In moving back with the expanding soil, the differences in the amount of movement around the foundation could occur, creating stresses that cause cracks.  The soil also might have shifted and exerts pressure on the foundation differently than before.  Soil that shrinks may not re-expand as much as it shrank because the spaces between the soil particles are squeezed reduced as it shrinks.  When the soil re-expands, the spaces between the soil particles might not be the same as before, causing stresses that create cracks.

A third reason for keeping the soil around the foundation evenly moist is one I hinted at earlier in this post.  The gap between the soil and the foundation becomes a water channel when it finally rains.  This issue is a problem mainly for basement foundations.  Don’t let anyone kid you, nearly all foundations are porous to a varying degrees, even those with some exterior water barrier coatings.  Water running down the foundation wall is absorbed by the foundation materials and transferred to the inside of the foundation.  If the foundation happens to have a crack in the right place, the water will have an open path through the foundation wall.

Water that isn’t absorbed by the foundation materials or doesn’t flow through cracks can cause issues around the foundation by eroding soil around the foundation.  In most areas, building codes now require that homes have a foundation drainage system.  Those systems work to capture a great deal of water around the foundation IF they are installed properly.  On the other hand, water has a mind of its own and seeks the path of least resistance.  Therefore, the water might choose to flow under the foundation and not into the foundation drainage system.  If enough of it travels through one area, soil erosion can occur, causing the whole uneven foundation support thing, which can case cracks, and/or worse shifting, of the foundation.

A final, not so directly an issue, is loss of vegetation around the foundation.  In particular for homes built on hillsides, loss of vegetation could result in loss of soil erosion control.  With soil erosion could come soil sliding.  Cracks in dry soil could also open channels to deeper soil layers that are not as well bound together as the upper layers, resulting in slides.

A couple of other things should also be kept in mind.  The foundation may not the only thing that has moved when it settled.  Everything sitting on the foundation might have also moved.  Foundation movement might be imperceptible but still be enough to cause cracks in other interior and exterior building materials. Further, movement is greater higher up in the building, which means that cracks might be found in upper floor materials without be found in lower floor materials.

Another thing to keep in mind is that movement creates stresses in the foundation and other building materials.  Those stresses might not cause cracks right away.  Those stresses could still be present only to cause cracks later on, such as when another condition creates additional stresses—the old straw-camelback syndrome.

I have thrown a lot at you in this post—and without pictures.  (Over time, I promise more pictures.)  The issues can be complex.  Still, they do not mean you need a structural engineer to look at every crack.  If you have doubts, then hire an engineer to check things out and hopefully provide assurance.  On the other hand, you might try keeping the soil around the foundation evenly moist and avoid having the need for an engineer.

Home weather barriers, vinyl siding and Hamilton County Ohio

July 29, 2010

In inspecting a home under construction, I recently ran into an issue dealing with a weather-resistant barrier.  This barrier is one that protects exterior wall materials from weather exposure, particularly water.  So, the best place to begin this discussion is by defining what a weather-resistant barrier is.  The American Vinyl Siding Institute states the following on their website:

What Is a Weather Resistant Barrier System? It is a system that includes water shedding materials and water diversion materials. Weather resistant barrier systems commonly consist of a combination of exterior cladding, flashed wall openings and penetrations, weather resistant barrier material, and sheathing. Effective weather resistant barrier systems will shed the water initially, control moisture flow by capillary and diffusion action, and minimize absorption into the wall structure. The level of weather resistance required is determined by the applicable building code and structure.

The 2007 Ohio Building Code, which basically is taken from the 2006 International Building Code, defines a water barrier, which is basically one of the major purposes of a weather resistant barrier, as:

WATER-RESISTIVE BARRIER. A material behind an exterior wall covering that is intended to resist liquid water that has penetrated behind the exterior covering from further intruding into the exterior wall assembly.

This code further details a weather-resistant barrier as:

1403.1 General. The provisions of this section shall apply to exterior walls, wall coverings and components thereof.

1403.2 Weather protection. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing, as described in Section 1405.3. The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, as described in Section 1404.2, and a means for draining water that enters the assembly to the exterior. Protection against condensation in the exterior wall assembly shall be provided in accordance with the International Energy Conservation Code.

1404.2 Water-resistive barrier. A minimum of one layer of No.15 asphalt felt, complying with ASTM D 226 for Type 1 felt or other approved materials, shall be attached to the studs or sheathing, with flashing as described in Section 1405.3, in such a manner as to provide a continuous water-resistive barrier behind the exterior wall veneer.

1404.1 General. Materials used for the construction of exterior walls shall comply with the provisions of this section. Materials not prescribed herein shall be permitted, provided that any such alternative has been approved.

1404.2 Water-resistive barrier. A minimum of one layer of No.15 asphalt felt, complying with ASTM D 226 for Type 1 felt or other approved materials, shall be attached to the studs or sheathing, with flashing as described in Section 1405.3, in such a manner as to provide a continuous water-resistive barrier behind the exterior wall veneer.

Section 1405.2 Weather protection. Exterior walls shall provide weather protection for the building. The materials of the minimum nominal thickness specified in Table 1405.2 shall be acceptable as approved weather coverings.

In looking at the home under construction for the first time, I noted that a weather-resistant barrier was not installed on the home.   Most people will recognize a weather-resistant barrier as the usually white paper-like wrap, most commonly with the name Tyvek printed on it in large letters.  Other similar wrap or other materials are also used.  That is where the problems began.

In inquiring about the lack of weather-resistant barrier, I asked for the drawings.  In reviewing the drawings, I noted that no weather-resistant barrier was specified.  When I inquired about why none had been installed, the builder informed me that the Hamilton County, Ohio Building Department did not require it.  Apparently, the building department believes that vinyl siding, which was being installed on this home, was an adequate weather-resistive barrier.

I decided to investigate further on the ultimate authority.  On the internet, I found that the Vinyl Siding Institute states in its Vinyl Siding Installation Manual (http://www.abtco.com/kp_abtco/docs/ABTCO_Vinyl_General_Installation_Instructions_.pdf):

Weather Resistant Barrier

Vinyl siding has always been designed as an exterior cladding, not a weather resistant barrier.  Vinyl siding is designed to allow the material underneath it to breathe; therefore, it is not a watertight covering. Because of its design and application, it provides a supplemental rain screen that enhances the weather resistant barrier system by reducing the amount of water that reaches the underlying weather resistant barrier.

What Is a Weather Resistant Barrier System? It is a system that includes water shedding materials and water diversion materials. Weather resistant barrier systems commonly consist of a combination of exterior cladding, flashed wall openings and penetrations, weather resistant barrier material, and sheathing. Effective weather resistant barrier systems will shed the water initially, control moisture flow by capillary and diffusion action, and minimize absorption into the wall structure. The level of weather resistance required is determined by the applicable building code and structure.

Best Practice: To achieve designed performance, vinyl siding must be installed over a weather resistant barrier system that includes 1) a continuous weather resistant material and 2) properly integrated flashing around all penetrations and where vinyl siding interfaces with other building products such as brick, stone, or stucco. Refer to the manufacturer’s installation manual for specific product applications and recommendations. Whichever product(s) you decide to use as part of a weather resistant barrier system, be certain the materials meet the applicable code by contacting the manufacturer of the weather resistant barrier material(s). Always consult the applicable building code for minimum weather barrier requirements in your area. Keep in mind that additional measures may provide better protection against water intrusion than the minimum requirements of the building code.

The Vinyl Siding Institute clearly states that vinyl siding is not an acceptable weather or water resistant barrier.  Since vinyl siding is not considered to be a weather or water resistant barrier, installing vinyl siding without a proper weather-resistant barrier cannot meet the requirements of the building codes for Hamilton County, as taken from the Ohio Building Code and the International Building Code and cannot be considered as proper building practices.  Furthermore, The Vinyl Siding Institute states that vinyl siding needs to be installed over a weather-resistant barrier, and basically describes the properties of a material such as Tyvek, although it is not the only weather-resistant barrier available.  This Institute further states that proper flashing is required for the siding.

So, am I making much ado about nothing.  I hope not.  Water, especially from wind driven rain can get behind any siding material, but more so vinyl siding.  This water then can reach the underlying wood materials.  The problem areas might not be behind where the water reaches the underlying materials, they usually are where that water flows after landing on the materials.  Water that gets behind the siding will flow down the face of the sheathing to points where it can pool, such as above windows and doors and at the base of walls.  At these points, it can enter into the wall cavity itself if those areas are not properly flashed.  It can also enter through gaps between the sheathing.

Once inside a wall, the water can be absorbed by the insulation.  Insulation holds water really well–nearly as well as a sponge.  If enough water is present, mold will grow because mold spores and their food sources are endemic.  Mold can further cause wood rot.  Other moisture-related damage can also occur, particularly to materials made from oriented strand board (OSB), a very common building material and one that has a bad habit of delaminating when exposed to enough moisture.  Do you think that repairing these materials can be expensive?  You betcha it can, particularly if structural members are involved.

What is the bottom line here?  If you have the abilities to review the construction drawings, do so very carefully and inspect closely for a proper weather-resistant barrier.  If you don’t have this expertise or ability, then hire someone who does, such as a capable architect or engineer.  And remember this point, drawings are best reviewed BEFORE construction begins.  My clients learned that lesson at a cost of $1800, and even then, the weather-resistant barrier was not ideal because the windows and doors were not properly flashed according to the manufacturer’s recommendations.

Is air sampling for mold a necessity?

February 22, 2010

I lost a home inspection job for this weekend and I believe I know why.  The job involved not just the routine inspection but also had a suspected mold problem.  Although I would have liked the income, I am more concerned that the potential client decided on another inspector because he was convinced that air sampling for a potential mold problem was needed.  The client said that possible mold was present and described construction that could create moisture conditions conducive to mold growth.  But, I told the client that usually air sampling for mold is not needed because no matter what, if you see mold, you clean it up.  If you find moisture problems that could lead to mold growth, even if no visible mold growth is present, you attempt to eliminate them.  A skilled inspector should be able to recognize both without the need for air sampling.

The truth is that no where is there a requirement for air sampling.  In fact, air sampling is usually not recommended.  The main reason is that the complexities of mold and sampling for mold usually creates more confusion than explanation.  The results are usually confusing, and many times do not mean anything.  Over the years, I have found that nearly every time I have collected air samples–and a lot of other types of mold samples other than clearance samples–the results create confusion and misinterpretation.  When I have been an expert consultant in legal cases, I most often do not have trouble discrediting others mold sampling results.  And the truth is to get any kind of statistical accuracy upon which to make significant conclusions, many more samples are needed rather than the two or three most so-called “mold experts” collect.

Over the years, I have found that when so-called experts do not really understand what they are doing, they rely religiously on protocols they learned in their two or three day mold courses.  Those courses teach them how to conduct sampling, but usually do not dig very deep into the logic behind the sampling.  In most cases, the limitations of the sampling are not explained.  Further, I suspect that even when the limitation are explained, most attendees at these classes do not really grasp those limitations because they do not have the background to understand them.  I know my background and all of the various bits of expertise, special training  and experience I have needed to understand those limitations, and it took over 25 years to get it.  So, I suspect highly that a person coming from a non-science background with less than a week’s training probably does not understand them.

The thing is air sampling for mold is a tool, just like many other tools needed to investigate such problems.  In fact, I can think of nearly 20 different types of sampling used to investigate mold problems.  In fact, many various air sampling methods exist besides the usual Air-O-Cell cassette usually used by so-called “mold experts” and I know of at least three air samplers that collect samples similarly to the Air-O-Cell.   I have found that many of the other sampling methods even provide more useful information than any air samples.  With air samples, you HAVE TO understand how air travels throughout an area to determine the validity of the sample and whether it provides information about a risk.

But, the most important tools that an investigator takes into an area is his/her visual acuity and knowledge.  I specifically stated visual acuity because the inspector needs to have an eye for detail.  I have been on many inspections with clients where I have pointed out possible mold or signs of moisture problems that the client did not even see.  The stuff between the ears can only be gotten one way and that is through long hours of learning, knowing the right people and a lot of hard work.  No one is going to stuff that expertise into someone’s head in a couple of days.

So, when it comes right down to it, I lost an job opportunity because someone else was much better at selling a likely unneeded service than I was at convincing the client that the service was NOT needed.  At the same time, the client had a part in my loss and  I don’t mean by just selecting the other person.  No, the client also came into the picture with beliefs–things read or heard.  In fact, I could hear doubt in the client’s voice when I said that I rarely take air samples.   When I get these calls, I try to educate the client.  Sometimes, I succeed and sometimes I don’t.  My only request to anyone reading this is that you listen and learn to ask the right questions.  I also recommend that you also dig deeper into the expertise of the person offering you advice.  It could save you a lot of money in the long run.


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