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.

The basics of humidification systems

October 6, 2010

In a previous post on virus and humidification, I promised to discuss more about humidification systems.  In this post, I am going to discuss the basics of humidification systems.  Humidity is a measure of the moisture in the air.  Technically, the humidity that everyone is usually talking about, including the weather guys is relative humidity.  Every so often, the term absolute humidity sneaks out of the scientific and engineering circles into the public.  This is a different measurement of moisture in the air; but that is a subject for another day when I pretty much run out of other topics—and I do have a list.

Humidification systems are simply devices for putting moisture into the air.  In our area, we only want to put moisture in the air during the winter.  In the summer, we are more concerned with getting out of the air.  The reason that people want to humidify air is that the air in our homes is extremely dry during the winter.  Even though outdoor air during the winter may have what seems like a normal humidity level, when that air comes indoors and is heated, the relative humidity levels drop to levels seen in a desert—somewhere around 10%.

For homes, a homeowner has really two basic choices in humidification systems:  central and portable.  A central humidification system supplies water to the air going into or coming from the air handler.  The humidified air is then distributed to all areas of the home.

Central humidification systems typically are recognized as a plastic box mounted on a return air duct near the air handler as seen in the photo below.  However, I recently saw on system mounted on the supply air duct, which may have been the work of an installation instruction-challenged installer.

A typical central humidification system

Inside the box is a web-like media through which air flows.  The air that flows through this media usually comes from the supply air duct just downstream from the air handler (the duct coming into the side of the humidifier in the above photo).  A humidistat connected to a sensor normally in the return air duct upstream of the humidification system (the little white box above the humidifier in the above photo) operates an electronic water valve that controls the water flowing onto the media (the valve can be seen alongside the humidifier in the photo above).  The humidistat is a control system for sensing moisture in the air similar to the way a thermostat senses temperature.  The water valve is connected to the home’s water supply.

When the humidistat senses that the moisture level of the air is too low, it opens the valve to let water flow over the media.  When the humidistat is satisfied, it closes the valve.  Air flowing through the media is supposed to pick up the moisture through evaporation and carry it into the return air stream.  Water flowing across the media that is not absorbed by the air is supposed to flow into an overflow that has a drain line to a nearby drain (the black tubing below the humidifier in the photo above).  In a few cases, the humidistat is located in a living area of the home, usually next to the thermostat.  Some humidistats are incorporated into the thermostat.

Most people will be more familiar with the portable humidification system, particularly since they are sold pretty much everywhere.  These units are self-contained humidifiers that have a water reservoir and a means for converting the water into a mist.  Some units also have a small fan to power air through the unit.  Portable humidifiers have three methods for turning the water into a mist.

The first method for turning water into a mist is a nebulizer that is simply a vibrating plate onto which the water dribbles.  The vibration breaks the water into a mist that is usually carried into the air by a fan-powered air stream.  These units are pretty simple devices that use the electric current to generate the vibrations in the plate.

The second method for turning water into a mist is a rotating disk that slings water at a comb-like device, which is supposed to break the water up into a mist.  The spinning disk operates both as a kind of pump to pull water up out of the reservoir and a means of slinging the water at the comb and a fan to push the mist out of the unit.  This method tends to generate larger water droplets than the other methods, which can lead to water falling on surfaces around the unit.  But, they are also commonly the cheapest units.

The third method for turning water into a mist is the old tried and true method from many of us boomers child-hoods is steam generation.  These humidifiers have a electrical resistance element that heats up when electricity runs through it, similar to the elements on an electric stove.  Water in contact with the heated element boils and is converted into steam.  The steam literally is forced out of the unit because of the energy it absorbs as it turns to steam.  This method of humidification is also used in most commercial and higher-end home humidification systems.

So, in summary, humidifiers convert water into water vapor through three methods; but all of them ultimately work through evaporation.  Central humidification systems use direct evaporation of the moisture into the air as it passes through a wet media, similar to the way that we evaporate water from our skin.  The other methods generate a mist with the intent to get it into the room air where the water will evaporate into the surrounding air.  For these mist generators, the smaller the size of the droplets in the mist, the better the water evaporates.  That doesn’t mean that central systems are more effective humidifiers than the others.  Steam systems are actually the most effective method, but take more energy to do the humidification.

I will end this part of the discussion there.  In the next post on humidification, I will discuss the pros and cons of central and portable humidification systems.

Minimizing Asphalt Shingle Buckling

September 30, 2010

We seem to have an organization for everything out there nowadays.  Well, engineered woods are no different.  One of these is a trade association that is concerned with products that pretty much all modern homes have.  Those products are oriented strand board (OSB) and plywood.  This organization is also concerned with glu-lam beams and other manufactured wood products.  Its name is APA-The Engineered Wood Association. APA at one time stood for the American Plywood Association, there forerunner of the current association.

One of the things that APA does is research in engineered wood products, and they share that research with building professionals and tradespeople.  People not in these trades can also access the APA publications on-line, although in most cases, the publications really are oriented toward professionals and tradespeople.  This past week, APA posted a new document on its website that is useful to the general public who are having roof work done or a home built.  That publication, in PDF format, is “Builder Tips:  How to minimize buckling of asphalt shingles“.  If you want to download this document, you will probably have to register, which is not such an issue because the APA uses that information to keep you informed of new and changed publications.  At least, I have found that to be a benefit.

I recommend that you stop by the APA website and get this document.  It is a good and easy read.  While you are there, you might also want to pick up, “Builder Tips:  Minimize nail pops”.  Nail pops result from nails working their way upward out of the wood deck due to a number of causes.  You can usually spot a nail pop as a tented part of a shingle as shown in the photo below:

Nail Pop Under a Shingle.

In future posts, I will discuss various aspects of roof issues.  I promise pictures.

Humidification and Virus

September 29, 2010

The Environmental Health Journal published an article this past month titled, “Modeling the airborne survival of influenza virus in a residential setting: the impacts of home humidification“.  The results of the research taken from the article are, “The presence of a portable humidifier with an output of 0.16 kg water per hour in the bedroom resulted in an increase in median sleeping hours AH/RH levels of 11 to 19% compared to periods without a humidifier present. The associated percent decrease in influenza virus survival was 17.5 – 31.6%. Distribution of water vapor through a residence was estimated to yield 3 to 12% increases in AH/RH and 7.8-13.9% reductions in influenza virus survival.”

What the article states that a slight rise in relative humidity in the room caused a slight drop in the influenza viruses in the air.  I have a couple of criticisms about the article, though.  The authors derived this conclusion based on limited data using modeling instead of actual sampling of the virus.  The lack of data does not really show how the trend would go for humidity versus virus concentrations.  Without data from actual virus, the question also exists whether the model is realistic or whether the results are repeatable.  I cannot really fault them because sampling for viruses is difficult at its least, particularly infectious viruses and research is expensive.

But, I am still concerned about whether the risks of a humidification system are worth the beneficial effect on virus.  Other studies have shown that hygiene–hand washing and avoiding sick people–are quite effective in preventing or minimizing virus-related illnesses.  Flu shots are also effective in preventing flu for which the sera are developed.  I can personally attest to that fact.  I also tend to believe that flu shots, even past ones, may help minimize the effects of other virus.

I will confess, though, that I am not a big fan of some humidification systems, particularly central humidification systems.  I have observed too many issues with them from basic design to maintenance-related issues.  In future blogs, I am going to go into more detail about humidification systems and their pros and cons, as I see them.  I even got off on that tangent writing about those issues for this blog.  I decided to reign in this post to stick with the topic of humidity and virus.

What can be drawn from this and other research.  I believe that humidity levels could have an effect on virus levels in the air.  I have known for a long time that when those sloppy wet infectious particles that are sneezed into the air, or fomites as the medical gang call them, they have a better chance of drying in low-humidity air.  Drying of the particles means that they become smaller and lighter, which in turn means that they can stay afloat in the air longer.  They can also be breathed deeper into the respiratory system where they can more easily set up shop.  The weird thing is that some virus actually survive better in the dried out state.   (Here are a couple of examples of research pointing to that conclusion:  “Dry air might boost flu transmission” and “Flu Mystery Solved? Why It Flourishes in Winter“.)  Elevated humidity is a good thing.  My dispute is with the way to humidify, and that will be the subject of other posts.

Take note: ALL new manufactured home installations in Ohio MUST be inspected

September 23, 2010

I am a certified inspector for the Ohio Manufactured Home Commission (OMHC).  About every month, the Commission meets to discuss issues that arrive relative to the installation requirements for manufactured homes.  At the meeting this month, the Commission discussed the fact that a large number of manufactured home owners are still unaware that manufactured home inspections have been required since September 2007.  Therefore, I thought that this would be a good subject to blog about.

Prior to initiation of the OMHC, the Department of Housing and Urban Development (HUD), powered by the manufactured home industry, developed rules to serve as a model code for all of the states.  The law that passed also dictated that all states would have to initiate a program for inspecting all new installations (sets) of manufactured homes.  At the least, the states had to use the HUD model code as a minimum code for each state.  Ohio adopted a slightly stricter version of the HUD model code, and at times various revisions to the Ohio code are made.

The basic fact is that the Ohio code requires all new installations of manufactured homes undergo inspections.  “New installations” does not mean installations of just new manufactured homes.  It means all manufactured homes, whether they are installed on private property or in manufactured home parks or whether they are brand new or years old.  Even if you are relocating the home from one manufactured home park to another, you must have its installation inspected.  Even if you are relocating a home from private land to a manufactured home park or vice versa, you must have it inspected.

Installations currently require three inspections: footing, electrical safety and final installation.  The footing inspection may not be needed if approval is given to an existing footing that is being reused.  Furthermore, all installations must receive a permit prior to any work beginning.  For information on the permits, the permit application forms and the steps you need to go through in the installation process, refer to this location: http://www.omhc.ohio.gov/Consumers/tabid/59/Default.aspx.  The permit is issued by the same certified OMHC inspectors that perform the inspections.  Local building departments and some Ohio Department of Health agencies perform manufactured home inspections as well as Third Party Agencies, such as my firm, Criterium-Cincinnati Engineers.  You can find a list of Third Party Agency  inspectors by county at this location:  http://www.omhc.ohio.gov/CallforInspections/tabid/57/Default.aspx.   Note that you can be fined if you begin work without obtaining a proper permit.

The rules require that installers licensed by the OMHC perform both the footing and installation work.  Most installers have unlicensed assistants helping them.  In these cases, the licensed installer must be on-site 80% of the time supervising the work.  Installers may also obtain the permit and line up the inspection agency.

After a home passes its inspections, the inspector will place a seal inside the electrical panel.  Note that this seal is only for that home’s installation on the site for which the seal was issued.  If the home is moved to another location, it will need to undergo the permitting and inspection process again and receive a new seal for the new location.

Several other important points need to be understood:

  • If a home was installed  after September 2007, it must still be inspected and meet the existing rules.
  • Homeowners may do their own installations; however, if a homeowner chooses to do the work, he or she is required to do all of the work him or herself, including obtaining a permit.  We highly recommend that homeowners not do their own installations because we have had nothing but bad experiences when they do.  In pretty much all cases, the homeowner is taking on much more work than they realize and likely does not have the proper equipment to do a complete installation.  Homeowner who are thinking about doing the work themselves should review the rules to which the home’s installation must adhere at this location:  http://www.omhc.ohio.gov/LawsandRules/tabid/66/Default.aspx (if you looked, yep, every one of ’em).  Whereas, most installers have had a number of years of experience.  They are also required to be trained and pass a qualifying test prior to obtaining a license.  We therefore recommend that homeowners have licensed installers do the installation.
  • We recommend that the homeowner have the installer obtain the proper permits.  If the installer obtains the permit, he or she is responsible for completing the work.  If the homeowner obtains the permit, he or she is responsible.  If additional work is needed for the home to pass inspection, having the installer responsible for the permit gives the homeowner leverage to assure the work gets done.
  • On the other hand, we recommend that the homeowner select the inspection agency.  Some installers have a “comfortable” relationship with some inspectors and, let’s just say, the homeowner might not be getting the inspection they should.
  • Permits are for 180 days only, which should be adequate time for the installation to occur.  An extension can be given; but, if one is needed, then something is definitely wrong.
  • The homeowner is not supposed to occupy the home until it receives a passing final inspection and is sealed.  The inspector can issue a temporary occupancy permit if he or she finds that the issues that need to be resolved for the home to pass inspection are not serious.  However, the temporary permit, as the name implies, means that the home must eventually pass inspection.
  • Most electrical companies will not connect the electric service to a home until after it passes the electrical safety inspection.  The problem has been that some homeowners have gotten the electrical service connected and then not completed the installation so that it passes inspection.  The Commission is currently working to close this loophole.  Inspectors are also going to get more aggressive at assuring that the installation is satisfactorily completed.

I have heard all of the excuses about why manufactured homes should not be inspected and complaints about the inspection requirements.  But, after performing nearly 600 manufactured home FHA inspections, I understand the requirements for every part of the rules.  The inspections are not intended to simply aggravate the homeowner.  They are there to assure that the home is installed safely and to help preserve the homeowner’s investment.  With proper installation, a manufactured home can last for many years.  I see no reason why a properly installed and cared for home cannot increase in value over time.

The warning bears repeating again, again and again

September 19, 2010

The warning bears repeating again, again and again.

The on-line version of the Chicago Sun Times carried this story today:

Infant drowns in water pail


In a previous post (https://criteriumincincinnati.wordpress.com/2009/12/02/a-sobering-reminder/), I discussed another infant drowning in a sump pump pit.  Granted, a drowning in a sump pump pit is a pretty rare event, especially since sump pits usually have lids that are supposed to be used with them.  In the case of the infant in the Sun Times article, the culprit is a common water pail.

But, water pails are not the only potential downing locations.  Every adult who is responsible for watching kids should know about the drowning potential of bathtubs, sinks or other bathing facilities.  What about toilets?  As I stated in the previous post and will repeat here, infants and toddlers can drown in only a few inches of water.  Exasperating the drowning potential is the fact that infants and toddlers are head-heavy.  If they fall into a container of water head-first, they likely will not be able to get out of the container, whatever it is.

Containers are not the only potential drowning places.  Fountains, pools, ponds, streams–any body of water should be off-limits to infants and toddlers.  If they are mobile, they are not the steadiest people on their feet.  On visits to Fountain Square in Cincinnati, I have watched many parents let their young ones walk on the lip of the various parts of the fountains.  I have to wonder what are those parents thinking.  What would happen if they looked away for a short time or could not make it to the fountain in enough time.

Apparently, the City of Cincinnati thought about this issue because the main fountain now has a low fence installed along the inside lip of the large fountain.  My son thinks it is because of other reasons, such as adults using the pool for other means.  Even still, maybe Cincinnati helped resolve another potential issue at the same time.

If you are a child’s caretaker, don’t just react.  Anticipate if you can what the child is going to do.  And take stories like the one in the Sun Times as a warning and be educated.

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.

5 Things that have changed in building design to cause today’s issues

September 16, 2010

I received a link to an excellent article by someone whose writing I follow.  His name is Dr. Joe Lstiburek and he is to me THE authority on building moisture issues.  His article is titled, “5 Things”, and the link to it is:  http://www.buildingscience.com/documents/insights/bsi-039-five-things/files/BSI-039_Five_Fundamental_Changes.pdf.

Those 5 things that Dr. Lstiburek lists as changes that have occurred to buildings to cause today’s moisture issues are:

  1. Increased thermal resistance.
  2. A change in the permeability of the linings that we put on the inside and outside of building enclosures.
  3. Water and mold sensitivity of building materials.
  4. The ability of the building enclosure to store and redistribute moisture.
  5. Complex three dimensional airflow networks that inadvertently couple the building enclosureto the breathing zone of the occupied space via the mechanical system.

Let me see if  I can translate from the engineer-ese.

  1. Thermal resistance is the ability of a material to transfer heat, similar to the way a wire conducts electricity.  A higher thermal resistance material, such as fiberglass, slows heat transfer.  Dr. Lstiburek says that with reduced thermal transfer, building materials do not dry as rapidly in newer buildings as older ones.
  2. Permeability is a measure of how easily moisture can move through a material.  Over the years, the exterior wall materials have become less permeable.  The result is that moisture that gets into walls cannot get out and moisture inside the home cannot get out of the home the way it used to.
  3. Dr. Lstiburek uses the term sensitive in his list of  Things, but then uses a better term later in his article–resistant.  Basically, the materials being used in today’s buildings are not as resistant to mold growth as those in older homes.
  4. Dr. Lstiburek states that older building materials were able to absorb and not be harmed by moisture than newer materials.  We still have buildings with lath and plaster walls that are over 100 years old because they could take moisture exposure.  The same moisture exposure would have demolished drywall in one exposure to the same moisture quantity as the older homes.
  5. In the older homes, the building exterior was usually more solid than now and it acted as an air barrier.  Nowadays, the exterior is not as resistant to airflow as back then.  The stud and joist cavities serve as runs for wiring, plumbing and supply and return airflow.  Every time a hole is made in a stud or joist, a new airflow path is created.  Then, we open holes in walls for electrical outlets, which are air paths.  So, the newer buildings are holier than the older ones–and not in a good way.

Dr. Lstiburek provides recommendations for resolving these issues in the latter part of his article, and you can read those as well as I.  So, check out the article and if I have not adequately translated the terminology in an understandable way, send in your comments and I will do better.  BTW, if you want other excellent articles on building construction, visit the Building Science website at http://www.buildingscience.com/.

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