You may be interested in Part I of this post. But continuing on... here are some of the problems when indoor humidity gets out of control.

High Humidity and Indoor Air Quality

• Fungi (that means mold!)
• Bacterial growth
• Viruses
• Biological growth
• Asthma
• Volatile Organic Compound (VOC) off-gassing
• VOC chemical interaction
• Wet windows
• Rotting sills
• Damage to pictures, books, furniture
• Dust mites
• Uncomfortable living conditions

"Humidity promotes mold growth and dust mite population growth. Both are significant indoor allergens and can set off allergic sensitivity..."

--American Academy of Allergy Asthma and Immunology

Problems With Low Humidity Levels

• Static electricity (ouch!)
• Dry skin, itchy skin, skin disorders
• Sore throats
• Bloody nose or nose irritation
• Germs spread easier
• Respiratory infections
• Viruses and bacteria
• Uncomfortable living conditions

In very dry environments, the mucous membranes in the nose and throat dry out. That leads to a really yucky feeling and leaves us more susceptible to colds and respiratory illnesses.

As far as nasty things like bacteria go, staphylococcus and streptoccoccus (try saying that ten times fast!) die 20 times faster at 45% RH than below 20% RH.

In addition to the health concerns, in super-dry conditions, the body feels chilled, even at higher thermostat settings. So people can burn more energy and get no benefit.

So What Is The Recommended RH Range?

Under most conditions, the International Indoor Air Quality Commission recommends RH levels should be kept around 45% - 55%. This gives the best mix of comfort and air quality. Most building and air quality authorities believe 45% is the optimal RH in a structure.

Sources of Humidity

Here's some fascinating math: in a 1,000 SF house at 70 degrees F inside, adding only 5 pints of moisture can raise the RH from 15% to 60%!

Wow! So what could produce that much water vapor? Here are some culprits, many of which we rarely think about as contributing to high RH:

• Showers (a family of 4 can produce 1 quart of water vapor per day)
• Cooking (can produce up to a gallon of moisture a day)
• Breathing (1 person typically produces 6 cups of moisture per day!)
• Humidifiers (no kidding!)
  
• Aquariums
• Plants
• Unsealed crawlspaces
• Improper ventilation (like bathroom vents terminating in the attic instead of outside)
  
• Water infiltration
• Leaky ductwork
  

Humidity in a house affects health, building materials, and personal comfort. Too high, and mold can grow and things can warp (among other things). Too low, then noses bleed and static electricity zaps (to name a few problems).

Relative humidity (RH) is the amount of water in the air compared to how much the air can hold (at that given temperature). The measurement is given as a percentage.

The warmer the air is, the more moisture it can hold. If I had a 100 gallon container and filled it full of water, it would be similar to a 100-degree F day at 75% RH. If I reduced the container size to 75 gallons and placed the same about of water in the container, it would be 100% full. Similarly, on a 75-degree F day, if the air contained the same amount of water as it did on the 100-degree F day, the relative humidity would be 100%. The air would now be completely satuated with water.

At this point, if the temperature was lowered any more, the air would not be able to hold the water and it would condense on objects. This is what is called "dew point" when we listen to the weather forecasts - the temperature at which moisture will condense from the air.

Because warm air can hold more moisture than cold air, the same moisture content will result in air with much lower RH in warmer temperatures than in colder temperatures.

What causes the stuff?

Mold... what an awful word. There are four things that influence mold growth. But before we dive into those, realize that mold spores are ubiquitous (that fancy word we haven't seen since we took the SATs all those years ago -- it means mold is everywhere!). When we walk inside a house or building, mold spores on our shoes follow us in.

When we turn on the whole house fan on a summer night, mold comes in through the window.

Mold is in Antarctica and the Arctic. As long as we stay on plant Earth, we have mold spores around us.

So what can we do?

Well, there are four things mold colonies need to develop. And we know the first -- mold spores -- are readily available.

Molds are natures way of breaking down dead organic material. When branches or leaves drop in the forest, molds break them down and turn them to nutrients. But many building materials -- wood and drywall come quickly to mind -- fill the bill for molds, since the second thing required for mold growth is a food source.

Third, molds need the right temperature. Unfortunately, molds that thrive in houses or buildings like the temperatures we keep our thermostats set at.

So there isn't anything we can do about 3 of the 4 things needed for mold growth.

But we can control item #4: moisture.

Moisture gets into the house from a variety of sources: water intrusion, leaks, poor ventilation, living in the house (showers and cooking increase the humidity level)... even things like fish tanks.

Next time, we'll look at exactly how to control moisture in a house.

Thanks for reading!

InterNACHI, ASHI and NAHI (the Big Three home inspection associations) guidelines are very specific about what home inspectors should do in an inspection.

Sometimes, though, I think it is just as effective to remember what inspectors shouldn't do, and to make sure clients have the correct understanding of exactly what a home inspection is.

What follows is a general list of what inspectors should not do, based on a combination of the NACHI, ASHI and NAHI guidelines, and from my own system.

1. Inspectors inspect. Tradespeople fix or build. Don't be a tradesperson who also inspects, as it is a huge conflict of interest. It is one thing to have experience in the trades, or to be a licensed builder. That provides great experience and educational base. But if you mix the two in an inspection, it looks like you are writing a laundry list of items to have the client hire you for later.
2. Inspectors are not Real Estate Experts. I am an inspector. Real Estate Experts comment on the market value, marketability, and the advisability or inadvisability of a property purchase. Inspectors don't.
3. I am a home inspector, not a code official. Effective inspectors don't say something is a code violation unless they are certified to do so. I can make suggestions or recommendations.
4. I report things as I observe things, but I never use fear or hype. I stick to an honest report of my observations during the inspection, as all good inspectors do.
5. I am not a prophet, so I should not attempt to predict how long something will last. Some products like roof shingles do have projected life expectancies, and that kind of information can be passed on to the client, as long as they understand it is not a guarantee. Although I can accurately answer this one...Client Question: what is the life expectancy of a water heater with a five-year warranty? My Answer: Five years and a day.
6. I report observations, but I don't debate opinions. If it isn't related to my inspection report, my opinion about anything on the property doesn't matter.
7. I don't project operating costs. Sure, the house may be super-green and designed to save a bundle on energy. But I don't know how someone is going to live. If they like 90 degrees during the wintertime, I don't care how energy efficient their house is... they won't be saving a bundle.
   
8. If something doesn't work, I report that it doesn't work. I don't determine why it doesn't work. Disassembling switches or receptacles or electronic components is not the inspector's job. See rule #1: Inspectors inspect, Tradespeople fix or build.
9. I want my clients to follow me during an inspection -- but safety rules dictate that I can't take them everywhere. My general liability insurance doesn't cover the client going on the roof with me. I love to have clients follow me around on an inspection -- it makes for a very effective and educational inspection, and I enjoy meeting with and learning about people. But there are some places I can't let a client follow. I know some inspectors don't mind if the client climbs on the roof with them, but I am not one of them.
10. The inspection report is the client's property, and his/her/their property alone. It doesn't get shared with anyone without their express blessing and written approval.

Did you know the following facts about lead?

FACT: Lead exposure can harm young children and babies even before they are born.

FACT: Even children who seem healthy can have high levels of lead in their bodies.

FACT: You can get lead in your body by breathing or swallowing lead dust, or by eating soil or paint chips containing lead.

FACT: You have many options for reducing lead hazards. In most cases, lead-based paint that is in good condition is not a hazard.

FACT: Removing lead-based paint improperly can increase the danger to your family.

If you think your home might have lead hazards, read on to learn about lead and some simple steps to protect your family.

People can get lead in their body if they:

Lead is even more dangerous to children than adults because:

If not detected early, children with high levels of lead in their bodies can suffer from:

Lead is also harmful to adults. Adults can suffer from:

Where is Lead Found?

In general, the older your home, the more likely it has lead-based paint.

Many homes built before 1978 have lead-based paint. The federal government banned lead-based paint from housing in 1978. Some states stopped its use even earlier. Lead can be found: