As an engineer with a doctorate in materials with many years of experience in industry, mainly heat treatment, and, in the maintenance of private and commercial property I like to share some insights about moisture. Moisture is the greatest enemy of any real estate and therefore great values in Florida.
BASIS IS THE SECOND LAW OF THERMODYNAMICS
Heat transfer or heat transport is the transport of energy in the form of heat. According to the second law of thermodynamics, heat transfer always takes place in the direction of places with lower temperatures. There are three types of heat transfer processes:
1. thermal conduction through mechanical contact,
2. convection, the carry along of thermal energy in a flowing medium,
3. thermal radiation, i.e. electromagnetic waves.
WHAT HAVE THIS DETAIL TO DO WITH OUR SUNSHINE STATE?
Outside we have high temperatures and high air humidity all year due to the location between the Gulf and the Atlantic Ocean and many heavy rains. See the Figure about the Moisture Index which shows severe conditions all over Florida and see another Figure about rainfall intensity in the United States. It shows about 7 to 8 inches per hour one of the highest intensities in the United States (Sources: InterNACHI®).
In order to ensure an air-conditioned climate in the houses and condos, they all have air conditioning. HVAC systems cool usually almost all year the indoor rooms down, to temperatures about 70 to 80 degrees Fahrenheit.
As a consequence, we have almost all year a temperature profile from warm to cold between the outside and the (cooled) inside of the buildings and the warm air wants to move from the outside to the inside of the construction. The point now is, that the outside air is not only hot, but, wet. The warm moist air now moves to the outside of the home, partially supported by wind or by rain pattering on the outer walls.
SECOND PROCESS OF THERMODYNAMICS: CONDENSATION
Condensation is the change of the state of matter from the gas into the liquid phase. Here we are talking about water vapor in the air and water on solid surfaces like on the building’s exterior walls.
The basic idea of functional state-of-the-art home and housing construction is controlling condensation due to vapor migration to prevent warm, moisture-laden air from contacting cool surfaces.
Therefore, in general, insulation is installed in exterior walls to prevent large temperature differences between the air and the (wall) surfaces. See the light red marked and with a wave sketched and filled area in the wall in the Figure.
In hot and humid climates like Florida, it is important to install an air and vapor barrier on the exterior side of the building envelope (yellow marked in the Figure). If this layer would be permeable, e.g. through deterioration of the outside paintings and stucco, the moist air will cool and the relative humidity rises because cooler air has a lower moisture-holding capacity.
See in detail the physical context in the water vapor Diagram. The arrow from right to left shows the rising relative humidity (RH) when the air cools down from 80 to 70 degrees Fahrenheit. The RH starts at 80 % on the dark blue RH-curve and crosses when cooling the far left and violet RH-curve for 90 %. On the way to 70 degrees Fahrenheit 100 % RH would be crossed (this curve is not shown) and the vapor will condensate. If the so-called due point is reached, with 100 % RH and here at about 72 degrees Fahrenheit, the water vapor will change its state of matter into the liquid phase – water droplets form on the surface.
All of us might know fogged and wet glass panes of a kitchen window when cooking on a cold winter’s day. The lower moisture-holding capacity on the cold glass surface leads to condensation.
In our example of valuable real estate property water droplets will condensate on the exterior wall. If there will be little cracks caused by deterioration or insufficient maintenance, it will have consequences which I like to discuss now.
CRACKS IN THE BUILDING ENVELOPE ARE WARNING SIGNS
If there is some deterioration on the outside envelope, water intrusion starts. Stucco walls are very popular in Florida. See the short video from a home inspection I carried out, which shows loose stucco on the exterior wall.
The same caution should be exercised with other designs and materials like masonry, brick veneer walls, vinyl, metal or wood sidings, and others. Other incipient cracks are less visible but also require action.
Water ingress can also be dramatic, especially during natural disasters like Hurricanes or Tornados, but that's another chapter.
Deterioration in the wall will continue. With consequences like
- decreased insulation
- increased energy consumption
- invading wood destroying insects or others like termites, carpenter ants and bees, and some beetles
- further moisture and water intrusion
Another effect can be mold growth with a negative impact on the health of the homeowner or home buyers.
POSSIBLE MOLD GROW
Another negative consequence is mold growth. Another Figure, the so-called Mold growth triangle shows the three preconditions first some mold spores – which are everywhere.
The second component for mold growth is Moisture, which we discussed before. And third, food for the mold spores - possible food is building fabric, textiles, and groceries.
It becomes clear that only the moisture component can be prevented and be directly influenced by us. Moisture is the greatest enemy of real estate in Florida.
Another Figure shows more than forty conditions that are conducive to mold growth. I like to mention some here, as well as some illustrations and photos in the attached Gallery confirm these findings:
· defects in systems or components that may allow water or moisture penetration (like we discussed before at the exterior building envelope),
· indoor humidity that is too high,
· the use of humidifiers,
· negative grading of the soil (rule of thumb for positive slope: at least 6 inch slope on the first 10 feet of soil away from the house)
· downspouts not discharging far enough away from the building,
· leaking gutters,
· improperly installed flashing,
· roof leaks,
· dripping water valves,
· a dirty air filter or a clogged condensate drainage in the HVAC
FURTHER RECOMMENDED MEASURES
All windows and doors should be in good condition as well. They should be dense. Otherwise, moist air penetrates as well to the inside of the residential property and will condensate on cold surfaces.
HVAC systems should be producing net-positive pressures on the inside of the building, with respect to the outdoors, to avoid the entry of outdoor air inward.
Try to avoid cooling the interior spaces of your home below the monthly average outdoor dew-point temperature. Because this is not always possible, please increase the set air conditioning temperature from e.g. 74 to 78 degrees Fahrenheit and follow the instructions in this report.
OTHER POSITIVE EFFECTS
When increasing indoor air temperature from e.g. 74 to 78 degrees Fahrenheit, about 20 % of the HVAC energy bill can be saved.
And, most importantly, the value of the property will compare favorably to similar properties provided regular professional home inspections are carried out and written reports recommendations for use, repairs, and maintenance are followed.
This essay reflects my opinion, is written to the best of my knowledge, and does not claim to be complete.
Dr. Jorg Demmel
Deterioration and lose Stucco caused by Moisture