By Dwight W. Uffer, BSCE

            We as Home Inspectors visit properties almost every week in which we find deterioration to the structure by wood decay and moisture damage.  Our normal course is to report the damage to the prospective buyer or other interested party who has hired us to perform a building inspection.  We do not under normal conditions get into the cause of the condition, however we may state in our report what we feel is the proper cure.  By explaining what should be done to cure a certain problem without also explaining or documenting the cause of the failure, what we have accomplished is to allow the failure to repeat itself.

            A case in point happened about 10-12 years ago in a home in Hartford County, CT. and the home owner shared his inspection report with me. The home inspector inspected the home for the prospective buyer and had noted that the home had originally been constructed during the early 1940’s as temporary housing, as was the entire neighborhood, for employees of a major defense contractor at that time.
The home had originally been constructed on a shallow foundation as the home was not intended to be a permanent structure.  In the ensuing years different families had owned the home and during those times someone had excavated a basement and installed partial footings and concrete block retaining walls to stabilize the earth along the perimeter of the structure.  The basement floor remained as earth and some water infusion was noted along the block walls which did not have tight mortar joints.  The furnace was moved at some point from the first floor living area to the basement in order to afford the occupants more living space as this home was only about 700 square feet.

            As the inspector was documenting his findings, he noted exterior paint failure, rotted window jambs and sills along with wood rot at the mud sills in certain areas of the basement.  His recommendation to the potential owner was to scrape and paint the siding and trim, have the window sills and jambs repaired with an epoxy and replace the mud sills were necessary with pressure treated material. He also advised the buyer to have the earth floor covered with plastic sheet to retard moisture. 

            The inspector’s client purchased the home, and was diligent in following the recommendations of the inspector.  He scraped and sanded the exterior of the home, primed the bare wood, and painted the siding and trim with two coats of quality paint.  The windows were replaced with new windows that had a vinyl exterior cladding and the mud sills were replaced as needed with pressure treated material.  The basement floor was covered with two layers of plastic sheet. 

            After about 3-4 years, the paint was peeling off of the home worse than it had before it had been scraped and re-painted. Some of the new windows were showing signs of deterioration (Condensation on the interior glass, soft wood under the cladding) and spotting of mildew were showing along the baseboards on the north side of the home.
The owner was not happy with what was occurring and decided to have vinyl siding installed over the existing wood shakes and encapsulate all of the trim with aluminum.
About a year later, the owner noticed that the gable end vents and the siding were blackened with mildew and some of the windows were condensating on the inside of the home.

            Deterred by what was happening to his home, along with the need to find a larger home for his growing family, he listed his home with a local real estate broker who advised him to have a home inspection performed as a marketing tool.  I was contacted by the seller, who still had his original inspection report which was discussed in the above paragraphs along with an explanation of his restoration work.

            The inspection was performed in May, the outside temperature was 68 degrees, humidity was about 40% and the weather was clear.  I began my inspection on the exterior of the home and noted the mildew staining around the gable vents on both sides of the home.  I also noted that the vinyl siding was covered with algae on the north exposure.  There was no vegetation overhanging the home, nor was there any large shrubbery planted against the foundation.  I inspected the exterior window jambs and sills and found that by putting pressure on the lower jamb with my finger, water would be evacuated from the splice in the vinyl cladding.  From these observations, it was apparent that a moisture problem was occurring within the home and further analysis would be required.

            We moved our inspection of the premises to the basement of the home which was accessible by a “Bilco” steel hatchway on the west side of the home.  The first thing that I noticed was that the headroom in the basement was about 5’10” and I am 6’ tall.  This was noted by my hitting my bald head on the header as I entered the basement.  The air in the basement was thick, indicating high humidity levels.  I took a humidity reading and found it to be in the range of 88% with the basement temperature being about 64 degrees F.  My next observation was that the insulation installed between the basement floor joists was wet and dripping water vapor in some areas, whereas in other areas of the basement it was completely dry.  I began to probe the floor joists and use my moisture meter to indicate what the moisture content of the wooden structural members was and
also to map out the areas of higher moisture content.  This procedure was also applied to the girder and to the mud sills.  After documenting the areas of high moisture content it was obvious that high levels of humidity were escaping the basement through the path of least resistance in the wall cavities and vacating through the attic gable vents.  Other areas of the basement, the wood members were soaking up the moisture and deterioration was occurring due to fungi. These areas were some of the same areas that had been repaired by using new pressure treated sills and rim joists.  What is required for “Fungi” to grow and deteriorate wood?  Moisture (high humidity), Temperature (40-100 degrees F), Oxygen, and a food source (wood cellulose).  If we removed any one of these components, we would stop the deterioration.  We know that we can’t remove the oxygen or the food source as both of these components are needed.  We can’t drop the temperature below 40 degrees F or the plumbing will freeze and it would be extremely uncomfortable in the home, nor can we afford to increase it to over 100 degrees F.  Keeping this in mind, the only component we can eliminate is the moisture (humidity).

We now have to look at the history of the home, and determine why, after standing for over 60 years, it has in the past 15 years begun to deteriorate.  What has been done to the home that has contributed to its demise? For that we must document what changes have occurred to the structure in the past 15-20 years.  The present owner can help us in this matter, as he has owned the property for half of that time period and may know what occurred as far as any renovation that may have occurred in the past.

What we find is that the prior owner moved the (1) furnace from the first floor to the basement area and installed metal duct work in the basement to supply heat to each room (4) on the first floor.  Originally the furnace was in a closet and had one heating register and one return.  The present owner made the following improvements: (2) The bathroom was enlarged and renovated. (3) The kitchen was renovated. (4) New “Thermo Pane” windows were installed along with metal insulated doors. (5) New roof installed (6) New natural gas hot water heater moved to the basement of the home.  (7) Electrical service upgraded to 100 amperes from 60 amperes and incorporation of circuit breakers.  (8) Vinyl siding and trim.

What can be observed from these renovations and modifications to the original structure?
The moving of the heating system (furnace) to the basement area increased the temperature of the basement as air leakage from the duct work was noted and the natural convection of heat from the system along with the flue pipe would raise the temperature.  Insulation was added to the exterior walls of the bathroom and kitchen when renovations were performed.  Installation of high efficiency windows and doors discouraged air movement.  Installation of the gas hot water heater in the basement was another source of heat in the basement. And to top it off, fiberglass insulation was installed in the basement between the floor joists.

VAPOR DIFFUSION
Water vapor moves in and out of a building basically in three ways: with air currents, by heat transfer, and by diffusion through materials.  Of these three, air movement is the dominant force because, like most fluids, air naturally moves from a high pressure area to a lower one by the easiest path possible.  This is generally accomplished through any available hole or crevice in the building envelope.  Moisture transfer by air currants is extremely rapid (in a range of several hundred cubic feet of air per minute) and amounts for more than 98% of all water vapor movement in building cavities.  Thus it is very important that unintended paths that it may follow be carefully and permanently sealed.  The other two driving forces are much slower processes and most building materials slow moisture diffusion to a large degree, although never stop it completely.

In decades past, buildings did not need to restrict the flow of airborne moisture, since when the building cavities got wet they also generally dried quickly due to the leaky construction methods that allowed air to move freely through the building envelope.  So the water vapor movement really didn’t matter much until the introduction of thermal insulation.  When insulation is added, the temperature of the water vapor can drop very quickly since its being isolated from the heat of the building (Winter) or from the outdoors in the summer if the building is air conditioned.

Whether from the indoors or outdoors, airborne water vapor entering the envelope of the building through holes around plumbing pipes, ductwork, wiring, and electrical outlets are some of the less obvious, yet important, points where air can move in and out of  the thermal envelope.  During the winter, any warm air entering the walls from the house cools and condenses it’s water vapor inside the building cavities and the wood decay process begins.

The law of physics governs how moist air reacts within various temperature conditions.  This behavior is technically referred to as “psychrometrics” A pyschrometric chart is used by professionals to determine at what temperature and moisture concentration water vapor begins to condense.  This is called “dew point” by understanding how to find dew point, you will better understand how to explain how to avoid moisture problems within your clients home or building. (US Dept. of Energy May 1999)

What can be observed in our inspection is that warm moist air is being drawn up into the wall cavities and other voids in the exterior of the home and the water vapor is condensing when it is slowed down by the thermal insulation in the wall cavities.  In areas in which there is no insulation, the moist air rapidly rises and is expelled through the gable vents and other openings.   Where the owner had renovated the bathroom and kitchen is the area in which damage to the sills occurred and also the area in which the clad windows were found to be deteriorated.  Wood decay was not observed in areas in which this older home had not been insulated.

In order to confirm these findings as well as to rectify a warranty claim made to the window manufacturer, the owner of the home volunteered to remove two of the windows in his home for us to evaluate.  This was conducted by myself and a field representative from “Anderson Window and Door Corporation”.  We decided to remove one of the deteriorated windows at the north side of the home and one from the south side (weather side).  The deteriorated window was removed and it was immediately noted that the lower jamb on both sides of the window was rotted along with the right and left corners of the pine sill.  We removed sections of the cladding along the lower jambs and sill and found additional deterioration.  We also found evidence of mold and mildew along the paper of the interior sheetrock wall.  We then removed the window on the south side of the home and found that the window was in perfect condition.  The wall matrix at the south side was wallboard and plaster and was also in good condition. 

The windows that were deteriorated did not fall into the category of being defective and the report was written that the cause of deterioration was due to high humidity levels in the home and poor ventilation.  (The representative did replace the windows as part of a technical evaluation that would be used in their training program)

I believe that the lesson learned in inspecting a home with indications of numerous areas of wood decay or other abnormal problems would be to have a company or individual with the proper credentials assess the cause of the problem before we suggest a cure that may not work.  It takes a lot of time, proper instrumentation and experience to properly assess problems that occur within the building infra -structure.  These are referred to as “Forensic Building Inspections” and should not be a part of a normal home inspection.

                                                                        Submitted: June 28, 2006

• Defects and Deterioration
• Electrical Wiring
• IC Rated Light Fixtures
• Water Vapor Diffusion

• Defects and Deterioration
• Electrical Wiring
• IC Rated Light Fixtures
• Water Vapor Diffusion