As a professional engineer, I perform pre-purchase house inspections for potential home buyers. In this case, I performed a post-purchase inspection of a residence in an upper-middle-income section of Cold Spring Harbor on Long Island in New York.

The owner bought the house about 18 months ago. The house was inspected by a structural engineer who found nothing structurally deficient in the residence. In fact, it was well built and met the standards for construction in the area.

The house was about 45 years old, and was extensively modified about 15 years ago, with a major kitchen renovation. At that time, a central air conditioning system was installed in the home.

Why I was called

I was called in by the present owner, who complained of a musty odor in the house. I told her on the phone that it might be possible to solve the problem with a duct and coil cleaning, but first I would have to investigate to find the problem (or problems, as it soon became apparent).

I went to the house and noted the musty odor. I opened up the return air grille in the ceiling of the second floor and saw a clean fiber glass air filter. The owner recognized that one should replace air filters on a regular basis.

However, it seemed as though the air was coming out of the return duct, not being sucked in. The airflow out of the 12 vents in the ceilings of the first and second floors was very low.

What I later deduced was that the coil was so clogged with dirt, very little airflow was going though the system. That is why it seemed that air was not being sucked into the return duct.

The reason for the clogged evaporator coil was that fiber glass filters were used in the residence, and they are not as effective as paper pleated air filters in collecting airborne dirt.

I noticed that the return duct included duct liner. I thought this was unusual. I did not see any reason to put duct liner in a return duct.

I went into the attic. The surface temperature of the outside of the air-handling system was warm. I knew there had to be duct liner inside the system. There was also duct liner inside the main trunk line, about 8 ft long.

The duct liner in the return duct was filthy, with 15 years of accumulated dirt. It was a porous fiber glass duct liner, with no surface coating to prevent dirt from lodging in the liner. I took out a small sample, about 1/2 in. sq, and showed it to the homeowner. There was a potent odor coming from it.

Off the main trunk line there was about 100 ft of flex duct in the attic. While there was insulation on the floor of the attic, there was no insulation between the rafters in the ceiling, so the attic was very warm.

Therefore, system efficiency was being compromised by having the evaporator coil in a hot location, since every time the air conditioning system came on, it first had to cool down the very warm system in the attic, which was a much higher temperature than the first and second floors.

The ceiling between the first and second floors was opened up about 15 years ago to put in the air conditioning system. The building heat is hydronic hot water baseboard radiation. Thus, the air conditioning system had to be separate from the heating system.

I believe that the ductwork above the sheetrock ceiling on the first floor may be constructed of flex duct. I was unable to verify the conditions, as I could not cut holes in the ceiling to determine what was behind the vents, or to open up a vent. If I had a borescope, I could have looked inside the system.

If there was flex duct in the first-floor ceiling, it would be impossible to clean. The use of flex duct in areas that are inaccessible, and impossible to access for cleaning, should be prohibited in building codes.

There was a supply duct between the first and second floors in a closet. I deemed it sufficiently accessible to allow the duct to be cleaned.

The basement had its own set of problems. It did not have any air conditioning, nor was there a dehumidifier. A musty odor was present in all the textile materials in the basement. I told the homeowner to either clean these materials or throw them out.

There were some old, decrepit sofas that were ready for the trash heap. The oriental rug could be cleaned, but the carpet was in very bad condition.

What the duct cleaner said

I contacted my duct-cleaning contractor that I use for duct and coil cleaning jobs. I told him of the conditions on the first and second floor. He told me that he would not take the job to clean the system. He honestly told me that the age of the system (15 years) and the condition of the duct liner made it impossible to properly clean the system.

He said it was a cheap installation. Duct liner is cheap to install compared with hard metal duct. When duct liner is lodged with dirt, it cannot be properly cleaned. My duct-cleaning company replaces it when they find it in systems.

He told me that about 75% of the residences on Long Island have systems like this house. His recommendation was to replace the entire system in the attic and replace the condenser and compressor unit located on the north face of the building.

I took down nameplate data from the condenser and compressor unit, and contacted the manufacturer. The system EER was 9.3, relatively good for the time, but obsolete by today’s standards, especially in a high-electricity-cost area such as Long Island.

Equipment for residential usage with SEERs as high as 16 is regularly advertised. With the state of the system being as it is, replacement with a more efficient system would probably cut energy costs in half.

My report to the homeowner

I wrote up my report to the homeowner, and told her that a duct cleaning would not be worth the money, as the condition of the system was not worth the effort. There was no guarantee that a duct cleaning could adequately clean the ductwork in the residence, and it would have to be done each year at great cost. It was not worth the effort.

I told her that the entire system, as much as could be accessed, should be replaced. I recommended the installation of a new system with exterior duct insulation. I told her that hard galvanized ductwork should be used throughout the attic.

I explained that the only way to clean the flex duct that may have been present in the ceiling of the first floor was to use a suction vacuum, and the use of a vacuum hose might shred the material to pieces.

Then I gave her a rough cost estimate of the work to be done in the house.

What contractors need to do

Installing contractors need to stop “cutting corners.” Contractors need to understand that they have to install systems that are easy to maintain, inexpensive to operate, and will be usable for the life of the building.

We need to stop putting in inefficient systems.

We need to perform quality work. We need systems that can be easily cleaned when necessary, with galvanized ductwork, exterior duct insulation, and paper pleated filters.

We have to sell owners on the need for a job done right. A poorly designed or cheap job only leads to trouble in the future.