[Editor's note: This installment of "System Mysteries" is a collaborative creative endeavor betweenThe Newsand Emerson Climate Technologies. These articles are designed to help clear up some diagnosis misconceptions. This installment invites readers to diagnose a home's indoor air quality (IAQ) problems. Do you have the correct answer to this troubleshooting question? If so, see the information at the end of this article about participating in our online contest.]

Dave is an air conditioning contractor. He specializes in the residential market, and tries to stay on top of the latest technologies and solutions available for the entire HVAC system. He prides himself on not being a parts swapper.

Lately he has been reading everything he can about IAQ in order to understand the impact it has on the HVAC system as a whole; he even went to a few seminars during the winter. Little did Dave suspect that he would be able to put the information into practice so soon.

Crawlspaces are notorious locations for duct leaks, often drawing in humid air.

Spring Service

Spring was a long time coming, it seemed, but it finally came. After running some highly targeted, very effective ads in a local paper, Dave was called to several customers' homes to perform a routine clean and check of their air conditioning systems in preparation for the warm summer months.

One homeowner had just purchased his 20-year-old home last year. It measures 2,000 square feet, 500 feet of which were added about five years ago to make room for a new bedroom and family room.

The home has a system typical of those found in northern Kentucky. A 2.5-ton heat pump system acts as the primary means of heating and cooling for the home; a 60,000-Btu, 80 percent AFUE natural gas furnace is the auxiliary heat source. Sheet metal ductwork runs throughout the original portion of the house, with duct board and flex duct installed in the 500-square-foot addition.

Before starting in on the work, Dave takes a few moments to get to know this new customer. Through conversation and some leading questions, he hopes to learn more about the HVAC system and how well it is working in the home.

During their talk, Dave learns two important facts:

1. The homeowner complains that the rooms in the 500-square-foot addition are either too hot or too cold when compared to the rest of the house. The homeowner says he can't seem to find a temperature that is comfortable in all areas of the house.

2. The homeowners' 10-year-old son, Jason, has been suffering from severe allergies.

Last fall, after seeing a TV advertisement, they purchased a single-room air cleaner for Jason's room to help combat his allergies. The air cleaner seemed to provide some relief last year, but going into this summer's cooling season, Jason's allergies have become aggravated again, and the room cleaner just doesn't seem to be as effective.

The homeowners have noticed their son's allergies seem to be getting worse and he is having more trouble breathing. The homeowners also mentioned that Jason's allergies seemed to improve when they were out of town during the holiday season, but immediately worsened when they returned home from vacation.


Dave strongly suspects that the IAQ of the home may be contributing to Jason's allergies - but where do the problems originate?

Dave knows that the effectiveness of room air cleaners is limited to the room in which the unit is located because, as their name states, room cleaners only clean the air for the space that they can draw from. He suspects that the effectiveness has declined due to improper maintenance and increased pollutants in the air, compliments of springtime.

As he begins the routine system maintenance, Dave remembers the things he has learned about IAQ. These homeowners have a dog. He knows that suspended particulates such as pet dander, pollen, mold, mites, and bacteria can make allergies worse.

He also wonders if anything involving the HVAC system is making Jason's problems worse. On previous inspections in other homes, Dave has seen microorganism growth on A coils and smelled firsthand the infamous odor from heat pump Dirty Socks Syndrome. Dave cleans gray and black mold from the A coil, but not until he takes a picture of it with his phone camera.

Next Dave tries to factor in the temperature-comfort problem in the addition. He notices that these customers have a mechanical mercury switch thermostat that looks original to the home.

Dave is a Kentucky contractor; he deals with smokers regularly. Until his customers can quit smoking, they may need help filtering tobacco smoke from the air.

Expanded Inspection

The home's ductwork is consistent with that typically found in northern Kentucky. A portion of the original ductwork runs through a crawlspace under the house. Dave has been on previous jobs where ductwork was not sealed or attached properly. There was even a job where a vole had gotten into the crawlspace and chewed through the ductwork.

After finishing the clean and check, Dave tells Jason's parents that he has some thoughts about possible sources of the homeowner's comfort issues. He believes he can identify the source of the air temperature and comfort problems. He might even be able to provide solutions that could wind up saving the customer money, but he can't guarantee that without further inspecting the system.

Dave also suggests that he might be able to identify some solutions that help alleviate Jason's allergies. He makes it clear that he is not an allergy expert; however, he knows that room cleaners are not an effective solution for filtering contaminants from an entire home. In fact, a normal home's IAQ is generally much worse than that experienced on a typical outdoor day. Would they like him to perform an analysis?

In the next room Jason sneezes, blows his nose, and wheezes. The parents and Dave set up a time the next day for Dave to take some system measurements.

In his analysis of the home's airflow, Dave must keep in mind that there was a 25-percent increase in the home's size when the addition was built onto the existing structure five years ago. He asks if the heating-cooling systems were upgraded during the addition.

Nope. This is the original equipment that came with the house. A friend's brother-in-law who was out of work (and some of his buddies) built the addition but didn't consider whether the furnace or heat pump would be able to handle the extra load.

Dave performs an ACCA Manual J heat gain-heat loss analysis. He takes room-by-room measurements of square footage and window space and, based on weather data for the home's location, he learns how much conditioning is required for each room.

He also calculates the amount of air required to deliver this conditioned air to the occupied space. The equipment is barely large enough for keeping the home conditioned under ACCA design recommendations. Apparently this home's system was not oversized initially, Dave thinks, which was a good thing at the time; but it's not appropriate now.

He also performs a Manual D ductwork analysis to ensure that the ductwork is properly sized to deliver airflow throughout the house. His calculations show that the 25-percent increase in occupied space was not accounted for in the equipment and ductwork specifications. The equipment and ductwork sizing are marginal at best, but should maintain comfort the majority of the time until the heating and cooling balance points are approached.

Dave takes airflow measurements at individual registers. The register in the room with the hot spot was delivering 200 cfm. It should have been getting 375 cfm.

He goes to the crawlspace to inspect the supply and return going to the room addition. He sees that the ductwork is not sealed. His flashlight beam shines upon the return duct from the family room addition, which has several large gaps at the joints.

After Dave concludes his inspection, which steps should he recommend to the homeowners to remedy the problems with the system?

Let's hear from you: What is your best answer to this troubleshooting question? Visit the Contractor Connection at www.emersonclimatecontractor.com to submit your answers. (Click on the link below.) Emerson Climate Technologies will award prizes to the winner and participants. The winner's answer will be published in an upcoming issue of The News. All entries must be received no later than April 8.

Publication date: 03/21/2005