Proper Installation and Maintenance

Evidence suggests that most HVAC systems are installed improperly. This results in systems that are improperly sized (generally too big), performing poorly and in some cases are unsafe. Improperly sized systems lead to premature equipment failure, poor performance, building degradation, moisture problems and comfort issues. Systems that are oversized also cost more! Consumers often balk at the price of having their homes professionally evaluated and having performance measured. This small savings now may also cost much more later when other problems occur. Generally speaking, a properly installed system, including properly designed, installed and sealed ducts can be downsized which results in savings on equipment and operating costs. The properly sized and properly performing system also saves by achieving expected life cycle and reducing other hidden problems which result from poor de-humidification, improper balance of supply and return air and pressure imbalances. The system is cost efficient and comfortable. This is why having performance measured BEFORE installing a new system makes sense. Many installers give free estimates, but install over sized equipment which operates inefficiently over the life of the system. This costs money in inefficiency and premature equipment wear. C.L.I. charges for performance evaluations and audits, but get results by reducing energy and equipment costs. This saves money over the long run.

Oversizing the equipment can lead to higher equipment costs, frequent cycling, high humidity during summer months, large temperature swings, high operating costs and shorter equipment life. Many technicians use rule of thumb methods for sizing equipment. This is not adequate in many cases. Systems should be sized according to ACCA Manual J or some comparable standard.

In addition to the problems noted above, systems which are poorly designed or improperly installed can lead to problems in other areas. These other areas include the building envelope and the indoor air quality in the building. This is why C.L.I. uses the multi-disciplined team approach when needed. This allows us to evaluate the building holistically which takes into consideration, all building components and systems. When changes are made to one system in the building, other systems can be affected.

Compiled Research Results: Field Studies on HVAC Performance

Duct Leakage, Energy, Building Pressures

Duct leakage accounts for up to 25% of total house energy loss. The ductwork in most homes is located, at least partially in unconditioned spaces such as attics and crawlspaces. It is when the ducts in these unconditioned areas leak that the problem begins. For example, if only 10% of the return air is pulled from a 120 degree F attic during the cooling season the system efficiency and capacity could be reduced by as much as 30%! With today's energy costs rising, that can cost a considerable amount of money, not to mention the loss of comfort. This is often compensated for by adding larger cooling systems at the homeowners expense. Systems are frequently oversized as a way of assuring adequate cooling capacity. Unfortunately, this adds cost for everyone. Builders have to charge more for the home and consumers pay more to condition the home. This problem could be alleviated, in part, by installing the ductwork properly or by retrofit procedures on existing homes. The cost of performing such projects will be offset by lower fuel bills and installing smaller systems. It will also make the home more comfortable and improve the indoor air quality.

Another issue which is often overlooked when considering duct leakage is the locations of the ducts in proximity to know airborne contaminants. Ducts are often located in attics and crawlspaces. If ducts located in these areas have substantial leakage they could be introducing indoor air contaminants into the living space. Some of the contaminants include mold, asbestos, particulate, fiberglass or cellulose insulation and others.

Finally, duct leakage can change building pressures. This can either pressurize or depressurize areas of the building and can contribute to moisture problems within wall cavities, back drafting or spillage of combustion gases into the building, condensation, poor performance from mechanical systems, radon gas issues and other problems. (see Proper Airflow, Proper Balance below)  

The graph at the left shows a de-pressurized mechanical room. In this case, the de-pressurization was significant enough to create both back-drafting and a potential for flame roll out which poses not only a carbon monoxide danger, but a fire hazard as well. C.L.I. Group, LLC evaluates pressure conditions to assure that these conditions are not present or possible under worst case conditions in the building. The graph shown was performed on a small commercial facility.

Leakage of air from ducts can cause or exacerbate air quality problems, in addition to wasting energy. In general, sealed duct systems specified with a leakage rate of less than 3% will have a superior life cycle cost analysis and reduce the likelihood of problems associated with leaky ductwork. Examples of excessive duct leakage leading to problems include:

By having a properly balanced system you can reduce or eliminate many of the complaints tied to buildings with forced air systems. These complaints often include rooms which are colder/warmer than others, drafts, etc

.

Iced coils resulting from poor airflow. The static pressure was found to be extremely low showing inadequate airflow prior to finding ice.	Ourside air intake was almost completely clogged when inspected.	Inside filter were completely clogged and non-functional.	Compressor was also iced.
Another view at coil. This unit was a de-humidification system serving an indoor pool. The failure fueled moisture, condensation and mold problems.	Iced coil in restaurant rooftop unit	Measuring static pressure across coil.	Return air at ceiling plenum. Dirty, mold, dampness. Poorly maintained.
Combustion exhaust vent was connected backwards. Combustion exhaust blowing against building (wet area).

Proper Air Flow and Proper Balance:

Duct leakage, improper fan settings, high static pressures and improperly set dampers can all affect the balance of your system. Depending on the particular circumstance and cause, these imbalances in the majority of cases will either pressurize or depressurize the building or areas of the building. These pressures can have significant effects on building components, indoor air quality, combustion safety, moisture and other issues. For example, studies have shown that in heating climates, such as we have in Northeast Ohio, pressurizing a building to even 1Pa can create moisture problems by forcing warm, moist air through leaks in the building envelope into walls, attic, etc. where it can condensate on colder surfaces. This is the main reason that attic condensation and mold are so often discovered in this area. Return air duct leakage can create a positive pressurization in a home of 1Pa quite easily.

On the other hand, if the majority of duct leakage is on the supply side, chances are that it will depressurize the building. This too can pose problems. Studies conducted on combustion appliances such as water heaters or central heating systems has shown that when negative pressures in the combustion zone reach -3 to -5Pa spillage and/or back-drafting of combustion gases can occur. This is a dangerous condition which can allow carbon monoxide to enter the building. This is unfortunately, one of the most misdiagnosed problems in buildings. In most cases, depressurization only occurs when certain conditions are present and many persons that are called to diagnose CO problems do not understand either the conditions or how to test for these conditions. C.L.I. Group, LLC uses state of the art equipment to test your building under a series of conditions to determine if the potential for spillage or back-drafting is present. We call this a "worst case depressurization" test. (See Pressure Diagnostics Below)

We can fully evaluate the building pressures and create an effective strategy for correcting any problems that are discovered. In most cases, an effective repair is not expensive and can have considerable results. The key is having the building pressures properly evaluated by a technician that understands how to properly measure building pressures and how to interpret the findings.

We now know how to deliver relief from:

Our technicians are NCI certified in Carbon Monoxide Analysis and Combustion Efficiency and Diagnostics. Having your systems evaluated by a certified technician assures that you are doing all you can to keep building occupants safe and systems running efficiently. Combustion Analysis and Carbon Monoxide diagnostics are not something reserved for commercial clients. All buildings which have combustion appliances, fireplaces, etc. should be evaluated annually.

Combustion Analysis

C.L.I. uses the state of the art Testo 325-M for performing accurate assessments of combustion in residential and commercial systems. A combustion analysis assures that your system is operating as intended by the manufacturer. This translates into lower fuel costs and a safer atmosphere for your family, employees or students. During an analysis of combustion the following parameters of the system are measured: Oxygen (O2) level, Stack Temperature, Draft in Flue (this assures that combustion by-products are being adequately vented out of building), Carbon Monoxide (CO), Carbon Dioxide (CO2) and on oil fired systems smoke samples are taken to determine a smoke number. Finally, the efficiencies of the system are determined from the parameters.

Once we have determined the parameters of the system, we can troubleshoot combustion problems and make adjustment recommendations. With the ever rising cost of fuel, a combustion analysis is worth the cost. Savings could be considerable when a system is operating at optimum.

Pressure Diagnostics

Today's buildings are being built tighter than ever before and many building owners are tightening up older homes as energy costs continue to rise. Tighter buildings can create pressure differentials which can cause de-pressurization in the combustion appliance zone (CAZ) and cause drafting problems in combustion appliances. The same is true of remodeling in your home. For example, finishing a basement and enclosing combustion appliances (furnace, water heater) can cause combustion air to be effectively cut off and create spillage or back drafting of combustion gases into the living space.

The graph on left (click to enlarge) shows the changes under a worst case de-pressurization test. Exhaust fans/appliances are turned on one at a time (baths, kitchen, dryer, etc.) and the combustion air and draft pressures are monitored for signs of de-pressurization. On the graph you will note that as the combustion air zone (green) depressurizes, the water heater vent (red) begins to backdraft rapidly. 

We often receive calls from concerned homeowners that have carbon monoxide monitors that alarm periodically. Many consumers assume because the alarms are only periodic that it is a defective monitor. However, in the majority of cases we have investigated we have found that worst case de-pressurization is only a periodic occurrence. This is a dangerous condition because consumers believing that the carbon monoxide monitor is defective unplug the unit or remove the battery. This exposes them to serious risk if combustion gas spillage or back-drafting is occurring. This is especially true if any combustion appliances are producing high levels of CO.

The graph on the left (click to enlarge) shows a simple graph of the effects of an older style central return air system in an older home. We discovered that the room was seriously depressurizing during an assessment at the same time the rest of the building was pressurizing. We had a vent added above the bedroom door and undercut the bedroom door. The graph was made after repairs were made to show what conditions were before the repairs. We first closed the door, then blocked the over door vent and finally blocked the door where we had undercut it. The depressurization of the room is fast and significant. Such conditions in a home can create condensation issues in interstitial wall spaces, can create condensation on surfaces by reducing surface temperature and cause spillage or backdrafting of combustion gases from fossil fuel fired appliances. Conditions, such as those described here and shown in the graph are very common in many older homes. The correction of such problems is not overly expensive but can correct several type of serious problems in the building.

When an energy survey of your home is performed, the consultant should have the experience and equipment to properly evaluate all of the conditions present and, through proper planning and design be able to address both energy and ventilation in a way which is safe and economical. There are many variables which should be evaluated when performing any energy consulting on a home. This is why C.L.I. uses several pieces of equipment and state of the art diagnostic software to give a thorough assessment of the building. Some consultants may use only a blower door, while others may use only an infrared imager. We believe that to properly assess the building, suggest needed improvements and verify the results, both pieces of equipment are necessary. When using a blower door, significant pathways may be overlooked. The blower door can quantify the leakage but not always find the source. However, when the door is used along with thermography these leakage pathways can be visualized and corrected.

 Fact is, when performing any service relating to energy loss, ventilation must be considered. There is such a condition as a home which is too tight. This is why (BTL) Building Tightness Limit number's and (DTL) Depressurization Tightness Limit's have been established. Air Tightness Zones may also be of some help when planning projects.

Having the building evaluated by someone experienced at assessing building pressures is a service that should be considered by all building owners. Most building owners never even consider building pressures because pressures cannot be seen. However, the pressures inside the building play a very vital role in the operations, safety and comfort of the building and it's occupants. Some of the issues that may relate to building pressures include carbon monoxide, indoor air quality, energy efficiency, building moisture issues and structural integrity. What makes this issue so important is the fact that it is frequently overlooked by contractors, home inspectors, fire departments and others involved in building construction and safety issues. For example, if the combustion zone is de-pressurizing under certain conditions and occupants are feeling symptoms, the condition or conditions which caused the de-pressurization may change when the person evaluating why your CO detector is alarming enters the area. This occurs because conditions have changed (e.g. doors have been opened, dryer is now off, the master bedroom door is now closed, etc.). This can leave a dangerous condition undetected. As you can see from the graph at the upper left, we track the sources of carbon monoxide and other problems by evaluating the pressures under specific operating conditions and monitoring those conditions.

Source: The Use of Blower Door Data, Max Sherman, Energy Performance of Buildings Group, Lawrence Berkeley Laboratory, University of California, Berkeley. LBL # 35173

To See a Sample Building Tightness Report Click Here

Carbon Monoxide Analysis

Carbon Monoxide is measured in all appliances and in ambient building air as the first step in a CO analysis. Then draft at all appliances is measured under different building conditions, such as with doors and/or windows opened and closed, with exhaust fans on/off, with attic or whole house fans on/off, etc.

Carbon monoxide can be produced in fossil fuel fired appliances for many reasons and may only occur under some specific set of conditions. It is the priority of our CO analysis to create and identify those conditions. By properly identifying the conditions present, any mitigation procedures which are needed can be addressed before there is a problem. When dealing with combustion and carbon monoxide issues, waiting until after the problem has shown itself may be too late.

Did you know that something as simple as closing a door in your home or turning on a bathroom fan could bring carbon monoxide into your building? It's true. As building pressures change, a negative pressure could be created and cause carbon monoxide to be sucked into the building. This is also true of other contaminants in and around buildings. Strange odors entering the building can often be traced to outdoor sources being pulled into the building by pressure differentials. The same odors can often be eliminated by evaluating pressures within the building and also across the building envelope and making some adjustments.

Recent CO Poisonings:

Long Term Effects of Low Level CO Exposure:

MEMORY
Medical research has shown that permanent damage can result to your memory, emotions, sensory and motor skills, sensitivity to chemicals and your nervous system. Short-term memory can be affected to the point some cannot write a whole sentence without losing their thought. Attention span can decrease substantially and the ability to comprehend words is diminished along with the possibility of a loss of intellectual ability.

SENSORY SYMPTOMS
Other symptoms include suffering from mood changes, depression, apathy and sleep disorders. Sensitivity to light, blurred vision, coordination, speaking disorders, partial loss of hearing or buzzing in the ear, and loss of strength are a few of the sensory and motors skills that are affected.

NUEROLOGICAL DISORDERS
Finally there are the neurological disorders such as seizures, tremors, and loss of speech. Some of these symptoms may recur frequently without additional exposure to CO. It is not completely predictable how and when someone will react to carbon monoxide, but it is certain that exposure to it has disastrous long-term effects. We owe it to our customers to provide monitoring of carbon monoxide levels with Low-Level Monitors, and to include CO testing as we service and install combustion equipment in our comfort systems.

Source: Jim Davis, National Comfort Institute

Additional Resources: