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BPI Written Exam - Section 3 Measurement & Verification of Building Performance

14. Recognize Contributing Factors to Comfort Problems

Comfort issues can be from a number of sources such as:

Imbalanced ductwork that give too much or too little air to rooms. The homeowner may have to overcool the home in the summer just to keep their bedroom cool.
Poor airflow from dirty filters or restrictive grilles.
Bad air circulation back to the return from a high room pressure.
Oversized HVAC sytems that short cycle.
Undersized HVAC systems that are never able to reach the thermostat set point.
Refrigerant leaks.
Dirty coils that are not able to transfer the heat from the inside of the home.
Excessive heat gain in the summer around unshaded windows.
Air barriers around stem walls, wall chases and soffits that allow outside air to heat or cool the interior walls.
Low insulation levels or misaligned insulation which allows the conditioned or heated air to escape faster than a properly insulated walls or attic.

The four factors that affect our comfort are:

Temperature. Temperature and temperature variability affect our comfort. By keeping the temperature consistent and between 70-80 degrees, most people are comfortable. Keeping consistent temperatures can be done with variable speed HVAC systems that keep the air moving for longer periods at a lower energy use, using a zoned HVAC system to monitor several different rooms at one time and having electronic dampers make adjustments, or air balancing the ductwork to account for heat gain. A properly charged, sized and designed HVAC system is also important for keeping and maintaining temperature.
Relative humidity. Relative humidity is a measure of the amount of moisture in the air. Like temperature, our indoor environment is often fighting against the temperature and humidity outside. Our best way to remove excess moisture in the air is using our HVAC systems to dry out the air and remove excess moisture. Running the air handler for longer periods helps to remove indoor moisture but air handlers are also a source of moisture if they don’t have proper drainage and ventilation (think of an air handler located in a basement or crawlspace with excess moisture build up). If humidity needs to be added to a home in hot and dry climates like Arizona, a humidifier can be wired and plumbed in-line with the air handler to increase humidity. Most people are comfortable between a relative humidity of 40-60%. Other factors that contribute to the homes humidity are the number of people and animals in the home, cooking, standing water, poor drainage and leaks.
Air movement. There are other ways to “hack” our comfort. This includes air movement by using ceiling fans to increase the rate of our perspiration evaporation, making our skin feel cooler. We can also increase air movement by increasing the velocity of air moving through the ductwork with dampers although this may cause an increase in static pressure, which can be bad if above 0.3 IWC (inches of water column).
Radiant temperature. Another way for homeowners to be more comfortable is to improve the radiant temperature of the surfaces around us. Radiant heating does not keep us warm by heating the air temperature but by heating the floor temperature and when we come into contact with the floor, it makes our bodies feel warm. Alternatively, we feel cold drafts of a single pane window in the winter not because the air is cold but because the chill of the window is pulling heat off our body towards the window.

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3a. Applied diagnostics and troubleshooting