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Home Performance and Humidity

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Home Performance Contracting is well understood to focus on the home as a system, making the envelope tighter and minimizing the heat gains and losses. One factor that seems to be missing in our coastal climate is dealing with the humidity year-round.

As homes have been built tighter and retro-fitted to be better performing, we have noticed that comfort complaints have risen. This can be attributed to ignoring the humidity. There is a year round latent load that is driven by the coastal winds off of the Gulf of Mexico. This can be immediately noted in condominiums where the concrete shell of a building can’t release what is being driven in from the doors on the windward side. Many condominium residents have resorted to consumer-type dehumidifiers to help, but they prove to be inadequate.

We received a call about humidity and comfort problems from a new customer with a bayside home built in the early 1980’s. On the initial visit, in February, the humidity was a high 65% with no demand for cooling, as the indoor temperature was 72 degrees. The wood floors were cupping, the homeowner’s allergies were flaring, and there was no solution offered by the customer’s previous contractor. It should also be noted that there are two closet installed geothermal systems on this 2400 square foot home and the fiberglass duct board systems were in very poor condition.

Our solution offered was to replace the duct system with sealed metal, relocate the larger geothermal system to the garage (to allow a properly sized return air duct), add media air cleaners to both systems, and add a whole house dehumidifier by Aprilaire. The Aprilaire dehumidifier was suspended from the garage ceiling and ducted into the main duct system. A separate humidity control allows for frequent sampling of indoor conditions as well as allowing the dehumidifier to control the system fan. The result is clean, dry air distributed throughout the home as needed to maintain humidity control without a call for cooling. An automatic damper controlled by the dehumidifier also allows a timed introduction of outdoor air into the home.

The results for the customer have been dramatic. Humidity is maintained at constant 46%, the duct system is filtered, tightly sealed and clean, and a controlled amount of fresh air is introduced. Previously, the homeowner, desperate for clean air, would open the bay side doors and make the humidity problem worse.

By dealing with the latent load using a small compressor, the comfort systems can do the job of lowering the temperature efficiently. Looking at the home as a system, we can see the factors that drive power consumption. We also must be fully aware of human comfort: Temperature, humidity and contaminants. If one of those factors is ignored, the customer will likely remain dissatisfied. If we address all of these factors, the customer can have a healthy comfortable environment as well as energy efficiency.

Pat Boykin
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Posted In: Building Performance, Residential Buildings

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