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If the humidity levels in your home are too high or too low, you could experience discomfort or even moisture-related issues. A whole-house dehumidifier can be an effective solution—especially in humid climates or during transitional seasons. This Old House plumbing and heating expert, Richard Trethewey, demonstrates the installation of a whole-house dehumidifier and shows how it can work in conjunction with your existing HVAC system to maintain optimal humidity levels in your home year-round.
How Do Whole-House Dehumidifiers Work?
Whole-house dehumidifiers are designed to work with your existing HVAC system to remove excess moisture from the air throughout your home. Unlike portable units that only dehumidify a single room, these systems integrate with your ductwork to provide comprehensive humidity control.
A whole-house dehumidifier operates similarly to an air conditioner but focuses solely on removing moisture. It does the following:
- Draws in humid air from your home
- Passes the air over a cold coil, causing moisture to condense
- Collects the condensed water and drains it away
- Returns drier air back into your home’s ductwork
This process allows the dehumidifier to maintain consistent humidity levels without affecting the temperature, making it ideal for use in spring and fall when cooling isn’t necessary. A whole-house dehumidifier can improve your indoor air quality, reduce the risk of mold and mildew growth, protect wood furniture and musical instruments, enhance comfort (especially in humid climates), and save energy by reducing the workload on your air conditioner.
Whole-House Dehumidifier Installation Process
Installing a whole-house dehumidifier requires professional expertise and should be done by a licensed HVAC contractor. The process typically involves several steps.
Choosing the Location
The ideal location for a whole-house dehumidifier is near your existing HVAC system, typically in the attic or basement. This allows for easy integration with your current ductwork. In the video, Trethewey explains the installation in an attic space as the HVAC technician positions the unit close to the air conditioning unit for efficient operation.
When choosing a location, check that the space can support the dehumidifier’s weight and provide adequate ventilation. You should be able to access this area for regular maintenance.
Mounting the Dehumidifier
Once you’ve determined a location, the dehumidifier needs to be securely mounted. This often involves the following steps:
- Attaching steel hanging bars to the roof structure
- Installing a metal pan to support the unit
- Placing the dehumidifier in the pan
- Ensuring proper clearance for maintenance access
Proper mounting helps you avoid vibrations and noise, which can affect the dehumidifier’s performance and longevity. Follow the manufacturer’s specifications regarding mounting angles and clearance distances.
Connecting to Existing Ductwork
Next, it’s time to integrate the dehumidifier with your home’s ductwork. Cut a new return air grille in a central location, such as a hallway ceiling, and install flexible ductwork from the dehumidifier to the new grille. Connect the dehumidifier’s output to the existing supply ductwork. Secure all connections and seal any gaps to prevent air leaks.
This setup allows the dehumidifier to circulate dehumidified air throughout the home. Sealing ensures that there are no unintended air losses, which can compromise the system’s efficiency.
Installing the Drain Line
Run a PVC condensate line from the dehumidifier to the outdoors. Make sure the line has a slight downward slope for proper drainage, and terminate the line in a suitable location away from the foundation.
Check the drain line regularly to confirm it’s free of obstructions. Clogged drain lines can lead to water backup and potential damage to the dehumidifier or surrounding areas.
Setting Up Controls
The final step involves installing and configuring the control system. Mount a humidistat near the existing thermostat and connect it to the dehumidifier. Set the initial humidity level to around 35%. You can always change this number later.
Maintenance and Upkeep
The dehumidifier’s filter should be replaced every two to three months or more frequently if you have pets. This ensures optimal airflow and prevents dust and debris from accumulating in the unit. Replacing the filter is a straightforward task but crucial for maintaining the dehumidifier’s efficiency.
Periodically inspect the condensate drain line to ensure it’s clear and functioning properly. A clogged drain line can cause water damage and reduce efficiency. If you notice signs of blockage, use a wet-dry vacuum or a plumbing snake.
Schedule annual maintenance with a qualified HVAC technician to do the following:
- Calibrate the humidistat if necessary
- Check refrigerant levels
- Clean the coils and internal components
- Verify proper operation of all systems
Whole-House Dehumidifier Cost
The cost of installing a whole-house dehumidifier can vary widely depending on factors such as the size of your home, the complexity of the installation, and the model chosen. According to Angi, homeowners can expect to pay between $1,300 and $2,800 for a whole-house dehumidifier installation.
While this is a significant investment, the long-term benefits include improved indoor air quality and comfort, the prevention of costly moisture-related damage to your home, and reduced energy costs from more efficient HVAC operation.
