The Ultimate DIY Guide to Installing a Mini Split in Your Bathroom


Installing a mini split in a bathroom requires careful consideration of various factors, including size, placement, insulation, ventilation, humidity, power requirements, condensation, and noise levels. This comprehensive guide provides a detailed, technical, and hands-on approach to help DIY enthusiasts with advanced skills successfully install a mini split in their bathroom.

Size and Placement

mini split in bathroomImage source: Flickr

The size of the mini split unit for your bathroom will depend on the square footage of the space. As a general rule, you’ll want to choose a unit with a capacity of 12,000 to 18,000 BTU per hour for a typical bathroom size of 100-300 square feet.

When it comes to placement, it’s recommended to install the mini split on an exterior wall. This is because the drainage and coolant lines need to be routed to the outside of the house. In smaller bathrooms, this may limit your placement options, so you’ll need to carefully plan the layout to ensure the unit fits and the lines can be properly installed.

To determine the exact size and placement, follow these steps:

  1. Measure the Bathroom: Use a tape measure to accurately determine the length, width, and height of your bathroom. This will help you calculate the square footage and select the appropriate mini split size.
  2. Identify Exterior Wall: Carefully inspect your bathroom layout and identify the exterior wall where you can install the mini split. Ensure there is enough clearance around the unit for proper airflow and access.
  3. Plan the Placement: Decide the exact location on the exterior wall where you will mount the mini split. Consider factors like proximity to power source, accessibility for maintenance, and minimizing visual impact.
  4. Verify Clearances: Refer to the manufacturer’s installation instructions to ensure you have the required clearances around the mini split for proper operation and safety.
  5. Account for Drainage: Determine the best route for the condensate drain line to the exterior of the home. This may require drilling through the wall or finding an existing opening.


If you’re using a ceiling cassette mini split with a branch duct, it’s crucial to properly insulate the area above the cassette. This will help maintain the efficiency of the system and prevent heat loss.

To insulate the area above the cassette:

  1. Measure the Ceiling Cavity: Determine the dimensions of the ceiling cavity where the mini split cassette will be installed.
  2. Select Appropriate Insulation: Choose a high-R-value insulation material, such as fiberglass or rigid foam, that is suitable for the application and can withstand the moisture and temperature conditions in the bathroom.
  3. Install the Insulation: Carefully cut the insulation to fit the ceiling cavity and secure it in place, ensuring there are no gaps or voids that could compromise the insulation’s effectiveness.
  4. Seal and Protect: Seal any seams or edges with a high-quality sealant or tape to prevent air leaks. Consider adding a vapor barrier if required by local building codes.
  5. Verify Clearances: Ensure the installed insulation does not interfere with the mini split’s airflow or installation requirements.


Proper ventilation is crucial in a bathroom to remove excess humidity and maintain air quality. While a mini split can help dehumidify the space, it’s essential to have a dedicated exhaust fan to effectively remove moisture from the room.

When planning the ventilation system:

  1. Determine Exhaust Fan Size: Calculate the required exhaust fan capacity based on the bathroom’s square footage and local building codes. As a general guideline, aim for a fan with a minimum of 50 CFM (cubic feet per minute) for a small bathroom, and up to 100 CFM for a larger space.
  2. Install the Exhaust Fan: Follow the manufacturer’s instructions to properly install the exhaust fan, ensuring it is vented to the outside of the home and not into the attic or other enclosed spaces.
  3. Integrate with Mini Split: Coordinate the placement and operation of the exhaust fan with the mini split system. Consider installing the fan and mini split on the same switch or control system for seamless operation.
  4. Ensure Adequate Airflow: Verify that the exhaust fan is effectively removing moisture and that the mini split is not short-cycling or struggling to maintain the desired temperature and humidity levels.

Humidity Considerations

Mini splits are generally well-suited for high-humidity environments like bathrooms, but it’s essential to check the manufacturer’s specifications and instructions for any humidity-related limitations or requirements.

To address humidity concerns:

  1. Review Manufacturer Specs: Carefully read the mini split’s installation manual and technical data to understand the unit’s maximum operating humidity range and any special considerations for high-humidity applications.
  2. Select a Dehumidify Mode: Look for a mini split model that offers a dedicated dehumidify mode, which will allow the system to effectively remove excess moisture from the bathroom air.
  3. Monitor Condensation: Keep an eye on the mini split’s operation and watch for any excessive condensation or water dripping from the vents. If this occurs, you may need to adjust the unit’s settings or consider adding additional dehumidification measures.
  4. Maintain Filters: Regularly clean or replace the mini split’s air filters to ensure optimal airflow and prevent the buildup of dust and debris, which can impact the unit’s humidity control capabilities.

Power Requirements

Ensuring the bathroom has sufficient power supply for the mini split is crucial. Depending on the size and model of the unit, you may need to upgrade the electrical system or add a dedicated circuit.

To address the power requirements:

  1. Determine the Mini Split’s Power Needs: Review the unit’s electrical specifications, including voltage, amperage, and phase requirements.
  2. Assess the Existing Electrical System: Evaluate the bathroom’s current electrical setup, including the size and capacity of the circuit breaker panel, the available circuit breakers, and the wiring.
  3. Upgrade the Electrical System: If the existing electrical system is not adequate, you may need to upgrade the circuit breaker panel, add a new dedicated circuit, or run additional wiring to accommodate the mini split’s power requirements.
  4. Hire a Licensed Electrician: It’s highly recommended to have a licensed and experienced electrician perform any necessary electrical work to ensure compliance with local building codes and safety standards.
  5. Verify Proper Grounding: Ensure the mini split is properly grounded to prevent electrical hazards and optimize the system’s performance.

Condensation Management

Mini splits can produce condensation, which needs to be properly managed to prevent water damage and maintain the system’s efficiency.

To address condensation:

  1. Inspect the Drain Line: Carefully route the mini split’s condensate drain line to the exterior of the home, ensuring it has a consistent downward slope to allow for proper drainage.
  2. Consider a Condensate Pump: If the mini split’s drain line cannot be gravity-fed to the exterior, you may need to install a condensate pump to actively remove the collected water.
  3. Insulate the Drain Line: Insulate the condensate drain line to prevent condensation from forming on the exterior of the pipe, which could lead to water leaks or damage.
  4. Monitor for Clogs: Regularly inspect the drain line for any blockages or debris that could impede the flow of condensate, causing it to back up and potentially overflow.
  5. Implement a Backup Plan: Consider installing a secondary drain pan or overflow sensor to automatically shut off the mini split in the event of a condensate drainage issue.

Noise Considerations

Mini splits can produce some level of noise during operation, which may be a concern in a bathroom environment. To minimize the impact of noise:

  1. Select a Quiet Model: When choosing a mini split, look for units with a low decibel (dB) rating, typically in the range of 40-50 dB.
  2. Optimize Placement: Position the mini split’s indoor unit as far away from high-traffic areas or seating locations as possible to reduce the perceived noise level.
  3. Utilize Sound Dampening: Consider installing sound-absorbing materials, such as acoustic panels or insulation, around the mini split’s indoor unit to help reduce noise transmission.
  4. Maintain the System: Regularly clean and service the mini split to ensure its components are operating smoothly and quietly. Worn or malfunctioning parts can contribute to increased noise levels.
  5. Adjust Fan Speeds: If the mini split allows for adjustable fan speeds, experiment with lower settings to find the optimal balance between cooling performance and noise level.

By following these detailed, technical, and hands-on guidelines, DIY enthusiasts with advanced skills can successfully install a mini split in their bathroom, ensuring optimal performance, efficiency, and comfort.


  1. Minisplit shared between a bedroom and bathroom – GreenBuildingAdvisor
  2. How do you cool bathrooms w/ Mini-Splits | The Garage Journal
  3. How stupid is putting a mini-split AC in a bathroom? : r/HVAC – Reddit