Can a Mini Split be Installed on a Stone House?

Installing a mini-split system in a stone house can be a challenging task due to the unique characteristics of the building. However, with proper planning and consideration of the specific requirements, it is possible to successfully install a mini-split system in a stone house. This comprehensive guide will provide you with the technical details and expert-level insights to help you navigate the process.

Challenges of Installing Mini-Split in a Stone House

The primary challenge in installing a mini-split system in a stone house is the need for access to large volumes of exterior air for the heat pump to operate efficiently. The air-to-surface heat exchange between the basement air and the deep subsoil may not be sufficient to manage the peak heating rate, as stone houses typically have high thermal mass and poor insulation.

Another challenge is the potential for vibration transfer from the outdoor unit to the interior of the house, which can make the living space unpleasant. The large volumes of air that need to be moved across the condenser coil during the winter months can also be a significant hurdle, as the air in the basement may need to cycle through the unit 25 times per hour to maintain the desired temperature.

Utilizing Existing Ventilation Systems

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If the stone house has covered coal shoots or existing ventilation systems that can be utilized, it may be possible to install the mini-split system in the cellar. The thermal mass of the earth around the stone-walled cellar can help moderate the temperature, but the volumes of air that need to be moved across the condenser coil are still very large.

To take advantage of the existing ventilation, you may need to:

  1. Assess the size and condition of the coal shoots or ventilation ducts to ensure they can accommodate the required airflow.
  2. Install high-efficiency fans or blowers to move the necessary volumes of air through the system.
  3. Insulate the ventilation ducts to minimize heat loss or gain and improve the overall efficiency of the system.
  4. Integrate the mini-split system’s controls with the existing ventilation system to ensure seamless operation.

Mounting the Outdoor Unit

When it comes to mounting the outdoor unit, there are two main options: wall mounting or ground mounting. Each option has its own advantages and disadvantages that must be carefully considered.

Wall Mounting

Wall mounting the outdoor unit can transfer vibrations directly throughout the house, making the interior space unpleasant to be in whenever the unit is operating. This is a significant concern in a stone house, as the high-density materials can amplify the vibrations.

To mitigate the vibration issue, you may need to:

  1. Use vibration-dampening mounts or isolators to decouple the outdoor unit from the wall.
  2. Ensure the wall is sturdy enough to support the weight of the outdoor unit without transferring excessive vibrations.
  3. Consider using a custom-built mounting bracket that is specifically designed to minimize vibration transfer.

Ground Mounting

Ground mounting the outdoor unit eliminates any vibrations into the house and may be a bit quieter. However, unless the house is constructed with poured concrete or concrete block and brick, it is not recommended to bolt an AC/heat-pump unit directly onto the side of the stone house.

Instead, the outdoor unit should be isolated from the structure of the house, either on a separate stand or platform. This can be achieved by:

  1. Constructing a sturdy, vibration-dampening platform or stand made of concrete, steel, or other suitable materials.
  2. Ensuring the platform is level and stable, with proper drainage to prevent water accumulation.
  3. Securing the outdoor unit to the platform using vibration-isolating mounts or rubber grommets.
  4. Considering the aesthetic impact of the outdoor unit and designing the platform or stand accordingly.

Integrating with the Stone House’s Thermal Mass

The thermal mass of the stone walls in a stone house can be a valuable asset when it comes to heating and cooling the building. By leveraging the thermal mass, you can:

  1. Utilize the earth’s thermal energy to help moderate the temperature in the cellar or basement, reducing the load on the mini-split system.
  2. Explore the possibility of using a ground-source heat pump system, which can take advantage of the stable temperatures in the earth surrounding the stone walls.
  3. Ensure the mini-split system is properly sized to account for the thermal mass, as it may require a larger capacity unit to effectively heat and cool the space.
  4. Incorporate thermal mass-based strategies, such as thermal storage or phase-change materials, to further optimize the system’s performance.


Installing a mini-split system in a stone house can be a complex and challenging task, but with the right approach and attention to detail, it can be done successfully. By understanding the unique characteristics of the stone house, leveraging existing ventilation systems, carefully selecting the outdoor unit mounting method, and integrating the system with the building’s thermal mass, you can create a comfortable and energy-efficient heating and cooling solution for your stone house.

Remember to always consult with a professional HVAC contractor or engineer to ensure the system is designed and installed correctly, and to comply with all local building codes and regulations.