Energy Services Bulletin, April 2004
 

Topics from the Power Line:
Insulation key to keeping wine cellar temperature consistent


Editor's note: The Energy Services Bulletin features real answers to real questions posed to our staff at the Energy Services Power Line. We hope you find it useful.

Question
We live in Sacramento, Calif., and would like to design an energy-efficient, residential-scale wine cellar that will maintain the required 55-degree F temperature. Should we build it above or below ground? Also, it was suggested that we use R-50 insulated concrete forms. Is this feasible?

Answer
Research data from the US Geological Survey, the Army Corps of Engineers and the National Water Well Association show that the average ground temperature below two feet in the Sacramento area ranges from 60 degrees F to 64 degrees F.

Assuming this data, here are suggestions for keeping the wine cellar at 55 degrees F.

  1. Construct the wine cellar completely underground with no outside windows. If the room is going to be occupied or used as a tasting room, local building codes may require a window. If so, specify a Class 20 window (U-0.20; vinyl or fiberglass framing, triple glazing, and low e glass).

  2. Insulate the cellar room walls adjacent to the rest of the building at the level of insulation you would normally install in a residential building, following the state energy code. Walls should be insulated to R-19 or R-21, and the ceiling at R-30. An R-10 insulated door of either fiberglass or steel should be used. Make sure that the door seals well when closed.

  3. Concrete walls do not need to be insulated providing they are underground. At the two-foot level and above, you will need to insulate the outside of the concrete. It is suggested you insulate down to the two-foot level with R-10 extruded polystyrene. It's not recommended to use insulated concrete forms that have an R-50 rating. The tested values are closer to R-20. The California Energy Commission rates the ICF system at an R-value of about 20.

  4. The concrete floor should not be insulated. This, along with not insulating the concrete walls below two feet, will help stabilize the room temperature at the adjoining ground temperature of about 60 to 64 degrees F. Check with the local building official to see if that area has any pockets of radon. If so, there will be special requirements for insulating and ventilating the wine cellar room.

  5. As the below grade room will have a stabilized temperature above the required 55 degrees F, cooling will be necessary. You may need to select a dedicated air conditioning system for the wine cellar room to cool it year around.

You might want to have your site tested for temperature at depths of one foot, two feet and eight feet as your site may not fit the data provided above. The site you have chosen for this project may differ from the 60-to-64-degree-F range if there is geothermal groundwater nearby. Also, the temperature will vary throughout the year as the ground heats up in the late summer months and cools down in the late winter months.

The following list of commercial Web sites provides information about wine cellar designs and cooling systems. Please note, this is not an endorsement of services or products, but rather, information about the availability of these services and/or products. We do recommend extending your research to other companies to get a full range of options.

  • Vino Cellars & Accessories addresses insulation, wall and ceiling framing and coverings, cellar doors, flooring, lighting, climate control systems and wine racks.
  • Vintage Cellars is located in San Marcos, CA. They also sell wine cellar cooling systems.
  • Wine Cellars Unlimited sells cooling systems for wine cellars. They also have wine cellar room designs listed on their site.
  • Sonoma Wine Rooms LLC designs wine cellar rooms and sells cooling systems.