UNIQUE SYSTEM TO COOL JEFFERSON'S HOUSE
Poplar Forest Newsletter, Spring 2000

Taking a cue from the original owner who prized innovation, Poplar Forest will experiment with a unique system to cool Jefferson’s retreat home.

“Poplar Forest will be breaking new ground with a ventilation system that our architectural team has designed,” says Executive Director Lynn Beebe.

“Our work will make a contribution to the preservation field.”

Appropriately, one of Jefferson's ideas  — his underground ventilation tunnels at Monticello —is incorporated as a component of Poplar Forest's air cooling system.

Says Travis McDonald, director of restoration, “What's new and different about our cooling method is that it is a single, flexible system that will allow us a wide range of options while shielding the Jeffersonian brick structure from damage due to modern grilles, ducts, and large equipment in the house.”

Cooling historic homes presents dilemmas for their stewards. They must balance the needs of preserving the original fabric of the house, presenting an authentic experience for visitors, and creating a comfortable environment for people.

Conventional air conditioning creates noise, vibration, and potential water leaks as well as requiring the destruction of some of the original brick for ducts and grilles. It also could take away from visitors’ enjoyment and understanding of Poplar Forest as a 19th-century historic structure.

Yet there was a need to consider visitor comfort and the effect of humidity on the brick. The solution here is an integrated mechanical system that emphasizes using the house’s natural system of ventilation as much as possible while still allowing for the use of more modern methods if temperature and humidity levels rise.

There are six levels of ventilation included in the system, composed of windows, blinds, fan, underground tubes, geothermal wells, and an underground pump house located 330 feet northeast of the house.

Weather permitting, Poplar Forest will replicate the natural ventilation method of Jefferson’s time by opening windows and closing louvered blinds.

If slightly more cooling is needed, the operation of a quiet, hidden fan that exhausts air out the south pediment window can be employed.

The next higher level of ventilation is achieved by activating underground air tubes, similar to what Jefferson used for venting two privies inside Monticello. At Poplar Forest, the tubes will draw in air geothermally cooled in the ground between the pump house and the main house that is then discharged under the stairways. A quiet attic fan will pull the cool air up and eventually out of the house.

The next level of cooling involves dehumidifying the air at the pump house and channeling it into the house.

The second, third, and fourth options can be used in conjunction with the natural ventilation of open windows and closed blinds.

With the fifth option, the pump house equipment would actually chill the air before sending it into the house. Again, the attic fan would help circulate the air throughout the house.

The sixth means more closely resembles conventional air conditioning by turning the air tubes into a closed system. Cooled air would recirculate through the underground tubes between pump house and retreat house.

Construction of the system will begin after archaeologists complete an investigation of the building site.

Once the equipment is installed, staff expect to experiment to determine how to ideally manage the system. A radiant heat system, hidden under the upper-level floorboards, already is in place for next winter. Preservation professionals had recommended a moderate level of heating to combat dampness in the air and condensation caused by extreme differences between indoor and outdoor temperatures.