McLean, VA 22102
Contract Value: $2,939,204
GC: James G. Davis Construction
Owner: The Madeira School
Engineer: Potomac Energy Group
The Madeira School is a grade 9-12 boarding/day school for girls located in McLean, VA. The two buildings renovated in this phase (Main Dormitory/Administration Building and East Dormitory) were originally built in 1930 and include dormitory rooms, supervisory apartments and administrative areas, and included the addition of a new one story administrative area attached to the Main Dormitory/Administration building.
The Mechanical scope included replacement of the existing oil fired boilers and window unit air conditioners with a new Geothermal water source VRV system for heating and cooling. Thirty 600’ deep wells were drilled in the existing Student Parking area, double HDPE loops installed and grouted in each well and then piped to an underground vault where the manifolds connect to two 6” HDPE supply and return lines (for redundancy) that terminate at a distribution header and Main Loop pump system in the East Dormitory. From there an HDPE supply and return line was run to the two buildings in this phase as well as the three Dormitory buildings that will be renovated in a future phase. This primary loop distributes water between the well field and decoupler piping located in each building. The secondary geothermal loop pumps in each building circulate water locally to the heating/cooling units located in each building.
Space heating and cooling within each building is accomplished by a combination of extended range water source heat pump units and water cooled VRF systems. Each of these systems utilize a reversing valve and localized compressor for extracting or rejecting heat into each building’s secondary distribution loop. Heat is rejected into each building’s secondary loop in the summer and extracted from the loop in the winter. Heat is transferred between the primary and secondary building loops and returned back to the East Dormitory header for return to the distribution headers in the vault where the water is distributed to the wells where the heat is rejected to or absorbed from the earth, depending on the season.
Challenges included fitting the new equipment and welded steel piping into the existing Mechanical Room spaces, new supply ductwork from the WSHPs to the existing Common Areas and installing the new outside air ductwork from the new Energy Recovery unit in both buildings to the individual spaces requiring it within the shallow joist spaces and high as possible ceilings. Extremely close coordination between all trades was required to obtain close-in inspections according to schedule to allow the finish trades adequate time to complete the buildings for student occupancy.