HVAC..................................

       Air pressure, air movement, air temperature; dust removal, mite reduction, dehumidification:  all were not just a matter of soft self-indulgence indoors, but of positive no-allergy health and the deterrence of rot, rust, fungus and mildew.  The Lazarus act on old buildings began, in my no doubt obsessional mind, with the provision of clean dry air, unobtrusively circulating.

-Dick Francis,  channeling architect/builder Lee Morris in his book Decider

Reasonable people will likely agree that my mind does not qualify as obsessional, but the decision about providing heating and cooling for the 29 apartment units in the Old School was not an easy one.   The 30,000 square foot building, when in use as a school, was heated by a gas-fired boiler.  One cold winter's day soon after we acquired the building we could actually hear the gas meter whirling as the boiler did its thing.  We quickly decided we could not afford to heat the empty building, so the boiler was shut down and the gas turned off.  Also, in the old-fashioned way of 1939 school buildings, the only air conditioning was a window unit in the principal's office.
      We knew several things to be true:  1) we needed air conditioning, 2) we needed each apartment unit to have its own HVAC (heating, ventilating, air conditioning), 3) we needed to be able to meter each unit separately so that the tenants would pay for their own utility usage, and 4) we needed a reasonable way to heat and cool the six corridors. 
       After considerable debate, we opted to use an all-electric Mitsubishi Split System to heat and cool the units.  The plan for installing these units seemed rather simple at first.   However, a consultation with the historical folks changed that it a hurry.   The systems operate with individual unit compressors.  We had planned to cluster these compressors for the first and second floor on the ground outside the building, and them obscure them with landscaping.  The historical folks vetoed that idea (and yes, they have veto power since it is a historical tax credit project).  They thought that passers-by being able to see +/- 18 modern compressors would detract from the classical historical structure.  One must admit that they were right.   So without a fight, we changed the plan and put all of the compressors, out of sight, on the roof.  What that meant though, is that the 35 line-sets running between the unit heads and the compressors had to find their way, unexposed, through the building to the roof.   It got complicated quickly. 
       To make sense of the photos, they start with the heads and work backwards to the compressors:

Most of the units have two heads.  One in the living area and one in
the bedroom.   The two-bedroom units have three heads.   The smaller studio
units only have one head

Installation

The supporting bracket

A line set awaiting the head.   The small visible pipe is the condensation line

line set and condensation line waiting patiently for next steps

Collected line sets heading to the roof

Remember the beautiful new roof?    Watching them cut
holes in it hurt

Our roofer will be very busy flashing all the penetrations.   It will require semi-
annual inspections on all the flashing to make sure the roof stays water-tight

setting the flashing for the soon to arrive line sets

Cut the roof and drill holes in the concrete deck.    Double ouch

The line sets make it through the roof

Line sets ready to connect to the compressors

It's like a compressor farm on the roof

There will be additional photos once they are finished.