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Life. cycle cons are based on a 25~year life cycle, with costs computed to present value with a real discount rate assumed at 2.?°/a. b'uel price escala~an is based on I~~:~ estimates for fihe South. Also, life cycle casts assume central plant equipment re~lacemen~s where applicable for the iven system: ahternativeltype as follows: So~ton clulher at year 2U; boilers at year 2a, DDS g r controls at year 15, pumps at year 24, l~~ condensing units at year. ~~, and cooh~ng tower ~r~th heat exchanger at year 2a. The ranking far systems based on estimates of u~stallation test ~esti~nates~do not include construction contingency or design fees}, frau~ lowest cost to highest cost, is as fallaws: 1. I7~ condensing units with hot water heat $3oo,2~D 2. 4~pipe boiler and chille~• $35~~,2So ~r water -7ource heat pump $44Q,32o The ranking far systems based on estimates of a 25-year life cycle cast, fra~n lowest cost to highest cast, is as falaws: l . ~-pipe boiler and chiller $ l,a?2,395 2. l~~ condensing wits with hot dater heat $ l,o~U,3~D 3. ''dater source heat pump $1,2G3,494 The .~- i e bailer and chiller option provides the lowest o~rerall hi.fe cycle cost although it has the second ~higl~est zntt~al instalhat~an cost as seen above. wlu.le the 1J~ condensing units with hat water heat ~ ravides the la~ves~t initial cost, the savings are not enough, to offset the operating and p .. .. maintenance casts associated with ~s alternative. As far the wS~P option, ~t cost rare than both tha other alternatives to install and had h~igl~er ea~ergy consumption. This was naainiy due to the lead attern afthis buiidin~ not being ideal. wSI~P~ 5ysterns ~vark best in buildings with bath p ~ ,., pernneter ~heat~rig} loads aid ~g~ ~nterna ~i.e. people, computers, h~ghts, etc. loads zn the winter, In lDis scenario the water source loop tau. be almost self~sustaining as heat is moved from the internal s" ~~aces with ~hi "h Drat hods to ~De perimeter spaces whi,~h rea~uire ~heating~ p g R~,~C~I~M~I~D,ATT4~NS ~Ve~ reco~m.end proceeding ~ritia design of the ~ourwpipe air hiandling unit system. `his systemm offers the hav~rest life c ~ the cost of the three systems evaluated. Although ~~ot cvnsidehed in the Y .. . . fife cycle cyst, this system nay be able to take advantage of portaons of the ex~st~rig 4wp~pe system and therefore offer simpler installation and haver Gast. Also due to li:rnited internal sensible loads, ~I~e 4•pip~e~ system provides the best of the altenla~ives studied far . dehun~idifi~ation b ~ utilizing Dad water reheat cons ire the air Dandling units. Y This installation, as analyzed, would require replacing the existing chiller and boilers and routing new piping where necessary. The existing air handling units would be repl~.ced with constant vah~ume units for the cell blocl~ areas and a variable air volume unit with. hat water reheat boxes far floe o~ ce areas.