Civil Engineering Reference
In-Depth Information
ASHRAE Standard (ASHRAE
2013a
) are generally being used to allocate proper
minimum outdoor air required for each space. Other provisions such as expected
infi ltrated air, assigned exhaust air or other airfl ow settings along with the desired
temperature, humidity and CO
2
level are being added to the calculations in this place.
The next step is to specify the characteristics of the construction material. Those
characteristics are such as type, typical size and heating characteristics of different
partitions, walls, roofs, slabs, skylights, windows, and doors. The heating character-
istics of windows and skylights (glazing) are usually represented in form of U-values
and shading coeffi cient, while the other construction materials are mainly specifi ed
only by their U-values, which is indicator of resistance of the construction material
against heat transfer.
After these basic primary inputs, designer shall input a detail description of each
specifi c space in the building. Depending on the size of the building, this step could
be the most time consuming procedure, since all the different spaces of the building,
their associated construction element maps, and designation of the internal loads
shall be specifi ed and added to the calculations at this time.
By the end of this step a relatively accurate physical model of the building and
its different spaces have been built into the calculations and the next step logically
is to defi ne the type and characteristics of the HVAC air systems and equipment
which will be used to air condition the building. This can include provisions such as
defi ning system types (e.g., fan-powered terminal unit with reheat, chilled beams,
fan coils); defi ning spaces with dedicated and/or supplemental cooling/heating
(e.g., fan-coils, split systems, unit heaters); ventilation airfl ow rates; dedicated out-
door air system (DOAS) vs. mixed-air unit; building pressurization; ventilation
schedule; infi ltration; design vs. minimum air change rates; supply air schedule;
exhaust air schedule; minimum terminal unit airfl ows; exhaust requirements; supply
fan type, CFM, total static pressure, brake horsepower; return fan type, CFM, total
static pressure, brake horsepower; motor effi ciencies; return air path (plenum,
ducted, room); supply air temperature heating, cooling; energy recovery, type,
effectiveness; auxiliary HVAC, type (e.g., under fl oor radiant heating); humidifi ca-
tion, type; system-specifi c requirements (e.g., chilled beam capacity).
The designer then shall defi ne the cooling and heating plant equipment and con-
fi gurations such as district plant; chiller or boiler type, number; pumping arrange-
ment, type(s), full load energy rate, equipment curve; design chilled and hot water
delta-T; chilled and hot water temperature reset, schedule; pump pressure optimiza-
tion; waterside economizer, schedule; heat recovery, parameters; cooling towers;
etc. Each air handling systems then should be assigned to the appropriate cooling
and heating plants. Minimum effi ciency of the different equipment, equipment
schedules, and desirable applicable controls such as thermostat set-point(s), drift,
schedules; humidistat set-point(s), drift, schedules; CO
2
sensors, set-point; airside
economizer, type; demand control ventilation; supply air temperature reset; fan
static pressure reset; pump head pressure reset; fan cycling; schedule (none,
occupancy-based, load-based); night purge; morning warm-up; and optimum start,
stop schedule shall be added to the calculation software at this time as well.
In addition, energy consumption rate of the different equipment and applicable
