Presenting an input summary

A presentation of results should also include a description of significant input assumptions, which will help a knowledgeable reader to confirm that your assumptions are appropriate. A summary of assumptions for inputs such as the following might also highlight values that are changed to represent each design alternative.

• Envelope component description and performance
• Internal loads: lighting power, receptacle load power, number of occupants
• Daylighting control
• HVAC: system type and performance, outdoor air ventilation rates
• Schedules: occupancy, HVAC
• Indoor conditions: heating and cooling thermostat setpoints
• Utility rates

The following tables are an example of a summary of input assumptions that might accompany a presentation of modeling results. In these examples, the baseline model assumptions are described, and the inputs that are varied for each alternative are identified in the columns in the right half of the table. The values for the changed inputs would be described separately. It can be useful to highlight uncertain assumptions for review, especially those that might have a significant impact on the analysis. In the example below, high-priority assumptions are highlighted with red shading.

General assumptions

Input	Source*	Baseline	Inputs changed in alternatives
			1	2	3	4	5	6
Weather file		weatherfile.epw
Utility rate		Utility X, time of use, $0.15/kWh average
Exterior energy end uses included in model (e.g. exterior lighting elevators)		4 kW exterior lighting

Envelope assumptions

(highlighted assumptions are priority for review)

Input	Source*	Baseline	Inputs changed in alternatives
			1	2	3	4	5	6
Floor area	Program	25,000 ft2
Stories		2
Floor to floor height	Architect	14 ft
Roof	Code	R-30 above deck
Roof surface	Code	0.55 reflectance
Walls	Code	R-19 in steel frame + R-5
Floor	Code	Slab on grade
Window U-factor	Code	0.50
Window SHGC	Code	0.25
Window VLT		0.30
Window area		35% WWR
Window shading		None

Room/zone assumptions

(highlighted assumptions are priority for review)

Input	Source*	Baseline	Inputs changed in alternatives
			1	2	3	4	5	6
Lighting power	Code	0.60 W/ft2
Receptacle power	Judgment	0.75 W/ft2
Occupant density	Judgment	200 ft2/person
Occupancy schedule	Program	8am-6pm M-F Off weekends
Thermostat setpoints	Judgment	70 heating 75 cooling
Daylighting control	Judgment	No

HVAC airside assumptions

(highlighted assumptions are priority for review)

Input	Source*	Baseline	Inputs changed in alternatives
			1	2	3	4	5	6
System type	Judgment	VAV reheat
Cooling source	Judgment	Chilled water
Heating source	Judgment	Hot water
Supply air flow		Autosized
Fan power/pressure	Default	5 in. w.c.
Fan control	Code	Variable speed
Cooling efficiency		NA
Heating efficiency		NA
Terminal unit control	Code	20% minimum flow, dual-maximum control
Outdoor air	ASHRAE 62.1	20 cfm/person
Economizer control	Code	Yes
Supply air temperature control	Code	Reset
Operating schedule	Program	5am-8pm M-F Off weekends

HVAC waterside assumptions

(highlighted assumptions are priority for review)

Input	Source*	Baseline	Inputs changed in alternatives
			1	2	3	4	5	6
Chiller type & qty	Judgment	(2) water cooled centrifugal
Chiller capacity		Autosized
Chiller efficiency	Code	0.50 kW/ton
CHW supply and return temp.	Judgment	44F
CHW temp. control	Code	reset
CHW piping configuration	Judgment	primary-only
CHW pump head	Judgment	80 ft
CHW pump control	Code	Variable flow
Cooling tower type	Judgment	Open, axial fan
Cooling tower fan control	Code	Variable speed
Cooling tower approach temp.	Judgment	8F
Cooling tower design wetbulb temp.	Judgment	75F
Condenser water temp. setpoint	Judgment	70F
Boiler type & qty	Judgment	(2) forced-draft natural gas
Boiler capacity		Autosized
Boiler efficiency	Code	80%
HW supply and return temp.	Judgment	140F, 100F
HW temp. control	Code	Reset
HW piping configuration	Judgment	Primary-only
HW pump head	Judgment	75 ft
HW pump control	Judgment	Variable speed

* Typical information sources

• Plans
• Specifications
• Building program
• Owner’s project requirements
• Communication with design team
• Energy code
• Software default
• Other references
• Modeler judgment