Integrated Energy Analysis | CODEX | IDL

Project setup

Set the site and floor area once — every module reads from here.

Idaho city (loads TMYx weather)

…or upload your own EPW

Building / zone floor area SF

No weather loaded — design conditions use ASHRAE defaults below. Pick a city to derive them from TMYx data.

Portable .codex.json — saves every input plus the site. Nothing leaves your browser. (Uploaded EPWs are re-attached on load.)

you enter auto-calculates

Building heat gain

—Btu/hr·SF · total — Btu/hr

1 Roof & walls — conduction —

Opaque envelope conduction, each surface separately.

q = U × A × DETD

Climate (design conditions)

Design dry-bulb (cooling)		°F
Mean daily temperature range		°F

Surfaces

Surface	Area (SF)	U-value	DETD (°F)	q (Btu/hr)
Total				—

2 Glass — solar gain —

Transmitted solar by orientation, using design cooling load factors (Reference Fig 2).

q = A × DCLF

Orientation	Area (SF)	DCLF	q (Btu/hr)
Total			—

3 Outdoor air —

Commercial buildings gain through ventilation; residential through infiltration.

Method

q = V × Q

Occupant density (per 1000 SF)		people
Occupants = density × area/1000	—	people
Ventilation rate		CFM/person
Outdoor air volume = rate × occupants	—	CFM
Ventilation factor		Btu/hr·CFM

Outdoor-air gain	—	Btu/hr

4 People —

Sensible metabolic gain. Occupants carry over from Step 3 (editable).

q = O × SHGO

Occupants		people
Sensible heat gain / occupant		Btu/hr

5 Lights —

Electric lighting gain — standard density, or a daylight-reduced rate.

Method

q = LPD × SF × 3.412 × ballast

Lighting power density		W/SF
Ballast factor		×

6 Equipment —

Plug & process loads — by inventory or by power density.

Method

q = watts × 3.412

Total connected load

7 Latent gains —

Moisture load, as a fraction of the sensible gains from Steps 1–6.

q = sensible(1–6) × latent %

Sensible gains, Steps 1–6	—	Btu/hr
Latent fraction		(decimal)

you enter auto-calculates from Heat Gain

Balance point temperature

—°F — below this outdoor temp, the building needs heating

Interior winter setpoint, T_i	— °F	Gain rate, Q_i	— Btu/hr·SF
Envelope loss, UA_env	—	Outdoor-air loss, UA_oa	—
Total loss rate, UA_total	— Btu/hr·°F·SF	T_b = T_i − Q_i/UA	— °F

1 Indoor temperatures

The balance-point equation works off the indoor–outdoor temperature difference.

Average winter interior setpoint (T_i, 24-hr)		°F
Warmest summer interior temp (for ventilation)		°F
Hours of operation per day		hrs

2 Internal gains —

People, lights, and equipment. These are the same internal loads computed in the Heat Gain module.

Source

Source	Btu/hr	Btu/hr·SF
People	—	—
Lights	—	—
Equipment	—	—

3 Solar gain — south glazing —

Daily solar gain through south glass, averaged over 24 hours.

Q_s = (V_S × A) / 24

South glass area (building south glazing)		SF
Daily vertical-south insolation, V_S (MEEB C.15 by city)		Btu/hr·SF

4 Envelope heat loss —

Conductive loss per degree, each surface. Areas seed from the building geometry; enter winter U-values.

UA = Σ (A × U)

Surface	Area (SF)	U (Btu/hr·°F·SF)	UA
Total envelope UA			—

5 Outdoor-air heat loss —

Loss from ventilation (commercial) or infiltration (residential).

Building type

Floor-to-floor height

Ventilation per person		CFM
Ventilation per area		CFM/SF

Air changes / hr (natural)	—	ACH

you enter auto-calculates from Heat Gain / weather

Cross-ventilation cooling capacity

—Btu/hr·SF of sensible cooling from wind

Capacity vs. indoor–outdoor ΔT

1 Airflow rate —

Wind-driven flow through the inlet opening.

V = C_v × A × v

Opening

Inlet (windward) openable glass area		SF
Operable fraction (share of glass that opens)		×
Operable opening area = glass × fraction	—	SF
Wind effectiveness factor, C_v (angle: ~0.5–0.6 perpendicular, ~0.25–0.35 oblique)		×

Wind speed

Preliminary wind speed (summer mean from weather)		mph
Reduction factor (terrain & height)		×
Adjusted wind speed = preliminary × reduction	—	mph
Wind speed in fpm (× 88)	—	ft/min

Airflow, V	—	CFM

2 Cooling capacity —

Convert airflow to sensible cooling at the design indoor–outdoor difference.

q_v = V × 1.08 × ΔT

Indoor–outdoor ΔT for ventilation		°F
Sensible cooling rate, q_v	—	Btu/hr
Floor area (project setup)	—	SF

you enter auto-calculates from Heat Gain / Cross Vent / weather

Stack-ventilation cooling capacity

—Btu/hr·SF of sensible cooling from buoyancy

Airflow vs. indoor–outdoor ΔT

1 Airflow rate —

Buoyancy drives warm air out high openings, drawing cool air in low ones.

V = 60 · K · A · √(2g · h · ΔT/T_i)

Smallest opening (inlet / outlet / throat)		SF
Stack height (inlet-to-outlet rise)		ft
Discharge coefficient, K		×
Indoor temperature, T_i		°F
Outdoor temperature, T_o (summer-night mean from weather)		°F
Stack ΔT = T_i − T_o	—	°F

Stack equation

Airflow, V	—	CFM

2 Cooling capacity —

q_v = V × 1.08 × ΔT

ΔT for cooling conversion		°F
Sensible cooling rate, q_v	—	Btu/hr
Floor area (project setup)	—	SF

3 Combined stack + cross optional —

When a building uses both, the driving forces combine in quadrature.

V = √(V_cross² + V_stack²)

Cross-ventilation airflow (from Cross Vent module)		CFM
Stack airflow (Step 1)	—	CFM
Combined airflow	—	CFM
Combined cooling capacity	—	Btu/hr·SF

you enter auto-calculates from Heat Gain / weather

Night-flush cooling capacity

—Btu/hr·SF — heat the cooled mass absorbs the next day

Mass vs. outdoor temperature over the day

1 Building & thermal mass —

Define the mass that stores nighttime coolth.

Building volume		CF
Mass surface area (ideal mass:floor ≈ 2:1)		SF
Mass:floor ratio	—	×
Mass volume		CF
Mass density		lb/CF
Specific heat		Btu/lb·°F
Mass heat capacity = density × sp.heat × volume	—	Btu/°F
Mass surface conductance		Btu/hr·SF·°F
Starting mass temperature		°F

2 Hourly mass simulation —

Hour by hour, the mass exchanges heat with outdoor air. The 24-hour outdoor profile comes from the warmest month of the loaded weather file.

Night-flush window — start		:00
Night-flush window — end		:00
Total mass cooling stored (night)	—	Btu
Sensible cooling rate = storage / 24	—	Btu/hr

3 Ventilation rate needed —

The airflow needed during the peak cooling hour to charge the mass.

CFH = Q_peak / (0.018 × ΔT)

Peak hourly storage	—	Btu
Outdoor / mass temp at peak hour	—	°F
Air changes per hour	—	ACH

you enter auto-calculates from Balance Point / weather

Solar savings fraction

—% of annual heating offset by passive solar

Load collector ratio (LCR)	—	Mass system	—
Pre-passive heating	— kBtu/yr	Post-passive heating	— kBtu/yr
Energy saved	— kBtu/yr	EUI saved	— kBtu/SF·yr

SSF vs. LCR — your system curve & operating point

1 Annual heating energy —

The pre-passive heating load — building loss coefficient times heating degree-days at the balance point.

E = BLC × HDD_{(T_balance)} / AFUE Building load coefficient (BLC)

BLC		Btu/DD
Balance-point temp (degree-day base)	—	°F
Heating degree-days at T_b (from weather)	—	°F·day

Annual heating energy

AFUE / system efficiency		×
Pre-passive heating energy		kBtu/yr

2 Thermal mass system —

Direct-gain configuration — sets the LCR→SSF correlation (Balcomb curves).

System type

A = low mass · B = medium · C = high mass; 1 = single, 2/3 = double/triple glazing.

3 Solar aperture & LCR —

LCR = BLC / A_p

South vertical glazing (seeds from building; raise to add collector)		SF
45° inclined south glazing		SF
Solar aperture A_p = vertical + inclined × 0.707	—	SF
Load collector ratio	—	Btu/DD·SF

↻ Compare mass systems

SSF each system would deliver at your LCR. Higher-mass / better-glazed systems capture more.

you enter auto-calculates from Heat Gain / weather

Earth-tube pre-conditioning

—Btu/hr·SF peak cooling — air tempered by the ground before it enters

Summer: outdoor → outlet	—	Precool	— °F
Winter: outdoor → outlet	—	Preheat	— °F
Heat-exchanger NTU	—	Offsets cooling load	—

Outlet temperature vs. tube length

1 Tube & soil —

Air drawn through buried tubes exchanges heat with the ground.

Tube

Tube length		ft
Tube diameter		in
Pipe material
Ventilation airflow (building outdoor-air rate)		CFM

Soil

Burial depth		ft
Distance to undisturbed soil		ft
Soil conductivity		W/m·K
Summer soil temp at depth (weather estimate)		°F
Winter soil temp at depth (weather estimate)		°F

2 Performance —

T_outlet = T_soil + (T_air − T_soil) · e^−NTU

Cooling design temp (weather, 1%)		°F
Heating design temp (weather, 99%)		°F
Summer outlet temperature	—	°F
Winter outlet temperature	—	°F
Peak cooling rate = CFM × ΔT × 1.08	—	Btu/hr

you enter auto-calculates from Balance Point / Heat Gain / Passive Solar / weather

Annual heating & cooling energy

—kBtu/ft²·yr site energy for space conditioning

	Conventional	After passive	Site energy	EUI
Heating	—	—	—	—
Cooling	—	—	—	—

Annual load by temperature bin heating / cooling

1 Annual loads — bin method —

Hours in each temperature bin (from the weather file) times the load at that temperature. Internal gains shift the effective balance point.

load = (Tbin − base) · UA + internal, per 5°F bin × hours

Heating base temp (deadband lower)		°F
Cooling base temp (deadband upper)		°F
Heating UA (skin; from Balance Point)		Btu/hr·°F
Cooling UA (skin + solar)		Btu/hr·°F
Internal gains (from Heat Gain)		Btu/hr

2 Passive savings —

Passive solar offsets heating; a passive cooling strategy carries the building up to its effective outdoor temperature.

Solar savings fraction (from Passive Solar)

Passive cooling strategy

3 Equipment efficiency —

Seasonal efficiency or COP converts the load into delivered site energy. Reference: electric resistance 1.0; heat pump 2.0–4.0; A/C SEER ÷ 3.412 = COP (code-min SEER 14 ≈ 4.1).

Heating seasonal efficiency / COP		×
Cooling seasonal COP (SEER ÷ 3.412)		×

you enter auto-calculates from Annual Energy

EUI & carbon

—kBtu/ft²·yr site EUI (all end uses)

Site EUI	— kBtu/ft²·yr	Source EUI	— kBtu/ft²·yr
Carbon intensity	— lb CO₂e/ft²·yr	Annual emissions	— t CO₂e/yr

Site EUI vs. Architecture 2030 targets met / not yet

End-use energy (site kBtu/yr)

1 Energy by end use —

Space conditioning carries over from Annual Energy. Add the non-conditioning loads.

Space heating (from Annual Energy)	—	kWh/yr
Heating fuel
Space cooling (from Annual Energy)	—	kWh/yr
Other loads (plug, lighting, DHW)		kWh/yr

2 Conversion factors

Source-energy multipliers and grid emission factors. Defaults follow SWL3; adjust for your grid.

Electricity source multiplier		×
Natural-gas source multiplier		×
Electricity emissions		lb CO₂e/kWh
Natural-gas emissions		lb CO₂e/kWh

3 Architecture 2030 baseline —

Regional average EUI for the building type — the baseline the 2030 reduction targets are measured against.

Baseline average EUI

kBtu/ft²·yr

you enter auto-calculates from EUI & Carbon / weather

Net-zero & PV sizing

—% of annual electricity offset by your PV

PV for net zero	— kWp · — ft²	Your PV	— kWp · — ft²
Annual demand	— kWh/yr	Annual generation	— kWh/yr

Annual balance — demand vs PV generation

1 Annual electricity demand —

Total site electricity carries over from EUI & Carbon (space conditioning plus other loads).

Total annual electricity (from EUI & Carbon)

—

kWh/yr

2 PV sizing —

Required capacity = annual load ÷ specific yield. Array area = capacity ÷ module power density.

kWp = load ÷ yield · ft² = kWp · 1000 ÷ power density

Specific yield (PVWatts; ~1,400–1,600 for Idaho)		kWh/kWp·yr
Module power density (~190 W/m²)		W/ft²
Required capacity for net zero	—	kWp
Required array area for net zero	—	ft²
Your PV array area		ft²

Exposed wall area		SF
Exposed roof area		SF
Infiltration factor		Btu/hr·SF

People gain		Btu/hr
Lights gain		Btu/hr
Equipment gain		Btu/hr
Occupant count (for ventilation)		people