Heating Losses- Infiltration and Ventilation

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Heating Losses-Infiltration and Ventilation

• ARCH-432

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Attendance

• Which civilization made it a point to layout
  whole cities to take advantage of passive
  heating? In what direction did the city streets
  run?
• Greece
• Rome
• Egypt
• Persia
• Babylonia

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Attendance

• The ancient Greeks did this. What was shown is
  Priene (Priene) (5th Century B.C.), which had
  all of the streets laid out in an East-West
  fashion, thus allowing all homes to point South.

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Attendance

• Only primitives and barbarians lacked
• knowledge of houses turned to face the
• winter sun, dwelling beneath the ground like
  swarming ants in sunless caves.
• Aeschylus

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Greetings Capt. Kirk
Aeschylus
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Attendance

• Aeschylus pronounced Ess ca less
• One of the earliest writer of Greek tragedy
  before him plays had single actors who could only
  respond to a chorus (group of people). Aeschylus
  increase the tragedy to two actors with dialog.

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Big Picture Moment
Ceiling
Partition
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Ceiling

• Five main types of heat loss
• 1. Transmission (conduction)
• 2. Infiltration (convection)
• 3. Ventilation (convection)
• 4. Radiation (radiation)
• 5. Moisture migration

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Summary of Heat Losses

• Wall
• Roof
• Floor
• Windows
• Doors
• Infiltration
• Ventilation

Envelope Losses
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What You Need To Know

• The difference between ventilation and
  infiltration
• Calculation methods for both ventilation and
  infiltration

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What You Need To Be Able To Do

• Calculate infiltration/ventilation loads
• Be able to reduce/mitigate infiltration and
  ventilation loads
• Employ techniques for increasing ventilation
  effectiveness

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Terms

• Infiltration
• Exfiltration
• Ventilation
• Direct Outside Air System (DOAS)

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Infiltration

• The uncontrolled introduction of outside air
  into a building.

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Infiltration

• The uncontrolled introduction of fresh air into a
  building.
• 1. Most subjective of all losses
• 2. Oftentimes the largest of all heat losses.
• Sometimes comprises up to 30 of the total
• heating load.
• 3. Ends up being an educated guess

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Why Is This Important?

• All buildings leak
• A tight building will leak .5 AC/H
• A leaky building can leak 3 AC/H
• Regardless of climate, air leaking into walls
  causes problems

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Ventilation

• The mechanical introduction of outside air (OA)
  to
• Replace Oxygen
• Dilute contaminants
• Pressurize the building

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Moisture Load
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Infiltration Calculation Methods

• Crack method
• Air Change Method
• Averaging method (I dont know so Im going to
  throw a dart method)

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Crack Method

• Presumes that an accurate estimate can be
  obtained by estimating the rate of infiltration
  per foot of crack for doors and windows
• CFM Ft. of Crack x Infiltration Rate
• QS 1.1 x CFM x (T2 T1) in BTU/HR

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Add Infiltration Through Open Door

• Determine Door Usage
• ? Number of People per Minute
• Determine CFM per person (D)
• CFM ? x D

LEED-NC Credit EQ 5 for providing vestibules.
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Infiltration by Crack Method

• Add CFM from Crack losses to CFM for Open Door
  losses

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Mitigate These Losses

• How do you reduce or mitigate these losses?
• (Review)

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Mitigation Strategies

• Pressurization
• QS 1.1 x CFM x (T2 T1)
• Vs.
• QS 1.1 x (CFH/ft of crack x ft of crack)/60 x ?T

You own the variables!
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Infiltration Variables

• Review
• Wind velocity and direction
• Stack effects
• Corner rooms
• Exhaust fans on or off
• Pressure zoning
• Frequency of use
• Maintenance

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Stack Effect
Review
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Air Change Method

• Often used in residential construction and in
  large warehouses and similar buildings
• CFM A.C.H. x Volume (ft3)/60
• or
• CFM Volume (ft3)/Frequency (minutes)

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Air Change Method

• Uses same formula for sensible
• Equals one room change
• Designer will use 0.3 to 2.0 air changes per hour
  (ACH)
• Occupancy
• Climatic condition (i.e. winter vs. summer)
• Construction (tight or loose)
• Least accurate of the three methods

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Table 2-8
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Heat Loss Due to Infiltration

• Infiltration
• Btu H (.018) x (ACH) x V x (Ti To)
• ACH air exchanges per hour
• V volume
• Ti inside temperature
• To outside temperature

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Heat Loss Due to Infiltration

• OR

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Heat Loss Due to Infiltration

• Infiltration
• Btu H 1.1 x CFM x (Ti To)
• CFM (ACH x volume) / 60 min per hour

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Heat Loss Due to Infiltration

• Infiltration
• Please Note
• For tight construction use 0.5 for ACH.
• For medium construction use .85 for ACH.
• For loose construction use 1.3 for ACH.
• For really bad construction use 2.0 for ACH
• For the summer months (cooling) use 70 of the
  winter values.

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Infiltration Ventilation
Btu Hour Loss due to Infiltration Main Area Btu Hour Loss due to Infiltration Main Area Btu Hour Loss due to Infiltration Main Area Btu Hour Loss due to Infiltration Main Area Btu Hour Loss due to Infiltration Main Area Btu Hour Loss due to Infiltration Main Area
CFM Ht. W. L. L. 1.10 air exch. vol. In cf / 60 Temp. Ch.
  12 46.66 74.66 74.66 1.10 0.5 41,803.63 348.36 76 29,123.19
                     
Btu Hour Loss due to Ventilation Main Area Btu Hour Loss due to Ventilation Main Area Btu Hour Loss due to Ventilation Main Area Btu Hour Loss due to Ventilation Main Area Btu Hour Loss due to Ventilation Main Area Btu Hour Loss due to Ventilation Main Area
Ht. W. L. 1.10 1.10 sf cfm exchange Occup. Temp. Ch.
  12 46.66 74.66 1.10 1.10 3,483.64 0.180 34.84 76 66,983.35
Ra Rp Occup/1000 Occup/1000
0.18 5 10.00 10.00
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Heat Gains Due to Infiltration

• Latent Load
• BtuH 4500 x (air exchanges x (volume) /60) x
• (W Final W Initial)
• (W Final W Initial) Difference Ratio Pounds
  of Moisture per dry air

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Heat Loss Due to Ventilation

• Ventilation
• Btu H 1.1 x (Ra x square feet of building )
  
• (number of people in the building x Rp )
• x
• (Ti To)

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Heat Loss Due to Ventilation
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Heat Loss Due to Ventilation

• Ventilation
• Ra Area Outdoor Air Rate
• Rp People Outdoor Air Rate
• Example Pharmacy
• Ra .18
• Rp 5

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Heat Loss Due to Ventilation

• Ventilation
• Btu H 1.1 x (.18 x 3,632) (30 x 5) x 76o
• 67,214

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Ventilation and / or Infiltration
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