Heating Losses- Infiltration and Ventilation ARCH-432

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

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

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 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.

Greetings Capt. Kirk Aeschylus

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.

Big Picture Moment roof Infiltration and Ventilation Ceiling Partition Exterior wall Glass conduction Floor Infiltration and Ventilation Ceiling Partition I. Heat Loss A. Five main types of heat loss 1. Transmission (conduction) 2. Infiltration (convection) 3. Ventilation (convection) 4. Radiation (radiation) 5. Moisture migration

Five main types of heat loss 1. Transmission (conduction) roof Exterior wall Glass conduction Floor Infiltration and Ventilation Ceiling Five main types of heat loss 1. Transmission (conduction) 2. Infiltration (convection) 3. Ventilation (convection) 4. Radiation (radiation) 5. Moisture migration I. Heat Loss A. Five main types of heat loss 1. Transmission (conduction) 2. Infiltration (convection) 3. Ventilation (convection) 4. Radiation (radiation) 5. Moisture migration

Summary of Heat Losses Wall Roof Floor Windows Doors Infiltration Ventilation Envelope Losses

What You Need To Know The difference between ventilation and infiltration Calculation methods for both ventilation and infiltration

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

Terms Infiltration Exfiltration Ventilation Direct Outside Air System (DOAS)

Infiltration “The uncontrolled introduction of outside air into a building.” I. Infiltration A. 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”

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” I. Infiltration A. 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”

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

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

Moisture Load

Infiltration Calculation Methods Crack method Air Change Method ‘Averaging’ method (‘I don’t know so I’m going to throw a dart’ method)

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 I. Crack Method A. Presumes that an accurate estimate can be obtained by estimating the rate of infiltration per foot of crack. 1. For doors, you must also add the volume of air that “infiltrates” when the door is in use. B. The CFM is then defined as CFM = Ft. of Crack x Infiltration Rate. C. Use Table 3.4 of your text.

Add Infiltration Through Open Door Determine Door Usage ת = Number of People per Minute Determine CFM per person (D) CFM = ת x D I. Add Infiltration Through Open Door A. Determine Door Usage 1. Owner or Architect will be the best source for ת, the number of people per minute B. Determine the CFM per Person (D) 1. From Table 3.5 CFM = ת x D LEED-NC Credit EQ 5 for providing vestibules.

Infiltration by Crack Method Add CFM from Crack losses to CFM for Open Door losses

Mitigate These Losses How do you reduce or mitigate these losses? (Review) Really good weather-stripping Pressurization Vestibules Revolving doors Seal cracks and openings CO2 sensors DOAS systems

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 ΔT You own the variables!

Infiltration Variables Review Wind velocity and direction Stack effects Corner rooms Exhaust fans on or off Pressure zoning Frequency of use Maintenance I. Infiltration Variables A. Wind velocity and direction B. Stack effects C. Corner Rooms 1. Remember, the wind blows on one side at a time! A. Use either the greater of the two CFM values or 70% of the total. D. Exhaust fan operation E. Pressure zoning F. Frequency of use G. Maintenance

Stack Effect Review

CFM = Volume (ft3)/Frequency (minutes) 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) I. Air Change Method A. Oftentimes used in residential construction and in large buildings like warehouses and other similar commercial structures. CFM = A.C. H. x Volume (ft3)/60 or CFM = Volume (ft3)/Frequency (minutes) B. Can also be determined by Code 1. For example, the UBC requires you to use not less than .5 CFM/square foot

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 Qsens = 1.1 x CFM x T

Table 2-8

Heat Loss Due to Infiltration Btu H = (.018) x (ACH) x V x (Ti – To) ACH = air exchanges per hour V = volume Ti = inside temperature To = outside temperature

Heat Loss Due to Infiltration OR

Heat Loss Due to Infiltration Btu H = 1.1 x CFM x (Ti – To) CFM = (ACH x volume) / 60 min per hour

Heat Loss Due to 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.

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

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

Heat Loss Due to Ventilation Btu H = 1.1 x [(Ra x square feet of building ) + (number of people in the building x Rp )] x (Ti – To)

Heat Loss Due to Ventilation

Heat Loss Due to Ventilation Ra = Area Outdoor Air Rate Rp = People Outdoor Air Rate Example: Pharmacy Ra = .18 Rp = 5

Heat Loss Due to Ventilation Btu H = 1.1 x [ (.18 x 3,632) + (30 x 5)] x 76o = 67,214

Ventilation and / or Infiltration