HVAC

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HVAC

• HEATING
• COOLING
• VENTILATION

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Human Comfort Zone

• As humans we try to maintain a body
• temperature of 98.6 F
• Three Mechanisms
• Heat generated within the body
• Heat gained from surroundings
• Heat lost to surroundings

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Human Comfort Zone

• We shiver to
• generate heat

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Human Comfort Zone

• We sweat to
• Give off heat

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Human Comfort Zone

• We get goose bumps

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Human Comfort Zone

• Blood Flow
• Decreases to hands and feet in winter
• Increase in summer to encourage heat loss

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Thermal Neutrality

• To be comfortable humans must loose heat at the
  same rate as it is produced or gained.

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Factors Affecting Human Comfort

• Air temperature
• Air Speed
• Humidity
• Mean radiant temperature
• Each has a direct influence on heat loss or gain
  to the human body

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Factors Affecting Human Comfort

• Air Temperature - This affects temperature
  differences between the body and the
  surroundings, consequently affecting the rate of
  heat loss or gain by convection.

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Factors Affecting Human Comfort

• Air Speed - This affects the rate at which
• the body loses heat by convection.
• An air temperature of 35F and a wind speed of 20
  miles/hour combine to give a wind chill
  temperature of 11.2F.
• Air speed is also very important during summer
  when the body is trying to lose heat to maintain
  comfort.

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Factors Affecting Human Comfort

• Humidity - Affects the rate at which the
• body loses heat by evaporation. During hot
• weather, high humidity increases discomfort
• by making it more difficult to evaporate
• perspiration into the air.

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Mean Radiant Temperature

• Mean Radiant Temperature' (MRT). This is defined
  as the temperature of a sphere at the point in
  question which would exchange no net radiation
  with the environment.

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Factors Affecting Human Comfort

• Mean Radiant Temperature (MRT) - MRT is the
  average surface temperature of the surroundings
  with which the body can exchange heat by radiant
  transfer.
• Radiant heat transfer to and from the body is
  quite apparent when sitting near a fireplace
  (high MRT) or large cold window area (low MRT).

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Mean Radiant Temperature

• In general for every 1 degree F that the MRT
  drops, the air temperature must be raised about
  1.4 degrees F to achieve comfort conditions. 
• How can you raise the MRT?
• Close blinds and curtains
• Solar Film on windows
• Seal heat leaks

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Comfort

• Comfort is achieved by either increasing the
  ambient temperature or by raising the mean
  radiant temperature of an environment.
• A higher radiant temperature means that people
  become comfortable with a lower ambient
  temperature and the reverse is also true.

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Bioclimate Chart
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Example 1

• Dry Bulb 73
• Relative Humidity 50

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In the zone
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Example 2

• Dry Bulb Temp. 78
• Relative Humidity 70

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Example 2

• Dry Bulb Temp. 78
• Relative Humidity 70
• Requires a wind speed of 250 FPM
• (25060)/5280
• MPH 2.84

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Example 3

• Dry Bulb Temp. 50F
• Relative Humidity 55

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Example 3

• Dry Bulb Temp. 50F
• Relative Humidity 55
• BTU/Hour 250

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Definitions

• Conduction
• A method by which heat is transferred from a
  warmer substance to a cooler substance by
  molecular collisions. Direct contact.
• Convection
• A method by which heat is transferred by
  currents in a liquid or gas.
• Radiation
• A method by which heat can be transferred
  through objects and empty space. Electromagnetic.

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Conduction Examples

• Liquid - Liquid - Pouring cold cream into coffee
• Liquid - Gas - Ocean and Atmosphere
• Gas - Gas Cold and warm weather systems mixing
• Solid - Solid Touch a hot pot on a stove

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Conduction Rate Factors

• Contact Area
• Type of Material Cast Iron vs Stainless Steel
• Temperature Difference
• Distance heat must travel

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Convection Examples

• In a closed room cool air will settle to the
  bottom while warm air will rise
• Bowl of soup Hot liquid in the center moves to
  the cooler outside where it drops and is reheated
  at the center and the cycle continues.
• Warm air rising through a heat register

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Radiation Examples

• The suns heat
• A bonfire
• Warm soil on a cool night

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Radiation Rate Factors

• Surface area
• Type of material
• Temperature difference

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More Radiation Terms

• Reflectance (or reflectivity) refers to the
  fraction of incoming radiant energy that is
  reflected from the surface. Reflectivity and
  emissivity are related and a low emittance is
  indicative of a highly reflective surface.
• For example, aluminum with an emittance of 0.03
  has a reflectance of 0.97.

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More Radiation Terms

• Emittance (or emissivity), refers to the ability
  of a materials surface to give off radiant
  energy. All materials have emissivities ranging
  from zero to one. The lower the emittance of a
  material, the lower the heat radiated from its
  surface.

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Emissivity or Emittance
Material Surface Emittance
Asphalt 0.90 - 0.98
Aluminum foil 0.03 0.05
Brick 0.93
Fiberglass 0.80 0.90
Glass 0.95
Steel 0.12
Wood 0.90
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R-Value

• R-Value is the measure of resistance to heat flow
  through the defined material. The higher the
  R-Value the less heat will transfer through the
  wall, making the system more energy efficient.
• U-Value is the reciprocal of the R-Value
• (1/R) and is a measure of the rate of heat loss

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WINDOWS - 4 Ways to Evaluate

• U-FACTOR
• Solar Heat Gain Coefficient
• Visible Transmittance
• Air Leakage

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U-FACTOR
U-FACTOR The rate of heat loss is indicated in
terms of the U-Factor of a window assembly. The
insulating value is indicated by the R-Value
which is the inverse of the U-Value. The lower
the U-Value the greater a windows resistance to
heat flow and the better the insulating value.
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Solar Heat Gain COEFFICIENT
The SHGC is the fraction of incident solar
radiation admitted through a window. SHGC is
expressed as a number between 0 and 1. The lower
a windows solar heat gain coefficient, the less
solar heat it transmits.
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VISIBLE TRANSMITTANCE
The visible transmittance is an optical property
that indicates the amount of visible light
transmitted. Theoretical values vary between 0
and 1, but most values are between 0.3 and 0.8
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Air Leakage
Heat loss and gain occur by infiltration through
cracks in the window assembly. Air leakage is
expressed in cubic feet of air passing through a
square foot of window area. .3 is recommended
for Oregon
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Low-E Windows

• Glass is coated with silver or tin oxide which
  allows visible light to pass through but reflects
  infrared heat radiation back into the room.
• Reduces heat loss
• Allows visible light to pass through but reflects
  infrared heat radiation away from the room
• Reduces heat gain

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High number for cold climate. Low number for warm
climates
The lower the number the better the insulating
value
The best windows have air leakage rating between
0.1 and 0.6 cfm/ft.
Varies from 0 to 1.0 The higher the the more
light is transmitted.
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Single-Glazed with Clear Glass
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Single-Glazed with Bronze or Gray Tinted Glass
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Double-Glazed with High-Solar-Gain Low-E Glass,
Argon/Krypton Gas
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Triple-Glazed with Moderate-Solar-Gain Low-E
Glass, Argon/Krypton Gas
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Ventilation

• Multi Point Fan Systems
• One fan located in the attic
• Connects to baths and kitchen
• Timed to run at high speed during high use times
  such as morning (showers, bacon ) and evening.
• Xvent

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Heat Recovery Ventilation

• How it works
• In the heating season the core transfers heat
  from the outgoing, stale household air to preheat
  the incoming, fresh air.
• Cross-current sections, ensure the two air
  streams are always kept separate preventing the
  incoming fresh air from being contaminated by the
  outgoing stale air.

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Heat Recovery Ventilation

• During the air-conditioning season, the HRV
  reverses this process, removing some of the heat
  from the incoming air and transferring it to the
  outgoing air.

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Heat Recovery Ventilation
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Ventilation

• Heat Recovery System - uses fans to maintain a
  low-velocity flow of fresh outdoor air into the
  building (incoming air stream) while exhausting
  out an equal amount of stale indoor air (exhaust
  air stream). Fresh air is supplied to all levels
  of the building while stale air is removed from
  areas with high levels of pollutants and moisture.

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Ventilation

• Heat Recovery System
• Air Exchange - Expels stale, polluted indoor air
  and gaseous pollutants and continually exchanges
  them with a continuous flow of fresh, revitalized
  outdoor air to improve Indoor Air Quality.

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Ventilation

• Heat Recovery System
• Excess Humidity Control - Helps prevent
  uncontrolled excess humidity by expelling excess
  humidity from the air, thereby reducing the risk
  of window condensation, mildew and mold, which
  prevents  structural damage and deterioration to
  your home.  

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Ventilation

• Heat Recovery System
• Heat Recovery Core - As warm air is expelled from
  your house, it warms the incoming cold, fresh air
  before its circulated throughout your home. The
  result is a constant supply of fresh air, no
  unpleasant drafts and greater home comfort.

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HRV
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HRV

• Sized to ventilate the entire house at a minimum
  of .35 air changes per hour.
• Minimum CFM requirement can be calculated as
  follows
• Determine square footage and multiply times
  ceiling height.
• Divide by 60 minutes
• Multiply times .35 (minimum air changes)

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HRV Calculation

• Example
• Determine square footage and multiply times
  ceiling height.
• Divide by 60 minutes
• Multiply times .35 (minimum air changes)

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HRV

• Calculate the minimum CFM for a home
• with 2000SF main level, 1000SF second level
  and 750 SF finished basement
• Note Main and second level have 9 foot
• ceilings and basement has 8 foot
• ceiling.

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Solution

• 3000 SF x 9 27000
• 750 x 8 6000
• Total 33000
• 33000/60 550
• .35 x 550 192.5 CFM

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HEPA Filter
High Efficiency Particulate Air Filter
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Energy Recovery Ventilators
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How are HRVs Installed?
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How are HRVs Installed?
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How are HRVs Installed?
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Radiant Floor Heat

• Three types
• Radiant Air Floors
• Electric Radiant Floors
• Hot Water (Hydronic)

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Radiant Floor Heat

• Types of installation
• Wet Installations
• Large thermal mass of a concrete slab floor
• lightweight concrete over a wooden subfloor
• Dry Installations
• Where the installer "sandwiches" the radiant
  floor tubing between two layers of plywood or
  attaches the tubing under the finished floor or
  subfloor.

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Radiant Floor Heat

• Air Heated Radiant Floors Not recommended for
  residential applications
• Electric Radiant Floors -

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Electric Radiant Heat - Wet Installation
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Wet Installation
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Wet Installation
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Dry Installation
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Dry Installation
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Hydronic Radiant Heat
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Wet Installation

• PEX piping in Concrete (thick slab)

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Wet Installation

• Thin Slab Application Gypcrete over plywd

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Electric Toe Kick Heat
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Toe Kick Electric Heat
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Heat Pump and Furnace
Indoor Cooling Coil
Thermostat
Furnace
Heat Pump
Air Cleaner
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Heat Pump and Air Handler
Thermostat
Air Handler
Heat Pump
Air Cleaner
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Air Conditioner and Furnace
Thermostat
Indoor Cooling Coil
Air Cleaner
Air Conditioner
Furnace
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Air Conditioners and Air Handlers
Thermostat
Air Handler
Air Conditioner
Air Cleaner
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Cooling
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