American Aldes Aldes SIP Ventilation Design Guide

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Local Ventilation
It is generally accepted by building-science experts and most code authorities that local ventilation is 
necessary  to  remove  high  concentrations  of  bathroom  and  kitchen  pollutants  such  as  humidity,  odors, 
and  cooking  by-products. As  a  guideline, ANSI/ASHRAE  Standards  62.1  and  62.2  recommend  that,  if 
local ventilation is operated intermittently, it must be capable of exhausting a minimum of 50 CFM for 
each bathroom and 100 CFM for the kitchen. If continuous ventilation is used, the rate is 25 CFM for each 
bathroom and 50 CFM for the kitchen.
Some jurisdictions allow an operable window to substitute for mechanical ventilation in a bathroom.  An 
open window will allow sound to infiltrate. For the purpose of FAA SIP ventilation programs, an operable 
window is not an allowable alternative to mechanical ventilation.
While ASHRAE Standard 62.2 is generally accepted by national experts as the mi\
nimum standard for 
ventilation, it is not a best practice. If it was, it would assign ventilation rates based on factors such as the 
number of occupants in a dwelling and the strength of pollutant sources.
Refer to local code authorities for jurisdiction-specific requirements. 
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1.5 CLIMATE ZONES
The ventilation recommendations outlined in later chapters are heavily influenced by the ASHRAE climate 
zone in which the structure is located. The continental United States is divided into seven specific climate 
zones, ranging from Very Hot in Zone 1 to Very Cold in Zone 7, as shown on the map below and in the 
table that follows. (Hawaii falls under Zone 1A, and parts of Alaska are Zone 8. See Appendix II.)
Additionally,  most  zones  are  divided  into  Humid  (eastern  half  of  the  United  States),  Dry  (most  of  the 
western states), and Marine (west coast states) sub-zones.
The climate zone and sub-zone dictate which ventilation solution is most appropriate for a dwelling. For 
example:
• Supply  ventilation  is  suitable  for  a  dwelling  in  Zone  2,  but  not  for  one  in  Zone  7.  In  Zone  7,  the 
positive-pressure  scenario  created  by  a  supply  system  can  push  humid  air  into  wall  cavities, 
where it can then condensate when meeting colder exterior walls. This condensation can cause 
mold and mildew issues.
•  Exhaust ventilation is suitable for Zone 7, but not for a dwelling in Zone 1. In Zone 1, the negative-
pressure scenario created by an exhaust system can pull humid air into wall cavities, where it can 
then condensate on colder interior walls, causing mold and mildew issues.
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• Balanced  ventilation  is  suitable  in  all  climates  since,  by  definition,  it  means  an  equal  amount  of 
air is supplied and exhausted from the dwelling and pressure is equalized. However, two fans are 
required to achieve balanced ventilation.
ASHRAE Climatic Zones
Climate Zone 1A - Very Hot/Humid Also known as tropical. Temperature is constantly high and does not vary greatly from 
day to night. High heat and humidity levels make thunderstorms common.
Climate Zone 2A - Hot/Humid Also known as tropical. Temperature is constantly high and does not vary greatly from 
day to night. High heat and humidity levels make thunderstorms common.
Climate Zone 2B, Hot/Dry Also  known  as  deserts  or  semi-deserts.  Transition  areas  between  humid,  tropical 
climates  and  warm,  moderate  climates.  Characterized  by  low  humidity  levels  (less 
than 50% RH) and high levels of solar radiation. Overall precipitation is typically low 
and often falls rapidly over a short period of time.
Climate Zone 3A, Warm/Humid Mixed, humid climates experience all four seasons, but season length and extremity 
vary by location. These regions receive more than 20 inches of rain annually. The 
average winter temperature typically drops below 45°F. Summers can be extremely 
hot and humid. Many of these regions will experience some snowfall and icing during 
winter months.
Climate Zone 3B, Warm/Dry Mixed, dry climates experience seasonal temperature variations and typically 
experience all four seasons. Season length and extremity vary by location. These 
regions typically receive less than 20 inches of rain annually.
Climate Zone 3C, Warm/Marine Temperate climates found on the coast. These areas typically do not have extreme 
seasons. Temperatures remain relatively mild year-round due to the high heat 
capacity of water. Marine climates only experience two seasons, summer and winter. 
Summer  months  are  dry,  while  winter  can  be  very  wet.  To  be  considered  a  marine 
climate, 65% of annual total rainfall must occur in less than six months of the year. 
These climates are generally humid, but moisture and precipitation levels can vary 
greatly by location.
Climate Zone 4A, Mixed/Humid Mixed, humid climates experience all four seasons, but season length and extremity 
vary by location. These regions receive more than 20 inches of rain annually. The 
average winter temperature typically drops below 45°F. Summers can be extremely 
hot and humid. Many of these regions will experience some snowfall and icing during 
winter months.
Climate Zone 4B, Mixed/Dry Mixed, dry climates experience seasonal temperature variations and typically 
experience all four seasons. Season length and extremity vary by location. These 
regions typically receive less than 20 inches of rain annually.
Climate Zone 4C, Mixed/Marine Temperate climates found on the coast. These areas typically do not have extreme 
seasons. Temperatures remain relatively mild year-round due to the high heat 
capacity of water. Marine climates only experience two seasons, summer and winter. 
Summer  months  are  dry,  while  winter  can  be  very  wet.  To  be  considered  a  marine 
climate, 65% of annual total rainfall must occur in less than six months of the year. 
These climates are generally humid, but moisture and precipitation levels can vary 
greatly by location.
Climate Zone 5A, Cool/Humid Mixed, humid climates experience all four seasons, but season length and extremity 
vary by location. These regions receive more than 20 inches of rain annually. The 
average winter temperature typically drops below 45°F. Summers can be extremely 
hot and humid. Many of these regions will experience some snowfall and icing during 
winter months.
Climate Zone 5B, Cool/Dry Mixed, dry climates experience seasonal temperature variations and typically 
experience all four seasons. Season length and extremity vary by location. These 
regions typically receive less than 20 inches of rain annually.
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Climate Zone 6A, Cold/HumidCold  climates  include  those  known  as  the  tundra,  taiga,  or  alpine.  These  climates 
are typically found close to the poles and include the majority of Canada, Northern 
Europe, and Northern Asia. Cold climates can be found at high altitudes in any region 
of the world. They typically have long, dark winters with short days; however, they can 
experience large seasonal temperature swings and very warm summers. Snow and 
ice accumulations are common in most cold climates.
Climate Zone 6B, Cold/Dry Cold  climates  include  those  known  as  the  tundra,  taiga,  or  alpine.  These  climates 
are typically found close to the poles and include the majority of Canada, Northern 
Europe, and Northern Asia. Cold climates can be found at high altitudes in any region 
of the world. They typically have long, dark winters with short days; however, they can 
experience large seasonal temperature swings and very warm summers. Snow and 
ice accumulations are common in most cold climates.
Climate Zone 7, Very Cold Cold  climates  include  those  known  as  the  tundra,  taiga,  or  alpine.  These  climates 
are typically found close to the poles and include the majority of Canada, Northern 
Europe, and Northern Asia. Cold climates can be found at high altitudes in any region 
of the world. They typically have long, dark winters with short days; however, they can 
experience large seasonal temperature swings and very warm summers. Snow and 
ice accumulations are common in most cold climates.
 
For specific ventilation solutions based on climate zones, refer to Section 3.
For specific climate zones by state and county, refer to Appendix II.
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1.6 CENTRAL VENTILATION SYSTEMS
A  central  ventilation  system  can  be  defined  as  a  centrally  located  ventilator  specifically  designed  to 
provide controlled movement of air in and out of the building for general ventilation. The purpose of a 
central  ventilation  system  is  to  provide  a  continuous  low-level  flow  of  air  in  and  out  of  the  building  to 
ensure a safe environment for the occupants and protect the structural i\
ntegrity of the building.
A  central  ventilation  system  provides  low-level  continuous  flow  using  one  of  three  methods:  supply, 
exhaust, or balanced. These methods are explained in more detail in Section 2. The continuous low-level 
flow of air removes and dilutes the pollutants commonly found in buildings.  A central ventilation system 
should not to be confused with a central heating and air conditioning handling unit (AHU). The differences 
between the two are explained in Section 1.7.
Advantages of Central Ventilation Systems
• Lower installed cost
•  Better performance
•  Significant  energy  savings  from  precise  ventilation  rate  control  and  ENERGY  STAR  rated 
ventilators
•  Precisely controlled ventilation rates with very effective air distribution
•  Minimal penetrations in the building envelope (no more than two for balanced operation)
Local ventilation, such as bathroom and kitchen fans, is designed to remove the high levels of humidity, 
odors,  and  other  pollutants  that  are  typically  created  by  an  event  such  as  taking  a  shower  or  cooking. 
This type of ventilation eliminates most of these pollutants at the source, but it does not capture it all. 
Moreover,  local  ventilation  methods  do  not  have  the  distribution  efficiency  to  provide  the  whole-house 
continuous ventilation that tight buildings need. Hybrid central ventilation systems provide continuous low-
level ventilation for the entire home, as well as local ventilation for kitchens and bathrooms, if necessary. 
Balanced Ventilation System Local (Exhaust) Ventilation System
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1.7 DIFFERENCES BETWEEN VENTILATION AND HVAC/AC UNIT
It is a common misconception that the home’s central heating and air conditioning handling unit (AHU) 
provides ventilation. In fact, the AHU is designed to recirculate existing indoor air through the air-
conditioning and/or heating units. This is a closed system that neither exhausts pollutants nor supplies 
fresh air to the home.
Ventilation  is  the  process  by  which  “clean”  air  (usually  outdoor  air)  is  intentionally  provided  to  a  space, 
and stale air is removed. This process is usually accomplished mechanically, but it can occur naturally in 
rare cases and under specific circumstances.   
Most confusion can be attributed to the typical installation of the AHU by Heating, Ventilation, and Air-
Conditioning (HVAC) contractors, as well as the assumption that air movement equals ventilation. 
Proper ventilation strategies are dependent upon the climate zone in which a home or building resides.  
To select the best ventilation strategy for a particular building, consider the regional climate zone and the 
project budget.  
Air Handling Unit
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1.8 VENTILATING WITH AN AHU
Using a fresh air duct to provide supply ventilation via the central heating and air conditioning \
handling unit 
(AHU) is not recommended, except in very limited circumstances (Refer to Section 2.2 for recommen\
ded 
supply  air  solutions).  AHU  are  designed  to  respond  to  thermostat  requests.  They  will  not  respond  to 
ventilation requirements without special equipment.
Disadvantages of Ventilating with an AHU:
• Unregulated amount of air being pulled into the building envelope
•  Potential damage to gas heat exchangers
•  Creates drafts and thermal discomfort in the winter
•  Excess  condensation  in  A/C  ducting  during  warm-moist  seasons  can  cause  water  to  blow  off 
coils, potentially causing mold to form in duct systems
•  No filtration of incoming air
•  Continuous operation of AHU to provide proper ventilation (even in non-cooling/heating seasons) 
can result in excess energy expense
•  Difficult to calibrate and deliver recommended ventilation rates
•  Unsuitable for cold climates (due to the positive-pressure scenario, as\
 explained on page 21)
Fresh 
Air 
Air Handler
Ventilating with an AHU
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1.9 OTHER INSTALLATION CONSIDERATIONS FOR RETROFIT PROJECTS
When introducing a continuously operating appliance to a home that did not have one previously, consider 
the following:
• The appliance should be silent
•  The appliance should be ENERGY STAR rated
•  The appliance should be low maintenance
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SECTION 2   
COMMON MECHANICAL VENTILATION  METHODS
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2.1 CONTINUOUS EXHAUST 
• A fan brings in outside air by creating negative pressure 
inside the building
•  Good for source contaminant removal
•  Requires dedicated air-intake points to direct outside air 
to habitable spaces
•  ENERGY STAR rated fan recommendedCentral Exhaust Fan
Exhaust Air 
Outlet
Air Flow
Air Infiltration
Positive Air  Pressure
Negative Air  Pressure
Exhaust Ventilation
Types of Equipment*
In-Line Fan (VS) Multi-Port Fan (MPVS) Air Inlets
*Remote-mounted fans are preferred for noise-free operation
Pros
• Central systems can combine spot (bathroom) exhaust and whole-building ventilation
•  Low power consumption
•  Relatively low cost
•  Good for Climate Zones 2B, 3B, 3C, 4B, 4C, 5A, 5B, 6A, 6B, 7A & 7C (see pages 12-14)
Cons • Potential to backdraft appliances and fireplaces
•  Cannot effectively filter incoming air
•  Cannot use in Climate Zones 1, 2A, 3A, and 4A (see pages 12-14)
•  Not suitable for use in warm-humid climates.
•  Warm, moist air will condense on cold surfaces in walls and leakage areas in building envelope
Residential SIP Ventilation Modification Design Guide