Transcript Why Mechanical Ventilation? - National Healthy Homes Conference

May 28-30, 2014
Nashville, TN
National Healthy Homes Conference
Fresh Air Ventilation Design
and Demand Control Ventilation
Katrin Klingenberg* and Ty Newell**
*Executive Director, Passive House Institute US | PHIUS
**Build Equinox
Mechanical Design Order of Operations
Optimize Orientation
Super-insulate + Air Seal
Optimize Window Performance
1st Utilize Passive Space Conditioning Strategies
2nd Utilize High Efficiency Active Strategies
Then…Zero Out with Onsite Renewables
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Ventilation Definition
Controlled movement of air into and
out of a building, generally using
mechanical means, through
deliberately placed holes in the
building envelope
© Passive House Institute US 2013 – CPHC Training
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Contaminants in Indoor Air
From
Outdoors
Pollens
Molds
Dust
RADON
CO
From
Indoors
People + Pets
Formaldehydes
Mold +
Bacteria
VOC’s
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CO2 + H2O
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Methods for Improving Indoor Air Quality
Source Control:
pets, harmful cleaners,
bathroom/kitchen moisture & odors,
off-gassing building materials
Ventilation:
bring in outside air,
exhaust “stale” air
Filtration:
clean the inside
air
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Why Mechanical Ventilation?
•A
“Mechanical” Ventilation
vs
“Natural” Ventilation
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Why Mechanical Ventilation?
“Controlled”
Ventilation
•A
vs
“Random” Ventilation
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Why Mechanical Ventilation?
“Controlled Ventilation” vs
“Random” Ventilation
• Optimal Locations
• Controlled Quantity
• Comfortable
Temperature
• Filtered, Clean
Source
• “Recycles” 8-15x the
• Energy of Operation
• RANDOM Times
• RANDOM Locations
• RANDOM Quantity
• RANDOM
Temperature
• RANDOM Quality
• Over or Undersized
(Windy vs Calm Day)
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Role of Mechanical Ventilation in Passive Houses
Primary:
Healthy Indoor Air
Secondary:
Filtering
Tertiary:
Heat
recovery
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Healthy Indoor Air
Ventilation = Hygienic Air
Mitigate accumulation and
concentration of pollutants
Limit odors
“Control” air humidity and
avoid mold growth
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Mechanical Ventilation Methods
Exhaust
Only
•
•
•
•
Depressurizes Building
Draws Air in Randomly
Poor Efficiency
May Hurt Building Durability
Supply
Only
•
•
•
•
Pressurizes Building
Forces Air Out Randomly
Poor Efficiency
May Hurt Building Durability
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Mechanical Ventilation Methods
• Neutral Pressure
• Air Inlet &
Exhaust
Balanced
Controlled
• VERY Efficient w/
Heat Recovery
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Heat Recovery Ventilation
•a
77F
Source: PHIUS
68F
Heat Recovery
Ventilation
Maintains Interior
Temperature
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ALL Ventilation
Through Energy
Recovery Unit
Air Extracted
from “Wet”
Rooms
Supplied to
Living/Sleeping
Rooms
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Image source: www.greenbuildingstore.co.uk/mvhr.php
Ventilation System Concept
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Dialing in Ventilation Flows
Supply Air: Greater of
• 18cfm/person (DIN1946)
• OR 0.3AC/h
• Typ Home: 71cfm
Max Design
Airflow =
Greater of
Supply/Extra
ct
Extract Air:
• Kitchen – 35 cfm
• Bathrooms – 24 cfm
• ½ Bath – 12 cfm
PH delivered ventilation exceeds ASHRAE 62.2, because PH sizes ventilation
systems to meet loads, not assuming a leaky envelope will provide any fresh air
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ASHRAE 62.2-2010
0.01 cfm* per 1ft2 (gross) + (7.5cfm x # of bedrooms +1)
Example: 1,800ft2 (gross), 3 beds
(0.01cfm x 1800) + (7.5cfm x 4) = 48cfm
*ASHRAE calls for 0.03cfm/ft2, but assumes 0.02cfm/ft2 infiltration
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Passive House
Minimum 0.30ACH (based on net enclosed volume)
Example: 1,800ft2 (gross)…~1,350ft2 TFA
Approximate volume: 1,350 x 8 = 10,800ft3
10,800 x 0.30 / 60 = 54cfm
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Ventilation System Duct Layout
Keep Ambient (Outside) Air Ducts
Short &
Well-Insulated w/ Vapor
Impermeable Insulation
Keep Conditioned (Inside) Air Ducts
Within the Thermal Envelope
Minimize Duct Losses
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Ventilation System Duct Layout
Minimize Duct Losses
Smooth Interior
Minimize Bends/Kinks/Constrictions
Low Velocity (< 3 m/s | ~600fpm)
Tightly Sealed (< 3% Leakage)
Size for Low & High Speed (Air Flow)
Short & Centralized Duct Layout
(Use Far-Throwing Diffusers & Coanda Effect)
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Exhaust Placement
•-
Bathrooms
Kitchens
• in far corner of
bathroom
• away from door…
• at least 6’ away from
cooktop
• with grease filter
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Ventilation Balancing
Total supply and total
exhaust (measured near
HRV/ERV) must be within
10% of one another
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Balancing at Register
-
Airflow at each register must be balanced to whichever
value below is greater
Balanced
to within
20% of
design
value
Balanced
to within
5 cfm of
design
value
© Passive House Institute US 2013 – CPHC Training
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Return Air Pathways
•-
http://www.bapirc.org/casestud/return_air/index.htm
© Passive House Institute US 2013 – CPHC Training
finehomebuilding.com
1” door undercut is
adequate for airflows up to
about 40cfm (<=1.0Pa)
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DCV FRESH AIR Conditioning
What is DCV?
•Demand Controlled Ventilation (DCV) actively senses
and manages carbon dioxide and volatile organic
compounds (VOC) levels
•“Smart” algorithms can control:
•Heating/cooling/dehumidification
•Energy “recovery”
•Energy efficient defrosting
•“Free” conditioning
•Conditioned air (warm air in winter, cool air in summer)
can be delivered to rooms in home
•DCV fresh air conditioning is an alternative to HRV (Heat
Recovery Ventilators) and ERV (Energy or Enthalpy
Recovery Ventilators)
Carbon Dioxide (CO2) Impairs Cognitive Performance
Strongly impairs: Initiative, Information Utilization,
Breath of Approach, and Basic Strategy
CO2 and VOC [ppm]
Pollutant Variation in Homes is Complex
2500
CO2 Sensor
VOC Sensor
2000
1500
1000
500
•Either CO2 or VOCs may dominate a home’s
pollutants
•Constant ventilation flow = too much or too little air
•Even “good” VOCs (chicken soup) should be flushed
to avoid odor absorption
3/8 12:00 AM
2/26 12:00 AM
2/16 12:00 AM
2/6 12:00 AM
1/27 12:00 AM
1/17 12:00 AM
1/7 12:00 AM
12/28 12:00 AM
0
DCV Development
Laboratory and Field Tests
2008 to current
Concept and initial results
presented at 2008 Passive
House Conference (Duluth MN)
UL Certification 2012
Cooling Ventilation Mode
•Cools and dehumidifies when beneficial, exchanging
energy between fresh air stream and exhaust air stream
•When “fresh air” is nicer than indoor air, maximizes fresh
air similar to opening the windows….except it knows to
close them when it isn’t so nice
•Unlike an open window, the air is filtered as desired
Cooling Recirculation Mode
•Additional cooling and dehumidification capacity when
desired through recirculation mode….helps maintain uniform
air quality and comfort conditions
•Can decide whether the DCV provides as much as it can, or
whether it operates only at a level of treating the fresh air
•Equinox House uses DCV and 1 ton mini-split combo
•Mini-split AC primarily needed for high occupancy time
and exceptionally warm/humid weather
Heating Ventilation/Recirculation Modes
Similar to cooling:
•Heats fresh air when
beneficial
•Can provide additional
heat if desired through
recirculation unifying
air quality and comfort
•Energy recovery from
frost (during cold
weather, 30% of energy
exchange is latent)
DCV Fresh Air Heating Data
Total CERV Power
~200cfm air flow
-Gross heat = 4.1kW
(35.5F to 100.2F)
-Net heat = 2.1kW
(67.2F to 100.2F)
Exhaust Air from
Inside, 67.2F
Room
Temperature
& Humidity
(21C = 70F)
Exhaust Air to
Outside, 36.7F
“Vent Heat”
Conditioned
Fresh Air to
Inside, 100.2F
Fresh Air from
Outside, 35.5F
DCV Controls
Master Controller
-secure wireless
(non-internet)
-color touchscreen
Remote Vent Switch
(battery free)
- Optional – kitchen,
baths, etc
Full Internet control and monitoring
Equinox House; Urbana IL
2 Occupants
2100sqft; 0.6ACH50
Setpoint = 900ppm
Denver Passive House
2 Occupants
4000sqft; 0.5ACH50
Setpoint = 1050ppm
Vermont Residence
4 Occupants
2000sqft; 1-2ACH50
Setpoint = 2000ppm
MH2 – Vermont
2 Occupants
1000sqft; 1ACH50
Setpoint = 1000ppm
Summary
•Ventilation system design should not be left as an afterthought
•Passive Building design purges the entire house
•Fresh air delivered where people live and exhausted from
spaces generating moisture and odors
•DCV (Demand Control Ventilation) automatically controls indoor
air quality and removes guesswork
Thank You!
Questions?
© Passive House Institute US 2013 – CPHC Training
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