Download Natural Ventilation

SMC National Sustainable Building
Advisor Program
Designing Innovative Ventilation
Systems for Good IAQ
Richard Scarborough
Environmental Inspections + Solutions
www.eisinc.ca
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Natural Ventilation
Back to the Basics
Breathe!
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What’s Happening?
When did it start?
How will it end?
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Global Warming
Per Goat and Mouse
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Global Warming
Conference
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You Can Build it
But Can you Ventilate it?
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There is no Hope
New Analysis
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Pollution May Cause 40 Percent
of Global Deaths
By Andrea Thompson, LiveScience
Staff Writer
http://www.livescience.com/
posted: 10 September 2007 09:11
AM ET
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No Hope for
Healthy Construction
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Where I’ve Lived
The Dutch “Blow Through”
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Where I’ve Lived
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Where I Live Now
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What I Build
Where it Started
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Thin Shelled Concrete Structure
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Thermal mass inside
Insulation outside
Performance = R60
10.0 earthquake proof
Tornado proof / Bullet proof
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What I Intend to Live In
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Jean
Nouvel
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Jean Nouvel
LA Green Condo
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New Construction
Energy Conservation
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Back to the Breath
What Sucks ?
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Wind:
• From high to low pressure
• You can’t push a rope
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Tornados: big time!
Houses: 99%
Humans: 100%
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nd
2
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Law of Thermodynamics
Air moves from high to low pressure
• The bigger the hole, the more the pressure,
the greater the flow
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Moisture moves from:
• Warm to Cool
• More to Less
• More to Less wins over Warm to Cool
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Implications for SoCal
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Stack Effect
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Chimney Effect
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Reverse Stack Effect?
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When?
Where?
How?
Implications
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Pressures
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1 Pascal = 0.004 w.g
=0.000295”hg. = 0.000145 psi
9.8692×10−6 atm
1 Pascal = 1 Post-it = 1 Gnat fart
Combustion Safety
• Worst case scenario
• The romantic evening
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4 Pascals to backdraft a fireplace or
water heater
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Natural Ventilation
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Design Considerations
• Site
• Building Materials
• Prevailing winds
• Climate
• Day lighting
• Operable windows
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Natural Ventilation
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Knowledgeable & Tolerant users
Input source and location
• IH and EH
• Intake vs. exhausts
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Natural Ventilation
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Wind Effect
Venturi Effect
Cooling Tower
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Displacement Ventilation
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Swamp Cooler
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Cooling
Tower
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Zion National Park
Downdraft cooling tower with evaporative media
at top, exhaust through clerestory windows.
Ref. WBDG
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Psychrometric Chart
Find the point of condensation
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Moving Moisture
Vapor
Diffusion
versus
Air Leakage
Where air goes water follows
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Foundations / Crawls
Where it all starts
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Codes arbitrary in creation of crawl
venting
New Seismic concerns create
labyrinths
Passive ventilation can’t work
Mechanic ventilation has inherent
problems.
Crawl should be mini conditioned
basement
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Foundations
Where it all starts
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Crawls
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Crawls
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Crawls
Disconnected Drier Vent
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CleanSpace – Basement Systems
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Crawls
What We Find
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Chlordane, DDT
What it did to me
Construction debris: mold food
Leaky HVAC ducting=pollution
distribution system
Self composting homes
• Are they green?
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What’s Wrong with this Picture?
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Fresh Air Dilution
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What’s your criteria?
• Smell
• CO2
• VOC
• TVOC
• SVOC
• Occupancy
• Season
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Fresh Air Dilution
• CO2 Sensor?
• Formaldehyde levels even after heat
treatment do not begin to drop off in
new home until after 2 years
• How sensitive are the occupants?
• ACH-(air changes/hr) How real is it?
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With turbulent flow, 5 changes necessary for
complete dilution.
Circulation laminar channeling at best
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Fresh Air Dilution
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ASHRAE 62
• Old: 0.35 ACH
• Politics as usual
• CFM per person/square foot
• Office, commercial, residential
• Schools, laboratory, smoking room
• How much is too much?
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Air Pathways
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Typical wall airflow in stick frame house =
6”/minute
Where’s the air barrier
Where are the penetrations
• “Own your hole”
• Pollutant pathways?
• CA Title 24
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SVOC’s not easily sealed in
Does your home suck?
Stack / Reverse stack effects
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Any air pathways?
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Mechanical Ventilation
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Push or Pull?
From where to where
Noise issues
Velocity – draftiness, sensitivity
Mixing
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Push me-Pull me
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Got Leaks?
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Multi-Task:
dryer vent
and water
heater flue
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Nike
“Just Do it!”
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Integrated with Heating and A/C
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Pressure
Differentials
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Case Study
Pt. Dume Doom
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Exhaust Ventilation
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Bathroom exhaust fans: 60-150 cfm
Dryers: 200 cfm
Kitchen exhaust: 100-2000cfm
With prudence, these can serve as
excellent whole house fans
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Total Exhaust
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500-2500 CFM
Big time suction
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LEED
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Make up your mind!
Underfloor designs – SMO library
VOC’s –
Reformulated VOC’s = ?
• Glycol based paints – the slow kill
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No concern for SVOC’s
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Winston Churchill
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“You can always count on
Americans to do the right thing after they've tried everything
else.”
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