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 2 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 3 Contaminants in Indoor Air From Outdoors Pollens Molds Dust RADON CO From Indoors People + Pets Formaldehydes Mold + Bacteria VOC’s © Passive House Institute US 2013 – CPHC Training CO2 + H2O 4 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 © Passive House Institute US 2013 – CPHC Training 5 Why Mechanical Ventilation? •A “Mechanical” Ventilation vs “Natural” Ventilation © Passive House Institute US 2013 – CPHC Training 6 Why Mechanical Ventilation? “Controlled” Ventilation •A vs “Random” Ventilation © Passive House Institute US 2013 – CPHC Training 7 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) © Passive House Institute US 2013 – CPHC Training 8 Role of Mechanical Ventilation in Passive Houses Primary: Healthy Indoor Air Secondary: Filtering Tertiary: Heat recovery © Passive House Institute US 2013 – CPHC Training 9 Healthy Indoor Air Ventilation = Hygienic Air Mitigate accumulation and concentration of pollutants Limit odors “Control” air humidity and avoid mold growth © Passive House Institute US 2013 – CPHC Training 10 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 © Passive House Institute US 2013 – CPHC Training 11 Mechanical Ventilation Methods • Neutral Pressure • Air Inlet & Exhaust Balanced Controlled • VERY Efficient w/ Heat Recovery © Passive House Institute US 2013 – CPHC Training 12 Heat Recovery Ventilation •a 77F Source: PHIUS 68F Heat Recovery Ventilation Maintains Interior Temperature © Passive House Institute US 2013 – CPHC Training 13 ALL Ventilation Through Energy Recovery Unit Air Extracted from “Wet” Rooms Supplied to Living/Sleeping Rooms © Passive House Institute US 2013 – CPHC Training Image source: www.greenbuildingstore.co.uk/mvhr.php Ventilation System Concept 14 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 © Passive House Institute US 2013 – CPHC Training 15 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 © Passive House Institute US 2013 – CPHC Training 16 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 © Passive House Institute US 2013 – CPHC Training 17 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 © Passive House Institute US 2013 – CPHC Training 18 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) © Passive House Institute US 2013 – CPHC Training 19 Exhaust Placement •- Bathrooms Kitchens • in far corner of bathroom • away from door… • at least 6’ away from cooktop • with grease filter © Passive House Institute US 2013 – CPHC Training 20 Ventilation Balancing Total supply and total exhaust (measured near HRV/ERV) must be within 10% of one another © Passive House Institute US 2013 – CPHC Training 21 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 22 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) 23 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 37