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Balanced Ventilation:Heat and Energy Recovery

Michael LeBeau | Conservation Technologies | Duluth, MN

Efficient Fresh Air forLow Energy Buildings

Better Buildings By Design

Conference 2010

Burlington, Vermont February 11, 2010

•Efficiency Vermont is a Registered Provider with The American Institute of Architects Continuing Education Systems. Creditearned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.

Better Buildings By Design 2010

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Learning Objectives

• At the end of this program, participants will be able to:– Discover why and when to choose heat or

energy recovery ventilation.– Identify how these technologies fit into a

systems approach to building. – Understand latest advances in technology and

resulting equipment-availability. – Implement balancing and verification

strategies.

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Different kind of air

• Ventilation

• Combustion

• Makeup

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Ventilation Services

• The removal of polluted air from a building and its replacement with fresh outdoor air.

– Pollutant / moisture source focused exhaust best.

– Distribution of fresh air into all habitable rooms.

– Controlled airflow based on need.

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An Integrated Approach to Building Systems

• Tight buildings for ventilation control• Quiet efficient mechanical ventilation• Safe combustion appliances• Whole building pressure management• Planned fresh air paths

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The Different Roles of Mechanical Ventilation

• Indoor relative humidity management.• Internally generated pollutant control.• Delivery of fresh, outside air to living

spaces.• To accomplish the above quietly and

efficiently.

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Types of ventilation systems

• Exhaust driven– Removing air from a building using fan power.– Usually not planning the replacement air path.

• Supply driven– Bringing outside air into a building with fans.– Letting it find it’s way out or providing a way.

• Balanced– Powered airflow both in and out at roughly the

same rate.

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All ventilation is balanced

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Mechanically Balanced Options

• Some combination of exhaust and supply options.

• HRV / ERV• Most effective as we succeed in our efforts

to build more airtight buildings.• Heat / energy recovery increasingly cost

effective as energy costs continue to climb.

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Fully Ducted

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Ducted ExhaustFresh to Furnace

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HRV or ERV?

• ERV best for cooling dominated climates.• ERV often not recommended below 25F.?• Total energy recovery?• HRV needs drain.• HRV core more durable.

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Equipment Ratings

• Home Ventilating Institute• HVI.org• Certified Product Directory

– Section 1 - Home Ventilating Fans– Section 2 - Static Vents– Section 3 - HRV’s and ERV’s

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Design Considerations• Ventilation needs are carefully assessed.• Ventilation strategy chosen from options.• Physical space limitations of building.• Climate driven needs factored in.• Operating costs (electrical and added heating

/ cooling loads) evaluated.• Installation cost.• Accessibility for maintenance.• Future upgrade options and associated costs.

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Installation Priorities

• Design ventilation rate actually achieved.• Quiet and comfortable delivery of services.• Understandable and effective controls.• Effective exhaust and supply distribution.• Durable equipment, materials and methods

used.• Integration with other building systems.• Doesn’t compromise building envelope.

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Maintenance Provisions

• Simple and obvious accessibility.• Durable maintenance features.• End user documentation and orientation.• Maintenance service options offered.• Maintenance reminders are ideal.

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System Sizing and Design

• Start with .35 ACH continuous• Factor in site, # of occupants etc• Plan on higher rates for first year• Consider potential usage of building as well

as current• Separate kitchen range exhaust• Choose from existing equipment choices

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Installation Requirements• Space for HRV

– Proximity to exterior hoods• Access to fresh air• Minimize flex duct use

– Drain nearby– Minimum 60 degree room– Noise concerns– Power

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System Requirements (cont)

• Space for duct runs– Separate wall stack per room– Room for adequate branch and trunk lines and

fittings• Duct joints sealed for proper distribution• Ducts outside of envelope insulated to R8• Controls and wire runs

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Bath (-)

Bedroom (+)

Kitchen(-)

Living Room(+)

Master Suite (+)

Bath(-)

Closet

Closet

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Fireplace F

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Fully Ducted Whole House Ventilation

(Building neutral relative to outside)

Clo

set

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Fully Ducted System

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High Efficiency HRV

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North American Advances

• ECM motors finally making an appearance.• Higher recovery efficiencies in ERV’s and

HRV’s

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88% Heat Recovery34 watts at 66 cfm95 watts at 150 cfm

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Defrost and equipment issues

• Using solar and internal gains to defrost or:• Using electrical energy to defrost.• Need to take a closer look at U.S. heat

recovery standards being discounted.

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The Physical Realities

• Space issues• Conflicts with other mechanical systems• Retro-fit options• Quality control• Available equipment options• Cost

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7” Trunk and 6” Branch Lines

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6” oval wall stacks

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Stackhead box for round grille

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Exhaust duct extended in soffit

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Branch lines joining trunk in floor trusses

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Sealed joints and fittings

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Properly sized, smooth ducts

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Exterior hoods with adequate opening for minimum restriction

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System Durability

• Ventilation fans need to be able to run continuously for years.

• Ducts, especially inaccessible ones, need to be durable, airtight and, ideally, cleanable.

• Filter housings should be able to take years of regular maintenance.

• Grilles should be cleanable.• Don’t sacrifice long term durability for short term

upfront cost savings.

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Maintenance

• Provide simple, understandable and obvious maintenance features.

• Educate end user or facility staff on maintenance needs, process and schedule.

• Offer maintenance services.• Automatic maintenance reminders are very

effective.

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Integration needs and opportunities

• Space needs – work with designers to dedicate space for equipment, ducts, exterior hoods and controls.

• Resolve structural and envelope penetrations created by system installation.

• Coordinate installation details with other trades – avoid conflicts and backtracking.

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Measure air flows and balance

• Air flows into and out of the house should be within 10% of balanced

• Excess fresh air flow will cause core frosting in cold weather

• Excess exhaust air flow will contribute to depressurization of house

• Measure air flows with dry, frost free core and clean filters

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Exhaust intakes will collect debris and need to be cleanable

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Fresh air spills out from behind this indirect lighting fixture

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An Example of a Central Ventilation Control

- Intermittent- Low speed - High speed- Dehumidistat- Maintenance

reminder

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High Speed Override Options

• Continuous low speed operation• Manual override at wall control• Touch pad switches (20/40/60 min.)• Crank timers• Dehumidistat

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High Speed Override Switch

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Make-up Air Modifications

• An HRV / ERV ducting can be tapped to provide make up air for exhaust devices.

• Diversion of exhaust air back indoors using motorized dampers and current sensors.

• Limited to airflow capacity of ventilator.• Takes advantage of residual heat in exhaust

air and existing blower and ducts.

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Maintenance RequirementsEvery 2-3 Months

• Clean filters • Check intake hood for blockage• Check control operation

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Maintenance RequirementsAnnually

• Clean core and interior • Inspect blower motors and defrost dampers• Flush condensate drain hose• Check blowers for caking• Clean exhaust grilles as needed• Maintenance contract

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Homeowner Orientation

• Proper use of controls• Cleaning

– Filters– Hoods– Ventilator

• Documentation and manuals• Contact numbers• Optional maintenance contract

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Fan Energy

• Fairly small electrical load but runs often or continuously.

• Significant aggregate savings possible with more efficient motors and strategies.

• ECM motors, smart controls and better duct design are main opportunities in North America.

• Natural and hybrid designs being developed elsewhere.

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Looking Ahead

• Consider future ventilation needs when designing ventilation for new buildings. Especially in difficult or expensive to upgrade components like ducts.

• Assume greatly increased energy costs in the near future when weighing options.

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Developments Elsewhere

• Natural and hybrid ventilation strategies growing in popularity in Europe and elsewhere.

• Very efficient fans being developed with smart controllers to assist natural stack and wind forces harnessed to provide ventilation.

• Integrated heat / energy recovery features to minimize energy penalties of ventilation.

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Norwegian hybrid vent research

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Natural ventilation w/ heat recovery near London (BedZed)

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Passive House Applications

• Ventilation Heat Distribution• Integrated Solar Thermal• Earth Coupled Outside Air Tempering

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Solar Thermal w/ Gas Backup

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Fresh air tempering/ Post core heating

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Water to air heat exchanger

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Pex tubing buried in excavation

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Make-up air via HRV Exhaust Diversion