Ventilation Design Considerations for Passive House ...€¦ · 43 Ventilation Design Considerations for Passive House Multifamily Residential Buildings SCENARIO 2 –LOW DENSITY,

1 Ventilation Design Considerations for Passive House Multifamily Residential Buildings

Ventilation Design Considerations for Passive House Multifamily Residential Buildings

Hugh CrowtherVice President, [email protected]

October 24, 2017


AGENDA

Ventilation Unit Primer

Centralized vs. Decentralized Ventilation Design

Winter Humidity Issues

Energy Impact - Sensible vs. Enthalpy Energy Recovery

Summary

Questions

1

2

3

4

5

6


VENTILATION UNIT PRIMER

PART 1

Integrating Swegon GOLD DOAS units with Mitsubishi VRF


ENERGY RECOVERY VENTILATION UNITS

Total (Enthalpy) Energy Recovery

> Recover heat and humidity

> Raise temperature and humidity in winter, cool and dehumidify in summer

> Enthalpy plate enthalpy wheel

> Sometimes called Energy Recovery Ventilators (ERVs)

Sensible Energy Recovery

> Recover heat but not humidity

> Raise temperature in winter but not increase humidity ratio

> Plate, wheel, heat pipe, run around loops

> Sometimes called Heat Recovery Ventilators (HRVs)


CENTRALIZED VENTILATION UNIT EXAMPLES


DECENTRALIZED VENTILATION UNIT – WALL MOUNTED


DECENTRALIZED VENTILATION UNITS – CLOSET/CEILING MOUNTED


VENTILATION UNIT – PLATE TYPE


Extract

Outside

Supply

Exhaust

Extract Outside SupplyExhaust

VENTILATION UNIT – WHEEL TYPE



Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust




Extract

Outside

Supply

Exhaust



DEFINITION OF EFFICIENCY (EFFECTIVENESS ETC.)

𝜺 =𝒄𝒇𝒎𝒔𝒂(𝑿𝒐𝒂 − 𝑿𝒔𝒂)

𝒄𝒇𝒎𝒎𝒊𝒏(𝑿𝒐𝒂 − 𝑿𝒓𝒂)𝜺 =

𝑿𝒓𝒂 − 𝑿𝒆𝒂 + 𝑷𝒆𝒍/𝒎 · 𝒄𝒑

(𝑿𝒓𝒂 − 𝑿𝒐𝒂)𝜺 =

(𝑿𝒐𝒂 − 𝑿𝒔𝒂)

(𝑿𝒐𝒂 − 𝑿𝒓𝒂)


SENSIBLE ENERGY VENTILATION UNIT (HRV)WINTER OPERATION

Outside Air (OA)

Exhaust Air (EA)

Supply Air (SA)

Return Air (RA)

15°F 65°F

72°F23°F

Exhaust Air Fan Heat Exchanger Return Air Filter

Outside Air Filter Supply Air Fan

Outdoors Indoors


TOTAL ENERGY VENTILATION UNIT (ERV)WINTER OPERATION

Outside Air (OA)

Exhaust Air (EA)

Supply Air (SA)

Return Air (RA)

15°F, 82% RH 65°F, 36% RH

72°F, 31% RH23°F, 81% RH

Exhaust Air Fan Heat & Moisture Exchanger

Return Air Filter


Outdoors Indoors

PHI Certification values:

> 84% heat recovery efficiency (min 75% required)

> 0.32 W/CFM (max 0.765 required)

Certified values, no PHI requirements:

> 84% moisture recovery efficiency


TOTAL ENERGY VENTILATION UNIT (ERV)SUMMER OPERATION

Outside Air (OA)

Exhaust Air (EA)

Supply Air (SA)

Return Air (RA)

88°F, 48% RH 77°F, 50% RH

75°F, 43% RH86°F, 43% RH

Exhaust Air Fan Heat & Moisture Exchanger

Return Air Filter


Outdoors Indoors

PHI Certification values:

> None (min 75% required)

> 0.32 W/CFM (max 0.765 required)

Certified values, no PHI requirements:

> 84% heat recovery (rejection) efficiency

> 66% moisture recovery


CENTRALIZED VS. DECENTRALIZED VENTILATION DESIGN

PART 2



CENTRALIZED VENTILATION DESIGN, (3) FLOORS, (1) ERV, (2) SHAFTS, (6) LONG DUCT RUNS

PENETRATIONS ERV1

Outside Air 1

Exhaust Air 1

Total 2

Occupied Space

Occupied Space

Occupied Space

Return Air

Exhaust Air

Supply AirOutside Air


DECENTRALIZED VENTILATION DESIGN(3) FLOORS, (1) ERV/ZONE, (0) SHAFTS, SHORT DUCTS

PENETRATIONS ERV1-6

Outside Air 6

Exhaust Air 6

Total 12

Occupied Space Occupied Space



ERV 1 ERV 2

ERV 3 ERV 4

ERV 5 ERV 6


ENERGY RECOVERY VENTILATION UNITS

Decentralized

> Operating cost and maintenance is in tenants control

> No common area duct runs

> Minimal fire damper issues

> No Common mechanical room requirement – space savings

> Cost advantage - depends

Centralized

> Maintenance in control of building owner

> Far fewer envelope penetrations (pressure testing)

> Generally more efficient (Fans, energy recovery device) DOAS units

> Equipment noise away from tenants – easier to attenuate

> Doesn’t use up apartment space

> Cost advantage - depends


WINTER HUMIDITY ISSUES

PART 3



WINTER HUMIDITY ISSUE

High humidity within apartment in cold weather creates uncomfortable indoor climate can cause condensation to form damage building, mold


CONDENSATION FORMATION

> The colder it gets, the easier humidity will form

> The higher the humidity level, the easier humidity will form

> Both at the same time is a bad thing

> Better glass helps (inside temperature is higher and stays above dew point longer)


SCENARIO 1 –HIGH DENSITY APARTMENT

> ASHRAE Std 90.1 and Passive House construction

> Sensible (HRV) and Enthalpy (ERV) energy recovery

> Decentralized and centralized ventilation


HIGH DENSITY APARTMENT


HIGH DENSITY APARTMENT

> 952 ft²

> 3 bedroom, 2 bathroom

> Design Occupancy = 4

> Laundry in common area

> Ventilation rate = 85 cfm

> Std 90.1 Infiltration = 72 cfm

> PH Infiltration = 20 cfm


SCENARIO 2 –LOW DENSITY APARTMENT

> ASHRAE Std 90.1 and Passive House construction

> Sensible (HRV) and Enthalpy (ERV) energy recovery

> Decentralized and centralized ventilation


LOW DENSITY APARTMENT


LOW DENSITY APARTMENT

> 853 ft²

> 2 bedroom, 2 bathroom

> Design Occupancy = 4

> Laundry in apartment

> Ventilation rate = 85 cfm

> Std 90.1 Infiltration = 141 cfm

> PH Infiltration = 39 cfm


ESTIMATING HUMIDITY LOADS


ESTIMATING HUMIDITY LOADS*

Source Pints Grains

5 Minute Shower 0.5 3650

Indoor drying of cloths 4-6 per load 29225-43840 per load

5-7 house plants 1/day 7300/day

Washing Dishes (Dinner, family of 4) 0.7 5100

Cooking (Dinner, Family of 4) 1.2 (1.5 with gas cooktop)

8770 (10950 with gas cooktop)

Respiration/Perspiration 0.4/hr 3040/hr

Evaporation, New Construction Materials 10+/day 73000+/day

1 Cord Green Firewood, stoed indoors for 6 mo 400-800 2.9M-5.8M

*Minnesota Extension Service, University of Minnesota


High Density 59.1 gr/lb

Low Density 52.7 gr/lb

HUMIDITY SOURCE ASSUMPTIONS

High Density 8770 gr/h

Low Density 8770 gr/h








> Air Infiltration

> 0.18 cfm/ft2@ 0.2” wc (Std 90.1)

> 0.05 cfm/ft2@ 0.2’wc (PH)

> Permeation – ignored

> Ventilation air

> 85 cfm

> Sensible Energy Recovery (dry air)

> Total Energy Recovery (retain 80% of moisture)

DEHUMIDIFICATION


SCENARIO 1 – HIGH DENSITY, DECENTRALIZED VENTILATION> HIGH DENSITY APARTMENT HAS high

internal humidity gain

> Infiltration from Std 90.1 construction helps dry out space

> Tight PH building builds up humidity in space

> Sensible recovery device recovers heat but air is dry – helps dry out space

> Total energy recovery device recoups 80% of humidity – causes humidity to increase

Dehumidification Result

Humidity

Gain

Infiltration Sensible

Energy

Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F

gr/hr gr/hr gr/hr gr/lb %

Std 90.1

Construction

33330 6240 7367 58 50.5

Passive House

Construction

33330 1733 7367 66 56.5

Sensible (HRV) Energy Recovery


Humidity

Gain

Infiltration Total Energy

Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

33330 6240 1473 69 59

Passive House

Construction

33330 1733 1473 77 65.7

Total (ERV) Energy Recovery


SCENARIO 1 – HIGH DENSITY, CENTRALIZED VENTILATION> High Density apartment has high internal

humidity gain



> Centralized sensible energy device behaves the same as decentralized

> Diversity from being connected to multiple apartments reduces increase in RH




Humidity

Gain


Energy

Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

33330 6240 7367 58 50.5

Passive House

Construction

33330 1733 7367 66 56.5


Humidity

Gain


Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

33330 6240 2947 66 56.5

Passive House

Construction

33330 1733 2947 74 63.6


SCENARIO 2 – LOW DENSITY, DECENTRALIZED VENTILATION> Low density apartment has 80%

humidity gain for same volume



> Sensible recovery device recovers heat but air is dry – helps dry out space

> Total energy recovery device recoups 80% of humidity – but not to an unacceptable level




Humidity

Gain


Energy

Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

26640 12230 7367 37 31.9

Passive House

Construction

26640 3397 7367 55 47.2


Humidity

Gain


Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

26640 12230.4 7367 69 42

Passive House

Construction

26640 3397 7367 66 56.5


SCENARIO 2 – LOW DENSITY, CENTRALIZED VENTILATION> Low density apartment has 80%

humidity gain for same volume



> Centralized sensible energy device behaves the same as decentralized

> Diversity from being connected to multiple apartments and lower humidity gain make total energy preferable




Humidity

Gain


Energy

Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

26640 12230 7367 37 31.9

Passive House

Construction

26640 3397 7367 55 47.2


Humidity

Gain


Recovery

Ventilation

New Hum

Ratio 72F

New Rel.

Hum. at

72F


Std 90.1

Construction

26640 12230.4 7367 66 39.5

Passive House

Construction

26640 3397 7367 63 53.9


Scenario Density Ventilation Std. Sensible vs. Total New Rel. Hum. At 72F (%)

1 HIGH DECENTRALIZED

90.1 Sensible 50.5

Total 59

PH Sensible 56.5

Total 65.7

1 HIGH CENTRALIZED

90.1 Sensible 50.5

Total 56.5

PH Sensible 56.5

Total 63.6

2 LOW DECENTRALIZED

90.1 Sensible 31.9

Total 42

PH Sensible 47.2

Total 56.5

2 LOW CENTRALIZED

90.1 Sensible 31.9

Total 39.5

PH Sensible 47.2

Total 53.9

SUMMARY


WINTER HUMIDITY SUMMARY

Passive House construction is tight

Ultra low leakage rates can cause humidity to build up in apartments especially high density apartments

Decentralized Total Energy Recovery Ventilation has risk

Humidity recovery causes humidity to build up to unacceptable levels. It may not be an issue in low density apartments

Centralized Ventilation units can help

The diversity from connecting to multiple apartments can reduce humidity build up and allow additional savings from total energy recovery


ENERGY IMPACT –SENSIBLE VS. ENTHALPY ENERGY RECOVERY

PART 4



ENERGY MODELLING> DOAS unit energy modelling program

> Compare two systems side by side

> Enthalpy Wheel vs. sensible wheel

> Scenario 1 – No cooling, hot water heating

> Scenario 2 - VRF DX cooling w/ HGRH and heat pump heating


MODEL SETUP


MODEL SETUP


WHEEL FROST CONTROL

Total recovery much greater than sensible due to lower frost point

Almost twice winter energy recovery

Wheel speed vs. energy transfer not linear

Must slow wheel down to a few rpm to get capacity reduction


SCENARIO 1- NO COOLING


Scenario 2 - VRF Heating and Cooling


VRF – Ventilation Unit Integrated Controls


VRF Electronic Expansion Devices


VRF – Hot Gas Reheat Solution


SCENARIO 2 - VRF COOLING AND HEATING


SUMMARY

PART 5


SUMMARY

Centralized vs. decentralized ventilation depends on the application

The are many parameters including technical and cost that impact this decision. Being able to seal the building for a pressure test should not be overlooked especially on tall buildings

Passive House construction and high humidity in winter should be considered

Be careful with high density apartments and decentralized total energy recovery. Centralized total energy recovery should be okay, Low density apartments should be okay but check!

Total Energy recovery saves energy and reduces operating cost

Total energy recovers 5-15% more sensible energy in winter plus maintain indoor humidity. It dehumidifies in summer. It reduces size of air conditioning by 25%


Questions?

Documents

Ventilation Design Considerations for Passive House ...€¦ · 43 Ventilation Design Considerations for Passive House Multifamily Residential Buildings SCENARIO 2 –LOW DENSITY,