Practical Approaches to Residential Ventilation for Improved

Transcription

Practical Approaches to Residential
Ventilation for Improved Durability and
Indoor Air Quality
by
Armin Rudd
Building Science Consortium
USDOE Building America Program
for
Durability and Disaster Mitigation In Wood-Frame Housing Conference
Madison, Wisconsin
08 November 2000
Building Science Corporation
PR-0002: Practical Approaches to Residential Ventilation for Improved Durability and Indoor Air Quality
Page 1 of 34
Providing durability for
little or no incremental
cost is a goal of the
Building A m erica program
Page 2 of 34
D u rability a n d m a intenance cost are direct
functions of:
• M o isture
• Heat
• U ltra-violet light
O f these three,
M o isture is the m o s t significant
November 2000
Page 3 of 34
D u rability can be insured w ith respect to
m o isture by:
• Providing a building envelope design that can dry
should it get w e t
• Preventing excessive pressurization and
depressurization of occupied spaces and cavities
• Installing controlled mechanical ventilation
system s
November 2000
Page 4 of 34
Purposes of mechanical ventilation
1. Point-source ventilation - Remove Pollutants
– exhaust fans: kitchen, bath, laundry
2. Whole-building ventilation - Dilute Pollutants
– supply, exhaust, or balanced fans distributing to all
rooms
Page 5 of 34
C lim a te Specific Design Solutions
© buildingscience.com
November 2000
Page 6 of 34
Central-fan-integrated supply ventilation
Interior closet or basement configuration
Thermostat
Humidistat
(optional)
Supply Air
To Interior Space
Return Air
From Interior Space
Exterior
Wall
Wall Cap with
Insect Screen
Control Wiring
Terminals
Heating/
Humidifying
Apparatus
Ventilation Air Intake
(locate away from
pollutant sources)
6" Insulated
Outside Air Duct
AirCyclerTM
Control
Air Distribution Fan
Air Handler Unit
Cooling/
Dehumidifying
Apparatus
Field measurement of outside
air duct pressure, used to set
balancing damper position
Filter/Air Cleaner
Register box
adapted with
slide-in filter
Balancing
Damper
Page 7 of 34
Ventilation Air Distribution and Mixing Control
Wires to low voltage terminals on central air handler unit
Page 8 of 34
Intermittent Operation
• Sizing
– intermittent flow equals constant flow reduced
by low background infiltration amount when
blower is not on, all divided by duty cycle
fraction
I
&
(Qco ) − ( V (1 − f ))
60
&
Qin =
f
Page 9 of 34
Intermittent Operation
• where,
ton
ton
f =
=
ton + toff ttotal
Page 10 of 34
Very cold climate
ventilation and moisture control designs
HDD > 8000
• 1st choice is continuously operating single-point exhaust
with intermittent central-fan-integrated supply limited to
7% of AHU flow
• 2nd choice is continuously operating single-point exhaust
with central fan recycling for distribution and mixing
(sealed combustion space/DHW heating)
• 3rd choice is balanced heat recovery ventilation with
central fan recycling for distribution, or fully ducted to all
rooms
November 2000
Page 11 of 34
Builders
Pulte Home Corp.
Centex Homes
Town & Country Homes
L ocation
Minneapolis, Minnesota
Subdiv isions The Grove at Elm Creek
Regatta
Eden Prairie
C limate
No. Homes
very cold
300+
Ventilation systems
• Continuously operating single-point exhaust with central fan recycling for
whole-house distribution and mixing, and with intermittent central-fanintegrated supply limited to 7% of AHU flow
November 2000
Page 12 of 34
Minneapolis ventilation study
Air Changes Per Hour (1/h)
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
6 7 8 9
Test ID Number
10 11 12 13
Page 13 of 34
Cold climate
4500<HDD<8000
• 10 cfm/person design
– 1st choice is central-fan-integrated supply limited to
10% of AHU flow
– 1st choice is continuously operating single-point
exhaust with intermittent central-fan-integrated supply
limited to 10% of AHU flow
– 2nd choice is continuously operating single-point
exhaust with central fan recycling for distribution and
mixing (sealed combustion space/DHW heating)
November 2000
Page 14 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
Sturbridge Construction
Prairie Crossing
Grayslake, Illinois
cold
350
Ventilation systems
• In 1996, started with low-cost blending supply system
- separate inline fan, no filter, 2 pickups, 1 supply
- complaints: fan noise and cold basement
• In 1997, changed to central-fan-integrated supply with fan recycling
- 6” insulated OA duct to AHU return, with balancing damper
- 7% outside air fraction, minimum 33% duty cycle
- filtration by AHU filter
- builder provides customer education
- no complaints after over 3 years
November 2000
Page 15 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
Town & Country Homes
Centennial Crossing
Vernon Hills, Illinois
cold
191
Ventilation system
• Central-fan-integrated supply with fan recycling
- no complaints after over three years
November 2000
Page 16 of 34
Monitored Runtime Data
Centennial Crossing, Lot 22
Apr (27-30)
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar (1-9)
Cool ON
(%)
0
1
7
10
10
5
0
0
0
0
0
0
Heat ON
(%)
12
2
1
0
0
0
4
13
20
31
23
25
Fan Recycling
Vent ON
Cost
(%)
($)
12
0.24
15
3.06
10
2.05
12
2.58
13
2.72
15
2.96
15
3.07
10
1.99
6
1.31
3
0.60
5
0.95
4
0.23
Notes: Fan recycling control set for 25 min OFF, 6 min ON (19% duty cycle)
Page 17 of 34
Cool ON
(%)
Aug
Sep
Oct
Nov
Dec
Jan
Feb
21
10
0
0
0
0
0
Heat ON
(%)
0
0
5
15
27
35
24
Fan Recycling
Vent ON
Cost
(%)
17
21
20
12
6
3
5
($)
3.52
4.24
4.12
2.33
1.35
0.54
1.00
Notes: Fan recycling control set for 20 min OFF, 8 min ON (29% duty cycle)
Page 18 of 34
Oct
Nov
Dec
Jan
Feb
Mar (1-8)
Cool ON
(%)
Heat ON
(%)
0
0
0
0
0
0
5
15
25
34
26
31
Fan Recycling
Vent ON
Cost
(%)
($)
24
14
9
3
6
3
4.97
2.81
1.81
0.68
1.18
0.17
Notes: Fan recycling control set for 20 OFF 10 ON (33% duty cycle)
Page 19 of 34
Mixed climate
HDD<4500
– 1st choice is central-fan-integrated supply limited to
13% of AHU flow
– 1st choice is continuously operating exhaust with
intermittent central-fan-integrated supply limited to 13%
of AHU flow
November 2000
Page 20 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
The Lee Group/Braemar Urban Ventures
Village Green
Los Angeles, California
mixed-dry
186
Ventilation system
• Specified single-point exhaust with central fan recycling for whole-house
distribution and mixing
November 2000
Page 21 of 34
Hot-dry climate ventilation designs
>45 F, <20” rain
• 1st choice is central-fan-integrated supply limited to 15%
of air handler flow
• 2nd choice is central-fan-integrated supply with
continuously operating single-point exhaust (sealed
combustion if in conditioned space)
November 2000
Page 22 of 34
Unvented-cathedralized attic configuration
Gable End Wall
Outside Air Duct
6" Insulated Flex-duct
AirCycler TM
Wall
Cap
Control
Supply Air
Gypsum Ceiling
Cooling
Coil
Heating
Coil
Main Return Duct
Central Return Box
Return Grille and Filter
Circular Filter
(cut from blank
and friction fit)
Balancing Damper
Above
Page 23 of 34
Outside air duct (filtered) connected to return filter grille pan
November 2000
Page 24 of 34
Builder
Pulte Home Corporation
Subdiv isions: Angel Park (2), Cypress Pointe (116),
Crown Ridge (105), Arbor View (88),
Stallion Mountain (760)
L ocation
C limate
No. Homes
Las Vegas, Nevada
hot-dry
over 1000
November 2000
Page 25 of 34
Lot 6
Arbor View
Indoor temperature variation
from the house average
Temperature Variation (F)
6
4
max
2
0
min
-2
avg
-4
-6
Return
Storage
Mbed
Great
Building Science
Hall Corporation
Dining
Bed 2
Page 26 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
Watt Homes
Four Seasons
Las Vegas, Nevada
hot-dry
106
Ventilation system
- washable filter behind central return filter grille
- no complaints after over 3 years
November 2000
Page 27 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
Arroyo Ridge
Tucson, Arizona
hot-dry
2
Ventilation system
- washable filter behind central return filter grille
- no complaints or concerns after over 2 years
November 2000
Page 28 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
Retreat at the Bluffs
Tucson, Arizona
hot-dry
156
Ventilation system
• Single-point exhaust
- upgraded fan in laundry room, wall switch
- complaints: fan noise, lack of filtration and distribution
• Changed to central-fan-integrated supply on following project:
Spanish Trails
November 2000
Page 29 of 34
Builder
Artistic Homes
Subdiv isions Mirabella, Tuscany,
Desert Springs
L ocation
C limate
No. Homes
Albuquerque, NM
mixed-dry
15 (will soon be 800/yr)
Ventilation system
- no complaints after three months
November 2000
Page 30 of 34
Hot-humid climate
>45 F, >20” rain
• Central-fan-integrated supply with fan recycling,
damper, and dehumidifier
– air handler unit in conditioned space closet, placed on
platform high enough to place dehumidifier underneath
– dehumidifier controlled by dehumidistat in conditioned
space
– normal thermostat driven cycling of air handler, and fan
recycling, distributes both ventilation air and dry air to
whole house
November 2000
Page 31 of 34
Hot-humid climate interior mechanical closet configuration
Thermostat
Humidistat
(optional)
Supply Air
To Interior Space
Control Wiring
Terminals
Exterior Wall
Wall Cap with
Insect Screen
Heating/
Humidifying
Apparatus
AirCyclerTM
Control
Central Fan
(blower)
Ventilation Air Intake
(locate away from
pollutant sources)
6" Insulated
Outside Air Duct
(slope up for first 4')
Air Handler Unit
Cooling/
Dehumidifying
Apparatus
Duct extension at
air handler return
(open at bottom)
Return Air
From Interior Space
40 pint/day
dehumidifier
Field measurement of outside
air duct pressure, used to set
balancing damper position
Balancing
Damper
Floor
Page 32 of 34
Builder
Subdiv ision
L ocation
C limate
No. Homes
East Hampton
Jacksonville, Florida
hot-humid
2
Ventilation system
- 6” insulated OA duct to AHU return, balancing damper
- filtration at air handler unit
- no complaints or concerns after over 6 months
Additional moisture control system
• 40 pint per day dehumidifier under air handler unit, with central fan
recycling for whole-house distribution and mixing
November 2000
Page 33 of 34
Page 34 of 34

Practical Approaches to Residential Ventilation for Improved

Transcription

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