Hot, Humid, and Still Cool? - Passive House Institute US

7th Annual North American Passive House Conference
2727-30 September 2012 Denver, Colorado
Hot, Humid, and Still Cool?
Corey Saft, Saft Architecture
saft.corey@gmail.com
Eric Helton, Bloomfield Research Labs LLC
eric.helton@bloomfieldresearchlabs.com
7th Annual North American Passive House Conference
2727-30 September 2012 Denver, Colorado
Session Learning Objectives:
• Unique challenges of designing a Passive House
for the Hot/Humid climate
• Monitoring and experiential data from the first
18 months of a Passive House in the
Hot/Humid climate zone
• Latent load issues in ventilation air in humid
climates
• Demands for human comfort in the deep South
of the U.S.
TEAM
Design & Development
Corey Saft, Saft Architecture
PHPP Consultant
Katrin Klingenberg, Executive Director, PHIUS
Data Analysis
Eric Helton, Bloomfield Research Labs LLC
Special Acknowledgement:
Latent load / ERV discussions & invaluable guidance throughout the entire project
Z Smith, Eskew+Dumez+Ripple
LeBois House
Lafayette, Louisiana
LeBois House
Lafayette, Louisiana
LeBois House
Lafayette, Louisiana
LeBois House
ENVELOPE
LeBois House
SYSTEMS
LeBois House
SYSTEMS
LeBois House
SYSTEMS
exterior walls - R-28
1” HCFC free Polyiso Rigid board
5.5” open cell insulation
Calculated Energy Values for the Saft Residence.
Heating Demand, kWh/m²yr, (kBtu/ft²/yr)
Peak Heat Load, W/ m², (Btu/h/ft²)
Cooling Demand, kWh/m²yr, (kBtu/ft²/yr)
Peak Cooling Load, W/ m², (Btu/h/ft²)
Specific Primary Energy Demand,
10 (3.17)
18 (5. 7)
15 (4.75)
14 (4.44)
116.8 (37.03)
-castor-based spray foam insulation
-100% water-blown, free from HFCs and PBDEs
roof – R-55
2” HCFC free Polyiso Rigid board
11” open cell insulation
kWh/m²yr, (kBtu/ft²/yr)
-castor-based spray foam insulation
-100% water-blown, free from HFCs and PBDEs
Airtightness = 0.55 ACH @ 50 pascal pressure
U-value R-value SHGC VT
picture
casement/awning
.15
.18
6.7
5.6
.29
.24
Dual Pane, 1 Low SHG Film Krypton
.52
.42
crawl space walls R-21
4” XPS
crawl space slab R-16.5
3” XPS
LeBois House
lafayette, la
LeBois House
CLIMATE
Climate & PH
LeBois House
CLIMATE
humidity
LeBois House
LATENT LOAD
after H. Gifford
humidity
LeBois House
LATENT LOAD
Air with dewpoint> 62°F
will have RH > 60% at 78°F
(must dehumidify to stay in
ASHRAE comfort zone)
after H. Gifford
LeBois House
LATENT LOAD
LeBois House
US COMPARISONS
LeBois House
LATENT LOAD
LeBois House
DATA COLLECTION
DataLogging
LeBois House
DATA COLLECTION: Temperature and Humidity
U12 Series Loggers: Used in Critical Locations
•Temperature
•Stated Accuracy: ±0.63 °F
•Uniformity Test: ±0.2 °F
•Relative Humidity
•Stated Accuracy: ±2.5 %RH
•Uniformity Test: ±1 %RH
H08 Series Loggers: Used in Peripheral Locations
•Temperature
•Stated Accuracy: ±1.5 °F
•Uniformity Test: ±1.5 °F
•Relative Humidity
•Stated Accuracy: ±5 %RH
•Uniformity Test: ±2 %RH
Note: Because the loggers were of a variety of ages, uniformity tests were done to
verify functionality. Measurement accuracy remains the manufacturer’s stated
accuracy.
LeBois House
DATA COLLECTION: Electrical Energy
4-Channel TED-5000
•Stated Accuracy: 2%
•Comparison to rolling
12-months of utility bills: ±2%
•Three Active Measurements
•Net Exchange with Grid
•PV Generation
•Mini-Split Heat Pump
LeBois House
DATA COLLECTION: Installation Locations
DataLogging
LeBois House
DATA COLLECTION: Installation
LeBois House
ENERGY
Monthly total electrical energy use and generation
LeBois House
ENERGY & COMFORT
LeBois House
60
40
20
Outdoor
Outdoor, Min or Max (Dashed)
Living Room Loft
Kitchen/Living Room
Bedroom 1
Bedroom 2
Bedroom 3
Crawlspace
Indoors, Min or Max (Dashed)
0
Monthly Average Relative Humidity [%RH]
80
60
Outdoor
Outdoor, Min or Max (dashed)
Living Room Loft (Thermostat Location)
Kitchen/Living Room
Bedroom 1
Bedroom 2
Bedroom 3
Crawlspace
Indoors, Min or Max (dashed)
40
20
Monthly Average Temperature [F]
80
100
100
COMFORT: Temperature and Humidity
Feb
2011
Apr
2011
Jun
2011
Aug
2011
Oct
2011
Dec
Feb
201120122012
Apr
2012
Jun
2012
Aug
2012
Feb
2011
Apr
2011
Jun
2011
Aug
2011
Oct
2011
Dec
Feb
201120122012
Apr
2012
Jun
2012
Aug
2012
LeBois House
60
40
Outdoor
Outdoor, Min or Max (Dashed)
Living Room Loft (Thermostat Location)
Kitchen/Living Room
Bedroom 1
Bedroom 2
Bedroom 3
Crawlspace
Indoors, Min or Max (Dashed)
20
Monthly Average Dewpoint Temperature [F]
80
COMFORT: Dew Point Temperature
Feb
2011
Mar
2011
Apr
2011
May
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2011
Nov
2011
Dec
2011
Jan
2012
Feb
2012
Mar
2012
Apr
2012
May
2012
Jun
2012
Jul
2012
Aug
2012
LeBois House
ENERGY
LeBois House
ENERGY
PHPP modeling and 12-month measured energy data
LeBois House
CONCLUSIONS
•Heating was rarely required, and the actual use was about 7% of the PHPP
predicted need.
•Cooling was more significant, but still only 70% of the predicted need.
•Primary energy was approximately 50% greater than predicted by the PHPP.
•Annual latent is estimated to be 15 kWh/m2/yr ( to no quota).
LeBois House
ENERGY
LeBois House
FACTORS RELATIVE TO THE LARGER THAN EXPECTED PRIMARY ENERGY:
• The addition of the stand alone dehumidifier in August 2011
• While the ERV is critical to performance, the measured performance (35%) is
less than rated and suffered a few operational issues over the course of the
study such as an extended period with an increasingly blocked intake duct
• The occupants maintained a large electronics collection, including computers,
video games, stereo equipment, an extra mini-fridge, projector and amplified
musical instruments.
• The house is a rental / irregular/inconsistent student lifestyle
80
60
40
20
Monthly Average Dewpoint Temperature [F]
Outdoor
Outdoor, Min or Max (Dashed)
Living Room Loft (Thermostat Location)
Kitchen/Living Room
Bedroom 1
Bedroom 2
Bedroom 3
Crawlspace
Indoors, Min or Max (Dashed)
Feb
2011
Apr
2011
May
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2011
Nov
2011
Dec
2011
Jan
2012
Feb
2012
Mar
2012
Apr
2012
May
2012
Jun
2012
Jul
2012
Aug
2012
0
500
1000
House, Net
House, Total
Minisplit
PV Generation
-500
Monthly Total Energy [kWh]
Mar
2011
Feb
2011
Apr
2011
May
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2011
Nov
2011
Dec
2011
Jan
2012
Feb Mar
2012 2012
Apr
2012
May
2012
Jun
2012
Jul
2012
Aug
2012
LeBois House
CONCLUSIONS
•The house exceeded the primary energy modeling by the PHPP for
12 months of data
•The 12-month measured heating and cooling energy totals were
below the PHPH model
•Comfort marginally maintained during the summer, but temperature
uniformity between the open and private spaces was impossible
•The PHPP model did not realistically model the high cumulative
latent loads induced by ventilation air in the hot/humid climate
•The HERS model was very accurate
LeBois House
CONCLUSIONS
•Point source heating/cooling is problematic
•A convective based strategy for distribution is problematic
•Latent load is problematic
LeBois House
FUTURE WORK
•The next major modification to the data collection project will be
a dedicated monitoring of the dehumidifier energy consumption
separately from the ERV and the mini-split
•Re-evaluate dehumidifier / ERV / minisplit sequencing
•Work with the PHIUS/PHPP software team to ensure latent loads
are handled realistically
•More flexible and realistic energy requirements by setting a Total
Source Energy and allowing each building to adapt this total, as
appropriate for the climate, to heating/cooling/dehumidification
LeBois House
FUTURE WORK
“Every building is a forecast. Every forecast is wrong.”
- Futurist Stewart Brand quoted in NRELs “Getting to Net Zero”
Acknowledgements
Monitoring Funding:
• PHIUS
• University of Louisiana at Lafayette
Latent Load and ERV Discussions as well as invaluable guidance throughout the
entire project:
• Z Smith, AIA, LEED AP BD+C, Director of Sustainability & Building
Performance, Eskew+Dumez+Ripple, New Orleans, LA
Data Collection:
• Hunter Duplantier
• Justin Aurbert
• Liran Timiansky
References
Corey Saft
saft.corey@gmail.com
Eric Helton
eric.helton@bloomfieldresearchlabs.com