7th Annual North American Passive House Conference September 27-30, 2012 Denver CO
CLIMATE INFLUENCES ON THE MECHANICAL SYSTEM OF A PASSIVE HOUSE Kara M McKernan – PE, CEM, LEED AP, CPHC
[email protected] Associated Design Group, Inc. – Boise, ID
7th Annual North American Passive House Conference September 27-30, 2012 Denver CO
Session Learning Objectives: •
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Review the boundaries and differences in climate zones in the United States Review insulation values at a city in each climate zone for certification as a Passive House Review mechanical system deviations based on climate Discuss obstacles in each climate zone for mechanical system/building envelope
2009 IECC Climate Zone Map
Source: 2009. International Energy Conservation Code.
City In Each Climate Zone Zone 1A – Miami, FL Zone 2A – New Orleans, LA Zone 3B – San Jose, CA Zone 4C – Portland, OR Zone 5B – Boise, ID Zone 6A – Minneapolis, MN Zone 7B – Jackson, WY Zone 8 – Fairbanks, AK Source: 2007. ANSI/ASHRAE/IESNA Standard 90.1-2007
2009 ASHRAE Handbook Fundamentals (IP) Design Conditions for Selected Locations
Source: 2009. ASHRAE Handbook, HVAC Fundamentals.
PHPP Climate Data
Weather 1: Cold, sunny day Weather 2: Cool, overcast day
Floor Plan
Upper Level: 620 sf Main Level: 593 sf Lower Level: 479 sf Source: By permission from Gilday Architects
Sections
Source: By permission from Gilday Architects
Elevations
Source: By permission from Gilday Architects
Boise, ID
R-24.3 R-13.3 R-34.4 R-28.3 44.5
R-38.0 R-13.3 R-34.4 R-48.4 32.1
R-43.8 R-23.6 R-42.6 R-53.0 12.7
R-60.4 R-42.9 R-75.7 R-111.7 -14.3
R-67.7 R-55.0 R-83.9 R-100.7 -5.8
Fairbanks, AK
Portland, OR
R-31.5 R-19.8 R-26.1 R-48.4 34.8
Jackson, WY
San Jose, CA
R-24.3 R-13.3 R-34.4 R-28.3 57.3
Minneapolis, MN
New Orleans, LA
Wall Above Grade Wall Below Grade Basement Slab Ceiling PHPP Heating DB (˚F)
Miami, FL
Final Insulation Values for PH Certificate
R-212 R-140 R-141 R-246 -21.8
* Fairbanks is limited on the solar heat gain available in the winter due to low solar radiation numbers in the climate data set. Without the solar heat gain, it is extremely challenging to pass in that climate.
Solar Radiation Comparison
Solar Intensity Map for the United States
Source: http://ecotechnousa.com/EcoTechnoNews/DidYouKnow/tabid/68/articleType/ArticleView/articleId/6/SolarMyth-4.aspx
Modified Glazing to Pass
Base Design Glazing
Necessary Glazing Modifications
North Elevation modeled in Miami, FL & Minneapolis, MN
South Elevation modeled in Miami, FL Fairbanks: all windows deleted on N, W & E elevations with large window on upper and main level to remain.
Specific Space Heating Load ASHRAE Fundamentals Heating DB (99%)
PHPP Heating DB
95btuh
51.7 ˚F
57.3 ˚F
New Orleans, LA
5,719btuh
35.4 ˚F
34.8 ˚F
San Jose, CA
4,339btuh
37.8 ˚F
44.5 ˚F
Portland, OR
6,771btuh
28.6 ˚F
32.1 ˚F
Boise, ID
8,161btuh
10.5 ˚F
12.7 ˚F
11,902btuh
-7.6 ˚F
-14.3 ˚F
Jackson, WY
8,886btuh
-9.0 ˚F
-5.8 ˚F
Fairbanks, AK
6022btuh
-38.1 ˚F
-21.8 ˚F
Heating Load Miami, FL
Minneapolis, MN
Leaving Air Temperature (LAT) from Heat Recovery Ventilator (Winter) ϑ2 , ˚F
ϑ3 , ˚F
Supply Air Leaving
Outside Air Entering
Exhaust Air Entering
Exhaust Air Leaving
ϑ1 , ˚F
ϑ2 = ϑ1 - ФHR * (ϑ1 – ϑ3)) ϑ1 = 99% Heating DB from ASHRAE ФHR = HRV efficiency ϑ3 = Room Temperature (68˚F in PHPP)
ϑ1
ФHR
ϑ3
ϑ2
51.7
0.84
68
65.4
New Orleans, LA 35.4
0.84
68
62.8
San Jose, CA
37.8
0.84
68
63.2
Portland, OR
28.6
0.84
68
61.7
Boise, ID
10.5
0.84
68
58.8
Minneapolis, MN
-7.6
0.84
68
55.9
Jackson, WY
-9.0
0.84
68
55.7
Fairbanks, AK
-38.1
0.84
68
51.0
City ϑ4 , ˚F
Miami, FL
Equation Explanation - LAT Required To Provide Heating Load Through HRV PH = 60 * V * ρcp * (ϑLAT - ϑ2) rework to solve for ϑLAT
ϑLAT = ϑ2 + [PH / (60 * V * ρcp)] PH = Heating Load (PHPP), btuh 60 = 60min/hr V = the volumentric flow rate of the air to air system, ft3/min (cfm) at external static pressure (ESP) calculated ρ = density of air, lbm/ft3 (0.075 lbm/ft3 at sea level, varies by feet above sea level) cp = specific heat of air, Btu/lbm˚F (0.24 Btu/lbm˚F at 70F and atmospheric pressure, 14.7 psia) ϑLAT = Leaving air temperature required to provide heating load from PHPP, ˚F ϑ2 = Leaving air temperature from heat transfer through air to air heat recovery ventilator, ˚F
Supply Air Temperature Required To Provide Heating Load Through HRV ϑLAT = ϑ2 + [PH / (60 * V * ρcp)] City
ϑ2 ˚F
Heating Load (PHPP), PH Btuh/kW
V cfm
ρ lbm/ft3
Cp Btu/lb˚F
Supply Air Temp. to provide heating load, ϑLAT ˚F
Miami, FL
66.3
95/0.03
237
.0749
0.24
66.7
New Orleans, LA
62.7
5719/1.7
237
.0749
0.24
85.1
San Jose, CA
64.2
4339/1.3
237
.0749
0.24
81.2
Portland, OR
62.3
6771/2.0
237
.0749
0.24
88.8
Boise, ID
59.2
9161/2.7
237
.0676
0.24
98.9
Minneapolis, MN
54.8
11902/3.5
237
.0727
0.24
102.8
Jackson, WY
56.2
8886/2.6
237
.0588
0.24
100.5
Fairbanks, AK
51.0
6022/1.8
237
.0737
0.24
74.9
Heating With HRV City
Heating Load (PHPP), PH Btuh/kW
Supply Air Temp. to provide heating load, ϑLAT ˚F
Can heating be provided by HRV? Is an electric duct heater necessary?
95/0.03
66.7
Yes/No
New Orleans, LA 5719/1.7
85.1
Yes/Yes
San Jose, CA
4339/1.3
81.2
Yes/Yes
Portland, OR
6771/2.0
88.8
Yes/Yes
Boise, ID
9161/2.7
98.9
No/Yes (preheat)
Minneapolis, MN
11902/3.5
102.8
No/Yes (preheat)
Jackson, WY
8886/2.6
100.5
No/Yes (preheat)
Fairbanks, AK
6022/1.8
78.3
Yes/Yes
Miami, FL
•Optional integrated 800W modulating preheater •1kW and 2.5kW duct heaters that can be modulated with the ComfoAir controls
Heating Options For Heating Dominated Climates
Tankless Hot Water Heater for DHW & Radiant Heat Piping Schematic
Specific Space Cooling Load Cooling Load
ASHRAE Fundamentals Cooling DB/MCWB/RH PHPP (1%) Cooling DB
Miami, FL
5,454btuh
90.7˚F/77.5˚F/56%
91.4˚F
New Orleans, LA
6,638btuh
91.9˚F/77.7˚F/53%
87.8˚F
San Jose, CA
0btuh
88.6˚F/66.2˚F/30%
75.2˚F
Portland, OR
3,537btuh
87.1˚F/66.5˚F/34%
82.4˚F
Boise, ID
1,966btuh
95.0˚F/63.1˚F/16%
85.1˚F
Minneapolis, MN
6,296btuh
87.9˚F/72.3˚F/48%
87.8˚F
Jackson, WY
0btuh
81.4˚F/54.5˚F/19%
69.5˚F
Fairbanks, AK
0btuh
78.0˚F/59.8˚F/34%
64.2˚F
Supply Air Humidity (RH2) from Energy Recovery Ventilator (Summer) ϑ2 , ˚F
RH2 , % ϑ3 , ˚F RH3 , %
Supply Air Leaving
Outside Air Entering
Room Air Entering
Exhaust Air Leaving
ϑ1 = outside air from climate data, ˚F WB1 = outside air wet bulb, ˚F WB3 = room air wet bulb (61), ˚F ФHRS = ERV sensible efficiency (84), % ϑ3 = indoor air temp (68), ˚F ϑ2 = ϑ1 - ФHRS * (ϑ1 – ϑ3)), ˚F ϑ4 = ϑ3 + ФHRS * (ϑ1 – ϑ3)), ˚F w = humidity ratio, lbs moisture/lb dry air ФHRL = ERV latent efficiency (60), % w2 = w1 - ФHRL * (w1 – w3)), lb/lb w4 = w3 + ФHRL * (w1 – w3)), lb/lb
ϑ1 , ˚F RH1 , %
ϑ4 , ˚F RH4 , %
Energy Recovery Ventilator
Most Humid City Modeled (Miami) City
ϑ1
WB1
ϑ3
WB3
ФHRS
ФHRL
ϑ2
ϑ4
RH1
RH2
RH3
RH4
Miami, FL
82.3
77.9
68
58
0.84
0.6
70.3
80.0
82.4
79.7
55
68.2
* These calculations don’t use ASHRAE cooling dry bulb and mean coincidence wet bulb since this isn’t always the worst case. The calculations should be performed and reviewed for multiple outdoor air conditions since conditions are always changing.
Miami Monthly Weather Data from Elite Software Psychrometric Analysis
Calculations to Determine Mini-split Moisture Removal Calculations performed using Elite Software Psychrometric Analysis and Design Software and Psychrometric Charts MSZ-FE12NA
144
2.1
Miami - Elite Software Psychrometric Analysis
Miami Psychrometric Chart for Mini-Split Latent Space Load: 1,817btuh
Latent Heat Removal Potential of ERV & Mini-split: 2,604btuh Therefore, two minisplits in Miami will provide adequate moisture removal for comfort
Cooling Options For Cooling Dominated Climates
* Zehnder is working on a dehumidification option to add to their ERV
Systems Chosen for Miami, FL Heating Load: 95btuh/0.03kW Cooling Load: 5,454btuh
Air to air heat exchanger with ERV core and integral 800 watt modulating pre-heater
Cooling only with two 9,000 btuh wall mounted indoor units in Kitchen/Living/Dining 205 & Master Bedroom 303
Systems Chosen for New Orleans, LA Heating Load: 5,719btuh/1.7kW Cooling Load: 6,638btuh
Air to air heat exchanger Inline dehumidification with ERV core and 2.5 kW on ventilation system duct heater with filter removed
Cooling only with two 9,000 btuh wall mounted indoor units in Kitchen/Living/Dining 205 & Master Bedroom 303
Systems Chosen for San Jose, CA Heating Load: 4,339btuh/1.3kW Cooling Load: 0btuh
Air to air heat exchanger with ERV core and 2.5 kW duct heater
Cooling and heating with 9,000 btuh wall mounted indoor unit in Kitchen/Living/Dining
Systems Chosen for Portland, OR Heating Load: 6,771btuh/2.0kW Cooling Load: 3,537btuh
Air to air heat exchanger with ERV core and 2.5 kW duct heater
Cooling and heating with 9,000 btuh wall mounted indoor unit in Kitchen/Living/Dining
Systems Chosen for Boise, ID Heating Load: 9,161btuh/2.7kW Cooling Load: 1,966btuh
Air to air heat exchanger with ERV core and 800W preheater
Cooling with a 9,000 btuh wall mounted indoor unit in Kitchen/Living/Dining
Systems Chosen for Minneapolis, MN Heating Load: 11,902btuh/3.5kW Cooling Load: 6,296btuh
Air to air heat exchanger with ERV core and 800W preheater
Cooling with a 9,000 btuh wall mounted indoor unit in Kitchen/Living/Dining
Systems Chosen for Jackson, WY Heating Load: 8,886btuh/2.6kW Cooling Load: 0btuh
Air to air heat exchanger with ERV core and 800W preheater
Systems Chosen for Fairbanks, AK Heating Load: 6,022btuh/1.8kW Cooling Load: 0btuh
Air to air heat exchanger with ERV core and 2.5kW duct heater
Summary •
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Passive House works in all climates, but may not be cost effective in extreme climates There will be less artistic freedom in extreme climates due to building envelope and mechanical system requirements to pass Changes in each component in the PHPP modeling software will affect other system components Utilizing a whole-system design strategy can help eliminate time spent on one aspect without reviewing every component, streamline the process and save the client money
Thank You!
Questions? Kara M. McKernan – PE, CEM, LEED AP, CPHC
[email protected]
