ASHRAE Journal - May 2011 - 86

solar NZEB projEct
in interesting manners. The temperature 80 variation, as previously discussed, indicates 70 the amount of mass participating in energy 60 storage in the house. The results in Figure 8 are similar to the time constant data previ50 ASHRAE Winter Conference ously discussed from October 2010 data, 40 with a time constant of 118 hours for the January 2011 data. 30 The carbon dioxide transient variation in 20 Figure 8 is perhaps the most straightforward Utility Space 10 to characterize of the other three factors. As Master Bedroom a relatively “inert” gas, and assuming that 0 Living Room there are negligible sources and sinks of Outside Ambient –10 CO2, its level changes by interaction with the surrounding outside ambient CO2. A –20 1/17 1/27 2/6 2/16 2/26 3/8 12/28 (12 a.m.) 1/7 simple model, analogous to that used for Figure 5: Interior ambient and exterior ambient temperatures in Equinox House from the temperature time response model is: January 2011 to early March 2011.  CO 2 − CO 2 a  ln   = − ( ach ) t 0.012  CO 2i − CO 2 a  Utility Space Master Bedroom where ASHRAE Winter Conference Living Room Outside Ambient 0.010 ach = air changes per hour t = time of test with zero time at the test beginning 0.008 CO2 = inside house ambient carbon dioxide 0.006 CO2i = inside house ambient carbon dioxide at beginning of test (time = 0) 0.004 CO2a = outside average ambient carbon dioxide (~390 ppm)
Humidity ratio (kgwater/kgair)

The time constant for CO2 is found to be 22 hours, and the reciprocal of this is the normal atmospheric ach value (ach = 0.045). The house interior volume is 790 m3 (28,000 ft3), which results in an estimated house infiltration level of 10 L/s (21 cfm) during this time period. The variation of humidity ratio during the vacancy period results in a time constant of 61 hours. If moisture transport was due purely to the water in the air, we would find that time constant for humidity transport would be the same as that determined for CO2. The 61hour humidity ratio time constant found from the Figure 8 data is roughly (very roughly) equivalent to the ratio of the moisture mass capacitance of the house per infiltration air mass flow. The moisture mass capacitance of the house (again, very roughly) is the sum of the air mass and an apparent building moisture absorption mass. Using the air infiltration level determined from the CO2 analysis and the humidity ratio time constant, we find
86 ASHRAE Journal

temperature (°F)

0.002

0.000 12/28 (12 a.m.) 1/7

1/17

1/27

2/6

2/16

2/26

3/8

Figure 6: Interior ambient and exterior ambient humidity ratios for Equinox House from January 2011 to early March 2011.
2,500 CO2 Sensor VOC Sensor 2,000

co2 and Voc (ppm)

1,500

1,000

500

0 12/28 (12 a.m.) 1/7

1/17

1/27

2/6

2/16

2/26

3/8

Figure 7: Interior carbon dioxide and volatile organic compound levels for Equinox House from January 2011 to early March 2011.
ashrae.org May 2011



ASHRAE Journal - May 2011

Table of Contents for the Digital Edition of ASHRAE Journal - May 2011

ASHRAE Journal - May 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Seismic Restraint
Plug Load Design Factors
Technology Award Case Studies:
State-of-Art School
Green School Lab
Eco-Friendly, Affordable, School
Building Sciences
Special Section
InfoCenter
Solar NZEB Project
Emerging Technologies
IAQ Applications
Washington Report
International Column
Products
People
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2011 - Intro
ASHRAE Journal - May 2011 - ASHRAE Journal - May 2011
ASHRAE Journal - May 2011 - Cover2
ASHRAE Journal - May 2011 - 1
ASHRAE Journal - May 2011 - 2
ASHRAE Journal - May 2011 - Contents
ASHRAE Journal - May 2011 - Commentary
ASHRAE Journal - May 2011 - 5
ASHRAE Journal - May 2011 - Industry News
ASHRAE Journal - May 2011 - 7
ASHRAE Journal - May 2011 - 8
ASHRAE Journal - May 2011 - 9
ASHRAE Journal - May 2011 - 10
ASHRAE Journal - May 2011 - 11
ASHRAE Journal - May 2011 - 12
ASHRAE Journal - May 2011 - 13
ASHRAE Journal - May 2011 - Letters
ASHRAE Journal - May 2011 - 15
ASHRAE Journal - May 2011 - 16
ASHRAE Journal - May 2011 - 16a
ASHRAE Journal - May 2011 - 16b
ASHRAE Journal - May 2011 - 17
ASHRAE Journal - May 2011 - Meetings and Shows
ASHRAE Journal - May 2011 - 19
ASHRAE Journal - May 2011 - Seismic Restraint
ASHRAE Journal - May 2011 - 21
ASHRAE Journal - May 2011 - 22
ASHRAE Journal - May 2011 - 23
ASHRAE Journal - May 2011 - 24
ASHRAE Journal - May 2011 - 25
ASHRAE Journal - May 2011 - 26
ASHRAE Journal - May 2011 - 27
ASHRAE Journal - May 2011 - 28
ASHRAE Journal - May 2011 - 29
ASHRAE Journal - May 2011 - Plug Load Design Factors
ASHRAE Journal - May 2011 - 31
ASHRAE Journal - May 2011 - 32
ASHRAE Journal - May 2011 - 33
ASHRAE Journal - May 2011 - 34
ASHRAE Journal - May 2011 - 35
ASHRAE Journal - May 2011 - State-of-Art School
ASHRAE Journal - May 2011 - 37
ASHRAE Journal - May 2011 - 38
ASHRAE Journal - May 2011 - 39
ASHRAE Journal - May 2011 - 40
ASHRAE Journal - May 2011 - 41
ASHRAE Journal - May 2011 - 42
ASHRAE Journal - May 2011 - 43
ASHRAE Journal - May 2011 - Green School Lab
ASHRAE Journal - May 2011 - 45
ASHRAE Journal - May 2011 - 46
ASHRAE Journal - May 2011 - 47
ASHRAE Journal - May 2011 - 48
ASHRAE Journal - May 2011 - 49
ASHRAE Journal - May 2011 - 50
ASHRAE Journal - May 2011 - 51
ASHRAE Journal - May 2011 - Eco-Friendly, Affordable, School
ASHRAE Journal - May 2011 - 53
ASHRAE Journal - May 2011 - 54
ASHRAE Journal - May 2011 - 55
ASHRAE Journal - May 2011 - 56
ASHRAE Journal - May 2011 - 57
ASHRAE Journal - May 2011 - Building Sciences
ASHRAE Journal - May 2011 - 59
ASHRAE Journal - May 2011 - 60
ASHRAE Journal - May 2011 - 61
ASHRAE Journal - May 2011 - 62
ASHRAE Journal - May 2011 - 63
ASHRAE Journal - May 2011 - 64
ASHRAE Journal - May 2011 - 65
ASHRAE Journal - May 2011 - 66
ASHRAE Journal - May 2011 - 67
ASHRAE Journal - May 2011 - InfoCenter
ASHRAE Journal - May 2011 - 69
ASHRAE Journal - May 2011 - 70
ASHRAE Journal - May 2011 - 71
ASHRAE Journal - May 2011 - 72
ASHRAE Journal - May 2011 - 73
ASHRAE Journal - May 2011 - 74
ASHRAE Journal - May 2011 - 75
ASHRAE Journal - May 2011 - 76
ASHRAE Journal - May 2011 - 77
ASHRAE Journal - May 2011 - Solar NZEB Project
ASHRAE Journal - May 2011 - 79
ASHRAE Journal - May 2011 - 80
ASHRAE Journal - May 2011 - 81
ASHRAE Journal - May 2011 - 82
ASHRAE Journal - May 2011 - 83
ASHRAE Journal - May 2011 - 84
ASHRAE Journal - May 2011 - 85
ASHRAE Journal - May 2011 - 86
ASHRAE Journal - May 2011 - 87
ASHRAE Journal - May 2011 - 88
ASHRAE Journal - May 2011 - 89
ASHRAE Journal - May 2011 - Emerging Technologies
ASHRAE Journal - May 2011 - 91
ASHRAE Journal - May 2011 - 92
ASHRAE Journal - May 2011 - 93
ASHRAE Journal - May 2011 - 94
ASHRAE Journal - May 2011 - 95
ASHRAE Journal - May 2011 - IAQ Applications
ASHRAE Journal - May 2011 - 97
ASHRAE Journal - May 2011 - 98
ASHRAE Journal - May 2011 - 99
ASHRAE Journal - May 2011 - 100
ASHRAE Journal - May 2011 - 101
ASHRAE Journal - May 2011 - Washington Report
ASHRAE Journal - May 2011 - 103
ASHRAE Journal - May 2011 - International Column
ASHRAE Journal - May 2011 - 105
ASHRAE Journal - May 2011 - 106
ASHRAE Journal - May 2011 - Products
ASHRAE Journal - May 2011 - 108
ASHRAE Journal - May 2011 - People
ASHRAE Journal - May 2011 - Classified Advertising
ASHRAE Journal - May 2011 - 111
ASHRAE Journal - May 2011 - Advertisers Index
ASHRAE Journal - May 2011 - Cover3
ASHRAE Journal - May 2011 - Cover4
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