ASHRAE Journal - February 2011 - 66

solar NZEB projEct	
21.0 20.8 20.4 20.2 20.0 19.8 19.6 19.4 19.2 19.0
1	

December Floor surface temperature (°c)

0 –0.5 Floor Heat Flux (W/m2) 10 7
3	 9	 Floor Dimensions (m) 5	 7	

20.6

–1.0 –1.5 –2.0 –2.5 –3.0 –3.5 –4.0 –4.5
1	 3	 9	 Floor Dimensions (m) 5	 7	

10 7 4
11	 13	 15	 17

4
11	 13	 15	 17

1

1

20.8	to	21	 20.6	to	20.8	 20.4	to	20.6	 19.8	to	20	 19.6	to	19.8	 19.4	to	19.6	

20.2	to	20.4	 19.2	to	19.4	

20	to	20.2 19	to	19.2

–0.5	to	0	

–1	to	–0.5	

–1.5	to	–1	

–2	to	–1.5	

–2.5	to	–2

–3	to	–2.5	

–3.5	to	–3	

–4	to	–3.5	

–4.5	to	–4

Figure 2 (left): Floor	surface	temperatures	during	December	2010	with	interior	ambient	temperature	of	21°C	(69.8°F).	Figure 3 (right):	December	floor	surface	heat	flux	levels	with	an	interior	ambient	temperature	of	21°C	(69.8°F)	and	a	ground	temperature	 of	10°C	(50°F)	at	depths	below	5	m	(16.4	ft). and 3 show the floor surface temperature and heat flux from the simulation model for Equinox House in December. At the depth of the footer (1 m [39 in.]) in December, the average ground temperature around the perimeter of the house is 8°C (46.4°F). We also conducted the simulations because we were interested in transient effects of foundations on Equinox House energy performance. Can the ground below a slab be a beneficial seasonal storage mass? Or, will it be a detriment that should be isolated with insulation? Some superinsulated home builders are placing as much as 300 to 400 mm (12 to 16 in.) of Styrofoam below their floors. With a material cost of $175/m3 ($5/ft3), this would be a cost of $10,000 to $15,000. Results from seven foundation situations, Cases 1 through 7, are shown in Table 1. As previously mentioned, Case 3 is the Equinox House configuration with ICF foundation walls and no slab insulation. For Cases 1 and 2, the building interior ambient air temperature is held constant throughout the year at 22°C (71.6°F). The varying ambient temperature cases in Table 1 means November through April are assumed to have an interior ambient temperature of 21°C (69.8°F), May and October are 22°C (71.6°F), June and September are 24°C (75.2°F), and July and August are 25°C (77°F), for an average annual interior ambient temperature of 22.3°C (72.1°F). Figure 4 compares the ground heat transfer for the ICF foundation with uninsulated slab floor cases with constant interior ambient temperature and with variable interior ambient temperature. It’s intuitive that setting the thermostat closer to the outside ambient temperature will reduce building conditioning loads. What is not so apparent is the interaction and impact with the ground heat transfer. Over the course of the year, the total energy transferred to the ground is the same, however the annual distribution of energy transfer significantly impacts the overall house energy requirements. The uninsulated floor with constant interior ambient temperature (Case 1) has less than 10% variation in monthly heat transfer, with an average heat flux of
66	 ASHRAE	Journal	
900 Monthly average Ground Heat transfer (Watts) 800 700 600 500 400 300 200 100 0 0	 1	 Constant	Interior	Temp. Variable	Interior	Temp. 2	 3	 4	 5	 6	 7	 6	in.	EPS	Variable	Interior	Temp. 12	in.	EPS	Variable	Interior	Temp. 8	 9	 10	 11	 12	 13

Month (january = 1)

Figure 4:	Ground	heat	transfer	comparison	for	an	uninsulated	 floor	slab	with	constant	interior	ambient	temperature	and	variable	interior	ambient	temperature	conditions.
–1,200 –1,000 Electrical Energy (kWh) –800 –600 –400 –200 0

Variable	Ground	Loss Variable	No	Ground	Loss 0	 2	 4	
Month (january = 1)

6	in.	EPS	Variable 12	in.	EPS	Variable 8	 10	 12	 14

6	

Figure 5:	 Electrical	 energy	 requirements	 for	 Equinox	 with	 no	 ground	insulation,	perfect	ground	insulation,	6	in.	(150	mm)	EPS	 ground	insulation,	and	12	in.	(300	mm)	EPS	ground	insulation.
ashrae.org	 	 February	 2011



ASHRAE Journal - February 2011

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

ASHRAE Journal - February 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Thermal Coupling of Cooling and Heating Systems
10 Common Problems in Energy Audits
Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
A Guide to Wireless Technologies
Building Sciences
Solar NZEB Project
Emerging Technologies
People
Special Section
InfoCenter
Commissioning
Products
Washington Report
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2011 - ASHRAE Journal - February 2011
ASHRAE Journal - February 2011 - Cover2
ASHRAE Journal - February 2011 - 1
ASHRAE Journal - February 2011 - 2
ASHRAE Journal - February 2011 - Contents
ASHRAE Journal - February 2011 - Commentary
ASHRAE Journal - February 2011 - 5
ASHRAE Journal - February 2011 - Industry News
ASHRAE Journal - February 2011 - 7
ASHRAE Journal - February 2011 - Letters
ASHRAE Journal - February 2011 - 9
ASHRAE Journal - February 2011 - 10
ASHRAE Journal - February 2011 - 11
ASHRAE Journal - February 2011 - 12
ASHRAE Journal - February 2011 - 13
ASHRAE Journal - February 2011 - 14
ASHRAE Journal - February 2011 - 15
ASHRAE Journal - February 2011 - Meetings and Shows
ASHRAE Journal - February 2011 - 17
ASHRAE Journal - February 2011 - Thermal Coupling of Cooling and Heating Systems
ASHRAE Journal - February 2011 - 19
ASHRAE Journal - February 2011 - 20
ASHRAE Journal - February 2011 - 21
ASHRAE Journal - February 2011 - 22
ASHRAE Journal - February 2011 - 23
ASHRAE Journal - February 2011 - 24
ASHRAE Journal - February 2011 - 25
ASHRAE Journal - February 2011 - 10 Common Problems in Energy Audits
ASHRAE Journal - February 2011 - 27
ASHRAE Journal - February 2011 - 28
ASHRAE Journal - February 2011 - 29
ASHRAE Journal - February 2011 - 30
ASHRAE Journal - February 2011 - 31
ASHRAE Journal - February 2011 - 32
ASHRAE Journal - February 2011 - 33
ASHRAE Journal - February 2011 - Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
ASHRAE Journal - February 2011 - 35
ASHRAE Journal - February 2011 - 36
ASHRAE Journal - February 2011 - 37
ASHRAE Journal - February 2011 - 38
ASHRAE Journal - February 2011 - 39
ASHRAE Journal - February 2011 - 40
ASHRAE Journal - February 2011 - 41
ASHRAE Journal - February 2011 - 42
ASHRAE Journal - February 2011 - 43
ASHRAE Journal - February 2011 - A Guide to Wireless Technologies
ASHRAE Journal - February 2011 - 45
ASHRAE Journal - February 2011 - 46
ASHRAE Journal - February 2011 - 47
ASHRAE Journal - February 2011 - 48
ASHRAE Journal - February 2011 - 49
ASHRAE Journal - February 2011 - Building Sciences
ASHRAE Journal - February 2011 - 51
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ASHRAE Journal - February 2011 - Solar NZEB Project
ASHRAE Journal - February 2011 - 63
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ASHRAE Journal - February 2011 - 66
ASHRAE Journal - February 2011 - 67
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ASHRAE Journal - February 2011 - Emerging Technologies
ASHRAE Journal - February 2011 - 71
ASHRAE Journal - February 2011 - 72
ASHRAE Journal - February 2011 - 73
ASHRAE Journal - February 2011 - 74
ASHRAE Journal - February 2011 - 75
ASHRAE Journal - February 2011 - People
ASHRAE Journal - February 2011 - 77
ASHRAE Journal - February 2011 - InfoCenter
ASHRAE Journal - February 2011 - 79
ASHRAE Journal - February 2011 - 80
ASHRAE Journal - February 2011 - 81
ASHRAE Journal - February 2011 - 82
ASHRAE Journal - February 2011 - 83
ASHRAE Journal - February 2011 - 84
ASHRAE Journal - February 2011 - 85
ASHRAE Journal - February 2011 - Commissioning
ASHRAE Journal - February 2011 - 87
ASHRAE Journal - February 2011 - 88
ASHRAE Journal - February 2011 - 89
ASHRAE Journal - February 2011 - 90
ASHRAE Journal - February 2011 - Products
ASHRAE Journal - February 2011 - Washington Report
ASHRAE Journal - February 2011 - Classified Advertising
ASHRAE Journal - February 2011 - 94
ASHRAE Journal - February 2011 - 95
ASHRAE Journal - February 2011 - Advertisers Index
ASHRAE Journal - February 2011 - Cover3
ASHRAE Journal - February 2011 - Cover4
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