Bear Creek Dome Radiant Floor Results
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Tessa Hill and Dennis Odin Johnson – Bear Creek Dome – North Branch, Minnesota
- Model: 1800 mid profile, 49′ diam. dome home
- Location:North Branch, Minnesota. Department of Energy Zone 7A (severe cold-moist) 9000 heating degree days.
- House size:3200 SF; slab on grade. Main floor 2100 sf, upper floor 1100 sf.
- Specifications: 18″ thick dome walls and dome roof, 16″ fiberglass insulation (R-Value=57 in triangles, R-Value=62 in riser walls), vented dome shell; slab has 2″ styrofoam under and 11″ styrofoam on edge of slab. Blower door test was .06 ACH
- Heating system:Radiant floor in 4″ concrete slab using 1500 lf of PEX tubing circulating water. Heating unit is 14 KW Seisco Electric “instant on” boiler with a secondary natural gas “Munchkin” boiler that you can switch to manually. Electric rate is off-peak interruptible rate of 4.2¢ /KW. * Note: Rate increase to 4.8¢ /KW in Feb. 2008 (14% increase).
- Built: 2007, moved into November 2007.
- Heating costs: See below.(Electric billings run from the 7th of each month. Natural gas billings are from the 17th).
- Air conditioning costs: The Summers of 2008, 2009 and 2010 had zero A.C. costs. The outside temps were 90°-95° F many days, yet the highest inside temps were 72°-74° F.
Winter 2007-2008 Radiant floor heating |
Month
Cost
KW Used
July 07 $0 None August 07 $0 September 07 $0 None October 07 $71 1680 kw November 07 $153 3640 kw December 07 $156 3720 kw January 08 $165 3940 kw February 08 $143* 2980 kw March 08 $97 2020 kw April 08 $73 1520 kw May 08 $16 340 kw June 08 —- —- Total: $765
16,660 KW Winter 2008-2009 Radiant floor heating
January, 2009, was extremely cold, the 4th coldest January on record. All of the days were below 32° (0° C) with some periods of 4-5 days where it never was warmer than 0° (-18° C). Month
Electric Heat
4.8¢ /kw
KW Used
Natural gas base monthly fee Actual gas used July 08 $0 None $8 $4.01 August 08 $0 $8 $4.73 September 08 $11 220 kw $8 $3.82 October 08 $55 1140 kw $8 $1.59 November 08 $152 3160 kw $8 $5.10 December 08 $216 4500 kw $8 $3.86 January 09 $244 5080 kw $8 $6.04 February 09 $150 3120 kw $8 $3.64 March 09 $140 2160 kw $8 $3.21 April 09 $30 620 kw $8 $4.21 May 09 $8 180 kw $8 $2.51 June 09 $8 $3.96 Total: $871
16,840 KW Total $96 $46.68 ($3.89) Winter 2009-2010 Radiant floor heating
Instantaneous hot water gas heater Month
Electric Heat
4.8¢ /kw
KW Used
Natural gas base monthly fee Actual gas used July 09 $0 None $8 $2.26 August 09 $0 $8 $1.71 September 09 $25 520 kw $8 $2.11 October 09 $97 2020 kw $8 $4.28 November 09 $115 2400 kw $8 $4.62 December 09 $223 4640 kw . $8 $3.07 January 10 $188 3920 kw $8 $5.00 February 10 $153 3200 kw $8 $3.88 March 10 $ kw $8 $5.96 April 10 $ kw $8 May 10 —- None $8 June 10 —- None $8 Total: $801
16,700 KW Total $96 $32.89 ($3.65)
Winter 2010-2011 Radiant floor heating |
Instantaneous hot water gas heater
Month
(Dates)
Electric Heat
4.8¢ /kw
KW Used
Gas Heating Cost Heating Therms Used Avg.Temp.(F) Natural gas base monthly fee Actual gas used 7/9/10 – 8/8/10 —- None 76 $8 $5.64 8/8/10 – 9/8/10 —- 78 $8 $3.45 9/8/10 – 10/8/10 $22 460 kw 69 $8 $3.94 10/8/10 – 11/7/10 $69 1440 kw 60 $8 $3.84 11/7/10 – 12/9/10 $175 3640 kw 47 $8 $3.69 12/9/10 – 1/10/11 $229 4780 kw . 21 $8 $3.67 1/10/11 – 2/7/11 $145 3020 kw 16 $8 $6.96 1/18/11 – 2/18/11 $65 73 8 2/19/11 – 3/20/11 $96 108 27 $4.50 3/20/11 – 4/18/11 $60 62 42 4/18/11 – 5/19/11 $32 33 52 $4.50 5/19/11 – 6/19/11 $5 5 68 Total: $640
13,340 KW $258
281 Th.
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Instantaneous hot water gas heater(used for baths, laundry, kitchen, etc.) Month
(Dates)
Electric Heat
4.8¢ /kw
KW Used
Gas Heating Cost Heating Therms Used Avg.TempF (C) Base monthly fee Actual gas used 6/19/11 – 7/19/11 —- None 76 (24) $9 $3.63 7/19/11 – 8/16/11 —- 78 (25) $9 $5.18 8/16/11 – 9/15/11 —- None 71 (22) $9 $3.55 9/15/11 – 10/16/11 —- None 62 (16) $9 $5.60 10/16/11 – 11/14/11 —- None $36 45 47 (9) $9 $4.50 11/14/11 – 12/15/11 —- None $89 107 32 (0) $9 $4.50 12/15/11 – 1/18/12 —- None $112 139 29 (-2) $9 $4.50 1/18/12 – 2/16/12 —- None $92 118 25 (-4) $9 $4.50 2/16/12 – 3/18/12 —- None $68 88 39 (4) $9 $4.50 3/18/12 – 4-17-12 —- None $25 38 53 (12) $9 $4.50 4-17-12 – 5-16-12 —- None $7 11 58 (14) $9 $4.50 5-16-12 – 6-17-12 —- None $13 20 70 (21) $9 $4.50 Total: $—-
None $442
566 Th.
Kim and Steve Long – Perry, Iowa
- Model: 1500 low profile, 45′ diam. dome home
- Location:Perry, Iowa. Department of Energy Zone 5A (cold-moist) 6500 heating degree days.
- House size:3600 SF total; 1700 SF basement, 1700 SF main floor, 200 SF loft.
- Specifications: 2×8 dome walls and dome roof. 7″ sprayed-in place foam (R-Value=27), unvented dome shell, no vapor barrier, permanent treated wood foundation walls with 2×8 studs, 7″ sprayed-in-place Icynene “soft” foam (R-Value=27). Basement walls have one side approximately 2/3 out of the ground. Blower door test was .03 ACH
- Heating system:Radiant floor in basement concrete slab using PEX tubes circulating water and PEX tubes under plywood of main floor with insulation under; heating unit is “Munchkin” natural gas boiler. There is a natural gas burning fireplace on the main floor, however; it is not used for the main heating. It is rated at 42,000 BTU output with 86% efficiency.
- Built: 2006 (moved in March 2007)
- Heating costs: See below. Please note that the domestic hot water system is also operating with natural gas. The average usage is based on 30 therms per month and is not in the heating total. *Also note that this dome was not complete until Fall 2008. The insulation under the main floor had not been finished, and the heating costs decreased as the proper insulation was finalized. Billings run from the 10th of each month through August 2009, when they switched to show billings to the 27th of each month.
- Also note that due to rising energy costs, the cost per therm nearly doubled this past heating season. The price per therm is noted in the chart below.
Month
Cost
Price pertherm KW or Therms Used
July 2007 $0 None August 2007 $0 None September 2007 $0 None October 2007 $35 $.60 33 therms * November 2007 $111 $.73 100 therms * December 2007 $142 $.74 128 therms * January 2008 $169 $.77 150 therms * February 2008 $120 $.86 134 therms * March 2008 $72 $1.00 80 therms * April 2008 —- $1.02 —- May 2008 —- $1.12 —- June 2008 —- —- 2007-2008Total: $649.00*
(see note above)
625 Therms Month
Cost
Price pertherm KW or Therms Used
Avg. Temperature Mean Avg. Temperature
July 2008 August 2008 September 2008 October 2008 November 2008 December 2008 January 2009 February 2009 March 2009 April 2009 May 2009 $5 $.77 7 65 June 2009 —- —- 74 2008-2009Total: $0
July 2009 —- —- 72 August 2009 —- —- 74 September 2009 —- —- 68 October 2009 $28 $.79 35 51 November 2009 $43 $.86 50 48 December 2009 $122 $.84 146 27 January 2010 $129 $.95 136 17 February 2010 $139 $.94 148 19 March 2010 $63 $.89 71 41 April 2010 $27 $.88 31 58 May 2010 $22 $.88 25 62 June 2010 —- —- 74 2009-2010Total: $573.00
642 Therms 50.0 Mean Avg. Temperature July 2010 —- —- 78 August 2010 —- —- 78 September 2010 —- —- 68 October 2010 $6 $.98 6 60 November 2010 $60 $.86 70 42 December 2010 $109 $.87 125 23 January 2011 $108 $.86 125 19 February 2011 $108 $.87 124 27 March 2011 $64 $.86 125 19 April 2011 $29 $.90 32 50 May 2011 $10 $.97 —- 61 June 2011 —- —- 71 2010-2011Total: $494.00
625 Therms 49.7 Mean Avg. Temperature July 2011 —- —- 80 August 2011 —- —- 78 September 2011 —- —- 66 October 2011 $7 $.99 7 59
Joyce and Rich Peake – Arden Hills, Minnesota
- Model: 1250 Low Profile 40′ diam dome home
- Location:Mounds View, Minnesota. Department of Energy Zone 6A (severe cold-moist) 8400 heating degree days.
- House size:3200 SF; walk out basement 1350 SF, main floor 1450 SF, loft 450 SF
- Specifications: 15″ thick dome walls & dome roof, 12″ fiberglass insulation (R-Value = 44), vented dome shell, riser walls 45″ high, 15″ thick with 15″ fiberglass (R-Value=51) Permanent treated wood foundation walls with 2×8 studs, 7 1/4″ fiberglass insulation (R-Value = 27)(Lower floor has 2×8 walls 3′ in ground with a walk out patio door on one side.)
- Heating system:Forced air, natural gas, high efficiency furnace (no wood stove)
- Built: 1984
- Heating costs: (Billings run from the 12th of each month.)
Month
Cost
Cost per therm KW or Therms Used
June 2007 $12.00 $1 4 July 2007 $12.00 $1 4 Aug 2007 $11.00 $1 3 Sept 2007 $12.00 $1 4 Oct 2007 $37.00 96¢ 30 Nov 2007 $96.00 $1.10 80 Dec 2007 $112.00 $1.10 92 Jan 2008 $116.00 $1.05 103 Feb 2008 $106.00 $1.15 92** March 2008 $65.00 $1.12 51 April 2008 $28.00 $1.18 17 May 2008 $8 base charge 0 June 2008 $8 base charge 0 Total: $530.00
398 Therms Winter 2008-2009 July, 2008 $8 base charge 0 Aug., 2008 $8 base charge 0 Sept., 2008 $8 base charge 0 Oct., 2008 $31 82¢ 28 Nov., 2008 $90 95¢ 86 Dec., 2008 $115 82¢ 130 Jan., 2009 $91 77¢ 108 Feb. 2009 $65 63¢ 90 March 2009 $32 53¢ 45 April 2009 $12 50¢ 8 May 2009 $8 base charge 0 June 2009 $8 base charge 0 Total: $476.00
495 Therms Winter 2009-2010 July 2009 $8 base charge 0 Aug. 2009 $8 base charge 0 Sept. 2009 $12 40¢ 10 Oct. 2009 $21 48¢ 27 Nov. 2009 $37 43¢ 67 Dec. 2009 $74 68¢ 109 Jan. 2010 $67 63¢ 93
** Indicates rate increase
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