Insulation Details

Insulation is a great way to save on energy bills. I am happy to report that new building codes do a reasonable job of ensuring reasonable energy bills. When we compared our home to homes built in the 50's, even those who upgraded to insulating windows and added attic insulation the savings were dramatic with our energy costs about 35% of theirs. But when we compared our house to newer built homes the savings were a more modest 70% of theirs. Below is a heat loss model that shows the energy savings for a typical 2000 sqft home using standard 2x4 construction with double pane windows, using 2x6 with insulating sheathing and low e windows, and finally compared to ICF and SIP construction with low-e/argon windows. Air infiltration was reduced as both ICF's and SIP's makes a very tight house adding to energy efficiency.

One advantage of using ICF's and SIP's is they are made of of foam insulation which holds it's full R-value under all conditions. Fiberglass insulation looses some of it's insulation value in colder temperatures. This is because the vapor trapped in the walls add dampness and/or ice which drops the effective R value.

	Here you can see the frost on our SIP roof. There is a good coating of frost on the main roof indicating there is very little heat loss.
	You can see the neighbors roof at the same time as the above shot. The house to the right only has frost on the eves of the roof indicating heat loss through most of the roof. The other neighbor has a light coating indicating better insulation than the house on the right but not as good as the SIP roof.

The analysis shows a typical January bill of $145 in a code constructed home, $108 for a well insulated 2x6 construction home and $68 for a SIP/ICF home. The costs are of 2001 at $.055/kwh. When one adds passive solar orientation, heating costs are further reduced. This is only the cost to heat and cool. Total savings are not as great as most people have a similar base level of energy use for lights, cooking and other appliances.

Inside Winter Temp		72
Inside Summer Temp		75
Outside Winter Temperature		30
Outside Summer		80
% of house shaded		20%
Cost/KW		$0.065
Air Conditioning SEER		11
Latent heat gal		3	19,457	BTU's
Allowance for latent heat & fans		80%
HSPF		7

		2x4 with wood sheathing			2X6 with insulating sheathing			ICF/SIP construction
			Winter	Summer		Winter	Summer		Winter	Summer
Heat Loss BTU/hr			(19,763)	2,965		(15,896)	2,311		(11,781)	1,645
BTU/Day			(474,321)	71,162		(381,511)	55,453		(282,735)	39,481
Living BTU's / day			50,000	40,000		50,000	40,000		50,000	40,000
Solar Gain South			63,000	8,750		63,000	8,750		63,000	8,750
Solar Gain E/W			4,000	60,000		4,000	60,000		4,000	60,000
Latent heat loss				19,457			17,511			15,566
Net (Loss) gain BTU/Day			(357,321)	199,370		(264,511)	181,715		(165,735)	163,796
KW per day			104.66	22.66		77.48	20.65		48.55	18.61
Estimated $/month			$ 145.78	$ 44.18		$ 107.92	$ 40.27		$ 67.62	$ 36.30
						26%	9%		54%	18%
			Winter	Summer		Winter	Summer		Winter	Summer
	Area	R	Heat Loss	Heat Gain	R	Heat Loss	Heat Gain	R	Heat Loss	Heat Gain
1st floor N Wall	380	11.5	-1388	165	19.8	-806	96	50	-319	38
1st floor N Window	60	1.9	-1326	158	2.4	-1050	125	3.5	-720	86
1st W window	40	1.9	-884	189	2.4	-700	150	3.5	-480	103
1st floor W Wall	240	11.5	-877	188	19.8	-509	109	40	-252	54
1st S window	70	1.9	-1547	332	2.4	-1225	263	3.5	-840	180
1st S window header	42	4	-441	95	10	-176	38	50	-35	8
1st Door	40	10	-168	36	10	-168	36	10	-168	36
1st S wall	308	11.5	-1125	241	19.8	-653	140	50	-259	55
1st E wall	280	11.5	-1023	219	19.8	-594	127	50	-235	50
1st Roof	1925	30	-2695	578	30	-2695	578	31	-2608	559
1st floor	1925	19	-1013	-101	19	-1013	-101	19	-1013	-101
Air Loss cubic ft	15400		-7277	866		-6306	751		-4851	578

Note I use total effective R for walls not the insulation value. While the insulation in the wall is R13 the studs have an R of 3.5. On the average there is a stud every 12 inches and a bottom plate and two top plates. By averaging the surface area the effective R value is 11.5.