IMPACT OF DIFFERENT SEQUENCES OF WALL MATERIALS ON DYNAMIC THERMAL PERFORMANCE OF THE WHOLE BUILDING

 

            Calculations of the annual heating and cooling loads for a one-story ranch house were performed for six types of exterior walls, structures 1–6 presented in Figure 1. We used the whole-building energy analysis program DOE-2.1E [5] and typical meteorological year (TMY) data for six U.S. climates—Atlanta, Denver, Miami, Minneapolis, Phoenix, and Washington D.C. Figure 6 shows the floor plan of the representative house, which was the subject of previous energy efficiency studies [2, 3, 22, 23]. It has approximately 143 m² of living area, 123 m² of exterior wall area, eight windows, and two doors (one door is a glass slider; its impact is included with that of the windows). The elevation wall area includes 106 m² of opaque walls, 14.3 m² of windows, and 2.6 m² of door area. The following building design characteristics and operating conditions were used during computer modeling:

Interior walls:	17.4 kg/m2 of floor area, specific heat 1.09 kJ/kgK
Furniture:	16.1 kg/m2 of floor area, specific heat 1.26 kJ/kgK, thickness 5.04 cm, total equivalent floor area 143 m2
Thermostat set point:	21.1EC heating, 25.6EC cooling
Window type:	double pane clear glass, transmittance 0.88, reflectance 0.08
Roof insulation:	R-5.3 m2K/W

 

            The base case calculation of infiltration used the Sherman-Grimsrud infiltration method option in the DOE 2.1E whole-building simulation model [24]. The average total leakage area was expressed as a fraction of the floor area of. In this work the average total leakage area was assumed as 0.0004. Values of the annual heating, cooling and total energy demand are collected in Table 4.

Results of the whole-building dynamic modeling showed that walls containing massive internal layers—1, 2, and 3—have the best annual thermal performance for the climates considered. The lowest annual heating and cooling loads are observed for wall 3, where all the thermal mass is concentrated in the wall’s interior. Wall 4, with all the insulation material located on the interior side, generates the largest energy demand. The energy demand for other wall configurations—those with concrete cores and insulation placed on both sides of the wall, 5 and 6—falls between the energy demand for wall 4 and the most efficient walls, 1, 2, and 3. These data indicate that for continuously used residential buildings containing massive walls, locating the insulation on the exterior of the walls is preferable with regard to energy savings.

Figure 7 shows the differences in the heating, cooling, and total loads between least-efficient wall 4 and most-efficient wall 3 for all locations; percentage differences are collected in Table 5. Percentage differences are, in most cases, higher for cooling than for heating and are especially high when heating loads are low. The highest differences in total loads, over 11%, can be observed for Atlanta and Phoenix; the lowest is for Minneapolis, 2.3%. This effect thus depends on climate and is more pronounced in the case of large solar gain and diurnal temperature differences. The average difference for all locations is 7.6%.

 

Table 4. Annual energy demand for the typical family house with different types

 of exterior walls  (GJ/year).

Wall No	Atlanta	Denver	Miami	Minneapolis	Phoenix	Washington D.C.
Heating
1	19.95	39.86	0.39	70.42	3.59	35.09
2	19.92	39.84	0.37	70.42	3.56	35.09
3	19.93	39.92	0.34	70.53	3.60	35.17
4	20.80	41.33	0.56	71.19	5.15	35.99
5	20.44	40.83	0.41	70.90	4.75	35.74
6	20.57	41.05	0.44	70.96	4.99	35.88
Cooling
1	6.08	0.78	34.88	1.47	28.84	3.26
2	5.99	0.78	34.60	1.39	28.77	3.17
3	5.91	0.77	34.08	1.33	28.74	3.03
4	7.94	1.98	36.61	2.31	30.75	4.79
5	7.16	1.61	35.45	1.90	30.10	4.04
6	7.44	1.79	35.73	2.04	30.34	4.30
Total
1	26.03	40.64	35.27	71.89	32.43	38.35
2	25.91	40.62	34.97	71.81	32.33	38.25
3	25.84	40.69	34.41	71.86	32.34	38.20
4	28.75	43.32	37.17	73.50	35.90	40.78
5	27.60	42.44	35.86	72.80	34.85	39.78
6	28.01	42.84	36.18	73.00	35.33	40.18