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Air Space R-values

 

HEAT TRANSMISSION THROUGH BUILDING STRUCTURE ELEMENTS AND AIR SPACES RESISTANCE VALUES

Heat transfer across an air space is the result of the combined effects of conduction, convection and radiation. The thermal resistance of an air space is also dependant on the position or orientation of the air space and the direction of the heat flow, ie: up, down or horizontal.

Since still air is an insulator, the thermal resistance of the air space will be dominated by the level of both convection and radiation. Other effects that influence the thermal resistance of an air space are the emittance values of the bounding surfaces of the air space, the mean indoor and outdoor temperatures and the temperature difference across the air space itself.

The tables below are;

Table 1 | Go to Table 2 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 13mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x 2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
Horiz – up

3 deg

23 0.4361 0.4202 0.4004 0.3586 0.29760 0.142

5 deg

23 0.3960 0.3828 0.3664 0.3311 0.2784 0.1375

7 deg

23 0.3628 0.3517 0.3378 0.3075 0.2615 0.1332
45° – up

3 deg

23 0.4959 0.4754 0.4503 0.3982 0.3243 0.1478

5 deg

23 0.4605 0.4428 0.4209 0.375 0.3088 0.1445

7 deg

23 0.4321 0.4165 0.3971 0.356 0.2957 0.1416
Vert – Horiz

3 deg

23 0.4907 0.4707 0.4461 0.3948 0.3221 0.1473

5 deg

23 0.4879 0.4681 0.4437 0.393 0.3208 0.1471

7 deg

23 0.4840 0.4645 0.4405 0.3904 0.3191 0.1467
45° – down

3 deg

23 0.4748 0.456 0.4329 0.3845 0.3151 0.1459

5 deg

23 0.4786 0.4596 0.4361 0.387 0.3168 0.1462

7 deg

23 0.4809 0.4617 0.438 0.3885 0.3178 0.1464
Horiz – down

3 deg

23 0.4823 0.4629 0.439 0.3893 0.3184 0.1466

5 deg

23 0.4810 0.4617 0.438 0.3885 0.3178 0.1464

7 deg

23 0.4798 0.4606 0.437 0.3877 0.3173 0.1463
Notes:1: The thermal resistance airspace values shown in the above tables are based on Robinson and Powlitch data validated by Oak Ridge National Laboratory.2: If the above table values are to be used for assesement of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The deltaT values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature differences, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.
Table 3 | Go to Table 4 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 20mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x 2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
Horiz – up

3 deg

23 0.4705 0.452 0.4293 0.3816 0.3132 0.1455

5 deg

23 0.4215 0.4066 0.3881 0.3488 0.2907 0.1404

7 deg

23 0.3863 0.3737 0.358 0.3243 0.2735 0.1363
45° – up

3 deg

23 0.5859 0.5576 0.5233 0.4542 0.3605 0.1549

5 deg

23 0.5232 0.5005 0.4727 0.4156 0.3357 0.1501

7 deg

23 0.4769 0.4580 0.4346 0.3858 0.3161 0.1461
Vert – Horiz

3 deg

23 0.7259 0.6829 0.6322 0.534 0.409 0.1632

5 deg

23 0.6789 0.6411 0.5963 0.5082 0.3937 0.1607

7 deg

23 0.6491 0.6145 0.5732 0.4913 0.3835 0.159
45° – down

3 deg

23 0.7207 0.6783 0.6283 0.5312 0.4074 0.1629

5 deg

23 0.7062 0.6654 0.6172 0.5233 0.4027 0.1622

7 deg

23 0.6916 0.6525 0.6061 0.5153 0.3979 0.1614
Horiz – down

3 deg

23 0.7144 0.6727 0.6235 0.5278 0.4054 0.1626

5 deg

23 0.7114 0.67 0.6212 0.5261 0.4044 0.1625

7 deg

23 0.7084 0.6674 0.6189 0.5245 0.4034 0.1623
Notes:1: The thermal resistance airspace values shown in the above tables are based on Robinson and Powlitch data validated by Oak Ridge National Laboratory.2: If the above table values are to be used for assesement of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The deltaT values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature differences, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.
Table 8 | Back to Table 7 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 90mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
18° – up

3 deg

23 0.5889 0.5601 0.5255 0.4557 0.3613 0.155

5 deg

23 0.5327 0.5091 0.4803 0.4213 0.3394 0.1508

7 deg

23 0.4904 0.4704 0.4457 0.3945 0.3217 0.1472
22.5° – up

3 deg

23 0.5958 0.5664 0.531 0.4598 0.3639 0.1555

5 deg

23 0.5386 0.5145 0.4851 0.425 0.3418 0.1513

7 deg

23 0.4956 0.4751 0.45 0.3978 0.324 0.1477
22.5° – down

3 deg

23 1.6444 1.4157 1.1966 0.8723 0.5752 0.1835

5 deg

23 1.5489 1.3408 1.1397 0.8386 0.5586 0.1815

7 deg

23 1.4719 1.2802 1.0933 0.8107 0.5447 0.1798
18° – down

3 deg

23 1.7709 1.5128 1.2682 0.912 0.5929 0.1853

5 deg

23 1.6771 1.4407 1.2145 0.8811 0.5781 0.1836

7 deg

23 1.6002 1.3813 1.17 0.8551 0.5656 0.1821
Notes:1: The thermal resistance airspace values shown in the above tables are based on interpolated data.2: If the above table values are to be used for assessment of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The delta T values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature difference, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.
Table 5 | Go to Table 6 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 40mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x 2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
Horiz – up

3 deg

23 0.5112 0.4894 0.4629 0.408 0.3307 0.1491

5 deg

23 0.4613 0.4436 0.4216 0.3756 0.3091 0.1446

7 deg

23 0.4245 0.4094 0.3907 0.3508 0.2922 0.1407
45° – up

3 deg

23 0.5947 0.5655 0.5303 0.4595 0.3638 0.1555

5 deg

23 0.5317 0.5083 0.4797 0.4209 0.3392 0.1508

7 deg

23 0.4866 0.4669 0.4426 0.3921 0.3203 0.147
Vert – Horiz

3 deg

23 0.8264 0.7711 0.7072 0.5865 0.4391 0.1678

5 deg

23 0.7161 0.6742 0.6248 0.5287 0.4059 0.1627

7 deg

23 0.6390 0.6054 0.5653 0.4854 0.3799 0.1584
45° – down

3 deg

23 1.1046 1.008 0.9014 0.7142 0.507 0.1768

5 deg

23 0.9791 0.9024 0.8161 0.6595 0.4788 0.1733

7 deg

23 0.8859 0.8227 0.7503 0.6159 0.4554 0.1701
Horiz – down

3 deg

23 1.2749 1.1479 1.0117 0.7817 0.5401 0.1807

5 deg

23 1.2565 1.1329 1.0001 0.7747 0.5367 0.1803

7 deg

23 1.2394 1.119 0.9892 0.7682 0.5336 0.18
Notes:1: The thermal resistance airspace values shown in the above tables are based on Robinson and Powlitch data validated by Oak Ridge National Laboratory.2: If the above table values are to be used for assesement of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The deltaT values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature differences, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.
Table 7 | Go to Table 8 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 90mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
Horiz – up

3 deg

23 0.5614 0.5353 0.5037 0.4393 0.3511 0.1531

5 deg

23 0.5091 0.4876 0.4612 0.4066 0.3299 0.1489

7 deg

23 0.4698 0.4514 0.4287 0.3812 0.3129 0.1454
45° – up

3 deg

23 0.6301 0.5974 0.5583 0.4803 0.3767 0.1578

5 deg

23 0.568 0.5413 0.509 0.4434 0.3536 0.1536

7 deg

23 0.5214 0.4988 0.4712 0.4144 0.335 0.15
Vert – Horiz

3 deg

23 0.7902 0.7395 0.6805 0.5681 0.4287 0.1663

5 deg

23 0.6846 0.6462 0.6007 0.5114 0.3956 0.161

7 deg

23 0.6137 0.5827 0.5454 0.4707 0.3708 0.1568
45° – down

3 deg

23 1.0114 0.9298 0.8384 0.674 0.4864 0.1743

5 deg

23 0.9077 0.8414 0.7658 0.6263 0.461 0.1709

7 deg

23 0.8303 0.7745 0.71 0.5885 0.4402 0.168
Horiz – down

3 deg

23 2.2773 1.9015 1.5548 1.0706 0.6639 0.1927

5 deg

23 2.19 1.8402 1.5136 1.0509 0.6562 0.1921

7 deg

23 2.1134 1.7858 1.4766 1.0329 0.6492 0.1915
Notes:1: The thermal resistance airspace values shown in the above tables are based on Robinson and Powlitch data validated by Oak Ridge National Laboratory.2: If the above table values are to be used for assesement of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The deltaT values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature differences, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.
Table 9 | Other Tables |

Thermal Resistance of Air Films
Resistance (m².K/W)
Wind speed (m/s) Surface position Direction of heat flow High emittance surface Low emittance surface
Still air Horizontal Up 0.11 0.23
Down 0.16 0.80
22.5°-slope Up 0.11 0.24
Down 0.15 0.6
45°-slope Up 0.11 0.24
Down 0.13 0.39
Verticle Horizontal 0.12 0.30
6.00 m/s (winter) Any position Any direction 0.03
3.00 m/s (summer) Any position Any direction 0.04
0.50 m/s (internal air movement) Any position Any direction 0.08
Table 2 | Back to Table 1 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 13mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
18° – up

3 deg

23 0.46 0.4423 0.4204 0.3744 0.3083 0.1443

5 deg

23 0.4218 0.4068 0.3882 0.3487 0.2906 0.1403

7 deg

23 0.3905 0.3776 0.3615 0.3269 0.2752 0.1366
22.5° – up

3 deg

23 0.466 0.4478 0.4254 0.3784 0.311 0.1449

5 deg

23 0.4283 0.4128 0.3937 0.3531 0.2936 0.141

7 deg

23 0.3975 0.3841 0.3675 0.3318 0.2786 0.1374
22.5° – down

3 deg

23 0.4786 0.4595 0.436 0.3869 0.3168 0.1463

5 deg

23 0.4798 0.4607 0.4371 0.3878 0.3173 0.1463

7 deg

23 0.4804 0.4812 0.4375 0.3881 0.3176 0.1464
18° – down

3 deg

23 0.4793 0.4601 0.4366 0.3874 0.3171 0.1463

5 deg

23 0.48 0.4609 0.4372 0.3879 0.3174 0.1463

7 deg

23 0.4802 0.461 0.4374 0.388 0.3175 0.1463
Notes:1: The thermal resistance airspace values shown in the above tables are based on interpolated data.2: If the above table values are to be used for assessment of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The delta T values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature difference, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.

 

Table 4 | Back to Table 3 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 20mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
18° – up

3 deg

23 0.5167 0.4942 0.4669 0.4106 0.1493 0.1493

5 deg

23 0.4622 0.4442 0.4219 0.3755 0.1443 0.1443

7 deg

23 0.4225 0.4074 0.3886 0.3489 0.1402 0.1402
22.5° – up

3 deg

23 0.5282 0.5048 0.4763 0.4179 0.1502 0.1502

5 deg

23 0.4724 0.4536 0.4304 0.3822 0.1453 0.1453

7 deg

23 0.4316 0.4159 0.3963 0.3551 0.1412 0.1412
22.5° – down

3 deg

23 0.7176 0.6755 0.6259 0.5295 0.1628 0.1628

5 deg

23 0.7088 0.6677 0.6192 0.5247 0.1624 0.1624

7 deg

23 0.7 0.66 0.6125 0.5199 0.1619 0.1619
18° – down

3 deg

23 0.7169 0.6749 0.6254 0.5292 0.1627 0.1627

5 deg

23 0.7093 0.6682 0.6196 0.525 0.1624 0.1624

7 deg

23 0.7017 0.6614 0.6138 0.5208 0.1619 0.1619
Notes:1: The thermal resistance airspace values shown in the above tables are based on interpolated data.2: If the above table values are to be used for assessment of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The delta T values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature difference, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.
Table 6 | Back to Table 5 | Other Tables |

Thermal Resistance of Parallel Un-ventilated Airspace m².K/W
Width of Airspace 40mm
Facing Surfaces and Emissivities
Orientation of Airspace & Direction of Heatflow Airspace Temperature Difference Mean Temp foil x2 foil x 1 foil x 1 foil x 1 foil x 1 no foil
dT K deg C 0.03/0.03 0.03/0.9 0.05/0.9 0.1/0.9 0.2/0.9 0.9/0.9
18° – up

3 deg

23 0.5446 0.5198 0.4899 0.4286 0.3439 0.1517

5 deg

23 0.4895 0.4695 0.4448 0.3937 0.3211 0.1471

7 deg

23 0.4493 0.4324 0.4115 0.3673 0.3034 0.1432
22.5° – up

3 deg

23 0.553 0.5275 0.4966 0.4338 0.3473 0.1523

5 deg

23 0.4965 0.476 0.4507 0.3983 0.3242 0.1477

7 deg

23 0.4556 0.4382 0.4167 0.3715 0.3063 0.1439
22.5° – down

3 deg

23 1.1898 1.078 0.9566 0.748 0.5236 0.1788

5 deg

23 1.1178 1.0177 0.9081 0.7171 0.5078 0.1768

7 deg

23 1.0627 0.9709 0.8698 0.6921 0.4945 0.1751
18° – down

3 deg

23 1.2068 1.0919 0.9676 0.7547 0.5269 0.1791

5 deg

23 1.1455 1.0407 0.9265 0.7286 0.5135 0.1775

7 deg

23 1.098 1.0005 0.8936 0.7073 0.5023 0.176
Notes:1: The thermal resistance airspace values shown in the above tables are based on interpolated data.2: If the above table values are to be used for assessment of in-situ performance, then the values should be treated as indicative since they will be dependant on prevailing environmental conditions.3: The delta T values shown in the above tables are relative to the temperature difference across parallel reflective airspaces that correspond to overall inside / outside temperature difference, 6K, 12K and 18K as shown in AS/NZS4859.1:2002.

 

 

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