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How to estimate the air gap in a celling/roof?

asked 2020-05-12 16:24:35 -0500

Red Fox's avatar

updated 2020-06-01 11:14:50 -0500


I'm creating a library of materials and making the "construction" in OS so I'm basicly creating a line of materials from outside to inside.

If the roof was horizontal the airgap in the attic would be uniform and I would use an airgap of the peak as 50cm. But with an inclinated roof if I use the peak its not the reality of it cause in the corners it have different heights.

My question is what height I should use in AIRGAP in the creation of a "component" in an inclinated roof as a type of average mesure? I was using half of one of the inclinated sides (aprox. 25cm) so I'm not so far from the peak and the bottom.

While writing I'm seeing how dificult the comunication may be so I use some drawings to try to show my question bettter.


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If this is an attic space, the most common approach is to model the attic as a separate thermal zone.

shorowit's avatar shorowit  ( 2020-05-13 07:50:58 -0500 )edit

Thanks for the help. I've edit the original post to make myself more clear

Red Fox's avatar Red Fox  ( 2020-05-15 12:06:49 -0500 )edit

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answered 2020-05-13 07:30:43 -0500

Masonrybiz's avatar

If I understand your question correctly you are asking, you’re essentially asking how to calculate air gap in an inclinated roof/ceiling in a cubic form (I.e. cu. cm, cu m., etc.). If so, you take half the base (of the triangle made by your rafters/trusses), in this case say it is 10m. & the peak of your roof is 62.86 cm. that equals 6.286 m2. Then say your house is 20m long, multiply last result by 20m for a total of 125.72 m3.

Let me know if I misunderstood your question!

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Thanks for the help. I've edit the original post to make myself more clear

Red Fox's avatar Red Fox  ( 2020-05-15 11:51:04 -0500 )edit

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Asked: 2020-05-12 16:24:35 -0500

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Last updated: Jun 01 '20