Enthoo Evolv ATX top vents
The top has vents in the ends as well as side vents.
End Vents:
Ends have 37x open slots 5.5mm x 12.9 mm = 26.3 sq cm of end airflow area.
Side Vents:
10x vents 5 mm x 61.6 mm = 30.8 sq cm side vent area - grill mesh blockage
Mesh has cc 0.85 mm holes with 1.6 mm spacing, so about cc 20% open = 6.1 sq cm of airflow area from 10x stock side vents
Stock venting with mesh has an open area of about 32.4 sq cm
With stock mesh removed it is 56.8 sq cm.
Removing the mesh increases top vent area by about 24.5 sq cm
By comparison a single 120mm fan has about 100 sq cm of open area.
Keep in mind that if top top fan radiator mount is used, all open areas not having fans must be sealed so air being pushed into the top cannot circle back down into case.
The simplest way to get more top airflow is to remove the 4 top mounting screws (2x in back and 2x in front ), pop the top loose and rest it back on the clip mounts.
This raised top 5.5 mm creating a 3mm gap on sides and 5.5mm on front. Case is 505 mm deep x 23.5 mm wide
0.5cm x 23.5cm x 2 = 23.5 sq cm
0.3cm x 50.5cm x 2 = 30.3 sq cm
Additiona l top vent = 53.8 sq cm
53.8 sq cm additional vent by simply removing top mounting screws and setting top on latches.
32.4 sq cm stock top venting.
56.8 sq cm airflow area with side vent mesh removed
110.6 sq cm airflow area with side vent mesh removed and top set on latches
Only draw back is to use top on/off switch, top must be latched back down or lifted off.
A 5.5mm spacer could be added by putting a screw into the push button in top, but thern if someone pushed too hard on the top micro-switch could be broken. I would not recommend it unless the latches in top of case are also spaced up the same amount.
And of course seal all holes not having fans in them in the top fan / radiator mount.