Is it helpful to open a venting skylight only when it's cooler outside then inside the house?

Question

Or is it a good practice to keep it open all the time to vent out the heat that builds up in the house, in this case my kitchen with a high ceiling.

Is it beneficial to leave it open a crack even when the central air is on?

Answer 1

I would close it when the central AC is on. The skylight vent is there to circulate air in the house. However, with only one opening the skylight vent is fairly useless...in order for it to function it has to pull air from somewhere likely from another open window in the house.

In other words, it should be closed if you are using energy to cool your house.

Let me give you another example:

Lets say the temperature outside is 88 degrees and the temperature inside is 72. Now assuming a 5 degree difference between the air on the floor of your kitchen and the roof of your kitchen then you have 77 degrees on the inside of the vent and 88 on the outside of the vent...so you would be trading 77 degrees for 88 degrees.