Sefaira Simulation about lowering total energy used per metre square per year

Hi Everyone,
I’m Janet. I have questions about how to lowering the total energy used per metre square per year.
1.Can anyone tell me what can I change the material of the roof and the U-value so that my total energy of the building will decrease?
2.Can anyone tell me what can I change for the roof glazing assembly U- value if I have a big roof skylight at the middle of my building? And the solar heat gain coefficient of the roof glazing?
3. Can anyone tell me what is uses of infiltration type and the design infiltration rate ? I do not understand the function of this section.

You’ll have more options if you upload the envelope to the web-version.
Assign different U-values instead of treated all the same.

1: https://support.sefaira.com/hc/en-us/articles/210495703-Envelope-Optimizations-Glazing-U-Factor?mobile_site=true

2: https://support.sefaira.com/hc/en-us/articles/202287149-Entity-Tagging-in-SketchUp-?mobile_site=true

3: https://support.sefaira.com/hc/en-us/articles/210495923-Envelope-Optimizations-Infiltration-Rates?mobile_site=true