The usual guidance is offered by most airlines, which is to arrive 2 hours before a domestic flight or 3 hours for an International flight. Interestingly the Airports own website says 2 hours is sufficient regardless of destination. Factor in how you are getting to the airport and be aware that some parking lots are located some distance from the airport, so for holidays and other busy times you should consider leaving home a little earlier.
Your IAH security wait times at Bush Airport can be shortened with TSA PreCheck membership. Check out today's estimated TSA PreCheck wait times at IAH Airport above in addition to open lane info. To find out more about joining or renewing TSA PreCheck membership visit and the associated benefits visit https://www.tsa.gov/precheck.
Security processing on the whole is as efficient as you would expect at IAH, though as with any large airport in the US, it can sometimes take what feels like a very long time to get processed at customs and immigration. If arriving at roughly the same time as other International flights lines in the security hall can be long. Overseas visitors connecting at Houston Bush Airport will have to collect and re-check their luggage before their onward travel.
For further details about the security wait times at Houston International Airport, TSA PreCheck, Global Entry, baggage allowances, lost and found and more visit https://www.fly2houston.com/iah/security