This does not mean that a window that is 24 inches high and 20 inches wide meets the requirements. The window still must meet the net square footage requirements. For example, if the window were 24 inches high, it would have to be 30 inches wide to have a net opening of 5 square feet. Also bear in mind that this is the opening that someone can escape through, not the opening in the wall or the window frame.
A problem that I encounter quite often in my home inspections is that the windows in older homes do not meet these requirements. This is because either the requirements were no in effect at the time the home was built or that the requirement have changes since then.
Do you have to add Egress Windows to an older home?
An older home falls under the Existing building code which states that as long as it met the requirements when it was built, it is considered to be in compliance with the code now. As far as the building code is concerned, you do not have to do anything (that is unless you start remodeling in which case you may have to update some things).
The question is should you?
Many of the homes I inspect have windows that would make it nearly impossible for the average person to get out of in an emergency. Remember that you and your loved ones are going to be living there. Nobody would want to be standing outside their home while it is on fire and know that a member of their family is inside and cannot get out.
If the windows in the home you are buying do not meet the egress requirements, I strongly urge you to consider making modifications to ensure that emergency escape is possible. If that can not be done right away, adding additional smoke and fire detectors would at least be a step in the right direction. I would also recommend saving money now so that the windows can be modified in the very near future.
If you need another reason to modify the windows, do it for me. I would be very upset to hear that one of my customers did not survive in their home because they could not get out in an emergency.