I don’t get involved with residential construction very often, but a local locksmith recently asked about the use of double-cylinder deadlocks on single family homes. His position is that he will not install them, but he was looking for a code reference to back him up.
When I checked the Massachusetts One and Two Family Dwelling Code, I found that double-cylinder deadlocks are prohibited. I found the same language in the 2009 edition of the International Residential Code (IRC).
Your local code might contain a different requirement, but here’s the paragraph from the 2009 IRC:
R311.2 Egress door. At least one egress door shall be provided for each dwelling unit. The egress door shall be side-hinged, and shall provide a minimum clear width of 32 inches (813 mm) when measured between the face of the door and the stop, with the door open 90 degrees (1.57 rad). The minimum clear height of the door opening shall not be less than 78 inches (1981 mm) in height measured from the top of the threshold to the bottom of the stop. Other doors shall not be required to comply with these minimum dimensions. Egress doors shall be readily openable from inside the dwelling without the use of a key or special knowledge or effort.