No exterior or historic architectural changes can be completed without a Certificate of Appropriateness or work will be stopped and rolling fines commenced until the home is brought back into compliance. Most historic windows will need to be repaired rather than replaced and modern windows (which look inappropriate for the period and don't actually incur any real energy savings) will rarely be approved for a historic home. Most residents in historic areas will discover their best draft savings is found with insulated curtains.
If it is in a historic area, any alterations to the outside of the structure will need the approval of the historic preservation commission.
Thanks! Your answer is awaiting moderation.