I recently received an offer via email from an construction employer. I would like to negotiate and was wondering if email would be appropriate.

If you are interested in the position (if you can get the salary worked out) respond to the writer asking for a time in which you can meet to discuss the offer.
Email does not work well as a negotiating tool. There is no human response and you are unable to pick up general body language.
Salary is a major part of any position and deserves face to face communication. Besides, you do not want the employer to take this to mean that you would rather hide behind email then to meet this head on.