No. You should not have to obligate yourself to maintain a secret to protect a builder who performed faulty workmanship that will likely void the manufacturer's warranty in the event you ever need to make a warranty claim. If you sign an NDA, and then you have a future problem, you are going to have to tell somebody that the original builder screwed this up. At this point, I would be very concerned about this builder and his motivations. If exterior trim is "failing" after only two months, what may fail in three months, or six? What else did he do wrong? Why would you agree to a nondisclosure agreement which will expose you to damages, lawsuits, etc., in the event you "breach" the nondisclosure provisions? Who ever heard of a reputable business that refused to stand behind its product or services without extracting a nondisclosure agreement after it screwed up? If this is an improvement to an existing home (not a newly constructed home), then contact the Maryland Home Improvement Commission, check on his licensing, and file a complaint. No matter what, insist that the contractor honor his existing contractual duties and warranties (there is always an implied warranty to perform in a workmanlike manner, and in accordance with building code and industry standards), without forcing you to enter into a new agreement. You already have a contract with him. You do not need to sign another. If you owe him any more money, don't pay it until he comes back to correct his defective work. I would also call the manufacturer to confirm whether there are any necessary steps or other precautions that need to be taken under these circumstances, in the event there are any latent defects, conditions, etc. (such as water penetration) that would have resulted from this defective installation. It may be you will have to open up more of the exterior siding to check on moisture penetration and to dry it out. What if there is moisture inside your walls, he seals it up, and you get a mold/mildew problem that is not discovered for months or even years? I doubt the builder will offer to do all that is recommended by the manufacturer if you do not insist on it (and determine what those things are on your own). Do not sign the NDA. You may be filing a claim against this guy in the future, and you must be free to disclose everything you know. Homeowners are best advised to have their contracts reviewed by a construction attorney before they sign, not after the work is started and problems arise; but that is par for the course in my business. You should probably consult with an attorney familiar with this area of the law.
If you don't sign the agreement, then you likely will have to spend time and money to go to court, or to the MHIC to make a complaint, in which case, your house sits without repairs and/or you have to pay out of your own pocket to make the necessary repairs. Keep in mind, you may or may not prevail in court or at the MHIC.
The builder is wanting to make things correct and protect itself and its reputation at the same time. Even if you went to court and ended up settling the matter, settlement agreements are usually confidential.
If it were my house, after having legal counsel review the non-disclosure, I'd probably let the builder make the repairs.
DISCLAIMER: Brandy A. Peeples is licensed to practice law in the State of Maryland. This answer is being provided for informational purposes only and the laws of your jurisdiction may differ. This answer based on general legal principles and is not intended for the purpose of providing specific legal advice or opinions. Under no circumstances does this answer constitute the establishment of an attorney-client relationship. For legal advice relating to your specific situation, I strongly urge you to consult with an attorney in your area. NO COMMUNICATIONS WITH ME ARE TO BE CONSTRUED AS ARISING FROM AN ATTORNEY-CLIENT RELATIONSHIP AND NO ATTORNEY-CLIENT RELATIONSHIP WILL BE ESTABLISHED WITH ME UNLESS I HAVE EXPRESSLY AGREED TO UNDERTAKE YOUR REPRESENTATION, WHICH INCLUDES THE EXECUTION OF A WRITTEN AGREEMENT OF RETAINER.
I agree with the prior response, but I would add that it all depends on the wording of the non-disclosure agreement, whether the builder is already obligated under the initial contract to make the repairs and whether there are onerous terms -- such as financial penalties -- if the Non-Disclosure Agreement is violated inadvertantly. If there are any terms in the Non-Disclosure that you are unsure of, or which you do not understand, it is worth the time and money to sit down with a lawyer for a consultation to get this straightened out.