Post this in the Windows forum. The pros there know their stuff.

Some manufacturers recommend exterior caulk under the nailing fin in addition to flashing as Worthy described. At the interior, most energy codes require low expanding foam in the gap between the window frame and the wall framing to meet air barrier requirements.

Look at what the window manufacturer's installation instructions recommends and the applicable energy code requirements and make them part of the contract.

Kasson & Keller, like all window manufacturers, makes different grades of windows. Which model and type are being offered and which did the homeowners you called use?.

--- Here are Kasson & Keller's installation instructions --- They are a bit disorganized but quite good. You didn't say where the project is located (other than by your name) but if you are near the ocean you should use the sill pan flashing option.

Sit down with the builder and determine how your windows will be installed and how the weather/air barrier will be integrated into that system and make it physically part of the written contract and make sure the installers have those instructions on site.

Kasson & Keller's installation instructions from their web site:

The internet display clips the bottom of the pages. Here are the full pages:

IMO these instructions are instruments of service and have been placed in the public domain by Kasson & Keller on their website and you should be able to include them in your contract with notes for alternate features and details without specific permission from the authors.

Nothing about them is a high quality window, average at best performance.

JDS thank you for providing such a detailed reply. Or builder is not trying to sell us additional weather proofing, it was just a comment made by his customer. We spoke to a few other customers this past weekend who all had good things to say about the windows. What I like about these windows so far is that they can only be installed by builders they've selected and trained to assure proper installation. The downside is there is no showroom. I have to set an appt with my builder to see a home he's built using those windows.

Here is what was written in our contract. We live in the northeast, not near any waterfront. It's not very specific, so should this be re-worded to protect us. Also he mentions caulk in the interior, but according to those installation instructions you provided, I also see use of caulk on the exterior.

Exterior Notes:

House wrap (Armor Wrap) entire house. Tape all joints air tight. Weather tight window wrap around all windows. Home will be made as air tight as possible for energy efficiency.

Interior Notes:

Paint and caulk all windows, doors and trim (satin white)

You still haven't told us which model window is being proposed, only the manufacturer's name so all I can tell you is that it appears to be a company that supplies windows to builders which is not a good sign.

The "interior and exterior notes" do not address the installation of the windows at all. You should add a requirement that the builder use the manufacturer's published installation instructions with a reference to which features you want since the instructions seem to recommend more than one method (i.e. sill flashing or not)

It appears the builder is not offering you a real construction specification, just a list of features which is common but it will not protect you.

There are very few acceptable house wraps on the market and since I can't find any information about Armor Wrap I must assume it is an error or a local lumberyard brand. In any case, it is unlikely to be acceptable so I strongly recommend you ask for Tyvek or Typar. It will be worth the additional cost. Alternatively, tell me the correct name and manufacturer of the wrap.

I am in MA; where in New England is the house located?