A Lauzon New Step engineered floor(chosed because we have radiant heat) installed 4 months ago - several of the boards have the top "wood" layer peeling off. One board has the whole top off. When complained to the installer, a claim was made and an inspector came. They are saying that my house is too dry, and that is why - humidity level @ 20%. Never prior to installing was humidity mentioned. Is this possible?

While 20% RH is too low, I think the peeling veneer is most likely a flawed board. It should not be much trouble for the installer to replace a few boards. See if he will do it for free or a low cost. Lauzon should have paid for the replacement. Here's their warranty. It does state RH should be at 35% or higher BUT, this is to reduce gapping at the seams and joints. The lamination should not be affected.

I. LIFETIME STRUCTURAL LIMITED WARRANTY
As LAUZON’s reputation has been built on reliable premium quality collections, our NextStep Fusion
Engineered Flooring is guaranteed to be free of structural defects in lamination, milling or grading, as a
result of manufacturing, for the lesser of (a) the lifetime of the Buyer, or (b) as long as the Buyer owns the
home in which the LAUZON product is installed. Wood is a natural product whose characteristics include
minor color variations, grain variations, knots and mineral streaks, which are not considered defects. Given
that wood is a product of nature, minor quality variations of up to five percent (5%) of total square
footage/meters purchased are not covered by this limited warranty (as per industry standards). Should an
individual piece be doubtful as to grade, manufacture or finish, the piece should not be installed. In geographic
areas that experience extreme climate and humidity conditions, it is natural, due to the inherent
properties of wood, for some minor expansion and contraction to occur which could result in some visual
changes. These occurrences are not covered by this warranty but should self-correct with seasonal climate
changes. To minimize this visual change, it is important to maintain relative humidity between 35% and
65% and to control radiant heating systems in a way not to exceed the maximum surface temperature
recommended in the LAUZON NextStep Installation Guide.

Replacing a board within an engineered installation is tricky at best, although it can be done.
Since most engineered products consist of a number of equal length sticks, our service dept has come up with an ingenious method of "board replacement. We plane the required number of proper length boards at the shop; planing the entire under-structure of the board, leaving only the top veneer. On site, we remove the top layer of the affected board(s) and using a combination of urethane adhesive for holding power, and a few drops of hot glue to hold the fillet in place while the real glue has a chance to set up.
A most remarkable, invisible resulting repair. Have been kissed by a client once for doing this. Unfortunately, he was a guy. (lol)

The financial brunt of this type of repair should be covered by the manufacturer since it is unlikely that lack of humidity would cause a fillet to come loose from the under-structure of the board.

However, I suggest you get humidity controls in place to avoid other problems, that would be your responsibility

Delaminating engineered is a manufacturing issue. The boards are defective.

Now, let's not automatically jump to the conclusion that the boards are defective.....are we talking actual delamination here, or wood sheer? Delamination is adhesive failure, plain and simple. On the other hand, I have seen floors in low humidity conditions that dry out so quickly, the veneer cups drastically and actually tears the wood fibers as it pulls away....the glue has not failed at all..you can actually see the torn fibers still glued to the plywood core! One particular job specifically comes to mind....the builder was claiming delamination and a manufacturing defect, but uninstalled boards were available for testing. All the samples passed a 3 cycle soak AND a 1 cycle boil without any adhesive failure...the wood tore itself away from the core because of the jobsite conditions.

I dont think anyone jumped to conclusions. The description of the posters problem was that the top layer was peeling off.
I understand and agree with what you are saying about low humidity conditions causing curling of the top veneer and and tearing the wood fibres.
But this would normally be evident in far more than a few boards if lack of humidity were the only culprit.
IMO the low (20%) humidity has exaserbated the problem of some panels not being properly assembled, but is not the root cause.

I guess the first question is how many boards are we talking about exactly. The initial post says "several". While I agree with what you said about the low humidity exacerbating an underlying defect, the main reason for my post was to point out that low humidity conditions can indeed cause fillets or veneers to pull loose, and that every aspect of the job should be considered before deciding it's defective material. Unfortunately, many consumers and "professionals" alike don't truly understand how important a consistent environment is when it comes to hardwood floors.

That being said, the vast majority of delam claims I've inspected have been manufacturing defects, but yes, it is possible for low humidity to result in a floor failure.

Start yelling shear and I will show you how the entire construction of the board is a failure waiting to happen. The entire construction design is flawed and considered defective if it is able to shear. The board should not be sold or marketed as an engineered!! Past engineered has always been able to handle higher humidity and much lower humidity then its solid counterpart. Shear is something new, eh? Where was shear 5-10 years ago?