Thermoformed glass protection system

The Stained Glass Restoration work carried out on Chartres Cathedral
has been criticised by experts on the  "Glass is More" website

    Florian Lechner, writes that: "Windows that no longer spread,
    expand and make tangible their radiance and imaging in the
    space, become mindless, neutered, stripped of an essential
    property.  This is happening in the Cathedral of Chartres."
    While Udo Zembok adds

        <URL:http://www.glassismore.com/core/content.php?option=viewitem&id=42&le=120&rd=845>

    "I think it would be appropriate also to describe the changes to
    the light (entering the cathedral through the windows) from a
    purely optical perspective, in other words the physics.  Without
    the thermoformed glass protection, light rays pass through the
    stained glass filtered only by the transparent coloured glass.
    By the laws of physics light rays are parallel and this is what
    causes colored lights to be projected onto the walls and floors.
    By adding the external protective skin, which is translucent and
    thermoformed, the light rays are now diffused and enter through
    the coloured panes in an indirect fashion which in turn further
    diffuses the projected light...."

        <URL:http://www.zembok.com>

Could someone enlighten me regarding the details of the thermoformed
glass protection system.  I assume this is not just hanging the
stained glass windows behind a protective outer glazing layer
consisting of a flat sheet of glass to protect the restored window
from the elements.  Glass experts to the rescue please!

David A. Scott
Professor


                                  ***
                  Conservation DistList Instance 29:32
                 Distributed: Sunday, January 10, 2016
                       Message Id: cdl-29-32-024
                                  ***