--- "Hammarberg, Eric" <[log in to unmask]>
wrote: > A few questions for you then some of my
comments.

> What is significant about the windows? What are the
significant attributes of the windows? What age are
the windows? Building? What repairs are reversible?

** Building and windows are 1937-38, placing them
right at the forefront of aluminium window use in
Australia (and I suspect, close to the forefront
worldwide).  Building is a department store, with
about 350 of these windows.

> Your answers should help guide you through the
following morass.
>
> 1.  None - the windows would have leaked at the time
of construction, and hence the leaking is significant.
-- Most buildings need to function and service the
tenants in a livable environment.

** I appreciate this.  The tenants have not complained
about leaks despite the fact that many of the windows
are left open on a close to permanent basis.

> 2.  Application of a sealant bead around the
perimeter of the sash to frame junction, thus
preventing the operation of the sashes. -- Sounds
worth considering if opening the sashes is not
important or significant.

** Fair call.  It is reversible, and whilst the intent
of current conservation works is to ensure the windows
are operable, in practice they are unlikely to be
opened in the future.  Likely to be the direction we
take if we decide we need to.

> 3.  Modification of the framing members by addition
of new beads containing gaskets to provide an internal
air seal. -- Not sure I understand enough but sounds
worth considering. What kind of modifications are
necessary?

** In the US, most building facades are designed so
that they are face-sealed, with waterproofing at the
outside line.  In Europe, Australia and to a lesser
extent Canada and Asia, the concept of pressure
equalisation chambers within the cladding system, and
the importance of the airseal line as distinct from
the face seal, is used to provide waterproofing to the
building.  This allows water to enter the cladding,
but drain out again.  With these windows, it would be
feasible to attach new aluminium beads containing a
neoprene gasket to the inside face of the window, so
that the gasket was compressed against the frame, thus
providing the inner air seal.  Not easy, visually
obtrusive from the inside, but probably effective.
Overkill in my opinion, but just canvassing the
options.  Hope this helps - a picture would do it much
better but (a) I can't draw very well, and (b) sending
pictures is a pain!

> 4.  Installation of a second line of glazing on the
inside of the windows to provide the primary
waterproofing and air infiltration seal. -- If the
windows leak air and water this would not be a good
idea. Water will accumulate behind the exterior
windows and allow water within wall section. This is
not a good idea.

** Refer to response to 3 above.  A second line of
glazing about 100mm back from the windows would work
very well in preventing gross water ingress as it
would equalise the pressure, and tend to prevent water
from entering the windows at all.

> How about exterior overglazing?

**  Visually very intrusive.

Thanks very much for your response Eric.

david

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