Interesting.  I've never really thought about it, but I thought that the
principle of the cavity wall (in cavity brickwork) was primarily to
allow any liquid water that penetrated through the external skin of
brickwork moisture to run down the inside face of the outer skin, onto
the flashing at the base of the cavity, and then drain out through the
weepholes in perpends in the brickwork.

 

I can see how the cavity would also facilitate air circulation, which
would promote drying out of the inside face of the outer skin of the
brickwork, which would further improve the performance of a cavity wall
(over the traditional solid masonry wall) with regards to moisture
content and dampness.

 

Putting aside the question of placing insulation into the cavity, the
reason for the cavity in the first place is a classic example of the way
we 'lose' knowledge over time.  Where is the primary source that
explains to us the rationale behind development of the cavity wall, as
contemplated by the people who actually developed the cavity wall
principle?

 

I encounter this conundrum regularly in the course of my work - current
favourites include:

 

*         A belief that you should never use acid in any form on
sandstone ... in a city where there is substantial anecdotal evidence
that for several decades, all sandstone buildings were washed down with
dilute hydrochloric acid upon completion ... I have been able to trace
back one source of the belief that acid should not be used to a 100 word
comment article in a South African trade publication which talked about
the damage caused by acid washing of a sandstone building ... reading
between the lines, my guess is that the acid in question was
hydrofluoric, which of course will have a disastrous effect on any
quartz-containing material.

*         A belief that all stone-faced precast concrete cladding panels
will fail if there is no grommet around the fixing clips between the
stone and the concrete (due to differential thermal and moisture-induced
movements)... which dates back to the first mention of this method of
fixing stone veneer facing to precast concrete in a version of the
Precast Concrete Design Manual dating from the early 1990s ... the
genesis of which does not appear to be based on any published research,
but on the opinion of a single individual.

 

So, to return to the original question about the insulation - there are
two paradigms to be questioned:

 

a)                  Should we fill the cavity space in a cavity masonry
wall with insulation?

b)                  Is "Insulsmart" a suitable material for use as
injected insulation i.e. will it perform adequately without adverse
effects on the surrounding historic fabric?

 

My reading of the collective wisdom proffered to date is that we haven't
adequately answered the first question, although consensus appears to be
that we shouldn't fill the cavity; and that we don't think "Insulsmart"
is a suitable material for the proposed use due to known problems with
injected foam materials, and the potential fire hazard ...

 

Time to get back to fee-paying work.

 

Cheers

 

David West

Executive Director

internationalconservationservices

T:     +61 (2) 9417 3311

M:    +61 (411) 692 696

E:     [log in to unmask]

W:    www.icssydney.com

sustaining your heritage

 

-----Original Message-----
From: The listserv where the buildings do the talking
[mailto:[log in to unmask]] On Behalf Of deb bledsoe
Sent: Thursday, 21 January 2010 9:06 AM
To: [log in to unmask]
Subject: Re: [BP] insulsmart

 

I went and read the msds, specs, etc. Supposedly non-toxic in a fire. 

Material is not an irritant, you can get it on your skin while applying.


Should not breathe the dust from cutting it. Duh.

 

I just remember so many stories from some ancient thread about 

completely screwing up a masonry/plaster cavity wall by filling it. 

Dewpoint in the wall changes and water builds up inside or outside the 

foam (or other insulating material) and causes issues with the plaster, 

the masonry or the foam itself, in breakdown of the materials and/or 

growth of mold.

 

There is supposed to be air circulating in a cavity wall.

 

~deb

 

Jim Follett wrote:

> 

> What about fire issues?

> 

 

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