That is the way I understand it. Supposedly less than a half inch prevents gas circulation up and down, or around and at least restricts it enough to make a fairly good thermal break.
y
From:
Sent: Monday, February 23, 2009 2:10 PM
To:
Subject: Re: [papercreters] CMU blocks with crete mortar?
Please don't get me wrong I not trying to argue what the space is because of
something I read on the web (hahaha [laughing at myself]) but I would think
that no mater what the space is it is the distance that is vertical not
horizontal that is important in convection airspaces loses. I.E. the flow of
the warm air up and cooling air down that is the issue here.
-x-
----- Original Message -----
From: Janoahsh <janoahsh@alaska.
To: <papercreters@
Sent: Sunday, February 22, 2009 10:22 PM
Subject: RE: [papercreters] CMU blocks with crete mortar?
What I have been told for over 30 years is ½" or 13mm. That's why
thermopane windows are spaced ½" .
Of course that's old info.
Janosh
_____
From: papercreters@
Behalf Of x
Sent: Sunday, February 22, 2009 12:05 PM
To: papercreters@
Subject: Re: [papercreters] CMU blocks with crete mortar?
I had read one source a whiles back that stated it was a quarter inch square
was the maximum size for an airspace that won't support convection of air.
That seemed very tiny but I remember that the source (which I can't remember
now) seemed very knowledgeable.
-x-
----- Original Message -----
From: Spaceman
> I'm afraid I can't answer that one. I know in principle how it works but
don't have the figures handy. The basic idea is that air rises when it warms
because it is lighter from expansion. As it rises cold air replaces it, and
becomes warmed in turn. As the cavity air warms and circulates, heat is
transferred towards cold surfaces, the air is cooled and sinks to replace
rising warm air. A quick search shows me many websites that state the
principle, but none with hard numbers for the minimum cavity that supports
convection of air.
>
> Spaceman
>
> Michele Marcell wrote:
>
> Ok. How small is that!!
> Michele
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