Double brick or Cavity wall

Hi!
My current project is to have an enclosed front porch - that is a add-on to the front of the house approximately 2 metres by 1 metre. I will have double glazed windows and insulated roof. I had intended t have cavity wall with a 2 inch/ 5 cm gap for insulation.
A surveyor acquaintance says that the firm he works for fits doubl brick without a gap so as to allow an extra 2 inches internally pe wall.
This all sounds very well, but won't that defeat the object of havin energy efficient / double glazing? Or should I be cutting my costs an having single glazing too? Any comments would be welcome.
Thank
-- Conrad
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On Tue, 22 Mar 2005 20:17:31 +0000, Conrad

I don't think that the gap in a double-wythe wall is there for heat conservation. As near as I can figure out, it does two things: It keeps water from soaking all the way through the wall when it rains continuously for April, and it makes a thicker and therefore more stable wall.
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Thanks for the above link - very informative. Also point taken abou the gap not being for insulation, but as a way to stop damp migratin through the complete wall. After all cavity walls were used for ver many before heat loss or conservation became an issue.
You would perhaps agree however that having a cavity wall does allo for having 'cavity wall insulation' added either during constructio (expanded polystyrene) or subsequently (as fibre for example).
Given that the porch will be double glazed etc I think I will choos cavity for the above reason. Thanks for the help it has brought me t a decision
-- Conrad
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