Hi!
My current project is to have an enclosed front porch - that is an add-on to the front of the house approximately 2 metres by 1 metre. It will have double glazed windows and insulated roof. I had intended to have cavity wall with a 2 inch/ 5 cm gap for insulation.

A surveyor acquaintance says that the firm he works for fits double brick without a gap so as to allow an extra 2 inches internally per wall.

This all sounds very well, but won't that defeat the object of having energy efficient / double glazing? Or should I be cutting my costs and having single glazing too? Any comments would be welcome.

Thanks

On Tue, 22 Mar 2005 20:17:31 +0000, Conrad
wrote:


Hi!
My current project is to have an enclosed front porch - that is an
add-on to the front of the house approximately 2 metres by 1 metre. It
will have double glazed windows and insulated roof. I had intended to
have cavity wall with a 2 inch/ 5 cm gap for insulation.

A surveyor acquaintance says that the firm he works for fits double
brick without a gap so as to allow an extra 2 inches internally per
wall.

This all sounds very well, but won't that defeat the object of having
energy efficient / double glazing? Or should I be cutting my costs and
having single glazing too? Any comments would be welcome.

Thanks

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.

www.bia.org



"Conrad" wrote in message
...

Hi!
My current project is to have an enclosed front porch - that is an
add-on to the front of the house approximately 2 metres by 1 metre. It
will have double glazed windows and insulated roof. I had intended to
have cavity wall with a 2 inch/ 5 cm gap for insulation.

A surveyor acquaintance says that the firm he works for fits double
brick without a gap so as to allow an extra 2 inches internally per
wall.

This all sounds very well, but won't that defeat the object of having
energy efficient / double glazing? Or should I be cutting my costs and
having single glazing too? Any comments would be welcome.

Thanks


--
Conrad

www.bia.org

Thanks for the above link - very informative. Also point taken about the gap not being for insulation, but as a way to stop damp migrating through the complete wall. After all cavity walls were used for very many before heat loss or conservation became an issue.

You would perhaps agree however that having a cavity wall does allow for having 'cavity wall insulation' added either during construction (expanded polystyrene) or subsequently (as fibre for example).

Given that the porch will be double glazed etc I think I will choose cavity for the above reason. Thanks for the help it has brought me to a decision.