Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of each
pane, and the middle of the pane clear.

Why does that happen?

--
Mike Barnes

Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

"Mike Barnes" wrote

Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of each
pane, and the middle of the pane clear.

Why does that happen?

It is difficult to avoid condensation completely particularly in a moisture
laden bathroom.
To get close you need:
Sufficient heat in the bathroom to keep the moisture in the air rather than
simply condensing on the nearest cold surface.
A very effective, well placed extractor fan and duct arrangement to remove
the warm moist air and replace with warm dry air (a hole through the wall
with a cheapo B&Q axial fan is unlikely to cut it in a bathroom of any
size).

Phil

TheScullster wrote:
"Mike Barnes" wrote

Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It is difficult to avoid condensation completely particularly in a
moisture laden bathroom.
To get close you need:
Sufficient heat in the bathroom to keep the moisture in the air
rather than simply condensing on the nearest cold surface.
A very effective, well placed extractor fan and duct arrangement to
remove the warm moist air and replace with warm dry air (a hole
through the wall with a cheapo B&Q axial fan is unlikely to cut it in
a bathroom of any size).

Phil

I think the OP is asking why the condensation forms in a particular pattern,
not why it forms at all.

--
LSR

In uk.d-i-y, Phil L wrote:
Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Sorry, I should have made myself clearer.

Why only in a strip round the edge of the pane?
Why not in the middle as well?

--
Mike Barnes

The message k
from "Phil L" contains these words:

Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Yes, but Mikes question was not why the condensation but why just round
the edges of a window.

I don't know the answer for sure but I think the most likely explanation
is that the area adjacent to the window frame is relatively sheltered
and retains a marginally higher level of humidity as a result.

Another possibility is that the frame itself is colder than the pane but
I think that is extremely unlikely.

--
Roger Chapman

"Mike Barnes" wrote in message
news
In uk.d-i-y, Phil L wrote:
Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Sorry, I should have made myself clearer.

Why only in a strip round the edge of the pane?
Why not in the middle as well?

The centre of the pane may warm up quicker than the frame of the window,
having less mass. As warming occurs, condensation will leave the centre of
the pane and remain around the edge. One would expect the opposite
phenomenon on cooling. IMHO


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

--
Mike Barnes

In uk.d-i-y, Bob Mannix wrote:
"Mike Barnes" wrote in message
news
In uk.d-i-y, Phil L wrote:
Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Sorry, I should have made myself clearer.

Why only in a strip round the edge of the pane?
Why not in the middle as well?

The centre of the pane may warm up quicker than the frame of the window,
having less mass. As warming occurs, condensation will leave the centre of
the pane and remain around the edge. One would expect the opposite
phenomenon on cooling. IMHO

Seems fair enough. So it would most likely occur in a room where the
temperature has just risen sharply, such as a bathroom after a shower.
Makes perfect sense now. Thanks.

--
Mike Barnes

LSR wrote:
TheScullster wrote:
"Mike Barnes" wrote

Today I noticed condensation on the bathroom windows in that clich�d
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It is difficult to avoid condensation completely particularly in a
moisture laden bathroom.
To get close you need:
Sufficient heat in the bathroom to keep the moisture in the air
rather than simply condensing on the nearest cold surface.
A very effective, well placed extractor fan and duct arrangement to
remove the warm moist air and replace with warm dry air (a hole
through the wall with a cheapo B&Q axial fan is unlikely to cut it in
a bathroom of any size).

Phil

I think the OP is asking why the condensation forms in a particular pattern,
not why it forms at all.

Cold bridges clearly marked?

Roger wrote:
The message k
from "Phil L" contains these words:

Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clich�d
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Yes, but Mikes question was not why the condensation but why just round
the edges of a window.

I don't know the answer for sure but I think the most likely explanation
is that the area adjacent to the window frame is relatively sheltered
and retains a marginally higher level of humidity as a result.

Another possibility is that the frame itself is colder than the pane but
I think that is extremely unlikely.


You think wrong then.

In article ,
Mike Barnes writes:
In uk.d-i-y, Phil L wrote:
Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Sorry, I should have made myself clearer.

Why only in a strip round the edge of the pane?
Why not in the middle as well?

The edge of the pane has cold bridges to the outside, in the
form of the frame and the glass pane separator in the sealed
unit. Also, you have a crevice formed where the glass meets
the frame, and natural drafts will tend to skate over a
volume of dead air in the crevice, allowing the crevice air
to cool and more likely drop below the dew point, where
condensation will start.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
The Natural Philosopher writes:
Roger wrote:

Another possibility is that the frame itself is colder than the pane but
I think that is extremely unlikely.

You think wrong then.

Depends when the window was manufacturered.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In uk.d-i-y, Andrew Gabriel wrote:
In article ,
Mike Barnes writes:
In uk.d-i-y, Phil L wrote:
Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clichéd
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?

It's when warm moist air meets a cool surface.

Sorry, I should have made myself clearer.

Why only in a strip round the edge of the pane?
Why not in the middle as well?

The edge of the pane has cold bridges to the outside, in the
form of the frame and the glass pane separator in the sealed
unit.

You guessed correctly that it's sealed double glazing. However the same
pattern is seen in pictures that pre-date sealed double glazing, and I
always assumed that a single sheet of glass was a better conductor than
a traditional wooden frame. Could be wrong, of course.

It just struck me that this pattern of condensation is something that's
often seen and accepted without questioning why.

--
Mike Barnes

Andrew Gabriel wrote:
In article ,
The Natural Philosopher writes:
Roger wrote:
Another possibility is that the frame itself is colder than the pane but
I think that is extremely unlikely.
You think wrong then.

Depends when the window was manufacturered.

Not usually. The frit seal on the edges of DG units are a classic case
in point as are aluminium PVC covered window frames.

Only single glazing in wood tends to be colder in the middle.

Mike Barnes wrote:
In uk.d-i-y, Andrew Gabriel wrote:
In article ,
Mike Barnes writes:
In uk.d-i-y, Phil L wrote:
Mike Barnes wrote:
Today I noticed condensation on the bathroom windows in that clich�d
"Christmas card" style - a strip of condensation round the edge of
each pane, and the middle of the pane clear.

Why does that happen?
It's when warm moist air meets a cool surface.
Sorry, I should have made myself clearer.

Why only in a strip round the edge of the pane?
Why not in the middle as well?
The edge of the pane has cold bridges to the outside, in the
form of the frame and the glass pane separator in the sealed
unit.

You guessed correctly that it's sealed double glazing. However the same
pattern is seen in pictures that pre-date sealed double glazing, and I
always assumed that a single sheet of glass was a better conductor than
a traditional wooden frame. Could be wrong, of course.

Lead/putty outside is one (possible) issue.

The other is less air movement.

A third is draughts round the frame edges


It just struck me that this pattern of condensation is something that's
often seen and accepted without questioning why.