Newly made oak windows and condensation

[Graham Orm]

.....
Jacob.
The drains that you describe are on the outside of the window and pass through a chamber that makes up the outer wall of the frame. It's designed to allow condensation from within the frame (not within the building) to escape, but more importantly any rainwater that gets into the rebate where the sealed units sit. If they were allowed to sit in frozen water they would fail straight away. There is no passage of water from inside to outside on any extrusion I have ever used in 20 years of fitting them. Nor have I ever seen such a thing in wooden windows. Obviously this could be a regional thing, I'd be interested in seeing a pic if you can find one? :wink:

OK I'm not sure about plastic windows I've hardly been near one. I knew they had weep holes though.

With trad windows drainage is a given - sashes drain via the meeting rail gap and by the bottom sash to staff bead gap. These should never be draft proofed. Casements drain via the bottom rail similarly. French windows (i.e. yer actual trad ones in France) often have a drainage detail much as I've described. Many larger buildings have drainage collection channels and means of taking the water outside. Here frinstance the windows sat on a stone cill with a channel cut just inside, (mirroring the drip channel you'd find in a stone lintel outside) taking water to a short length of 1/2" lead pipe sticking out just under the centre front of each window. In other buildings I've seen timber drainage channels integral with the frames.This sort of detail was universal, commonplace and is easily overlooked - there isn't much to look at!

I'll certainly be looking for it now!

 

[Jacob]

....
I'll certainly be looking for it now!

Bigger buildings - Victorian public buildings etc. Domestic buildings had self draining draughty windows instead.

 

[Graham Orm]

It might be a while before I get chance but will certainly have a look when I get near a period building likely to have them. I the days that they were built you wouldn't think that condensation would be a problem because of lack of heating.

EDIT: Although come to think of it I grew up in a house with just 1 coal fire and in the winter the bedroom windows would be frozen on the inside, this was obviously condensation.

 

[Jacob]

It might be a while before I get chance but will certainly have a look when I get near a period building likely to have them. I the days that they were built you wouldn't think that condensation would be a problem because of lack of heating.

Our chapel built 1874 had a huge coke boiler and 4" cast iron pipe central heating. Add a congregation of 300, blasting out Rock of Ages on a cold day, condensation would have been squirting out of every drain!
An alternative in chapels (and other public buildings) is controlled ventilation - often through decorative grills in ceilings with shutters on pull chords with warm air perhaps going to a short chimney from the roof space. I've seen these chimneys removed as apparently useless (no fireplaces connected!) which has then brought about condensation problems

 

[MIGNAL]

It might be a while before I get chance but will certainly have a look when I get near a period building likely to have them. I the days that they were built you wouldn't think that condensation would be a problem because of lack of heating.

EDIT: Although come to think of it I grew up in a house with just 1 coal fire and in the winter the bedroom windows would be frozen on the inside, this was obviously condensation.

Oh yes. I remember the icicles on the inside. Fortunately I was a young chap and as such it didn't really bother me. It would fking bother me now though!

 

[MMUK]

The units with a 14mm air gap are undersized by modern standards. 20mm Is the optimum gap

Actually, several years ago a study found that the optimum air gap is 16mm. They also found that Argon filled units are the best thermal insulators. The reason for 28mm being industry standard is that before this was found out, 99% of manufacturers had invested in tooling to make glazing beads for 28mm units to replace the skinnier units used previously in the belief that bigger was better. Status Profiles, now no longer in existence, even catered for a 32mm unit!

 

[CaptainBarnacles]

Wow! A wealth of great information, thank you everyone for your constructive advice. To tackle a few of the points raised:

The condensation occurs mainly on the glass, however I did notice yesterday that there was a little moisture on the frame itself so I suppose it's safe to say that the oak is more thermally conductive than the uPVC with it's air gap.

The house has been well insulated and sealed during the renovation process. It makes absolute sense that the moisture that would otherwise have been condensed onto walls, ceilings and floors is now getting concentrated on the windows which will be the coolest surface in the room.

Most of the condensation occurs overnight on bedroom windows. I didn't know just how much moisture we humans exhale into the atmosphere, that was quite a surprise! We always keep the bedroom doors ajar during the night but clearly this doesn't provide for a circulation of air adequate to remove sufficient moisture from the room to prevent condensation occurring.

I am kicking myself somewhat because during the renovation process we had planned to include a whole-house ventilation system with heat recovery. Sadly it was axed at the last moment as we just couldn't afford it.... ahhh hindsight is a wonderful thing. I could easily add HR ventilation to a couple of the rooms easily enough as they have a roof space adjacent but the rooms that suffer the worst of the condensation do not. I am wondering if I could vent these rooms (either passively or using a low speed fan) into a stairwell. That would be easily achieved as they are separated by just a stud wall.

Jacob, your wealth of knowledge never fails to amaze me. I have never seen, or even heard of, the drainage channels that you suggested. I'll be looking for pictures or diagrams of that system as I am just so intrigued. Unfortunately I think it is too late to add such a feature as the second lot of windows are almost complete.

Prior to us renovating the house it stood empty for over ten years with no heat and little ventilation. The walls are up to 18" thick in places and the local stone is quite porous so I would imagine it could hold a lot of moisture but as they were lined with breathable membrane I would hope that most of that moisture will be lost to the outside, not inside. What I never understood was that if the membrane can breathe surely it can allow the passage of water vapour in the air??

The glazed units were fitted the correct way around - eventually! I did fit the first one the wrong way around not knowing that they had a specific orientation. When I proudly announced to my wife that I had fitted the first window she came to inspect it, started peeling the stickers from the glass and noticed (in large bold print!) words to the effect "glaze with this side outwards". She called me a few interesting names and I retired back to the workshop with the window and my shame

The units are argon filled and we would have had a slightly larger gap but the glazing company advised that rather than using two panes of 4mm glass we should use a 4mm and a 6mm for additional noise reduction (we live by a fairly busy road and noise reduction was high on our list of priorities). The theory is that different thicknesses of glass will absorb different frequencies.

Again, a huge thank you to everyone for the fabulous wealth of information, advice and suggestions. I will have to consider what direction to go from here but I now have a much clearer idea of why the condensation forms where it does and what I might do to combat it. I'll let you know how it goes.

Paul.

 

[Graham Orm]

I don't know if you spotted in my post so I'll just say again. An electric extractor fan set on a timer to run for 3 hours each morning after we had left cured our problem.

 

[andypa]

It might be a while before I get chance but will certainly have a look when I get near a period building likely to have them. I the days that they were built you wouldn't think that condensation would be a problem because of lack of heating.

There's a Victorian country house (now a hotel) that I've been to a few times. I saw they had drainage channels on the leaded windows. The channel was cut into the stone cill along the width of the bottom of the window on the interior. It then went through to the outside through another channel in the centre of the cill. The hole to the outside had been filled with caulk so now useless :roll: .

You can see the exterior cill channels on this pic from google streetview -

 

[Sheffield Tony]

If there happen to be any of us old enough ( :shock: ) to remember when railway carriages had wooden window frames, these always had a channel and a few drain holes - usually with a brass insert, presumaby to keep the water out of the exposed end grain within the hole.

 

[billybuntus]

Our home is made of stone and after lots of internal insulating of wall using kingspan I'm managed to eradicat emost condensation issues. Aside from the windows.

Upstairs windows stream water and cause mould round the window cills.

I've had a 300W dehumidifier running for the best part of two years. For the most part its solved most of the remaining condensation issues and keeps the house sub 50% RH which is comfortable.

May I suggest one of these?

http://www.johnlewis.com/karcher-wv...0066672eeb&s_kwcid=ppc_pla&tmad=c&tmcampid=73

 

[Jacob]

You don't need a de-humidifier your windows are doing it for you - you just need to drain it away.
This isn't a problem it's a good thing to have condensation in a situation where you can take it in hand (down a drainage channel, weep hole or whatever) with no energy input and just minor design details to sort out.

 

[MMUK]

The best thing you can do is ensure a source of permanent ventilation to help stabilise temperatures and keep air flow. This could be trickle vents in the window frames or a through wall air brick or an extractor fan.

 

[Graham Orm]

You don't need a de-humidifier your windows are doing it for you - you just need to drain it away.
This isn't a problem it's a good thing to have condensation in a situation where you can take it in hand (down a drainage channel, weep hole or whatever) with no energy input and just minor design details to sort out.

Jacob, as much as I'm entertained by your 'I'll fight anyone in the pub' approach to most threads, I feel I must risk life and limb and tackle you head on. I'm sorry but that's a prehistoric viewpoint.
Are you saying that you would be comfortable with water streaming down your windows every day and out of draughty weep holes? Would you not be better off tackling the problem at source and having almost zero condensation? Don't forget if there's condensation on the glass, everything in the room will have a very high moisture content, including furniture, plaster, bedding and clothes stored there. Not a healthy environment. We're in the 21st century now Jacob, not the stone age, look around, you'll see all sorts of exciting things.....carpets....electric lights and every conceivable jig that you can imagine!

 

[CaptainBarnacles]

I don't know if you spotted in my post so I'll just say again. An electric extractor fan set on a timer to run for 3 hours each morning after we had left cured our problem.

Sorry, I did notice your post and that sounds like a plausible solution but I don't think it will work for us. Having just decorated the house and got everything straight I didn't want to have to punch holes through the thick stone wall to install extractors. There's also the issue of heat loss. My wife and I both work from home so running an extractor will cool the house considerably (unless we install a heat recovery model) which wouldn't make sense given that we had paid to heat the house in the morning to then suck all the warmth out again. My final nail in the coffin would be the noise aspect. In my experience extractors allow the passage of noise all too readily. We have extractors in bathrooms and in the kitchen and even with the anti-draft flappy thinggies installed the noise from the road is quite considerable.

Thanks, Paul.

 

[Jacob]

I don't know if you spotted in my post so I'll just say again. An electric extractor fan set on a timer to run for 3 hours each morning after we had left cured our problem.

Sorry, I did notice your post and that sounds like a plausible solution but I don't think it will work for us. Having just decorated the house and got everything straight I didn't want to have to punch holes through the thick stone wall to install extractors. There's also the issue of heat loss. My wife and I both work from home so running an extractor will cool the house considerably (unless we install a heat recovery model) which wouldn't make sense given that we had paid to heat the house in the morning to then suck all the warmth out again. My final nail in the coffin would be the noise aspect. In my experience extractors allow the passage of noise all too readily. We have extractors in bathrooms and in the kitchen and even with the anti-draft flappy thinggies installed the noise from the road is quite considerable.

Thanks, Paul.

Passivent? Air is drawn out by natural convection etc from of damp areas (kitchen, bathroom, main bedroom) via ceiling grills to the roof ridge. Air is drawn in via wall grills in the dry areas (living rooms etc) with a bit of humidity control on inlets and outlets. Seems well rated by people who use it but a bit low tech for the techies - no hums, LEDs, switches, dials etc.

 

[Jacob]

.....
Are you saying that you would be comfortable with water streaming down your windows every day and out of draughty weep holes?

Not every day by any means and only in winter at that.

....Don't forget if there's condensation on the glass, everything in the room will have a very high moisture content, including furniture, plaster, bedding and clothes stored there. Not a healthy environment.

Quite wrong. If the condensation is on the glass it has been extracted from the air and the room et al will be drier for it. Even more so if it's trickling away to the outside. I now have 16 drain channels in this building and you can see the water dripping out as the inside dries. Passive dehumidification.
PS the weep holes are tiny - I use 10mm copper pipe. No draft at all except in a severe gale but then only very local. But a little air exchange is essential anyway.

We're in the 21st century now Jacob, not the stone age, look around, you'll see all sorts of exciting things.....carpets....electric lights and every conceivable jig that you can imagine!

And you will see madly extravagant hi-tech solutions to simple low-tech problems! Some old low tech solutions still work very well. No one needs a powered dehumidifier.

PS it occurred to me that you could have one single glazed "condensing" window and all the others DG with no condensation. Just a thought. Better than having a machine buzzing away night and day and running up the bills.

 

[CaptainBarnacles]

Passivent? Air is drawn out by natural convection etc from of damp areas (kitchen, bathroom, main bedroom) via ceiling grills to the roof ridge. Air is drawn in via wall grills in the dry areas (living rooms etc) with a bit of humidity control on inlets and outlets. Seems well rated by people who use it but a bit low tech for the techies - no hums, LEDs, switches, dials etc.

I have not come across these before. I'll give them a good look. I am all in favour of low tech solutions where they will work effectively. The house was designed to consume as little energy as possible so the more passive systems we have in place the better. That said I would carefully weigh up the energy efficiency (in terms of heat loss) against a heat recovery ventilation system. I think I know which would cost least to buy and install though

 

[Jacob]

Passivent? Air is drawn out by natural convection etc from of damp areas (kitchen, bathroom, main bedroom) via ceiling grills to the roof ridge. Air is drawn in via wall grills in the dry areas (living rooms etc) with a bit of humidity control on inlets and outlets. Seems well rated by people who use it but a bit low tech for the techies - no hums, LEDs, switches, dials etc.

I have not come across these before. I'll give them a good look. I am all in favour of low tech solutions where they will work effectively. The house was designed to consume as little energy as possible so the more passive systems we have in place the better. That said I would carefully weigh up the energy efficiency (in terms of heat loss) against a heat recovery ventilation system. I think I know which would cost least to buy and install though

Heat recovery is a good idea but gets a very bad press it seems. Works well (economically) designed-in to big new developments but not in old buliding conversions.

 

[Jacob]

.....
Are you saying that you would be comfortable with water streaming down your windows every day and out of draughty weep holes?

Not every day by any means and only in winter at that.......

And only in the mornings. It disappears as the day warms up. Some down the weep holes, some back into the ambient air.
Looking at my steamy windows at the moment, drying rapidly as they are warmed by a bit of wintery sun and heat from morning household activities.

PS Just put some washing on the rack - another thing you don't need if you have condensing/draining windows, is a tumble drier. Clothe dry very quickly even in winter, thanks to the de-humidifying effect