New upvc patio sliding doors condensation on plastic not glass

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Oldman

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Kent. UK
After putting up with alloy framed almost double glazed patio doors since 1970's I bit the bullet this year against raised heating costs to replace them with upvc. They were the biggest size they could go with standard thickness glass at around 2.6m x 2.4m high.
Fitting was a disaster with the wrong spec frame fitted, 1 double glazed unit shattered, a fitter who couldnt get the locking to work smoothly so drilled out oversize the lock and the handle plastics making the lock and sliding door unacceptable. I had them resupply everything except 1 unit of glass and get a different fitter. All went fairly well 2nd time around. They have been in around 2 months now & with the weather here in Kent getting colder at night I notice condensation on the outer glass first thing in the morning, but none on the inside which is how it should be. But what I do have is condensation on the sealing area where the inner slider and outer fixed vertical upvc parts meet.
sweating strip.png
sweating strip.png
As far as I can see, this arrowed part is going to be a cold spot as the only thing sealing it from the outside world is 2 plastic brush strips maybe 5mm wide mounted on a strip of plastic 1 attached to each side of the inner sliding vertical.
Here is what the brush/felt strips look like.
sweating seal strips.jpg
sweating seal strips.jpg
Is this I wonder the same with all modern upvc sliders?
 
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So nobody here has similar sliding patio doors or they all sweat along the slider join area and nobody told me?
 
Perhaps the frames are warped and a good seal is not being achieved. Have you tried putting a straight edge on both elements to check this? Maybe shining a bright light through the joint when closed will reveal weaknesses in the seals.
 
I've no intimate knowledge of plastic doors, but in reality they are a composite construction with a steel core structure, though I'd expect them these days to incorporate thermal breaks.

The brush seals should be fairly effective since they'll be trapping a column of insulating air between them when the door's shut. Does the jamb (frame upright) look parallel to the stile (door upright) - I can't tell from the photos. Are the seals achieving good contact and compressing slightly?

Was the outer frame foamed in against the wall reveal around the opening?

Grasping at straws, I'm afraid. :-(
 
The plastic frame only needs to be a few degrees cooler than the nice warm moist air inside your home and condensation will form. When outside temperatures drop to low single figures that temperature differential is greatest and the likelihood of that condensation is greater.
We have this problem in our nice new very well insulated bungalow. We have all the trickle vents open, bedroom window open at night along with bathroom and kitchen windows open during the day for a couple of hours.
Our plastic window frames have condensation as do our metal bi-fold doors that have a thermal break in the extrusions.
The condensation you have forming also seems to line up with where the cavity may be in your walls. If the cavity has not been closed, that is bricked up, the cold air in the cavity is in direct contact with the back of the warm plasterboard lining to your door reveal.

If you stopped breathing you would probably not have a problem.

Colin
 
Thanks for the replies, the frame itself doesnt seem warped nor does it have an excessive gap anywhere where the brushes (4 in total) contact the frame/jamb & stile. The brushes seem to be as tight as they can be, the 2 outside brushes appear to have a strip of clear sheet midway in the construction to help seal the brush even more.
As to heating, during the day 18 to 20 deg is the indoor temperature and at night it drops to 16 deg. The humidity 1mtr away from the doors is 75% at night with single figure outside temps.
I dont know if they foamed in this replacement set of doors, they were a pretty close fit.
I guess I will have to live with it, the water runs down into a gully below the slider and I assume drains somehow from there, though I have been clearing it manually.
I could get less humidity in that room by purchasing a dehumidifier, but running that for 5-6 months of the year wasnt something I planned for, I can turn on the AC in dry mode to drop the humidity with the kw involved thats a non starter, I can open a window for an hour or so, then watch the gas CH struggle to bring back the temperature, or I can just live with the condensation I guess. A roll of kitchen towel is a darn sight cheaper than any of the above.
 
The (assumed internal) humidity figure of 75% is quite high which may be compounding the problem. Without knowing far more details of the property construction, age & location together with occupancy including domestic use habits it is rather difficult to advise. However, I did find this article on line which may be of help.
 
if it were my house, I would check tumidity with a hygrometer. In really winter cold of Manitba, I once tried to recover heat from our dryer. Big mistake, big water damage to paint under windows with only two loads. In my subsequent business in carpentry, I've encountered man other people doing exactly that. One fella even had 80% humidity causing a whole house full of properly fitted mdf doors to swell to non-closable status.

And BTW, his bathroom exhaust fan was totally non-functional- it had never been cleaned since the house was new, probably 50 years of dust accumulated. That's worth checking.

Another client had a whole house ventillation system with a heat recovery capability. Massive condesation occurred in a house that shouldn't have had any...cause was that the installers of the HRV had hooked up all the ducting, but forgot to remove the plug to the ouside vent, ergo it was not working at all- resulting in the massive condensation..

Then, for a few dollars you can buy an infrared thermometer and easily scan for cold air leaks at the arrows indicated in the pix. Lots of surprises there!

For the patio doors, I'd also get out the 6' level and ascertain that both sides of the frame are parallel, and plumb ie, no twist and that frame is square. and that top and bottom are also level and flat. Measuring corner to corner both ways will tell yu if your door frame is square, or a n out of square parallelogram.

The doors almost certainly have adjustments on them to ensure that the meeting rails align and that the closing edges meet and seal.

That furry sealing stuff stuff is called Schlagel, and comes in various sizes.

And as an added concept, I have had to, several times, repair vinyl windows whee the spray foam sealant has distorted the frames

Good luck

Eric in the colonies.
 
The (assumed internal) humidity figure of 75% is quite high which may be compounding the problem. Without knowing far more details of the property construction, age & location together with occupancy including domestic use habits it is rather difficult to advise. However, I did find this article on line which may be of help.
Thanks for that link, I found it useful.
 
if it were my house, I would check tumidity with a hygrometer. In really winter cold of Manitba, I once tried to recover heat from our dryer. Big mistake, big water damage to paint under windows with only two loads. In my subsequent business in carpentry, I've encountered man other people doing exactly that. One fella even had 80% humidity causing a whole house full of properly fitted mdf doors to swell to non-closable status.

And BTW, his bathroom exhaust fan was totally non-functional- it had never been cleaned since the house was new, probably 50 years of dust accumulated. That's worth checking.

Another client had a whole house ventillation system with a heat recovery capability. Massive condesation occurred in a house that shouldn't have had any...cause was that the installers of the HRV had hooked up all the ducting, but forgot to remove the plug to the ouside vent, ergo it was not working at all- resulting in the massive condensation..

Then, for a few dollars you can buy an infrared thermometer and easily scan for cold air leaks at the arrows indicated in the pix. Lots of surprises there!

For the patio doors, I'd also get out the 6' level and ascertain that both sides of the frame are parallel, and plumb ie, no twist and that frame is square. and that top and bottom are also level and flat. Measuring corner to corner both ways will tell yu if your door frame is square, or a n out of square parallelogram.

The doors almost certainly have adjustments on them to ensure that the meeting rails align and that the closing edges meet and seal.

That furry sealing stuff stuff is called Schlagel, and comes in various sizes.

And as an added concept, I have had to, several times, repair vinyl windows whee the spray foam sealant has distorted the frames

Good luck

Eric in the colonies.
I have a humidity meter and an infra red temp probe. The door verticals are not out of shape and when measured the part arrowed with the brushes attached is 3-4 deg C colder than the rest of the inner frame.
I also found the concrete floor had a temp difference of 4 deg C within 1mtr of the doors. As this is a 1960's detached house I think I can be sure that there is no underfloor insulation in this part of the house, so thats probably expected.
The area where the doors are is a large L shape kitchen diner 20 x 24ft with an open 20 x 24ft lounge adjoining, so not much isolation can be done.
What I did find was the trickle vents in the kitchen windows were closed. The kitchen extract works fine btw.
The humidity was down to 66% within 1mtr of the doors first thing this morning and with 17deg room temp and later 19deg once the heating came on there were NO water droplets on the plastic.
So im going to leave it for a few days to see if opening the trickle vents was the answer.
Thanks everone for their input :)
 
We live in Devon, which means it rains a lot. Our heating is all off peak electric, not exactly cheap, but zero maintenance over 35 years. At comfortable indoor temps, the RH is usually about 75%, which will ensure your wardrobe contents are growing mould. Ventilation without heat recovery is expensive; the 1980's building regs did not require provision for ventilation (other than opening windows). It's a 4 bed house with 2 retired occupants, home most days. Unventilated, the dehumidifier is set to 60% and removes at least 3l a day in damp weather. Most of the energy used turns to heat, which is useful when it's colder. It has to be well below freezing before we see a little condensation on the double glazing and uPVC window frame corners.
 
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