Window efficiency and building control

Are you able to lift the window board to see what the frame is sitting on? If no packers are underneath and it's sitting completely on the outer brickwork then it'll be cold bridging off that exterior brick. If it's sitting over a cavity, is the cavity completely sealed underneath it? If not then cold air from the cavity will be cooling the inner frame and you could get condensation forming. If the window is not sealed properly externally then again cold air will be finding its way around the entire frame and cooling it.

What windows are they?

I have aluminium windows and suffer really bad condensation when the temp drops really low. My triple glazed aluminium windows which are a completely different frame only get very minor misting in the bottom corners of the glazing unit at that high humidity lower temperature time in November / early December.

They’re aluk 5 ones. I’m not sure what they are sat on. I Did notice that the sides and top had a bit of foam strip in the gap but the base didn’t - I queried this but apparently it was to allow drainage.

Edit : they are on an aluminium sill (cill?) but I’m not sure what’s under thst.

The sliding door is the worst- the bottom 30 cm or so of the pane mists on that too - I assume conducted up from the frame.

I’m no expert, and I’m sure one will be along shortly, but you could go and look at the FENSA website in the meantime. They are the organisation that (are supposed to) maintain standards of window replacements to building regulations.

I can't see any details on them but if they have a total u value of 1.6 or better then they are passing building regs.
Can you take some pics of the outside around the frame edge? Also internally around the frame edge?

Also measure the depth of the window within the outer brick to determine how far inboard they are in the reveal. Closer to the room the better to stay warmer.

https://uk.aluk.com/en-gb/products/windows/58bw

They might be these ones, although I expect a non - “hi” version as I’m sure there used to be hi and non hi versions so probably not quite as good. Outside and inside edges to the brick/reveal are covered with trims. I’ll take some pictures in the morning.

They’re about 35mm inset I’d say. Cill sticks out and is hollow aluminium I think.

The thing is to get the condensation we are, I don’t think they can have a u value of 1.6.
Probably poor Installation as you suggest.

My double glazed poorly fitted windows have a u value of better than 1.6 but still get awful condensation at the base like you in our bedroom and adjoining ensuite. Both windows I made sure were foamed in during renovations and taped, I also have an mvhr system so decent fresh air too. My bathroom has a triple glazed window and only gets condensation when the door is shut and you have a bath or shower. I don't even mop it up, it dries and sorts itself out. I was very careful with how the triple glazed windows are fitted, they are all at least 30mm over the cavity closer and foamed and taped. They still feel cool to the touch due to being metal but do not get condensation.

I can only put it down to the frame design, where they are placed in the reveal and the inner frame still touching the outer brick somewhere.

So even after foaming and taping you still get condensation on them?

I was hoping that might solve the problem.

However given they sit on an aluminium Cill which presumably conducts the heat from the outside to the inner unless there really should be a thermal break between the Cill and the frame.

I had the whole house done, triple glazed, seems to be somewhat of an expensive (very) mistake.

Yes even foamed and taped and didn't help when the temp has really dropped. My kitchen window by the sink is the worst of the lot though. Got the thermal camera on it, the cill was 2C internally. The aluminium cills are still thermally broken but if the part of the cill that is thermally broken still sits or touches on an outer cold surface then it will still get very cold.

It will be how they are fitted that is the issue I'm sure. I have Warmcore triple glazed and they are so much better both to the frame being better and the fitting.

If it’s sitting over a cavity, is the cavity completely sealed underneath it? If not then cold air from the cavity will be cooling the inner frame and you could get condensation forming.

This was exactly the case with our doors on the first floor. Lifted up the sill and rammed a couple of cans of foam in - big difference.

Hi can you ask Aluk to check the spec/ installation for you? Did you use an approved installer? Most window manufacturers will try to help if you’re encountering problem’s especially with critical performance. It sounds like Marybeth the thermal break is either not working very well or the cill installation is bridging the thermal break.
Alu windows can be problematic for poor thermal breaks and we have just had a very cold period where issues like this are massively exaggerated too?
I’d contact Aluk tech department and ask for some help, start off non combatively and they should be able to try to help you resolve if it’s an installation issue?

Also we’re insulated cavity closers checked when being installed as like molgrips says if the frames are just sitting over the cavity with no closers it will make it worse?.

How do you lift the Cill to put foam in?

Does the cill go all the way under the frame? If it does then isn’t being a conductor of coldness.

Oddly I get less condensation around most of my tiled reveals Vs the ones with trims. the tile and grout goes up to the window as they were added after where as the trim simply hides a gap.

I’ve no idea about cavity closers. I suspect not as They didn’t bother to put much foam in at all and some they didn’t put any foam in- I know that much.

I will ask aluk - good shout. I’m a bit worried a problem I might come up against is that aluk only extrude the aluminium, another company chop it up and bolt it together and then another fit them. I had that when I asked about the lack of foam strip at the bottom.I expect the Cill is made by some one else again.

The other thing that seems rubbish is I’m sure the mitred joints are leaking air (albeit that will be an easier fix).

I’ve had the problem for a few weeks so when it cooled down but before it got really cold

Get some pics up of the worst offending ones, also show the poor mitre joins too.

1. Building regs level of insulation and bridging details are not that great.
2. "As built" can be very different from "as designed"

Sill will go under the frame but will be thermally broken. All window systems have to assessed in a laboratory. Installation issues are the most likely cause unless you also generate a lot of moisture? Dry clothes on a radiator for example?

Thanks @wooksterbo and others here are some pics

https://postimg.cc/gallery/5v2k2x9

And a cill
https://postimg.cc/gallery/52Kgn8f

Not sure on the mitres but in theory they are aesthetic only and the innards of the frame will be sealed anyway with the various Chambers.

It's certainly looks like poor fitment may be the cause, only real way to see what could be the issue is window boards off and reveal plasterboard off but I cannot guarantee that doing this and fixing and sealing all gaps will make it all go away. It really depends on how and where the window sits in the reveal. How thick is the frame and can you measure externally from the frame to the edge of the outer brick and ignore the quadrant piece fitted on the front of the frame.
I can only put yours down to cold bridging due to placement in the reveal.

My triple glazed bifolds have a tiny bit of condensation at the bottom of the frame but only on 1 set of doors, I have 2 meeting each other so they in effect open an entire corner of our extension. The extension is cooler due to all the glass and the roof windows which are again triple glazed but no solar gain as extension is north facing. I wish I didn't bother with the roof windows.

You can see mine, here (excuse the mess and clutter) :

https://photos.app.goo.gl/FN8RaLL2RBiaid6e9

The window frames are 58mm thick so pretty thin.

I’ll have to try and get some foam in there and hope that helps. As has been said above there is the question of whether there is too much humidity so little hope of admission of liability I suspect. I don’t think there is too much humidity though - the upvc front door frame doesn’t get it and the frame is noticeably cooler at the bottom than the top. We have a dehumidifier when drying clothes.

So your previous guess of 35mm inset + 58mm will mean they are within the 100mm outer brickwork so no thermal protection as it were. Are they a narrow triple glazed unit too? Mine are 44mm I think. At least it looks like you've got half decent warm edge spacer bars. My older double glazed units still use an aluminium spacer bar.

Focus on under the cill and see how you go.

I think they’re meant to be 32mm units.

Feeling like a total plank for not sticking with cheaper upvc which are i assume are much more sympathetic to crap Installation. Not sure whether just to bin them for upvc or try and fix the problem which might just be pouring good money and time after bad. With 20 odd windows and doors it’s gonna be adding another year to my working life!

Don't rush to buy all new windows. If you were to go to that extent then I would at least look at removing plasterboard reveals and window boards, get all that fixed first and then if you did decide to replace the windows they would be fitted at the right depth.

The reveals are just plaster on brick/block i think. How would I change to fit at a better depth? That could be done for the existing windows I assume. But would be a fairly big job i assume. I guess could only go so far otherwise the cill wouldn’t project very much. Exterior is just standard brick.

Interesting reading - we nearly pushed the button on aluminium windows but covid paused it.

It was the narrower frame profiles compared to UPVC that were the deciding factor but having read the above and the increased costs might lead us to UPVC.

Plasterboard and board off, see if cavity closers exist. If not you can retrofit some like I did or foam and seal pir board in the cavity so it's flush with the cavity openings. You can also make sure the cavity insulation is filled right up to the closers. You may need to pull out windows a bit further out to give you space to close the cavity if they are open. Once cavities are sealed off then window is refitted with possible replacement 180mm deep cills. Window would be positioned as far over the cavity as possible with the weight still being transferred to the outer leaf on plastic packers. Packers are then cut back and you can foam the gaps around the window and then tape. Seal externally with the sealant of your choice. Refit window boards and then add plasterboard back in making sure that if plasterboard adhesive is used you add to full perimeter of the board to make sure no air movement (belt and braces)

My current downstairs toilet awaiting new window board and plasterboard. Top piece over lintel I have a 25mm pir board backed plasterboard piece cut to size ready for the plasterer.
https://photos.app.goo.gl/1N9SKYGz9v2N3NW67

Blue tape is tescon airtight window tape. Grey boards are the cavity closers and black paint is Blowerproof airtight paint.

Just prepare yourself that it may not fully work if you still have a lot of moisture in the house or the temperature is low in various rooms. I used to get loads of condensation on the downstairs toilet window. None now and it's warmer after the work I did. It still drops in temp thanks to many other factors to do with the rest of the house so it's not all hawaiian shirts and sun glasses in there but it made an improvement.

Not a small job then - I wouldn’t be able to attempt that myself- My windows are 2.5 x 1.4 or something like that so would need to take the glass out I’d have thought. As it wouldn’t be DIY Labour cost probably going to add up a fair bit.

The foam as much as possible in situ is probably the only option for me. Which presumably will result in some filling the cavity (if I can) as i don’t the cavity is properly closed. I’ve no idea how good one insulation in the cavity is.

Is it better to try and foam from inside or outside?

Both ideally so no void is left around the frame.