Condensation on aluminium door frame

[jimbob80]

Our builder has recently installed a large aluminium sliding door.

 

The frame includes a "thermal spacer" that is between the inside and outside frames. The manufacturer claims this will insulate the inside frame and stop it getting cold. 

 

Following installation, we have found that we frequently get condensation on the frame (but not the glass). If I clean the condensation, it returns in about 24 hours. The builder says this is because we have too much humidity and not enough ventilation.

 

I have purchased a humidity meter and read up on the science of dew points and and the installation instructions for the window system: Our humidity level is typically 50-55%. This seems pretty normal and nothing exceptional. The calcs suggest that with an internal temperature of 20°C and humidity of 50%, the dew point is 9.3°C. This means condensation is expected to form below this temperature. It is colder than this outside for most of the winter.  The installation instructions for the window system say the cill should be on plastic packers to insulate it from the masonry and the frame should be fixed through the thermal spacer (plastic bar). I think our cill sits directly on the masonry and is held in with metal clips that connect it to the masonry. Taken together, I think the problem is that our frame isn't correctly insulated from the masonry, the frame gets cold and this leads to the condensation.

 

Please can I ask:

 

a. Is it normal for aluminium frames to be very cold on the inside? Is condensation normal?

 

b. Is it most likely caused by our (excess) humidity, poor frame design or incorrect installation?

 

c. Is my explanation plausible or is there something else I have missed? 

 

 

 

 

[Redbeard]

Is the house newly-completed? I knew someone who was very worried about their 'thermally-broken' alu windows in their new-build suffering from considerable condensation. However, once the plasterwork had dried out the condensation stopped occurring. I was not there at the time so I cannot comment on the actual frame temperature.

 

I am not convinced that your humidity is excessive. I too am concerned that there is no isolation between frame and masonry, but tell us more about your house. Is it new or old? Is the frame connection to the inner or outer skin if it's a cavity wall? If it's not a new house but *is* a cavity wall, fixing to an un-insulated cavity closer (probably a brick) could, I think/wonder, effectively 'by-pass' the thermal break.

Edited Wednesday at 20:47 by Redbeard
More re humidity and structure

[SteamyTea]

Get yourself a cheap IR thermometer and see what the temperatures actually are.

 

Would not be unusual for an aluminium frame to cold on the inside, the thermal conductivity in around 236 W.m^-1.K^-1

I think glass is better than that.

 

[Jilly]

I was worried about this when we moved in, and we got condensation in the Al frames. As the building dried out over the next year or so, it’s stopped happening except on really cold nights. I also aim for RH of 55%. I couldn’t face the disruption of taking the doors out just to check…

Edited Wednesday at 20:52 by Jilly

[Mike]

23 minutes ago, jimbob80 said:

Is it most likely caused by our (excess) humidity, poor frame design or incorrect installation?

It could be any of those.

 

It could be poor frame design as it's very unlikely that all thermal breaks perform equally well. There are plenty of PassivHaus certified aluminium frames that are suitable for 'cool temperate' climates (which includes the entire UK climate) which, it seems, are tested at -5°C & 50% relative humidity (though I may have that wrong). I'd be surprised if they would permit condensation on the internal surface. But I've never investigated their criteria in that much detail, nor installed them. But if the thermal break is inadequate, then condensation could certainly occur on the inside face.

 

It could also be because the windows is fitted to a reveal that doesn't have an adequate insulated cavity closer between inner & outer skins. We'd need more information about the wall to evaluate that.

 

[Andehh]

We have two bedroom windows that both suffer bad condensation when low single figures and colder, bottom 25% of all frame. Both North facing! Only two windows that do other then shower room.

 

The ally sliders we have get light condensation along the bottom (cold bridged), but nothing to worth about.

 

We're 18 months in and have MVHR.

 

Ally windows are great for slim premium and metal.... But they will never be as thermally good as PVC etc.

 

For the dozen times a year the condensation is at risk of trickling into the wood window cill I'll mop it up... But just one of those 'not ideal, can't fix it.... Learnt to live with it'

[Iceverge]

1 hour ago, Andehh said:

But they will never be as thermally good as PVC etc.

 

Preach. 

 

If uPVC was there times the price everyone's would think it was amazing.

[jimbob80]

Thank you for the many suggestions and comments. I really appreciate it.

 

Some more information:

 

1.       The house is an old building with (empty) cavity walls. It has recently had a large extension. The extension has foam cavity insulation.

 

2.       The majority of the original house has double glazing without trickle vents. Some newer windows have vents. It doesn’t have MVHR.

 

3.       The extension has an aluminium window, aluminium sliding door and an aluminium patio door. All of the aluminium units have the condensation problem but is much worse on the sliding door.

 

4.       In each case, the aluminium frame cill sits directly on the outer masonry. There are no packers underneath as specified in the install instructions.

 

5.       The frame is anchored (at the sides and top) to the inner masonry using metal ties. The majority of the ties appear to be in the frame rather than anchoring through the thermal break (as specified in the install instructions).

 

6.       My working theory is that the cill position and/or the metal ties have effectively 'by-passed' the thermal break and created a cold bridge between the inner/outer frame and the inner/outer masonry. The window system manufacturer specifies that the cill should be on packers and the anchored through the thermal break. We don’t have either of these.

 

7.       At the sides and top, the small 8-10mm gap between the frame and the masonry is filled with expanding foam.

 

8.       We were advised not to have cavity closers because the plaster finish would crack. Instead the cavities are closed with plywood. This is starting to feel like a big mistake!

 

9.       We have identified that there is no foam cavity insulation below the largest aluminium frame. It is just a cavity. Maybe, this is contributing to the condensation problem (which is much worse at the bottom).

 

10.   The frame is noticeably colder at the bottom and get less cold further up. Similarly, the condensation is much worse at the bottom and less higher up. This correlates with the theory that the cill is sat directly on the masonry and is a cold bridge to the outside.

 

11.   The plastering was completed about a month ago. It has long since changed colour and appears to be dry. We thoroughly dried the frames to remove all condensation. It returned 24 hours later.

 

12.   We are aware that the problem may be exacerbated by the recent plastering but given the humidity level is now around 50% and unlikely to get much lower, the dew point calculation suggests dew (condensation) is likely over a wide range of winter temperatures and realistic inside humidity levels when the inside frame is at a much lower temperature than the room.

 

13.   Thank you for the suggestion to measure the frame temperature with an IR thermometer. I will try this. I suspect it is cold (near outside) temperature.

 

14.   If it only happened a few times a year, we could probably live with it. The problem is we haven’t had it long enough yet to know if this will be the case. The big question, is condensation normal on modern aluminium frames? I get the sense that this shouldn’t regularly happen and there is a problem in either the product or, more likely, the installation.

[Andehh]

I'm afraid it feels like the ship has sailed, you are where you are!

 I have everything you could want in theory, full filled cavities, cavity closures which I then sealed to the brick work, expanding foam I think in the bottom under window, MVHR, long since dried out house etc etc etc.... And we still get condensation in some areas.

 

If I were you, buy a dehumidifier, enjoy the added benefits it gives you in an even dryer house, bit of added warmth, and run it through the winter.

 

You can't win everything!

[Andehh]

10 hours ago, Iceverge said:

 

Preach. 

 

If uPVC was there times the price everyone's would think it was amazing.

 

The snob factor... Which I couldn't get away from myself...., albeit it we originally envisaged our windows differently (supplier (expletive deleted)ed up the style, and it wasn't spotted until installation... So we really got shafted!). Instead we paid more for lower performing windows "because aluminum". But PVC!? as if we'd build a whole new dream home and then fit PVC! 😉 Who says marketing and self smugness isn't worth buying into!!!!
😆

[Mike]

On 02/01/2025 at 00:35, jimbob80 said:

6.       My working theory is that the cill position and/or the metal ties have effectively 'by-passed' the thermal break and created a cold bridge between the inner/outer frame and the inner/outer masonry.

This certainly seems to be key problem - the window / door should ideally be positioned mid-way across the (filled) cavity, or as close to that as can be sensibly be achieved, so that no broken metal touches both the inner and the outer leaf. If that's not the case, I'd seriously think about getting it refitted.

[j_s]

It'll come down to how much it annoys you.

I had aluminium windows (I forget the actual frame manufacturer now but well known) fitted 12 years ago in my 2006 build. They looked nice but some were ice cold feeling inside. The glazing was as good as you can get for double glazing. We had awful condensation on the lower part of the frames on anything remotely approaching colder days and in November when it was humid and damp outside and the temperature also dropped a bit.

 

I had an extension fitted in 2018 which was the catalyst to gutting nearly every room in the house back to block to reveal the usual bodges a sorry excuse for a construction company would make. I also decided to start again with most of the windows and put in triple glazing with Warmcore windows (uPVC inner with I think an insulated foam, with aluminium attached on outside and in but is still structural, definitely different to how they normally thermally break aluminium windows). I stupidly left in several of the old aluminium windows but changed more and more of them apart from 3 that would mean ripping out the redone reveals that had new cavity closers, windows were also airtight taped in as well as the bespoke coated ply window boards were fixed in with L shaped brackets behind the plasterboard further down the wall. I can't bring myself to rip the entire reveals out again to put the new windows in with the likelihood of cracking the celcon lightweight aerated block work. Guess which windows still get condensation on. This is with mvhr too. Luckily it's now only an issue when the temperature drops to -1 or below.

 

The other thing to note is that all 3 of the windows that get condensation were closer to the outer brickwork and not properly sitting off the brickwork with packers. All my redone triple glazed units are on packers and sit in as far as I can at around 50mm to 60mm from the outside edge of the brickwork.

 

Sorry for the long post, in a nutshell, you can either accept it and get some microfiber cloths and wipe it down daily or rip it out at a reasonable expense and get it fitted the right way. That's not to say you will eliminate the condensation as the aluminium door frame might still be an issue if it's not a great design.