Condensation and 3G windows

[SteamyTea]

8 hours ago, AliG said:

You should probably also put the wood into the house to acclimatise before it is laid.

I understand the concept of this, but usually in a new build, the indoor climate is not the final climate i.e. colder and damper.

 

42 minutes ago, Adsibob said:

Why should humidity be lower for installing a bonded floor? Is the concern that if it is too high the bonding won’t glue properly?

I would think it is down to the adhesive.  Do you know the chemistry of the adhesive type i.e. PVA, PU, acrylic, epoxy?

[joe90]

I am busy re plumbing my ASHP and UFH as the heating is not performing as it should but thanks to great help here should be sorted tomorrow, I have turned my MVHR up a notch so will see if it makes a difference to the condensation in the morning as it it forecast to be cold again tonight with clear skies.

[Russdl]

Out of interest @joe90 how long ago did your last ‘wet trade’ finish?

[joe90]

1 minute ago, Russdl said:

Out of interest @joe90 how long ago did your last ‘wet trade’ finish?

At least two years ago.

[Adsibob]

3 hours ago, Russdl said:

Thats my gut feeling but it still doesn’t quite add up as others on here have enthalpy units and don’t seem to experience the same problems, @joe90’s experience is similar but his windows are 2g so that may explain his occasional condensation. It was cold again last night and there was condensation on most windows (some with thick curtains, some without) 
 

We went for the enthalpy expecting future occupancy to be low as I work away a lot. Maybe that was a mistake. 
 

Maybe the house does need to dry out further as suggested in this thread (I hope not, humble pie sounds revolting). 
 

Investigations are ongoing, but at a slight pause as I’m out of area at the moment. 

Were you advised/informed by the vendor that an enthalpy exchanger was appropriate for your home? If so, could you try and make it their problem and see if they will swap out your heat exchanger for a regular one, even if only on a trial basis? Alternatively, do you have summer bypass? If so, would activating that put the exchanger out if play so that you can check whether that is the cause? Obviously that wouldn’t be a permanent fix, but might be a useful diagnostic test, though I confess I’m not entirely sure how the summer bypass works.

[Russdl]

38 minutes ago, Adsibob said:

Were you advised/informed by the vendor that an enthalpy exchanger was appropriate for your home?

No, it was all my own doing. 
 

38 minutes ago, Adsibob said:

Alternatively, do you have summer bypass? If so, would activating that put the exchanger out if play so that you can check whether that is the cause?

That seems like a great idea, I can look into that.
 

Actually, already thinking about it whilst typing.
 

I can measure the RH at the supply vents compared to the intake air before it gets into the MVHR which I’ll be able to do easily. I would expect the supply RH to be higher with the bypass because of the enthalpy but I should be able to see how much higher and then take it from there. 
 

Thanks for the idea ??
 

I could also measure the exhaust RH each side of the MVHR unit. 
 

@Adsibob, you’re a genius!

 

 

(I guess I’ll need the temperature at each reading as well, and then wonder what I do with numbers I get - apart from post them here to be deciphered)

Edited January 13, 2022 by Russdl

[Onoff]

On 11/01/2022 at 12:26, Roundtuit said:

Should be able to do it yourself with a hired meter.  Was the system designed for you by the supplier?  If so, they should be able to give you the design air flow rates for each terminal.

 

With these MVHR systems don't you  / get given calculated air flow rates then use an anemometer at each "vent" to set up? That's what most on here seem to have done to balance things. There was one floating about for loan on here...

[Russdl]

39 minutes ago, Onoff said:

get given calculated air flow rates then use an anemometer at each "vent" to set up?

 

Yes you do. Well, I’m pretty sure I did, just need to find it in my files. 
 

I fitted the required restrictor rings, switched it on and as all seemed completely hunky dory I moved the commissioning aspect all the way to the back burner and beyond. That could prove to be mistake number two (of the MVHR mistakes - there are many others). 
 

The commissioning will be brought to the front of the hob and set to boost soon. 

[PeterW]

On 11/01/2022 at 08:26, Russdl said:

The MVHR has an enthalpy heat exchanger.

 
This is a red herring ..!! These work by allowing RH from the extract to the intake but it is at a level that is balanced by the internal level being extracted. Good explaination here. 
 

https://www.paulheatrecovery.co.uk/components/moisture-heat-exchanger/

 

I am wondering if you haven’t got the proper flows and you need to balance the system and also need to get some industrial level drying like others have said - a new build contains hundreds of litres of water, I would start by drying out what is there, balance the MVHR and then see where the levels end up. 

[Russdl]

@PeterW I don’t agree that it’s a complete red herring. As the link says “...up to 75% moisture recovery...”

 

I completely agree that it needs to be properly commissioned to be able to investigate further. 

 

I hope it doesn’t need industrial drying, mainly because of the pie. 

[ProDave]

Just to add to this debate, we have an enthalpy mvhr unit.  It was not deliberately chosen, but like a few other bits in this house one came up cheap on ebay. Kingspan had been re badging mitsubishi units and I believe Kingspan abandoned that enterprise and several ended up cheap on ebay.  I did not know until we had it that it was indeed an enthalpy unit.

 

I have had no problems with it, and the only window that gets any condensation is the 2G velux window in the en-suite.  At the time of buying that window I debated 2g or 3g and as it was a small window I concluded the heat loss of a 2g window was low enough not to worry about.  I do wish now I had paid a bit more for the 3g version to reduce or eliminate the small amount of condensation we get around the edges of the window.

[PeterW]

But MVHR moves tiny amounts of air compared to a dehumidifier.  You need to start at the basics 

[JohnMo]

Would it be be easier you use a sheet of toilet roll, place it near the mvhr inlet/outlet terminal, if stays in place its an extract, if it blown off it's a supply terminal.

 

Cut and paste from passivhaus magazine, which make me wonder if you are just chasing your tail, with a dehumidifier, with the enthalpy heat exchanger?

 

"Vaisey points out that on the other hand, if the relative humidity internally is too low, it can lead to dry skin, itchy eyes, and a dry nose and throat, creating a very uncomfortable environment for the occupants. It is suggested that the ideal level of relative humidity in a home is between 40% and 60%.

 

The major sources of moisture inside the home are the occupants, cooking, showering and plants. When an MVHR system without an enthalpy heat exchanger is used, that moisture is lost to the outside — all that is transferred to the incoming air is heat. These systems also remove moisture from incoming air.

 

However, the Flair 325 comes with an optional enthalpy heat exchanger. This works by allowing water vapour from the extracted internal air to transfer to the incoming air, raising the relative humidity.

 

The quantity of moisture that is transferred depends on the relative humidity of the indoor and outdoor air and may run to about 60%. This is particularly useful with cold, dry alpine environments, with low levels of relative humidity. The enthalpy heat exchanger also recovers both thermal and latent energy from the extracted internal air, energy which would ordinarily have been lost to the atmosphere.

 

“The average relative humidity in the UK is between lows of 70% and highs of 90% which is considered high, suggesting humidity recovery is not that big an issue in the UK,” Vaisey says."

 

Would it be worth getting hold of a thermal camera, to see if you have local cold spots?

 

Any water pipes in the wall close too or above where you have condensation?  We had pressure tested our pipes, and had a drip every hour or so in service, took a while to find the issue.

[Russdl]

@JohnMo I know with certainty which duct does what so there’s no issue there. 
 

39 minutes ago, JohnMo said:

 

Would it be worth getting hold of a thermal camera, to see if you have local cold spots?

I wouldn’t mind one but I don’t think it will help with this specific situation. 
 

41 minutes ago, JohnMo said:

Any water pipes in the wall close too or above where you have condensation?

No, all water pipes are through internal walls/floors and any condensation appears on the window panes. 
 

42 minutes ago, JohnMo said:

We had pressure tested our pipes

Sadly we didn’t despite all the promises. I’ve been wondering about a hidden leak but if that were the case I would have thought it would have shown by now. 

[joe90]

1 hour ago, ProDave said:

Just to add to this debate, we have an enthalpy mvhr unit.  It was not deliberately chosen, but like a few other bits in this house one came up cheap on ebay. Kingspan had been re badging mitsubishi units and I believe Kingspan abandoned that enterprise and several ended up cheap on ebay.  I did not know until we had it that it was indeed an enthalpy unit.

I did the same ?‍♂️, yes I am yet to balance mine as well as @Russdl. Despite my turning my MVHR up yesterday and overnight, with a hard frost I still had condensation this morning, but mine are only 2g.

[SteamyTea]

How many sweaty people are currently working in this building?

[LA3222]

Not sure why this thread is now 5 pages long other than stubbornness. 

 

Get an industrial dehumidifier and spend 2 or 3 weeks drying the house. 

 

It will cost 60 quid and give you a baseline.

 

Next, turn that off and observe. If the humidity goes right back up again then you have proven the issue lies elsewhere.

 

At the minute it's all finger in the air speculation of it might be this or that.

 

I am baffled at the determination to ignore all suggestions relating to getting a dehumidifier in. It's only 60 quid?‍♂️

[Adsibob]

6 hours ago, LA3222 said:

Not sure why this thread is now 5 pages long other than stubbornness. 

 

Get an industrial dehumidifier and spend 2 or 3 weeks drying the house. 

 

It will cost 60 quid and give you a baseline.

 

Next, turn that off and observe. If the humidity goes right back up again then you have proven the issue lies elsewhere.

 

At the minute it's all finger in the air speculation of it might be this or that.

 

I am baffled at the determination to ignore all suggestions relating to getting a dehumidifier in. It's only 60 quid?‍♂️

I still think it's more likely to be the enthalpy exchanger as i just think they are not suitable for this kind of climate, unless there is a very good reason you don't want to over dry the air, like you are providing a ventilation system for a respiratory ward in a hospital or for a tropical greenhouse. And I'm stubborn. lol.

[Onoff]

6 hours ago, LA3222 said:

At the minute it's all finger in the air

 

Can't a wet finger held in the air be used to determine draughts? 

 

 

[PeterW]

2 hours ago, Adsibob said:

I still think it's more likely to be the enthalpy exchanger as i just think they are not suitable for this kind of climate, unless there is a very good reason you don't want to over dry the air, like you are providing a ventilation system for a respiratory ward in a hospital or for a tropical greenhouse. And I'm stubborn. lol.

Got one, it works fine and RH in the property runs at about 52-62 with it. Quite a lot of others have them too. 

[Peter M]

As this thread is entitled "Condensation and 3G Windows" and not being fully clear by what is meant as "3G" in the title I thought that I would chance my arm and post this reply here and add a picture of what we are experiencing with condensation, or at least that is what the window company is saying is the core contributor to the 'condensation'

 

Our build is nowhere near completed as far as wet trades are concerned as we have not started the plastering yet, the floor has been poured but is now dry and the house has no form of heating yet so the temp outside is pretty much the same as inside and is pretty much sealed apart from the odd draught around the opening as they have not yet been fully sealed.

 

We are really concerned that this is a much bigger issue than condensation being caused by the head or heads of the screws that is fixing the sill to the bottom frame, window company explanation not mine, the pooling of water is being experienced on about four windows at present, was about eight but it seems to alter depending the direction of the rain/wind, if you have any thoughts or ideas I'd be pleased to hear from you. All windows are double glazed in core insulated aluminium from a largish supposed expert company.

[IanR]

3G = triple glazed

 

Just to be clear, Is the white/silver section that is running close to horizontal the window frame? and the sill you mention, is it the external sill, not shown in the picture.

 

I can't make out the black cylindrical object in the top right hand corner.

 

Does this only happen when it rains?

 

Do you ever see condensation on any surface. Or is it the absence of evidence of condensation that has lead the installer to say "it's forming on the screws"

Condensation is more likely to form on the inside in your scenario, where the internal air is slightly warmer than external and saturated due to the drying out process, then coming into contact with a cooler surface of the frame or glass.

Edited February 4, 2022 by IanR

[Peter M]

Hi Ian, the frames are anthracite grey so what you can see in white is the protective film, the black cylindrical object is the hinge on this particular window as it is a tilt inwards arrangement.

 

Only have ever seen this a day or so after it rains, not immediately, or when I have hosed & washed the windows down after I had been doing some dusty work on the cementboard cladding.

 

The house is dry no wet trades in progress and the floor has dried out, laid in June 2021, no evidence of condensation/water on any internal surface only from BELOW some of the frames.

[IanR]

19 hours ago, Peter M said:

Only have ever seen this a day or so after it rains, not immediately, or when I have hosed & washed the windows down

 

It's sounding more like a leak than condensation. Are the external finishes all on, you mentioned the sill being in place. Is it possible water is getting on to the rebates and trickling down to pool under the sill and find a way through what is probably expanded foam under the frame?

[Peter M]

The external finishes are not all in place yet, which will be just a strip of HardiPlank cladding to the inside of the opening, some have been done and some haven't but the water ingress is happening on finished and unfinished window openings, but what I did do was to go around all the openings that I could easily reach from the ground without erecting a tower, which will be erected later, and sealed with low modulus silicone sealant on top of the expanded foam that the window company had pumped in between the epdm barrier and the brick or block structural opening.

 

The black sheet that you can see in the picture on the inside sill is the epdm the water sitting on top of is the epdm which in turn is stuck to and around the frame to 'seal' the whole window unit from any outside moisture and to improve the airtightness and then stuck by way of a further adhesive strip on the reverse side, 4 inches wide, if the water is forming on top of the epdm it can only be coming from within the frame units that have found their way into the bottom casement section and not drained out through the face drainage slots, water by it's very nature will always find the path of least resistance to drain down unless there is a watertight seal preventing such action. There is no foam between the framing and the epdm seal just the adhesive, approx 2 inches wide sticking the epdm to the frame.

 

I'm loathed to carry on with the finishing detail around the windows until I am 100% sure that the water coming in is sorted and that the window does not have to be removed which will cause all sorts of damage in doing so.