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Concern about MVHR’s effect on engineered and laminate flooring


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Our MVHR was put in a while back, but it has not been commissioned yet because the house is still very dusty and dirty, with quite a bit still to do. We have two rooms still to plasterboard and all of the ground floor and master bedroom to plaster. Most of the house still needs to be painted and then the flooring will go down, with some rooms having Pergo laminate and other rooms having engineered oak.

Both the laminate and the engineered oak say that the product should be allowed to aclimatise for at least 24h before installation. It has been in the house for a few weeks already, but with the MVHR off, the humidity must be 70% or 75% at least. The current plan is to commission the MVHR after the flooring goes down. But this was driven by a desire to avoid clogging up the MVHR with dust. I’m now wondering whether MVHR will cause the humidity to drop fairly dramatically by 15% or more, and if that happens after the flooring has been installed, couldn’t it cause the flooring to buckle/fail?

Should I reschedule things so that cleaning happens earlier so that we can commission the MVHR and then install the flooring?


 

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I would go ahead and get the MVHR up and running.

 

If you compare the cost of your flooring cf regular replacement filters then.. if the flooring goes wonky then.. big disappointment.

 

It's also all the other finishes such as doors, facings, say you kitchen cabinets etc.. start "breaking" them in now and if issues arise it's easier to address now than later?

 

 

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Your house will remain at a high humidity for a quite a while, as the house dries out.  So don't worry.  We commissioned ours after the flooring went due to dust etc.

 

Things to watch out for with the flooring, is the sub floor humidity.  This may be too high to accept the new flooring.  Your flooring supplier will have a means of measuring the floor humidity (takes about 24 hours).  Even though our concrete floor had been down for a year, we still had high humidity and had to epoxy coat, where the wood flooring was going.

Edited by JohnMo
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3 hours ago, JohnMo said:

Your house will remain at a high humidity for a quite a while, as the house dries out.  So don't worry.  We commissioned ours after the flooring went due to dust etc.

 

Things to watch out for with the flooring, is the sub floor humidity.  This may be too high to accept the new flooring.  Your flooring supplier will have a means of measuring the floor humidity (takes about 24 hours).  Even though our concrete floor had been down for a year, we still had high humidity and had to epoxy coat, where the wood flooring was going.

Thanks @JohnMo. Are there any down sides of epoxy coating? We have one room where we are sticking engineered herringbone directly onto screed that was poured almost 4 months ago. So as it’s only one room, it will hopefully not be expensive to expoxy  coat it, though something else I haven’t budgeted for. Any other downside apart from cost.

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3 hours ago, Gus Potter said:

I would go ahead and get the MVHR up and running.

 

If you compare the cost of your flooring cf regular replacement filters then.. if the flooring goes wonky then.. big disappointment.

 

It's also all the other finishes such as doors, facings, say you kitchen cabinets etc.. start "breaking" them in now and if issues arise it's easier to address now than later?

 

 

Interesting… I see you and @JohnMo disagree on this. I will wait for a few more to join in. My concern wasn’t just the filters but also the ducts. 

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3 hours ago, JohnMo said:

our flooring supplier will have a means of measuring the floor humidity (takes about 24 hours).  Even though our concrete floor had been down for a year, we still had high humidity and had to epoxy coat

I can only give my experience, but is based on multiple large concrete floors with floor coverings.

Flooring contractors nearly always said that their tests showed excess moisture and they would not lay without an extra for a sealing layer.

I resisted this because of 1. cost (which was silly high for a coat of cheap sealer). 2. we would be trapping water in the floor for ever. 3 I didn't always believe them.

After a couple of weeks more severe ventilation (just doors and windows open at opposite sides) we tested it ourselves if in any doubt, signed a  form saying we accepted responsibility, and instructed the floors to go down.

There was never  a problem.

 

These floor were 150 to 200mm concrete on polythene, and had been laid for 8 to 10 weeks.

Therefore these dry out more slowly than thinner screeds.

 

I can't comment on your circumstances of course but with timber flooring it must be drier, so patience is required, but sealing...perhaps not.

 

It is vital to do as the manufacturers say about acclimatising, as I learnt to my cost with home parquet. although on old, dry concrete, it first expanded and then shrunk, leaving gaps.

I suggest you live without the flooring for quite  a while with the heating and heat recovery working.

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MVHR will dramatically change the atmospheric and surface conditions once up and running. Timber, flooring, worktops etc. Should “normalise” in these conditions before being fitted or they are likely to move/crack/split etc.

timber is quite happy in wet conditions as long as it stays wet. It’s the change from wet to dry and vice versa that cause problems.

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All I will say is the Passivhaus Trust mvhr install guidance says 

 

"MVHR must not be run until post construction cleaning has been completed and commissioning of the system

is to be undertaken."

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Hmm, conflicting views expressed on this thread. Not really sure what to think. Whilst what @markc says sounds plausible, as soon as I analyse it further it can’t be right. Worktops are never given an opportunity to aclimatise, regardless of the humidity in the kitchen they are being installed in. The worktop company install the worktop on the same day that they bring it to the property, and I’m fairly sure that happens around the world in all sorts of humidity. I would also like to think that given I’ve paid CVC over £10k to supply, design and install my MVHR they would have pointed out this was an issue. I will give them a call in the morning to ask them, but I suspect I will do everything except the wood flooring, then turn the MVHR on for 48h then install the wood. Query whether this issue also affects the Topcrete poured floor we are having? 

Edited by Adsibob
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  • 2 weeks later...
On 23/01/2022 at 08:49, JohnMo said:

All I will say is the Passivhaus Trust mvhr install guidance says 

 

"MVHR must not be run until post construction cleaning has been completed and commissioning of the system

is to be undertaken."

Thank you for bringing some sanity to this thread.

 

On 23/01/2022 at 20:01, Adsibob said:

Hmm, conflicting views expressed on this thread. Not really sure what to think. Whilst what @markc says sounds plausible, as soon as I analyse it further it can’t be right. Worktops are never given an opportunity to aclimatise, regardless of the humidity in the kitchen they are being installed in. The worktop company install the worktop on the same day that they bring it to the property, and I’m fairly sure that happens around the world in all sorts of humidity. I would also like to think that given I’ve paid CVC over £10k to supply, design and install my MVHR they would have pointed out this was an issue. I will give them a call in the morning to ask them, but I suspect I will do everything except the wood flooring, then turn the MVHR on for 48h then install the wood. Query whether this issue also affects the Topcrete poured floor we are having? 

OK.

Firstly it would be, in no way, shape or form, the responsibility of the MVHR supplier to advise you on timelines for you installing floor coverings or any such correlation between that and the amount of humidity that is in the house OR how you manage that!! That would be the responsibility of you, or your M&E consultant, and for them to liaise with your PM to make sure that is strategized BEFORE even choosing or installing such systems. They wouldn't stand by your front door checking if you've got a brolly if it was a rainy day...... ;) 

Switching on your MVHR before your painting and decorating, second fix woodwork, kitchens and bathrooms are all installed is suicide.

HIRE A DEHUMIDIFIER.

Edited by Nickfromwales
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19 minutes ago, pocster said:

Not sure BoJo would be much help.

Agreed, but at least we'd all be too pissed to give a feck about warped wooden floors that we laid to early. ;) "Bring your own booze", to coin a phrase recently quoted by the media..........

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Just to update everyone, 3 industrial sized dehumidifiers were switched on 4 days ago (today is day 5), one on each floor. They are each almost 1m3 in size.

Builder doesn't want to install the tado thermostats yet because we haven't finished painting, so I've ordered some hygrometers from amazon which are arriving today and I will take some readings. They are hoping to start laying herringbone engineered oak flooring on Monday on the top floor. This is not a screeded floor, so no humidity from the floor. It was plastered about 6 weeks ago, and mist coated two weeks ago so will hopefully be fairly dry. Will update later today once we've taken some humidity readings, but presumably I'm targeting a reading of between 56% and 60% humidity? I don't like the air too dry, as it dries my throat.

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So I'm not sure I've done the right thing. We took humidity readings 6 days ago and I was surprised to see it was only 60% plus or minus 1% on each the three floors of the house, so pretty much target humidity, or maybe a few percentage points over. I went back later in the day, when they were painting and humidity had risen to 63%. So I left the dehumidifiers running for 6 days. Yesterday morning they were showing 39% to 41% and I slightly panicked as I thought this was too low. Given the machines are costing me quite a bit to hire I told my builder to send them back, thinking they would be returned in the next few days. But actually within a couple of hours the hire company had already come to pick them up. Today I checked again and the humidity has risen from the 41% recorded yesterday morning to about 49%. I'm wondering if I was a bit premature in returning the machines. Probably should have just switched them off for a few days to check.

The oak flooring is being laid, so let's just hope it doesn't rise to higher than 56% or so over the next few days... 

Edited by Adsibob
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It's winter so the air is quite dry. Our engineered floor does move a bit with the seasons. The T&G joints open up a bit in winter and close up in summer when it's more humid. Not really an issue for us. Ours is 18mm secret nailed to joists with UFH between. 

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4 hours ago, Temp said:

Our engineered floor does move a bit with the seasons. The T&G joints open up a bit in winter and close up in summer when it's more humid. Not really an issue for us.

How can you tell it moves? How does this manifest visually?

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Just for info.. 

 

I read somewhere that if you glue the T&G (rather than secret nail it to joists) then it's important to ensure the joint is well glued. I forget which website I read this on but they said its not good enough just to run the nozzle of the glue bottle along the groove, you should use a brush to make sure it's all  properly coated.

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3 hours ago, Temp said:

Just for info.. 

 

I read somewhere that if you glue the T&G (rather than secret nail it to joists) then it's important to ensure the joint is well glued. I forget which website I read this on but they said its not good enough just to run the nozzle of the glue bottle along the groove, you should use a brush to make sure it's all  properly coated.

 

might be alright, however, as stated, timber will move and if it can't move at the t&g it could split the board. once saw a lovely 6 panel oak ext. door, the only problem was the dozy 'joiner' (wood worker) glued the panels into the grooves, first summer and every panel split

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