Black mould and condensation

[untitled]

Hello,

My last post a few years back focussed on damp which I thought was rising due to external skirting bridging the DPC. I have since installed a French Drain around the property with a raised decking above and a non hydraulic lime mortar rendered skirting above the DPC. Further investigation has shown that probably the damp experienced in my house was not caused principally by rising damp as the bricks seem mostly dry. Anyway a few years on and the damp is no better, in fact I think it's getting worse. This is despite using a vented tumble dryer instead of radiators to dry clothes in winter.

I would like to seek some more advice if possible. There's quite a list of questions I have so I apologise if this post is too long.

The property is a ground floor victorian solid brick with single glazed sash windows. We primarily use gas central heating but occasionally light a fire (which helps a lot). The property was converted into a ground floor flat and my wife and I life there with our son. The floors are raised timber with no floor coverings, carpet etc and there is a cellar that is nearly always completely dry. The windows are drafty and generally I'd say there is plenty of natural ventilation. The walls are a mixture of natural lime and gypsum plasters as one would expect, given the number of hands the property must have been in. There is no wallpaper but the walls are painted with matt vinyl emulsion.

The black mould is becoming a big problem extending in both bedrooms and the living room but not the bathroom, kitchen or hallway. The kitchen has no extractor, only the natural ventilation through a drafty window. There is no ventilation in the bathroom except a basic fan that comes on for 30 mins every time the light is switched on.

I am not in a position to hack off all the gypsum plaster, re-apply a lime mortar and re-decorate the entire flat with lime wash or similar. I have investigated a few options to reduce the problem and would like your thoughts if possible (Thank you).

My questions are thus:

1) Would it be beneficial to replace all the single glazed sashes with double glazed windows? (they do need replacing)
2) Is there an option to redecorate over matt emulsion with a clay based paint or similar to absorb some of the condensation?
3) I have looked into Positive Input Ventilation systems (PIV) wall mounted to drive fresh air into the property. However it seems odd that it could help because it's already drafty enough. Has anyone used these and is it worth installing. We have no loft
4) If PIV systems are worthwhile could we use our cellar to vent (suck) stale air out of our house (in a similar way to the vented tumble dryer) for example?
5) Are more sophisticated extractor fans worth looking at and de-humidifiers for that matter? Running costs are a concern.
6) If there are any other possible solutions to look into I'd jump at the chance!
7) I am not interested in any kind of DPC injection.

I have attached some images of the damp... it does look a bit like a horror story!

If anyone can help then I would be very grateful!

Thank you.

 

[Abi Cott]

I'm a bit new at this, but with damp there appear to be 3 options.

1. It's coming up
2. It's coming down
3. It's condensation

You appear to have dealt with option 1. Are you confident about option 2 with regards to the flat upstairs? If it's option 3 a fan to simply circulate the air might assist

 

[Feltwell]

I think for anyone to do a proper assessment they'd need to see the property, but my suspicion now would be that it's condensation, if that's the case it will be colder areas of the room that are affected. Next to the window would therefore make sense.

I take it that you've thoroughly "looked up" and there are definitely no issues with leaky guttering, failed flashing, flat roofs etc etc?

So, what do the bedrooms and living room have in common that the other rooms don't? The obvious one is people - you spend more time in there than the other rooms, breathing out water vapour. However, I too live in a Victorian house with a mixture of "leaky" unrestored single glazed sash windows and restored draughtproofed single glazed sash windows, and I don't have any mould issue beyond a tiny bit around the margin of the glass in the windows (which is pretty normal for a single glazed window) - the only difference between the leaky windows and draught proofed windows here is what you'd expect, the draughtproofed ones get more condensation on the glass. What else can you think of that those rooms have in common? Are the affected areas all facing in one direction, for example?

A dehumidifier is an easy one to try, we've got one which is only used very occasionally but it is surprising how much moisture they suck out of the air. The fact you say that when you light a fire, it helps a lot - how do you mean it helps, do you mean you see less condensation on the windows or have you measured the relative humidity in the rooms? If you've not measured the RH then it could be worth doing, a meter is cheap enough to buy. A fire will of course pull lots of fresh air in and push moisture laden air out, so it makes sense to see an improvement.

I'd be surprised if your cellar is actually dry - very few are! It maybe that you're just not seeing condensation. I'd check the RH before pulling any air in from there.

On your questions:-

1) I don't see why DG would give you an improvement - if it's cold areas of wall around the windows and elsewhere where the damp is settling due to condensation. Yes, you'd get less condensation on the glass, but that doesn't sound like where your problem is.
2) You can absorb condensation but it's still there and you're not fixing the issue - if that is what it is!
3) and 4) I know nothing about PIV but suspect that extra ventilation could well be your key, in which case PIV could be a good answer. Why would you want to push air into the cellar? I presume it would need to vent outside.
5) Extractor fans would I think just give you an almighty heating cost. A dehumidifier is not a long term solution but could be worth trying as a quick & easy to see if things improve
6) If it is condensation settling on cold areas then insulating those cold areas could be part of a solution. Also, you've not mentioned the exterior of the walls - is penetrating damp due to poor pointing or one wall getting all the driven rain onto it a possibility?
7) Good!

Hope that helps

 

[Flyfisher]

So, what do the bedrooms and living room have in common that the other rooms don't? The obvious one is people - you spend more time in there than the other rooms, breathing out water vapour.

That was my first thought as well. People breathe out a lot of water vapour and if it can’t escape then it will condense on cold surfaces. Our SG bedroom window is often wet on cold mornings but if we leave it slightly open then it is almost dry. Of course, this makes the room colder, and although we’re ok with a cool bedroom I appreciate this might not suit everyone. This ventilation vs insulation thing can be tricky.

Also, I’m not 100% sure of this, but I’ve read that mould growth is an indicator of condensation rather than penetrating damp. This is because penetrating damp tends to bring out salts from within the mortar whereas the common black mould requires freshwater to thrive, of which condensation is a good source. On this basis, a dehumidifier would be a good, if temporary, way to reduce condensation. I’d guess it would need to be used for a few weeks to see if it has any effect but it could be a good diagnostic tool.

I'd be surprised if your cellar is actually dry - very few are! It maybe that you're just not seeing condensation. I'd check the RH before pulling any air in from there.

Me too. Our cellar never seems particularly damp in the winter months, probably because the colder air cannot carry as much moisture than the warmer summer air, but in the summer we’ve had water drips form on the joists of the floor above - possibly an example where good ventilation is not such a good idea as the humid summer air meets the colder cellar environment. We now run a dehumidifier in the cellar during the summer months and it has cured the ‘drips’ problem and gives us a good supply of demineralised water as a byproduct!

 

[untitled]

Thanks Feltwell and Flyfisher for the comments.

I'm convinced it is condensation and not damp from elsewhere. We do actually have a damp patch on the living room wall which is from the pointing and this is different to the mould problem. In fact as flyfisher mentioned, this wall, although damp and exterior and in a shady Easterly orientation, has no mould growth but is definitely damp. The patch is also dark from moisture but not black from mould. However I take the point that this one source of extra moisture. This has what I feel is an obvious fix which is to re-point with lime mortar and I intend to do that next Spring. It is obviously adding to the RH but as you both say there is a pattern suggesting condensation from us living here! Another point to mention is that the kitchen is located centrally in the flat and has no door so plenty of steam can migrate through the property.

The mould only grows in rooms we occupy and only on walls that have an exterior element to them. However I cannot see how I could insulate these on a solid brick property without re-lining the walls (?) which is not an option. Our property is a mid terrace but semi detached in the sense that it has a side passageway outside to the rear garden. Although south facing these walls get very little sun because of shading from next door. The other wall that is affected is North facing in our bedroom... a room used by my wife all day to make her jewellery (heavy occupancy).

However all the windows in the whole flat stream with condensation all the time from say October onwards. They leak air, are rattly and need replacing. I'm very interested in the DG or no DG for the sashes and I get what you say Feltwell about the condensation on the windows just be a punctuated focal point for RH which otherwise may move somewhere else in the house??? I'm very interested in getting more info about what to do when replacing the old ones... I might start a new post on this! I've attached a photo of the typical level of daily condensation on the windows.

When I referred to the fire (wood burner) helping I meant that within say one hour of lighting the fire the windows are dry. Next morning back to streaming again.

I take the point about the cellar... it only looks dry because the air is cold. I was wondering if one could use the cellar space to house an air pump to force air flow into the house and simultaneously suck used air out and vent it through the coal scuttle hole (much like our tumble dryer). I suppose though that this would increase heating costs as you say when referring to extractor fans.

Likely I will go with a dehumidifier in the first instance. Perhaps wall mounted in the centre of the property high up (in front of the kitchen) and look to generally reduce the condensation. I'll get a RH meter as well and monitor the changes. I also believe that some dehumidifiers come with a sensor for RH and switch off when a limit is reached.

If I get anymore info on Positive Input Ventilation I will post it. It seems that some swear by it but I'm struggling to see how this would help us if the property is already so air leaky.

So thank you both so much for your help and input! We will cut down on our breathing and I'll tell my son to definitely talk a little less!

Much appreciated.

 

[Cubist]

Hi There,
Just a thought as your problem may just be due to something fairly simple and relatively inexpensive to fix, or at least significantly improve. When we were preparing to give this old place a lick of paint shortly after moving in we discovered some small patches of black mould in the bathroom and kitchen. Initially I was not too surprised given that the problem seemed to be restricted to the most moisture laden rooms in the house but it did make me wonder if perhaps the problem could be more extensive - after all we had just bought the place and the PO had probably, albeit cheaply, redecorated throughout in preparation for the sale.

To cut a long story short, I ultimately found that a water-proof, presumably washable, emulsion had been used on the interior walls - several coats in fact - which effectively blocked any opportunity for them breathe as they should. The impact was to some extent off-set by the exposed timbers of the frame which absorbed much of the moisture and perhaps helped to limit the extent of the mould. Ultimately, I ended up removing all the paint back to the plaster and re-painting with breathable products. Eight years later and theres no evidence of the mould returning.

Looking at the pictures you have provided it may be worth your while checking the paint on your walls to see if someone has used non-breathable paints in the past. I found that the stuff used in our place would frequently peal off in strips several inches long that were slightly flexible which seemed to prove my belief they were some kind of plastic, water-proof emulsion.

Hope this helps but keep us posted concerning how you get on.

Cheers,
Cubist

 

[Feltwell]

I think your condensation thoughts sound like they are spot on - the damp & mould is occurring in the coldest places in each room, exactly where condensation will happen.

I don't think DG will cure your problem, in fact it could make it worse without other actions being taken as well. Firstly, you're taking away a cold surface that some of the moisture is condensing on now - secondly, and more significantly as you stand now, your new windows even with trickle vents will probably have less ventilation than what you have today.

So, logically, what can be done? Well, unless you're a big fan of having boiling pots of pasta on the go all the time and wet washing everywhere, I can't believe that 3 people are putting a substantially bigger-than-normal amount of moisture into the air, you've got plenty of background ventilation, so why the problem that others in similar situations don't see? All I can think is that you've got some unusually cold surfaces. To cut the condensation you've either got to reduce the RH - through a dehumidifier or increased ventilation - or bring the cold surfaces up to a temperature where condensation doesn't happen.

How could you do that? You could:-

- Dry line walls with insulated plasterboard. Very invasive, makes the rooms smaller, stops any breathability (which may or may not be a problem).

- Use a system like Warmshell - still very invasive but it's breathable https://www.lime-green.co.uk/warmshell/warmshell-interior

- Take existing plaster off and use an insulating, lime-based plaster, back the same level as the current plaster. This could be the way to go I think - at least in a trial area to begin with. Yes, you won't get anywhere near the insulation values that dry lining or Warmshell would give, but so long as it's enough it'll stop the condensation and you won't get the other problems. Here's an example:- https://www.lime-green.co.uk/products/lime-systems/ultra

- Any other areas, like voids in window frames for example, may need packing with insulation.


The good thing is of course, if this works, it cuts your heating bills, costs nothing to run, requires no maintenance and is silent - unlike all the mechanical options to reduce RH.

Another thought, if you did want to lower the RH, as well as PIV, have you looked at heat recovery units - MVHR systems? I know very little about them but the theory looks good!

 

[CliffordPope]

I've never been fully convinced by the concept of breathability - I find it difficult to visualise what is really meant to be happening.

We have warm and moist air inside a room, and assume that it will want to breathe outwards through the wall and waft away outside.
Why should the air want to pass outwards - why doesn't the air outside breathe inwards? Surely the room would need to be slightly pressurised, to push it outwards?

The warm air holds more moisture than the cold outside air. As the warm air begins its passage through the wall, it surely begins to cool? So it will be shedding moisture all the way, until finally it reaches the outside and is almost as cold as the air it is going to mix with?
Or is the warm air supposed miraculously to stay warm all the way through the wall?

What happens to the moisture deposited inside the wall?
Assuming that it too prefers to migrate outwards (why?), what does it do when it reaches the outside? If it's raining outside and the wall is wet because rain is rarely vertical, the additional water from inside the house is hardly going to evaporate - the wall is going to stay wet until the weather changes and becomes warm and sunny?

So to be free from condensation we either need:
An unheated house with the windows open
A very hot house with the windows shut
We all wear breathing masks and air pipes connected to extractors.

 

[MatthewC]

I've never been fully convinced by the concept of breathability - I find it difficult to visualise what is really meant to be happening.
...
What happens to the moisture deposited inside the wall?
...

Firstly Clifford, whatever one's understanding of breathability, I want to say that IT WORKS! I moved in here in July 2011 after 8 months work, using the things I had learned from this forum and from Mike Wye (I did their one day course), and this house has been warm and dry.

Secondly, as I understand it, there is no air passing through the wall, just water. It does this by capilliary action at the molecular level I think. If you coat the inside wall with vinyl paint, any condensation can only sit on the wall and evaporate inside the house when the inside temperature and humidity allow it. Otherwise, anywhere the condensation sits, black mould is likely to appear. However, if your wall is breathable then the moisture is continually absorbed into the wall where it spreads itself by capilliary action. The water that gets to the outside (preferably in the pointing, not the stone) will evaporate to the atmosphere.

NB By taking the moisture away from the inside room, it becomes easier to raise the temperature of the room. People often are unaware of the latent heat of evaporation which is defined as the amount of heat that you need to add to a liquid to turn it to a vapour without raising its temperature. Thus if you retain that moisture in the room then you have to add a significant amount of heat just to get the water into water vapour and only then can you raise the temperature of the room. The water is effectively sucking the heat from any heater.

I'm sure someone else will be along soon with a more cogent explanation!

Matthew

 

[Flyfisher]

I've never been fully convinced by the concept of breathability - I find it difficult to visualise what is really meant to be happening.

We have warm and moist air inside a room, and assume that it will want to breathe outwards through the wall and waft away outside.
Why should the air want to pass outwards - why doesn't the air outside breathe inwards? Surely the room would need to be slightly pressurised, to push it outwards?

I tend to think of these things more in terms of equilibrium rather than absolutes. Firstly heat. It's not so much the inside warm air that 'wants' to pass outwards, it's more that the difference in temperature between inside and outside will 'want' to equalise and this always means thermal energy moving from a hot area to a cold area until both are at the same temperature. Indeed, it requires a source of energy In order to maintain a difference in temperature, hence our various forms of heating systems (and the same applies to a refrigerator - energy is required to keep the inside cool against the natural tendency for it to heat up to the exterior temperature). Insulation will of course slow down the rate of heat transfer but it cannot ever prevent it.

In terms of moisture, the same sort of thing applies. Assuming a permeable structure (and of course that may not be the case!), a high concentration of water vapour inside will tend to migrate to a lower concentration outside until an equilibrium is reached (and the reverse is also true). However, if a high concentration of water vapour is contained within an impermeable structure, then the water vapour cannot migrate and will remain in place. Worse, if the temperature falls below the dew point then the water vapour will condense into liquid water, which is what is happening on the cold windows (and other cold areas) in this case. I reckon it would be a safe bet that the rooms in question have been painted with modern paints and that, by virtue of their acrylic content, that have significantly reduced the permeability of the rooms in question, leading to a build up of water vapour and the condensation problems being discussed.

Of course, these things are not 'either/or', they are a matter of degree. Even the most permeable structures can suffer from condensation if the generation and build-up of water vapour is greater than the ability of the structure to absorb and dissipate it. An extreme example would be a bathroom with the window wide open but the mirror still steams up when a hot shower is in full flow - but shut off the shower and the open window would quickly dissipate the excess water vapour, equilibrium would be returned and the mirror would unfog. In a building, however, such things happen far more slowly and equilibrium may take many hours, days, perhaps weeks, to be achieved - or, if the occupants run hot showers many times a day, constantly boil pans in the kitchen with no extraction and dry their washing on the radiators (OK, extreme scenario!) then it may never be achieved, with all manner of problems as a result.

 

[88v8]

We have some mould here but only in our half-timber rooms, where there is a geological thickness of modern paint. PO repainted the walls with obsessive frequency, perhaps to cover the mould. Ironic that his painting was exacerbating the problem.

The Ebac 2650E dehumidifier is quiet and fuss-free. We have one in our cellar, it's on 24/7 but only runs when the humidity requires. One cannot dial in a percentage but there are various settings. It can be connected to a drain, or emptied when full which is how ours works. It does indeed work much more in summer. Partly this is because our house is intrinsically damp but dries out in winter with the two woodburners in daily use.
https://www.ebac.com/dehumidifiers

The kitchen should have an extractor, the kitchen should have an extractor!!!!! ..... used without fail when cooking and perhaps whilst washing up. Otherwise the kitchen just feeds moisture into the house. The easiest installation may be into a pane of a window. Otherwise through the wall.

The bathroom may also be an issue depending whether bath or shower and how connected it is to the rest of the house and whether people open the window whilst bathing. Even a slow extractor with a humidity switch set at about 60%, will be a big help.
http://www.bathrenovations.co.uk/humidity-sensor-extractor-fans-for-bathrooms/
Again, a fan can be installed into a window pane, just make sure your chosen fan has this facility.

We have recently changed some of our windows from single glaze to dg. A lot less moisture on the windows. Howevere, that does not mean the moisture has gone, just that it's not on the windows. When it was on the windows I could and did vacuum it off with the Karcher - you have a Karcher of course? - but now I can't.
Hmmm.

Ivor

 

[untitled]

Another thought, if you did want to lower the RH, as well as PIV, have you looked at heat recovery units - MVHR systems? I know very little about them but the theory looks good!

I understand the PIV system to be more appropriate for air leaky properties where as heat recovery systems are best used in sealed buildings and passive houses. I've read several times that heat recovery won't give any value for money when used in a drafty house.

Thanks for all your suggestions... Honestly it has been so helpful! Whilst I'd love to be able to hack off all of the gypsum and paint this is not realistic at the moment.

On a note about breathability... it truly does work. My example is as follows:

For 3 or 4 years we had constant black mould and wet (dripping) walls underneath our two south facing sash windows. At that time (before I knew mould needed fresh water to thrive and not water containing salts from brickwork) I though we had rising damp. Anyway so I scraped off the paint and found gypsum plaster underneath. Below this level was a fairly thick cement render. When I reached the bricks I was expecting to find damp or wet brickwork but in fact it was bone dry. I re-rendered these areas with lime mortar and lime plaster then painted with a breathable paint. We have had zero damp there and no mould since. It's just a shame I can't do the same for the whole house... or internally insulate either.

In conclusion, at the moment I see the only way forward is to rely on a dehumidifier and a fan in the kitchen + upgrade the bathroom fan as Ivor suggests. I have already ordered this dehumidifier online: https://www.airconcentre.co.uk/pro...atinum-dehumidifier-3-year-warranty-meaco20le

I will let you know how this progresses.

In terms of DG or single glazed I'm going to have a heck of a job convincing my other half that DG might make the problem worse! The theory of course is sound given that matter is neither created nor destroyed and the RH in the house will still be there although not evident on the glazing. Oh and yes... we do have a Karcher and it's quite therapeutic to use! I'll probably start a new thread on the Double Glazing because there might be some issues with Building Regs if we replace like for like.

You've all been so helpful and this is a fantastic community!

Many many thanks indeed.

 

[Matt Green]

Have a look at humidistat fans: you may find you can install one or more to good effect in the areas most prone to condensation.

 

[CliffordPope]

Secondly, as I understand it, there is no air passing through the wall, just water. It does this by capilliary action at the molecular level I think.

Then I have been confused by the frequent use of the term "breathable". I always understood this to mean the passage of a gas, in this case that of air containing water vapour, also a gas.
You are saying the wall does not "breathe" in that sense - it is actual water, creeping through the structure - more like "soaking" or "seeping" then than "breathing"?

I can see that heat will pass outwards through the wall, because it is colder outside.
What I still don't understand is how water vapour inside a warm room manages to migrate by some means through a wall and escape through an outer surface damp from rain. I can see it will do it in a warm summer, but condensation occurs in a damp British Autumn/Winter/Spring.

 

[untitled]

UPDATE:

The dehumidifier arrived last Sunday and it has made such a difference to the feel and comfort of our house. The damp smell has all but disappeared and whilst the rooms feel cooler they actually feel fresher and much more comfortable. The CH seems to work better as well.

The dehumidifier is as follows: https://www.airconcentre.co.uk/prod...atinum-dehumidifier-3-year-warranty-meaco20le

The humidistat registered 79% generally around the house. How accurate it is I don't know. After a couple of hours in my son's room (small space) it was down to 55%. Our bigger bedroom was again at 79% and now it runs fairly consistently at 61-62% with the machine at half speed. It has dropped below 55% on full speed. Clothes feel dryer and the air is so much more pleasant. Water was actually pooling out of our fireplace back wall (single skin 4 inch brick) when the machine was on in the living room and we easily collected 18 litres of water in one day.

I've attached a window before/after photo. Ok.. it is much warmer today (12C) so less condensation is expected but the difference is phenomenal. If you can see any pinpoints of water on the after photo it's because it's raining outside... not inside as before!

Thank you all again so much for the advice!

 

[Flyfisher]

Good news! Thanks for posting that follow-up. It's always good - and helpful - to know how successful any changes have been and this result seems pretty good proof of the problem being condensation rather than 'damp' related. Given the success with reducing condensation, I would expect the mould problem to also reduce or disappear. Perhaps cleaning off the existing mould with a mild bleach solution would help in resetting things so you can monitor any future occurences?

 

[untitled]

Indeed.

I will clean off the mould and report back over the next few months but at the moment I can safely say that our home is once again feeling healthy and the change is unbelievably drastic.

A visit from a sash window restorer is soon to be booked.

Thank you so much flyfisher!

 

[Spoilt Victorian Child]

UPDATE:

The dehumidifier arrived last Sunday and it has made such a difference to the feel and comfort of our house....

Water was actually pooling out of our fireplace back wall (single skin 4 inch brick) when the machine was on in the living room and we easily collected 18 litres of water in one day.

I have no experience of dehumidifier use, but isn't 18l of collected water in one room a lot for one day? It sounds huge. Does it collect that amount every day? Was this when you were still drying clothes on radiators?

The dehumidifier sounds like a good remedy, and I suspect the mould won't come back for as long as you're using it, but I still wonder why there is so much water vapour in the house in the first place?

 

[untitled]

The dehumidifier sounds like a good remedy, and I suspect the mould won't come back for as long as you're using it, but I still wonder why there is so much water vapour in the house in the first place?/quote]

The guidance and information shared in the previous posts seem to indicate why our house was/is so humid. Essentially although we have rattly windows our walls have large patches of gypsum plaster on them and are generally painted with modern emulsion paints. Coupled with the fact that we hadn't invested in decent extraction in the bathroom and kitchen meant that our RH had increased so far as to create plenty of black mould. The posts illustrate this quite well I think. I'd also add that the fireplace in my sons room is blocked up to make a desk and also in the living room we have installed a woodburner but even so essentially the chimney is wholly blocked apart from two small vents. We need to try to keep the woodburner door open sometimes to let air up the chimney.

It is no exaggeration to say that the dehumidifier has worked wonders. So the 18l in one day was without drying clothes. We use a tumble dryer for this installed in the cellar which vents out of the coal shuttle hole. After reading your post I asked my other half how much she has collected from our bedroom over two days use.

Answer: 35l.

Yes it is incredible but right now it is working away on half speed and the RH is 58% fairly consistently. I think the answer here is that we are consistently creating more moisture than we can imagine and this is stored everywhere... clothing, cupboards, doors etc. Our door now closes easily but before it continually brushed against the frame making an annoying 'honking' noise whenever opened.

I would seriously recommend. Our house is less cold and if we do turn the CH on it makes a significantly quicker heating impact.

We all feel so much better.

 

[Flyfisher]

Our house is less cold and if we do turn the CH on it makes a significantly quicker heating impact.

We all feel so much better.

The faster CH responsiveness is a result of not having to heat up all those litres of water contained in the air as water vapour, as MatthewC previously pointed out.

It will be interesting to see how the current 58% humidity gradually drops over the next few weeks as everything dries out and the house reaches a new equilibrium. But don't overdo it because too little humidity will be uncomfortable. I've read that 40-50% is a good range but I'm sure there will be loads of guidance about this online.

Glad to hear you're all feeling so much better already.