Damp and mould in our home

Doozergirl

LunaD said:

coffeehound said:

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

If you have a condensing boiler, then reducing the floww temperature dial down to about one-third of maximum will ensure that it runs efficiently.  It might then need to be run for longer, but it should still work out cheaper.  However if you have a hot water tank, this method won't heat it up enough unfortunately, though you might be able to work around that.

Thank you. So is the answer to keep windows closed all the time? No ventilation? 

No.  No one is suggesting that you never open a window but it isn't going to solve a chronic condensation problem.  

Doozergirl

LunaD said:

Doozergirl said:

coffeehound said:

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

You're wrong.   Trickle vents trickle, and you NEED consistent air changes in a house,  not to trap it, which is why opening windows does not work.   We're not supposed to live in sealed boxes.   Old houses breathe constantly through their numerous draughts, newer or refurbished houses need constant background ventilation.  

You don't lose huge amounts of heat through trickle vents, certainly not enough for the house to ever feel cold, which is exactly what happens when you open a window.   

I have mechanical ventilation with heat recovery in our house which is the gold standard, but the minimum standard for building control is the list I wrote in my previous post.  New houses don't have condensation issues precisely because they have the items I've listed.  They don't need to open windows to not have a house full of mould.  

If I turned my MVHR off right now, the humidity level would rise very quickly and I would have condensation on my incoming water pipe - the only uninsulated thing in the house, within a very short period of time.  Opening the windows wouldn't relieve it.  

Can I ask what is the mechanical ventilation you have in your house? 

Mechanical Ventilation with Heat Recovery (MVHR). You can google it.  It costs thousands and was put in when we built the house.  It probably isn't suitable for your situation.  

theoretica

LunaD said:

coffeehound said:

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

If you have a condensing boiler, then reducing the floww temperature dial down to about one-third of maximum will ensure that it runs efficiently.  It might then need to be run for longer, but it should still work out cheaper.  However if you have a hot water tank, this method won't heat it up enough unfortunately, though you might be able to work around that.

Thank you. So is the answer to keep windows closed all the time? No ventilation? 

Try one and then the other back and forth a few times and see how the measured humidity changes.  Then you will know how much of a difference it makes.

neilmcl

Have you looked into PIV (Positive Input Ventilation) systems?

LunaD

neilmcl said:

Have you looked into PIV (Positive Input Ventilation) systems?

I’ll look into this. Thank you.

neilmcl

LunaD said:

neilmcl said:

Have you looked into PIV (Positive Input Ventilation) systems?

I’ll look into this. Thank you.

The Nuaire Drimaster range seems to be a commonly used system but I'm sure there are others. In fact I think there was a recent post from someone who'd recently had one installed.

FreeBear

LunaD said:

FreeBear said:

Doozergirl said: I would definitely query whether your house is adequately insulated, or if it genuinely is and it hasn't slumped in the cavity, then you really aren't heating the house adequately as cold walls are usually needed for condensation to be a problem,

It would be worth getting hold of a thermal imaging camera and going round to see if there are any cold spots - Octopus (the energy supplier) loan them out to their customers, but are restricting to those in financial hardship at present. Might be worth checking with your local council as some may have one available. Get those cold spots checked out and deal with them where appropriate.

A damp wall is a cold wall which attracts condensation, leading to further damp. A vicious circle.

Thank you. I’m with OctopusEnergy I’ll look into that. What will it show needs doing if it detects an issue?

so if an outside wall feels cold it’s damp? What could be causing that as all pjs outside walls feel cold in our bedrooms?

A thermal camera will show you which areas of a wall is warm and which parts are cold. This recent thread has some thermal images attached and you can clearly see the location of some (hidden) hot water pipes - https://forums.moneysavingexpert.com/discussion/comment/78747496/#Comment_78747496 - Taking some images of a cold external wall, and you'll see dark colours representing the cold spots.

Just because a wall is cold won't necessarily mean it is damp - Much of it depends on the relative humidity of the air inside as well as the temperature. Black mold is certainly an indicator of damp, but that in its self does not prove the existence of condensation - A damp wall could be the result of a leaking gutter or slipped roof tiles/slates.

I have had a small room that was always cold with chronic condensation problems. I ended up stripping the walls back to bare brick (most of the plaster just fell off) and fixed Celotex insulation boards up before replastering. But this room has solid brick walls and the work was extreme redecorating.

LunaD

FreeBear said:

LunaD said:

FreeBear said:

Doozergirl said: I would definitely query whether your house is adequately insulated, or if it genuinely is and it hasn't slumped in the cavity, then you really aren't heating the house adequately as cold walls are usually needed for condensation to be a problem,

It would be worth getting hold of a thermal imaging camera and going round to see if there are any cold spots - Octopus (the energy supplier) loan them out to their customers, but are restricting to those in financial hardship at present. Might be worth checking with your local council as some may have one available. Get those cold spots checked out and deal with them where appropriate.

A damp wall is a cold wall which attracts condensation, leading to further damp. A vicious circle.

Thank you. I’m with OctopusEnergy I’ll look into that. What will it show needs doing if it detects an issue?

so if an outside wall feels cold it’s damp? What could be causing that as all pjs outside walls feel cold in our bedrooms?

A thermal camera will show you which areas of a wall is warm and which parts are cold. This recent thread has some thermal images attached and you can clearly see the location of some (hidden) hot water pipes - https://forums.moneysavingexpert.com/discussion/comment/78747496/#Comment_78747496 - Taking some images of a cold external wall, and you'll see dark colours representing the cold spots.

Just because a wall is cold won't necessarily mean it is damp - Much of it depends on the relative humidity of the air inside as well as the temperature. Black mold is certainly an indicator of damp, but that in its self does not prove the existence of condensation - A damp wall could be the result of a leaking gutter or slipped roof tiles/slates.

I have had a small room that was always cold with chronic condensation problems. I ended up stripping the walls back to bare brick (most of the plaster just fell off) and fixed Celotex insulation boards up before replastering. But this room has solid brick walls and the work was extreme redecorating.

Thank you for your help. So in my daughters room where she gets the damp/mould, she’s  got 2 outer walls and the damp is near the bottom of these walls. Granted some of it is where she’s got a set of drawers and her bed so I know that’s why the damp/mould is coming through on the bottom half of the wall but she’s got an area on her outer wall where nothing is up against it and it’s growing green mould/black and peeling off the wallpaper. She then has on the upper part of the external wall in the corner where it just looks like damp with a little bit of black . It is mainly across the bottom half of the walls, where she does have some furniture but like I’ve said some parts are not covered by furniture and it still grows mould. The walls will feel cold as well in those areas. So I’m not sure what that could be because it’s not  all high up if it was tiles or something on the outside .

donemedosh

We have issues with condensation /damp but are working on the possible cures. I have been told by a damp proof installer that if it is wet & damp outside do not open the windows as this lets damp air in. But I would certainly get dehumidifier & as others have said it is a balancing act between heat & air flow.

FreeBear

By the sounds of it, you have more of a problem that can be attributed to cold spots & condensation alone - Not entirely convinced that ventilation is going to cure it.

Are the walls rendered externally ?

If so, are there any cracks showing that could allow rain to penetrate ?