How to address my humidity issues

Aloysius1972

I am trying work out the best solution or solutions to my house’s high humidity and resulting condensation/mould issues. I would welcome any advice.

So, it is a large 5 bedroom Victorian semi over floor floors in Manchester. This includes a converted basement and two bedrooms with low or sloping ceilings in the roof space. My hygrometers suggest humidity is high all around the house, currently between around 68-70% on the ground floor living space (which is kept warmest at around 19-20c)) to 73-78% in the colder basement and attic rooms. Unsurprisingly at these levels we do get condensation and mould issues in some places. Strangely the basement is largely OK (perhaps the membraned walls help) as are the kitchen and bathroom. The worst issues are in the attic rooms (particularly the sloping ceilings) and in one corner of a first floor bedroom. There are only three of us in the house so we are not producing vast amounts of moisture as a household. Still, humidity remains very high even if we have been away a few days.

We have had the sloping ceiings reboarded with insulated plaster board and I am keen to work out the best next things to do before we redecorate those rooms. Here are some of the things I am considering:

1. Fit a powerful externally extracting cooker hood. I have only just realised our hood is only recirculating! As we do a fair amount of home cooking this seems a no brainer at the main source of moisture, especially as the kitchen/diner is not enclosed and is the centre of the home.

2. At the very least keep bathroom windows open more after showers and consider an extractor fan in there.

3. Add some background heating in the attic rooms (we rarely use them so they have been unheated). Also fling windows open for a bit each day (which we had never really done).

4. Consider some kind of active ventilation. Have been reading about PIV but I am wondering if it will be ineffective given the size of the property but also because there isn’t much of a loft. There is a very small space above one ceiling at the roof apex but the hatch is tiny and would need to be extended.

5. Is a heat recovery fan an alternative to sit on the small landing outside the two attic rooms (whose doors are next to each other)? Not sure I want one in each room given they are bedrooms.

6. Passive ventilation vents in the bedrooms perhaps but have read very mixed views on these.

7. Large dehumidifier on attic landing outside bedrooms perhaps? I bought and returned a 25L unit last week as it was noisy like a generator (advertised as ‘whisper quiet’!) but mainly because it was only extracting about half a litre of water per 24 hours operating non-stop in 70%+ humid rooms. Maybe a better quality one would extract more and be a little quieter, but I am also conscious that running it most hours (which it is likely to do on an open landing in a humid house) will prove expensive in electricity.

Thoughts gratefully received!

CapricornLass

Does your rainwater flow directly into the drains, or do you have soakaways?  Have you checked to see if they are blocked at all?  

We had soakways, but last year, we invested the time and effort in replacing them to meet modern regs, i/e, at least 5m away and not 1m as it used to be.  This has made a huge difference to the level of damp that is in our house.   We also maintain our house at 18C all year round

A specialised damp surveyor might also be worth it.  You will have to pay for this (my son paid £400 for a 3 bed terrace house, and he's in Salford so not far away)  but they will check damp courses, walls, venitlation etc.  and advise you what can/needs to be done, so worth considering.

Grenage

We have a Meaco dehumidifier; it's pretty effective.  Moist air rises, so having it higher in the house will be most effective. 

We also have an older house, and humidity is generally about 70 unless we are running the dehumidifier.  We have solar panels and cheap nighttime electric, so I have a timer to come on during daylight hours and cheap rate.  It's not particularly quiet - I don't think any of them really are.

Aloysius1972

Grenage said:

We have a Meaco dehumidifier; it's pretty effective.  Moist air rises, so having it higher in the house will be most effective. 

We also have an older house, and humidity is generally about 70 unless we are running the dehumidifier.  We have solar panels and cheap nighttime electric, so I have a timer to come on during daylight hours and cheap rate.  It's not particularly quiet - I don't think any of them really are.

I was thinking about running it on a timer to limit the cost and noise disturbance so it is on overnight only. But it seems none of the current dehumidifiers allow a timer plug to operate them as they will go into standby only and need the on button to be used to go through their start up routine.

i don’t know what size yours is but does my experience of a 25l unit extracting only half a litre per 24 hours sound like it was malfunctioning compared to your experience? This was on a landing outside two open rooms with 70% humidity.

Emmia

I'd consider humidistat fans in the bathrooms as they'll extract moisture when it goes over a certain level. We had damp and mould problems and 70%+ humidity in our flat, putting humistat fans in both bathrooms dropped the humidity by about 20% within a few days. It now tends to hover at 50-55%.

We have vent axia fans which are very quiet. 

We also have a meaco dehumidifier and that's very effective, but I mostly use it now when I'm drying washing inside.

Grenage

Aloysius1972 said:

Grenage said:

We have a Meaco dehumidifier; it's pretty effective.  Moist air rises, so having it higher in the house will be most effective. 

We also have an older house, and humidity is generally about 70 unless we are running the dehumidifier.  We have solar panels and cheap nighttime electric, so I have a timer to come on during daylight hours and cheap rate.  It's not particularly quiet - I don't think any of them really are.

I was thinking about running it on a timer to limit the cost and noise disturbance so it is on overnight only. But it seems none of the current dehumidifiers allow a timer plug to operate them as they will go into standby only and need the on button to be used to go through their start up routine.

i don’t know what size yours is but does my experience of a 25l unit extracting only half a litre per 24 hours sound like it was malfunctioning compared to your experience? This was on a landing outside two open rooms with 70% humidity.

We have their 20l model.  It's quite effective but the temperature needs to be 17+ for them to work well.  I don't have any experience of other brands, but I know ours turns back on when the timer kicks in. 

Basically if it is on when the power gets cut, it will start back up when it is restored.

If the air is very moist it can fill the tank in a day.

Albermarle

It is a bit unusual for a Victorian house ( high ceilings, open fireplaces, bit draughty generally , to have condensation problems.
Maybe you just have to leave some windows a bit open ?

WIAWSNB

Aloysius1972 said:

I am trying work out the best solution or solutions to my house’s high humidity and resulting condensation/mould issues. I would welcome any advice.

So, it is a large 5 bedroom Victorian semi over floor floors in Manchester. This includes a converted basement and two bedrooms with low or sloping ceilings in the roof space. My hygrometers suggest humidity is high all around the house, currently between around 68-70% on the ground floor living space (which is kept warmest at around 19-20c)) to 73-78% in the colder basement and attic rooms. Unsurprisingly at these levels we do get condensation and mould issues in some places. Strangely the basement is largely OK (perhaps the membraned walls help) as are the kitchen and bathroom. The worst issues are in the attic rooms (particularly the sloping ceilings) and in one corner of a first floor bedroom. There are only three of us in the house so we are not producing vast amounts of moisture as a household. Still, humidity remains very high even if we have been away a few days.

We have had the sloping ceiings reboarded with insulated plaster board and I am keen to work out the best next things to do before we redecorate those rooms. Here are some of the things I am considering:

1. Fit a powerful externally extracting cooker hood. I have only just realised our hood is only recirculating! As we do a fair amount of home cooking this seems a no brainer at the main source of moisture, especially as the kitchen/diner is not enclosed and is the centre of the home.

2. At the very least keep bathroom windows open more after showers and consider an extractor fan in there.

3. Add some background heating in the attic rooms (we rarely use them so they have been unheated). Also fling windows open for a bit each day (which we had never really done).

4. Consider some kind of active ventilation. Have been reading about PIV but I am wondering if it will be ineffective given the size of the property but also because there isn’t much of a loft. There is a very small space above one ceiling at the roof apex but the hatch is tiny and would need to be extended.

5. Is a heat recovery fan an alternative to sit on the small landing outside the two attic rooms (whose doors are next to each other)? Not sure I want one in each room given they are bedrooms.

6. Passive ventilation vents in the bedrooms perhaps but have read very mixed views on these.

7. Large dehumidifier on attic landing outside bedrooms perhaps? I bought and returned a 25L unit last week as it was noisy like a generator (advertised as ‘whisper quiet’!) but mainly because it was only extracting about half a litre of water per 24 hours operating non-stop in 70%+ humid rooms. Maybe a better quality one would extract more and be a little quieter, but I am also conscious that running it most hours (which it is likely to do on an open landing in a humid house) will prove expensive in electricity.

Thoughts gratefully received!

Ahem.
1. Like, d'uh. Yes, extract every cubic inch of cooking moisture.
2. Like, d'uh. Yes, fit an extractor in the bathroom. Vent Axia make a Bluetooth model that constantly runs - silently - and then adjusts for moisture and - yes - smell.
3. You have attic rooms. I presume they are similar? Cool. Ok, leave one as it is, and in the other one crack open the window(s) a couple of inches, leave the door closed, and shut off the heating. Check them both after a few days. Guess which one will be bone dry without a trace of mould? Yes, the cold room with the open window.
Everything else, forget it - an avoidable waste of money.
Note down the rooms you actually use. Heat them to a comfy level, and trickle vent them. When not in use, turn the heating right down but properly ventilate them.
All other rooms, treat them like that 'test' attic room - heating off, doors closed, windows as open as you can. If it's cold and howly in there, great - it'll also be bone dry.
Ventilate ventilate ventilate.

MattMattMattUK

Aloysius1972 said:

I am trying work out the best solution or solutions to my house’s high humidity and resulting condensation/mould issues. I would welcome any advice.

So, it is a large 5 bedroom Victorian semi over floor floors in Manchester. This includes a converted basement and two bedrooms with low or sloping ceilings in the roof space. My hygrometers suggest humidity is high all around the house, currently between around 68-70% on the ground floor living space (which is kept warmest at around 19-20c)) to 73-78% in the colder basement and attic rooms. Unsurprisingly at these levels we do get condensation and mould issues in some places. Strangely the basement is largely OK (perhaps the membraned walls help) as are the kitchen and bathroom. The worst issues are in the attic rooms (particularly the sloping ceilings) and in one corner of a first floor bedroom. There are only three of us in the house so we are not producing vast amounts of moisture as a household. Still, humidity remains very high even if we have been away a few days.

We have had the sloping ceiings reboarded with insulated plaster board and I am keen to work out the best next things to do before we redecorate those rooms. Here are some of the things I am considering:

1. Fit a powerful externally extracting cooker hood. I have only just realised our hood is only recirculating! As we do a fair amount of home cooking this seems a no brainer at the main source of moisture, especially as the kitchen/diner is not enclosed and is the centre of the home.

2. At the very least keep bathroom windows open more after showers and consider an extractor fan in there.

Ideally yes to both of these, an extractor in the middle of the house might be difficult, in the bathrooms it is absolutely essential. 

Aloysius1972 said:

3. Add some background heating in the attic rooms (we rarely use them so they have been unheated). Also fling windows open for a bit each day (which we had never really done).

This will not really help that much, the condensation happens when the the warm moist air hits the cold external wall, so unless you keep the room warm enough to keep the walls warm you will not really gain much. The ventilation will help though. In those rooms it might be worth keeping the doors shut and putting a disposable moisture absorber in them near the area that gets condensation and replacing them as needed. If there is not a lot of damp air getting in there then that will take care of it. 

Aloysius1972 said:

4. Consider some kind of active ventilation. Have been reading about PIV but I am wondering if it will be ineffective given the size of the property but also because there isn’t much of a loft. There is a very small space above one ceiling at the roof apex but the hatch is tiny and would need to be extended.

PIV can be great but it does make your home colder, or you need to heat the incoming air which can be expensive in winter. They can be fitted relatively easily, a small unit in the top of a wall and drilled through to the outside. 

Aloysius1972 said:

5. Is a heat recovery fan an alternative to sit on the small landing outside the two attic rooms (whose doors are next to each other)? Not sure I want one in each room given they are bedrooms.

Not really, no.

Aloysius1972 said:

6. Passive ventilation vents in the bedrooms perhaps but have read very mixed views on these.

Trickle vents on windows yes, anything else probably not. Or just open the windows on the smallest settings once a day or so.

Aloysius1972 said:

7. Large dehumidifier on attic landing outside bedrooms perhaps? I bought and returned a 25L unit last week as it was noisy like a generator (advertised as ‘whisper quiet’!) but mainly because it was only extracting about half a litre of water per 24 hours operating non-stop in 70%+ humid rooms. Maybe a better quality one would extract more and be a little quieter, but I am also conscious that running it most hours (which it is likely to do on an open landing in a humid house) will prove expensive in electricity.

Thoughts gratefully received!

I have a Meaco 10L dehumidifier, it is a bit loud when running, but not intrusive if say watching TV, though I would not want one in the bedroom. At maximum power it draws 155w, that means about 3.7kWh per day or around 90p, however unless you have a serious damp issue it will not need to run 24 hours a day, 2-4 a day is probably more than adequate. You can set it to run when the humidity gets above a certain level, when not actively working it consumes 1.3w. 

Aloysius1972 said:

Grenage said:

We have a Meaco dehumidifier; it's pretty effective.  Moist air rises, so having it higher in the house will be most effective. 

We also have an older house, and humidity is generally about 70 unless we are running the dehumidifier.  We have solar panels and cheap nighttime electric, so I have a timer to come on during daylight hours and cheap rate.  It's not particularly quiet - I don't think any of them really are.

I was thinking about running it on a timer to limit the cost and noise disturbance so it is on overnight only. But it seems none of the current dehumidifiers allow a timer plug to operate them as they will go into standby only and need the on button to be used to go through their start up routine.

i don’t know what size yours is but does my experience of a 25l unit extracting only half a litre per 24 hours sound like it was malfunctioning compared to your experience? This was on a landing outside two open rooms with 70% humidity.

They do not like being shut on and off with using the power supply, it will damage the compressor and cause the unit to fail prematurely. 

Half a litre per 24 hours seems low, but what was the humidity at the end of that period? They could dry out the room they are in, or a hallway, but without adequate circulation they will not dry a whole house out. Also remember that the maximum extraction rate is based on 80% humidity at 30c ambient, though in a 20c house and 70%rh you should get 3.5-4.5L of water if there is enough circulation to keep the unit supplied with humid air. 

You can get a quieter model if you go desiccant, but they are not as good as compressor so stick with the latter. One thing to think about is that it might be worth putting it on a foam mat, depending on your floor construction that might significantly reduce how you perceive the sound. 

Aloysius1972

Thanks for all the advice. 

I was always conscious that the high humidity in the property was an issue even when we had not been at home producing moisture. So if the attic rooms are, say, 70% in these circumstances wouldn’t something else be needed.

my worry about venitlation is that the outside air here is often even more humid. I know that the RH drops when it is heated up indoors, but if the rooms have no heating this won’t happen and I will just be increasing the humidity further won’t I?

Emmia

Aloysius1972 said:

Thanks for all the advice. 

I was always conscious that the high humidity in the property was an issue even when we had not been at home producing moisture. So if the attic rooms are, say, 70% in these circumstances wouldn’t something else be needed.

my worry about venitlation is that the outside air here is often even more humid. I know that the RH drops when it is heated up indoors, but if the rooms have no heating this won’t happen and I will just be increasing the humidity further won’t I?

Normally outside air is less humid, if we have the back doors and windows open to create through draught, we can get the humidity down to around 45%, but clearly if you've got the heating on, you don't want to do this!