Relative Humidity

[MICH43L]

Hi all,

Big old Victorian Semi-detached house, hermetically sealed with too much wallpaper, a damp cellar wall, (although cellar is reasonably well ventilated and shut off from the rest of the house) .

When we moved in the bathrooms didn't have extractor fans, have fitted one, planning to do the other shortly.

One loft room has been converted and insulated, the other is cold and damp and will need taking back to brick and pitched roof and redoing. (There's currently insulation packed between the roof joists and no air gap).

A "5 bed house" dehumidifier is running on the landing, probably under spec for the size of house.

Relative humidity is around 53% and the house does have a propensity for mould which is a health concern.

What to do first?
A second dehumidifier.
Tanking slurry on the cellar wall.
Bathroom renovation with extractor.
The other loft room.
Strip the wallpaper and re-skim to let the walls breath a bit.
Something else?

 

[Safety First]

Just a few thoughts in no particular order...
Reduce moisture production- so yes get extractor in all bathrooms and kitchen if poss, too. Presume you are not drying clothes indoors either?
How long have you been using the dehumidifier? It can take many weeks to get a house 'dry' such that the dehumidifier (with inbuilt humidistat) actually turns off of it's own accord. Don't know what type of Dehumidifier you have but some have this feature and instructions note that it will take maybe weeks to get down to a level (with being on 24/7) before it only turns on occasionally to regulate.
Have you got two humidistats. Cheaper one's can vary a lot. I have three and there's a 15% variance between them. Don't know which is correct!
Unless the wallpaper is vinyl, I would not imagine there is that much moisture trapped within the walls that cannot get out.

When we have the chance, I have set the dehumidifier in the bathroom- in the bath with a drain off and gone away for the weekend. With no doors being opened and nobody adding to the moisture levels, it can be a very effective spell of use.

 

[Newboy]

1) Reduce moisture production - kitchen, bathroom, laundry

2) Improve ventilation/air ciculation

3) Insulation

4) Heating

 

[gasbanni]

Where's all the moisture coming from ?

Heat and ventilation are the answer but obviously it's a bit of a conundrum as heats expensive !

These are not too expensive and could be installed fairly easilly in some parts of the house.

https://www.bhfunlimited.co.uk/prod...MI27Oks7m31wIVij8bCh1KKQmjEAQYAyABEgI7APD_BwE

There various manufacturers....thats just one.

Victorian house....... are the chimney stacks allowing trickle ventilation. The external walls ....... I'm assuming they're solid this can decrease the moisture content and reduce heat loss
https://www.promain.co.uk/liquid-plastics-liquid-plastics-k501-7359.html

Don't use silicone .......This product has been used on old listed structures up and down the land.

Try opening up the chimneys and fitting wood burners ....This will give you heat and plenty of airflow. If the flues don't need lining the stacks will warm up, true I'm talking heresy here as the stoves will be less efficient.....but there is this .......when the house was built it will have had open fires warm stacks and loads of air flow !!

 

[MICH43L]

Thanks all for the comments. Yes, kitchen uses gas cooker and no proper extraction (just into chimney space, so we tend not to use). Need to sort this.

Condensor drier in utility room, usually shut door and open window.

Dehumidifier (dd128) is filling up (2.3L) every 12 hours. I like the idea of putting it in the bath on drain when we go away.

To measure RH I can recommend the ThermoPro units. You can put them around the house (and outside).

Gasbanni:
Moisture probably coming from the bathroom, kitchen, cellar, vents in loft room. We had the pointing done last year, not sure if there's some damp generally in the brickwork.

Wood burners.... Have you been talking to my wife?!

 

[gasbanni]

If the chimney is open and not capped extracting from the gas cooker in to it is fine and actually beneficial.
passive stack ventilation is good for the stack itself and if you fit an extractor in to it solves two potential problems !

You seem to have excessively high levels of humidity and your activities producing water vapour are no more than anyone's else's so something seems amiss.

Bricks absorb water and it evaporates on fine days.......the pointing ! See the other post on this for older houses.

You need heat and ventilation !

 

[Ian H]

If the chimney is open and not capped extracting from the gas cooker in to it is fine and actually beneficial.
passive stack ventilation is good for the stack itself and if you fit an extractor in to it solves two potential problems !

Is that right? I'd not even thought of that.

We have opened a chimney to put a cooker in but until I just read your post I'd not thought of venting it up the chimney!! I guess any grease get caught in the filter.

 

[Safety First]

I would say that your chimney, 5 years down the line will be a pretty nasty place unless your ducting goes all the way to outside. Chimneys are happier with air flow generally, but soley greasy steam is something else.

 

[Newboy]

If the chimney is open and not capped extracting from the gas cooker in to it is fine and actually beneficial.

Venting into the stack will leave you with a damp (and possibly greasy & smelly) stack. The stack will not warm up enough along it's full height and the moisture from cooking will condense in it.

 

[MICH43L]

Ye, I've read more posts on the chimney subject than I'd like to admit to. Suffice to say that I wish now that I'd specced into the original job some ducting that went up and then a 90 degree turn and out through the wall in the ceiling gap. Be a right mess to do it now.

 

[gasbanni]

Venting into the stack will leave you with a damp (and possibly greasy & smelly) stack. The stack will not warm up enough along it's full height and the moisture from cooking will condense in it.

No, the stack along as it's got air movement will be fine, filters catch the grease and the stack has continual draught because of the passive stack ventilation.

You only get a damp stack if the bottom is sealed and the top is open to atmosphere, you then get a cold slug of air in the stack, condensation forms on the inside surfaces that eventually work through to the stack to form damp patches inside. Put a vent at the bottom of the stack so you allow air movement and the stack dries out.

As is attested by problems with damp stacks that I've cured.

It's mostly steam the goes up the flue not grease, how come when we've changed chimney stack extractors on new kitchens when there's old ones that have been fitted and used for years theres no damp or grease ?

 

[gasbanni]

I would say that your chimney, 5 years down the line will be a pretty nasty place unless your ducting goes all the way to outside. Chimneys are happier with air flow generally, but soley greasy steam is something else.

You don't get greasy steam from vegetables, never seen a damp greasy stack when old extractors have been removed to put a new one in a domestic setting .....dirty yes ....greasy and damp no.

Commercial is obviously a different thing ......but from a domestic kitchen ....never seen it.

 

[Doggit]

It's an old Victoria house, and it's cold because it has single skin walls, and you very likely keep the windows closed to keep the heat in, hence the excess moisture in the house. You've said that there's a damp wall in the basement, but nothing more about it, nor how you tested it, but if it's well ventilated, then there shouldn't be an issue. Warm air rises, but cold air sinks.

Average humidity in Manchester is between 69 and 87, so 53% in the house would actually seem pretty good, and you may be worrying unnecessarily. You've got a propensity for mould due to the cold walls, and a lack of ventilation, that's all.

 

[gasbanni]

It's an old Victoria house, and it's cold because it has single skin walls, and you very likely keep the windows closed to keep the heat in, hence the excess moisture in the house. You've said that there's a damp wall in the basement, but nothing more about it, nor how you tested it, but if it's well ventilated, then there shouldn't be an issue. Warm air rises, but cold air sinks.

Average humidity in Manchester is between 69 and 87, so 53% in the house would actually seem pretty good, and you may be worrying unnecessarily. You've got a propensity for mould due to the cold walls, and a lack of ventilation, that's all.

More reason than ever to use K 501 !

https://www.promain.co.uk/liquid-plastics-liquid-plastics-k501-7359.html

Works like magic .......

 

[Safety First]

never seen a damp greasy stack when old extractors have been removed to put a new one in a domestic setting

Commercial is obviously a different thing ......but from a domestic kitchen ....never seen it.

Your experience of removing extractors (and without nasty surprises) I cannot contest. But a chimney open only at the bottom (vs open at both top and bottom) will be only momentarily pleased to have a kitchen extractor piped into it.
I'm not sure, but is it going to draw air when there is no cooking going on? I.e. might start to dry out a little?
I just don't think it's ideal- as in why stop there if there is a better plan? Maybe there isn't.. If it were my worst DIY problem, i'd be a happy man!