Wall vents - good or bad.

[ant87]

Wall vents - good or bad idea. 

I have an old pre war house ( 1910 )

Had cement reponting at front, lime and cement mix on side and gypsum plater on walls in 2023 but see damp and mold at the corners of my living room walls and with the skirting boards all over the house.

 

I have a piv system in place due to poor ventilation and high humidity levels. I have trickel vents and open windows daily. 

 

Damp specialist said he would install 2 vents in the living room would clear up the damp and mold as he believes it is all due to lack of ventilation than modern methods simpley don't work. 

In my situation above does any one think vents will do any good or even make things worse? I have read a number of things that " ya they do wonders" and also " don't go never them they will make matters worse"

 

Mold low but high vent is advised by the damp specialist.

 

Any advise on vents please would be great 

 

Many thanks

[Mr Punter]

If there are trickle vents and they are not closed they should provide enough fresh air.

 

A dehumidifier is a cheap to run way of reducing humidity.  Get one where you can run the condensed water to the outside via a hole in the wall and piece of hose, so you can leave it switched on.

 

If the PIV is not doing the job, consider switching it off.  Constant running extracts may work better.

[Mike]

2 hours ago, ant87 said:

Damp specialist said he would install 2 vents in the living room would clear up the damp and mold as he believes it is all due to lack of ventilation

That would be a rather extreme measure.

 

To avoid condensation:

• Minimise the generation of moisture within the house (when cooking or showering / bathing)
• Extract excess moisture at the point at source (kitchen & bathroom extract fans, preferably humidity-controlled, or more sophisticated technology)
• Provide background ventilation to allow other moisture to escape (trickle vents plus PIV in your case, or more sophisticated technology)
• Keep surfaces warm (insulation and/or adequate heating)

And, if you still have a problem, I second @Mr Punter's suggestion of a dehumidifier.

[EdHat]

I find extractor fans in the kitchen and bathroom make the biggest difference and keeping doors to these rooms closed. Consider ones with a humidistat.

Activity in these rooms can cause big spikes in relative humidity (RH) and temperature. When the temperature then drops, after cooking and showering finishes or as the air moves to colder parts of the house, the RH raises further.

 

If you have extract fans in the kitchen and bathrooms and still have issues then I too would advise getting a decent dehumidifier.

You can set them at say 60% RH and they will turn on when it gets above this, preventing RH getting high enough for condensation and mould growth.

Meaco is a good brand and their units are low wattage

[ant87]

Thank you all for you advice. I was wondering just having vents and no insulation with only central heating would it really make a difference?

 

From what am hearing to make a big difference you need vents, insulation and proper hearing like heat pumps. 

 

The mold you see above i cleaned off and I am running a demidifher for 6 hours a day and dont see an damp or mold as of yet. I been running it on and off every day for a week in the living room. I now got a humidity detector and as I run a demidifher only in the day I noticed when I get up the living room humidity is above 75% each day and when the demidifher is on it lowers to 60% by the late afternoon. So the demidifher seems to do the trick but isn't idea but tbh might be my best option.

[Redbeard]

Insulation is your best option, as is good ventilation, and depending on your view, PIV might not be 'good ventilation'. There is an argument that, since it has no formal 'outs', it can just push warm, moist air into gaps in the building fabric, where it may condense out. A (still cheap) alternative is decentralised mechanical extract ventilation (dMEV) which uses extract in the wet areas to pull fresh air in through trickle vents in the 'dry' rooms.

 

Internal or external insulation in the long term. Internal more limited re space and re the risk of interstitial condensation (condensation occurring on the old wall behind your new insulation) if you are not v careful. EWI needs careful detailing, possible roof extension and sometimes moving windows/replacing them in a different position in the 'sandwich'. But you can usually insulate more if you do it externally.

[Andehh]

Another vote for a dehumidifier! Centrally located, empty twice a week, 20 second job!

Edited Saturday at 22:03 by Andehh

[Mike]

On 18/01/2025 at 09:35, ant87 said:

I was wondering just having vents and no insulation with only central heating would it really make a difference?

It would help, but it would enable the PIV to push more air out through the new vents, which would consequently reduce the PIV airflow in other rooms - though that's not necessarily a problem if you have trickle vents elsewhere. Unless the wind pressure blew the wind into the room through the vents. You could just leave the window cracked open and have the same effect. Either way it would increase your heating bill.

 

As above, a dehumidifier would be a preferable solution.