Positive input ventilation

[Squaredy]

13 hours ago, Conner said:

Crap cavity wall insulation conned by the free scheme in the 2000,

What type of cavity wall insulation is it?  I had mineral wool, which was acting like a sponge - so I paid to have it removed.

[Conner]

3 hours ago, Squaredy said:

What type of cavity wall insulation is it?  I had mineral wool, which was acting like a sponge - so I paid to have it removed.

Yes it’s the mineral wool. Most of the problems are above the windows only 2 courses on bricks above these so no wall  insulation. I will see what insulating properly in the loft dose

[Dan Maynard]

This sounds like your problem is cold surfaces. Warm air holds more moisture than cold air, and for any particular amount of moisture in the air there is a temperature at which it starts to condense out.

 

The cold glass surface is why old single glazed windows usually had lots of condensation in winter, but with double glazed the inside glass surface is warmer and so not below the dew point.

 

If you insulate behind the plasterboard should raise the internal surface temperature above the dew point and so stop condensation happening there.

[Squaredy]

4 hours ago, Conner said:

Yes it’s the mineral wool. Most of the problems are above the windows only 2 courses on bricks above these so no wall  insulation. I will see what insulating properly in the loft dose

Have you used a moisture meter on your walls?

[carlos]

On 25/01/2023 at 19:30, Squaredy said:

I have six hygrometers in my house, all giving humidity of about 50%.  Guess I don’t need a PIV system then!

what sort of hygrometers do you use?, thanks

[Conner]

Well gents as she who makes all the decisions has decided to have the wardrobes pulled out. I have found the cause of my condensation problem. The problem area is directly under a vent in the roof so cold bridging as the cold air from outside blows directly onto the insulation creating a cold area on the ceiling. Some ducting needed me thinks.

[carlos]

34 minutes ago, Conner said:

Well gents as she who makes all the decisions has decided to have the wardrobes pulled out. I have found the cause of my condensation problem. The problem area is directly under a vent in the roof so cold bridging as the cold air from outside blows directly onto the insulation creating a cold area on the ceiling. Some ducting needed me thinks.

or could the vent be leaking?!!!!

not sure what sort of roof set up you have but if the insulation is only on the ceiling level and the rafters are uninsulated then would there be much temp difference between above the ceiling insulation and outside?? hope that made sense!!

[Conner]

55 minutes ago, carlos said:

or could the vent be leaking?!!!!

not sure what sort of roof set up you have but if the insulation is only on the ceiling level and the rafters are uninsulated then would there be much temp difference between above the ceiling insulation and outside?? hope that made sense!!

Yes I think the temp difference is the problem. There is a small patch in the same place in the other bedroom. Traditional roof construction tiles and felt. I have checked the vents many times for leaks. Today is dry but a cold wind. The ceiling directly below the vent is very cold compared to the rest . Will duct the vents at 90’ into the loft

[GarethM]

Fitted wardrobes in older houses are a spawn of Satan for dampness as it stops air circulation.

 

Granted we leave the doors open, which kinda defeats the purpose of a wardrobe.

 

Might be a timber Vs MDF argument, for natural wicking away moisture I dunno.

[Muddy42]

2 hours ago, Conner said:

Well gents as she who makes all the decisions has decided to have the wardrobes pulled out. I have found the cause of my condensation problem. The problem area is directly under a vent in the roof so cold bridging as the cold air from outside blows directly onto the insulation creating a cold area on the ceiling. Some ducting needed me thinks.

 

the problem looks very localised for a cols spot on a ceiling? I would have expected it to fan out more