Damp inside wall - likely cos cold room next door

[LivinginKata]

I have a number of rental units. The bedrooms all have air cons. Built 19 years ago and no problem until 2 months ago. New guys moved in one unit a 6 months ago. Work night in club,, Run air con very cold 18 when get home 05.00. Lady next door not use air. The adjoining wall starts to get wet by 13.00.

 

Just to confirm there is no connection between the 2 air cons. Each has own compressor line and water drain on own side of wall and don't connect. 

 

All previous guests in these units used air con lightly while sleeping. This lady does not want use for health reasons. I am assuming it might be some sort of thermal inversion causing condensation on the warm side.

 

Question - how can I solve this. Yes, I know get another tenant that uses air con. But serious answers please. Some sort of easy wall treatment like a paint or spray.  

[VocalNeal]

Ask him if he can run a 20 because of condensation in adjoining room. He might... 

 

My wife has it set at 22 and still uses a fan.

[johng]

If the problem is the wall being too cold..( thin wall ? )

then I think the answer would be  installing insulation, vapour barrier and then another "skin" to the wall  ?

so not easy or very cheap.

 

However are you sure the water is not coming from a water leak from the roof,the aircon, a pipe buried in the wall  or even rising damp ?

[tjo o tjim]

Dehumidifier for the tenant that doesn’t like AC. 

[LivinginKata]

4 hours ago, VocalNeal said:

Ask him if he can run a 20 because of condensation in adjoining room. He might... 

 

My wife has it set at 22 and still uses a fan.

 

We have talked with him a number of times. Asked if he has any condensation. His bedroom no problem. Nice guy but he gets to set the temperature.

 

We run ours at 24.

[LivinginKata]

4 hours ago, johng said:

If the problem is the wall being too cold..( thin wall ? )

then I think the answer would be  installing insulation, vapour barrier and then another "skin" to the wall  ?

so not easy or very cheap.

 

However are you sure the water is not coming from a water leak from the roof,the aircon, a pipe buried in the wall  or even rising damp ?

 

Yes, Thin single block wall. 

 

For sure no external water leak. Can't think rising damp as condensation starts at ceiling level and rolls down over a number of hours. And apartment is 19 years old with no previous problems.