Another Insulated plaster board question

YourAverageJoe

Hi,

I am currently building a concrete block house. There is 70mm of xtratherm board in the cavity. I was intending to put insulated boards on the internal wall. I had intended putting 50 or 60mm boards inside but having read posts mentioning the rule of thumb i have decided to use 30mm (not including the plaster board). Can anyone tell me if there is a potential mould problem with this setup or how i could calculate the potential myself?

Poor Uncle Tom

If you have condensation constantly occuring on the coolest surfaces in a room, you need to regulate ventilation and heating to stop this happening. Happens most in late autumn, winter and spring.

Every house and sometimes every room has a different moisture content as they have different moisture sources. Say, cooking in the kitchen, showers in the bathrooms, washing machine/drier in the utility room, etc., and people and pets throughout the house.

Regulation of heating and ventilation will ensure the moisture laden air is removed from the house. It is this simple but it takes a lot of management.

heinbloed

YourAverageJoe wrote: »

......if there is a potential mould problem with this setup or how i could calculate the potential myself?

Yes and maybe.

There is always a potential mould problem with internal insulation.
Once an external wall is covered internally with a thermal insulator it's temperature will drop, the risk of condensation increases.
The calculation of the "dynamic dew point" is complicated but can be done manualy.
To get it quickly and relyable done check with your architect/engineer. There is a program called " wufi " and now as well " wufi + "( see www).

The Glaser method (which was used previously and sometimes still is) is only for statical temperatures and moisture levels. An external wall is exposed to changing temperatures and moisture levels, therefore the "dynamic" calculation is to be prefered.