Condensation on window

[shaking]

We recently had our house renovated which included having all the external walls insulated. In my sons room his window sill is often damp and has spots of mildew. The other day I had to use a cloth to mop up the actual water on the sill. Should this be happening?

 

[peteb]

I have this same problem. I'll wait for an expert opinion to bow to. But its likely that the house is too air tight. The heat is kept in the house with no venting and when it hits the window where the otherside is cold it creates the water. As the moisture has no where to escape to it gathers on the sill and probably causes mould in the corners of the window. Which is what happens to me.

 

[Slim]

We recently had our house renovated which included having all the external walls insulated. In my sons room his window sill is often damp and has spots of mildew. The other day I had to use a cloth to mop up the actual water on the sill. Should this be happening?

Hi, did the renovation include double or triple glazing? W had that problem when we had single glazed plate glass but have never had that since installing DG. Having said that, we have vents in all bedrooms(draughty yokes but required!).

 

[flowerman]

You probably dont have enough mechanical ventilation in the house and you have too much warm and stale air stuck in the house.
Like a human needs air to breath,so too does a house in order to remain fresh.

 

[shaking]

We didn't replace the windows as they were already double glazed. I must open the vent in the room, I had it closed due to the cold weather but it makes sense that it needs air.

 

[roker]

Are you drying cloths in the house? do you have an extractor fan over your cooker? have you any gas appliances, these generate water?

 

[Leo]

Are drying cloths in the house? do you have an extractor fan over your cooker? have you any gas appliances, these generate water?

People generate moisture vapor as well, and we have generally high levels of humidity in Ireland, so you'll never eliminate all sources.

It's a common issue where the external walls have been insulated. Your existing windows are likely much less effective insulators, and are therefore colder to the point where condensation will form. Better windows, triple glazing, would improve the situation, but better ventilation will be your best bet.

 

[Guns N Roses]

I must open the vent in the room, I had it closed due to the cold weather but it makes sense that it needs air.

Having the vent closed is the most likely cause of the problem. Drying wet clothes on radiators is also a common cause of condensation on windows.