Vapor barrier in the ceiling

[okaenrique]

Hello,

I am renovating the roof on two bedrooms in my house built in '77. There is no vapor barrier today. Do I need a vapor barrier?

How should a vapor barrier be installed between the beams and the new gypsum ceiling? The insulation between the ceiling and the attic is mineral wool.

I am also going to install new gypsum boards on existing walls. Do I need a vapor barrier in between?

The attic is not insulated today.

 

[Tompafix]

Hi,

I'm renovating the roof of two bedrooms in my house built in 77. There is no vapor barrier today, do you need a vapor barrier?

How should you place a vapor barrier between the studs and new gypsum ceiling? The insulation between the ceiling and the attic is rock wool.

I will also put new plasterboards on the existing wall, do I need a vapor barrier in between?

The attic is not insulated today.

Sorry, but I'm not quite following.
You write that there is insulation, then you write that it is not insulated?
Did I understand correctly that you are going to renovate two bedrooms under this rock wool insulation, but the attic is unfinished?
How thick is the layer of insulation today?

 

[okaenrique]

Sorry, but I'm not quite following.
You say there is insulation, then you say it isn't insulated?
Have I understood correctly that you are going to renovate two bedrooms under this rock wool insulation, but the attic is unfinished?
How thick is the insulation layer today?

That's right, the attic is unfinished (attaching a picture).

How thick is the insulation layer today?

20 cm
There is some type of plastic today between the insulation and the interior ceiling, I don't know if it is a type of vapor barrier (attaching a picture).

 

[Tompafix]

Absolutely right, the attic is unfinished, (attaching a picture).


20 cm
There is some type of plastic between the insulation and the interior ceiling today; I don't know if it is a type of vapor barrier (attaching a picture).

If there is plastic between the interior ceiling and the insulation, it is most likely the vapor barrier. But with 20cm of insulation, it doesn't make a huge difference, as the dew point is usually outside of this.

 

[okaenrique]

If there is a plastic layer between the interior ceiling and the insulation, it is most likely the vapor barrier. But with 20cm insulation, it doesn't matter that much, as the dew point is usually outside of this.

How thick should the insulation be?

 

[Nissens]

If there is plastic between the inner ceiling and the insulation, it is most likely the vapor barrier. But with 20cm of insulation, it doesn't make a huge difference, since the dew point is usually outside of it.

Of course, the vapor barrier matters. It prevents moist air from inside from getting into the insulation.

 

[Jonatan79]

Double vapor barrier is unnecessary.

 

[Tompafix]

20cm was the standard in the past. Now, much more insulation is used, around 40-60cm, in new houses.

 

[Tompafix]

Of course, the vapor barrier matters. It prevents moist air from the inside from reaching the insulation.

Yes, but the vapor condenses outside the insulation with not so thick layers of insulation.

 

[okaenrique]

Double vapor barrier is unnecessary.

Is the one in the picture a vapor barrier?

 

[Nissens]

Yes, but the steam condenses outside the insulation with not so thick insulation layers.

It depends on the temperature outside/inside.
Say it's 15 degrees outside and 20 inside. Then there's only a 5-degree difference and the condensation is guaranteed to end up inside the insulation.

Regardless, the vapor barrier plays an important role in preventing humid air from inside the house from reaching the insulation.

 

[okaenrique]

It depends on what the temperature is outside/inside.
Let's say it's 15 degrees outside and 20 inside. Then there's only a 5 degree difference and the condensation ends up inside the insulation for sure.

Regardless, the vapor barrier has an important role in preventing moist air from inside the house from getting into the insulation.

Is the one in the picture a vapor barrier?

 

[Nissens]

Is it a vapor barrier in the picture?

It could be, as it's in the right place. What contradicts this is that it looks a bit too thin, and I have never seen black age-resistant plastic.

 

[okaenrique]

It could be that, it is in the right place. What contradicts that is that it looks a bit too thin, and I have never seen black age-resistant plastic.

Here is another picture

 

[Nissens]

Here is another picture

It doesn't look like a vapor barrier, in my opinion. On the other hand, I can't say what it actually is either. Maybe some kind of vapor brake?