ᐅ Insulating and Ventilating the Attic Space?

Created on: 25 Apr 2014 13:48
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SvShS
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SvShS
25 Apr 2014 13:48
Hey

We are currently in the shell construction phase of our house.
Now the question has come up whether the attic should be insulated or only the "attic floor" (sorry, I can’t think of the exact term right now).
The attic is meant to be storage space, among other things for books and such that do not tolerate moisture well. And that’s where my problem lies. So far, we have been told to insulate both the attic floor and between the rafters up to the ridge.
Now my question is: how does ventilation and condensation management work in this case?

  • Do I need special ventilation tiles, so I could avoid insulating between the rafters?
  • If I insulate, I’m not allowed to ventilate continuously or open windows in the attic daily, which is not exactly convenient.
  • Insulate and install radiators to avoid temperature fluctuations in winter, and possibly reduce or eliminate condensation.

Maybe also relevant: We are building for KfW55 standard. However, the attic won’t have any windows.

Regards
€uro
25 Apr 2014 16:50
Hello,
SvS schrieb:
...Now the question arose whether the attic should be insulated or only the "attic floor" (sorry, I can’t think of the right term right now)....
=> UGD (uppermost floor ceiling)
SvS schrieb:
....The attic is only intended as storage space, including for books and such that don’t tolerate humidity well. And that’s where my problem is. So far, we have been advised to insulate the "attic floor" and also between the rafters up to the ridge...
A strange recommendation!
SvS schrieb:
....

Now my question is how ventilation and condensation control works?...
That depends on the specific roof construction. There are different options here!
SvS schrieb:
....We are building to KfW55 standard. But we won’t have windows in the attic...
Then careful planning and proper sizing of heating, domestic hot water, and ventilation systems is essential. Otherwise, KfW55 will only be on paper.

Best regards
f-pNo25 Apr 2014 17:34
Hi,

I am not an expert. However, we just had a conversation yesterday with our site manager, who told us the following:

The insulation in our house is also installed on the top floor ceiling. We also plan to use the attic for storage one year after moving in—once the "final drying" is complete—and to finish it with OSB boards (is that the correct term? I need to double-check). Access to the attic is through a pull-down stairs.

The site manager’s advice was this:
If the stairs are opened only rarely per year (7 to 10 times), the insulation setup is completely sufficient. However, if the "large room" in the attic is used more frequently and the pull-down stairs are opened often, warm, moist air from the living area moves into the attic. This then condenses on the "cold" membrane (what was the name again?) and water runs down it. The normal roof ventilation is no longer adequate for this. So, if the use is expanded, an additional insulation layer of 6cm (2.4 inches) should be applied between the rafters. I understand that this means the moist warm air will no longer condense on the cold membrane because the roof is already insulated between the rafters. The moist warm air will then be removed through the regular roof ventilation.

However, we plan to use the attic only for storage and therefore won’t need this.

(I hope I have explained this correctly and clearly in my layman’s terms.)