ᐅ Do ventilation ducts need to be insulated?

Created on: 27 Feb 2020 10:46
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Golfi90
Golfi9027 Feb 2020 10:46
Hello everyone!

Our ventilation system (Zehnder) is installed in the attic.
The attic is insulated with 160mm (6 inches) of compressed mineral wool.
The ceiling below is also insulated, I believe with 240mm (9.5 inches) of compressed mineral wool.

The DN75 (3-inch) pipes running from the ventilation system to the rooms are simply laid on the roof boarding.

Do these pipes need to be insulated?

The attic is NOT heated. The rooms below, of course, are heated...

Our plumber says that the pipes do not need to be insulated.

What do you think?
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denz.
27 Feb 2020 11:08
Well, your attic is insulated, right, or am I misunderstanding?
Mine is not insulated. The ventilation unit is not located there either but in the utility room, although the pipes run along the ceiling of the top floor. The ceiling of the top floor is insulated with 22cm (9 inches). The pipes (flat channel) are therefore embedded in the insulation and have a coverage of 17cm (7 inches). So, basically like yours with 16cm (6 inches), except that you have even more space between the insulation and the pipes.
Mycraft27 Feb 2020 11:16
Golfi90 schrieb:

Do the pipes need to be insulated?
Most likely not, since you have an insulated attic.
Golfi9027 Feb 2020 11:27
The attic is insulated, yes.

But it is not heated.

So, in winter it can get quite cold up there...
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Grundaus
27 Feb 2020 11:42
What material are the pipes made of? Condensation forms on metal pipes. In addition, sound transfers more easily without insulation.
Mycraft27 Feb 2020 11:56
He is referring to DN75. These are typically the common blue, green, or white PE pipes. There should be no condensation forming when installed in an insulated attic.

Of course, the only way to be certain is through a calculation.

I usually recommend installing ventilation systems within the heated envelope to avoid any issues. However, in this case, the situation is already set. Clearly, something could be done afterwards, but without a calculation, it is just guessing since the rest of the roof is already insulated and that should be sufficient.