ᐅ Insulation of the Attic in an Old Country House

Created on: 28 Jul 2020 22:04
M
Mayooox
M
Mayooox
28 Jul 2020 22:04
Hello fellow home builders,

My partner and I recently became proud owners of an old country house with a sizable plot of land. The ground floor is finished and was mostly renovated when we purchased the property.
Now we are starting the conversion of the attic. I have a few questions about this and would appreciate your expert advice.

So far, the attic has no insulation at all. Installing insulation is our top priority.

The wall insulation is planned as internal insulation. Exterior wall – insulation – interior cladding (gypsum boards).
The structural engineer recommended a minimum of 14cm (5.5 inches) of insulation with WLB035, with at least 4cm (1.5 inches) of ventilation space behind it for internal insulation. Air supply from below and exhaust through the cavity. I understand the basic idea behind this.
However, I’m not clear about the exact construction details.
How does the fresh air enter from below? Will there always be a visible gap between the floor covering and the drywall partition?
And can I omit a vapor barrier with a ventilation cavity? Or is the most sensible build-up exterior wall – 4cm (1.5 inches) ventilation cavity (battens) – mineral wool insulation – vapor barrier – drywall?

Unfortunately, only the extension roof has an underlay membrane installed. For most of the roof, you can look directly up at the concrete roof tiles from below.
Removing the tiles and installing an underlay membrane is hardly an option due to the effort and costs involved. I have read several times that an alternative looks like this:
Install insulation with at least 4–5cm (1.5–2 inches) of air space to the roof tiles; put the vapor barrier on the inside, followed by the interior cladding (we also want to use gypsum boards here). Essentially, this is just a ventilated roof build-up. Does anyone have experience with this? The roof pitch is 42°.

Dachboden mit Holz-Balken, Staub, Spinnweben und Tonziegeln.

Unterseite eines Dachstuhls: Holzbalken und rote, gewölbte Dachziegel; Staub sichtbar.

Dachbodenansicht mit freigelegtem Dachstuhl aus Holzbalken und Sparren, Licht durch schmale Spalten.


Many thanks in advance to everyone who can help.
J
Joedreck
29 Jul 2020 06:53
Regarding interior insulation, I recommend consulting a true expert. Interior insulation can be very critical when it comes to issues like mold and humidity.

Roof: fill the space between the beams with mineral wool, leaving a 2cm (0.8 inch) gap to the roof tiles. Then, nail beams or battens across on top and fill the space there again. After that, install a climate membrane and gypsum board. Done.
As a general rule for insulation: the more, the better.
Regarding heat protection: mass is power.
K1300S29 Jul 2020 07:41
Put differently: The supply air obviously comes not from inside but from outside.
M
Mayooox
30 Jul 2020 06:26
Thank you for the responses.
I still don't quite understand the ventilation from behind. How does the fresh air from outside get between the insulation and the wall? The masonry is closed after all.
K1300S30 Jul 2020 08:29
It's about the roof, right? The roof covering is not airtight.
J
Joedreck
30 Jul 2020 08:56
The interior wall insulation definitely needs to be planned and explained to you by a professional. I am self-taught and do a lot myself, but even I am extremely cautious when it comes to interior insulation, as it can quickly lead to serious building damage and mold.