Saddle roof/insulation into the ridge or up to/on the intermediate ceiling?

...I am extremely surprised that a TÃœV inspector is said to have made these statements

Likewise! Does that perhaps indicate the quality of a TÃœV inspector?

Best regards

Hello,

you should actually have reliable information regarding the necessary execution

This is how it looks with us: upper floor ceiling made of precast concrete slabs. Roof hatch specially installed for KfW 55 house. The vapor barrier lies on the ceiling.

Concrete ceilings in usual floor slab thickness are almost vapor-tight and airtight. Therefore, the use of a vapor retarder foil is normally not necessary.

On top of that, in the middle (so that the construction company, which is now bankrupt anyway, could quickly save money) an area of about 20 m² with polystyrene boards. The build-up as follows: 18 cm reinforced concrete ceiling. 1 layer PE foil glued and on top 24 cm XPS insulation WLG035. The rest was filled with glass wool. At the same height.

20 m² of walkable polystyrene boards? Minimum requirement according to Energy Saving Ordinance 2009: approx. 14–20 cm (U-value of 0.24 W/m[SUP]2[/SUP] K), recommended are 22–28 cm.

Thermal bridges exist everywhere the continuous insulation layer (to prevent cold bridges between insulation mats, it makes sense to lay the mats double-layered with staggered joints) of the ceiling is interrupted or ends. For optimal thermal protection, the insulation of the exterior wall should seamlessly transition into the ceiling insulation. Otherwise, thermal bridges remain (especially with concrete ceilings) where the ceiling rests on the exterior wall.

Now the confusion: Is that enough, or do you still need the rafter insulation as well?

If no deviating specifications were made in the Energy Saving Ordinance calculation for the building project => KFW 55 <= these measures are usually sufficient.

Rhenish greetings

Depending on what you want to store up there, it would be better to extend the insulation all the way to the top. The attic gets cold in winter and a certain amount of moisture will form.

Hi!

How does moisture form again? Otherwise, of course, it is true that moist warm air can enter the attic through diffusion (which is not really the case with the current construction) or through the floor hatch, etc. Since the attic, whether insulated or uninsulated, is cooler than the rest of the house, this air will condense there.

And now it wouldn’t be very smart to leave this area as it is. So I either have to insulate and heat – or not insulate and (so to speak automatically) ventilate! Of course, you should also do without a foil. This is how it was done in our house – although I can’t say what the fabric-like underlay membrane is made of – and it works great.

Summer heat is immediately discharged again and all the books etc. are fine.

Best regards,
Tomtom.

Hello Philiboy83,

not too long ago, I faced the same "problem". I did some research on the internet and came across an article about it. I decided to insulate all the way up to the ridge. I’m happy to send you the link via PM.

Hope I could help you?! Let me know what you decided.

Have you already made a decision? We want to insulate the attic because sooner or later we will use the space anyway. Therefore, we are insulating up to the ridge. But if you can rule that out, I would save the money if I were you. However, once you are at it, it is of course easier to insulate it right away. With insulation, boards, etc., it will be difficult to access later if you decide otherwise.