ᐅ DK Summer House Insulation & Wall Construction

Hello everyone,

I hope you can help me with my renovation project.

I am currently renovating a small summer house from the 1970s in Denmark (approximately 40 m² (430 sq ft) of living space). Typical Danish summer houses often have relatively thin timber stud walls; in my case, they are currently 7 cm (2.75 inches).

The original wall structure was:

• Wooden cladding nailed directly onto the studs (without ventilation)
• A wind barrier made of a type of tar paper underneath
• 7 cm (2.75 inches) of mineral wool insulation between the studs
• Gypsum board on the inside

The walls are now completely stripped down, and the old insulation has been removed. Unfortunately, the walls were heavily infested with mice, which likely got in from the floor area. Addressing the floor sealing and closing holes to prevent mice ingress is therefore also on my to-do list.

The planned new wall build-up from outside to inside is:

1. New ventilated wooden cladding
2. Breathable wind barrier / membrane
3. Timber studs with 7 cm (2.75 inches) of mineral wool insulation
4. 12 mm (0.5 inch) OSB airtight glued
5. Installation cavity inside of about 4-5 cm (1.5-2 inches)
6. Wood paneling as interior finish

Since the house is only used occasionally and not permanently heated, I expect stronger temperature and humidity fluctuations. At the same time, we want to use the house both in summer and winter.

My main question:

• Would you insulate the installation cavity additionally or leave it intentionally empty?

The additional 4-5 cm (1.5-2 inches) of insulation would of course be interesting from an energy perspective, especially since the main insulation of 7 cm (2.75 inches) is rather limited. On the other hand, I often read that additional interior insulation can be problematic because the OSB layer could get too cold, potentially causing condensation issues—especially in buildings that are not heated continuously.

I am also concerned about the following:

• Do I need to pay attention to specific values or parameters with the breathable wind barrier?
• Has anyone had experience with products like “Nordland Vindspærre diffusionsåben”?
• What do you think about using 4 cm (1.5 inches) Gutex wood fiber boards on the outside instead of a classic breathable wind barrier? Does that make sense in my setup, or is it unnecessarily expensive?

Thank you very much!
Julian