ᐅ Insulation of a Bungalow Built in 1967

Hello,

I have been offered a used bungalow for purchase. I would like to know your opinion on the insulation of the house.

The plans show:
Dunloplan
2.5cm (1 inch) of asphalt + Sillanisol.
2 layers of 500-gram bitumen paper
10cm (4 inches) concrete mix 1:8
15cm (6 inches) rolled gravel

Foundations: rammed concrete B160

Wall thickness: 30cm (12 inches)

Thank you and best regards

Stefan

Hi Stefan, in 1967, insulation was not very common yet. If I understand your description correctly, only the Sillanisol.2 could be insulation, which would be about 1–2 cm (0.4–0.8 inches), likely coconut fiber (which was common at the time). For comparison: today, you would install at least 10 cm (4 inches) of insulation (below and above the concrete slab). The 30 cm (12 inches) masonry is very sturdy. You don’t mention anything about the roof or the top floor ceiling. For your purchase: if you want comfort, you definitely need insulation; this would be the same with any other house, for example from the 70s or 80s.
Regards, Susanne Junghans from
Junghans&Partner, energy concepts and subsidy applications, Landau

Hello,

thank you for the quick reply.

Regarding the (flat) roof, the plans state:
"Trisoca" gravel-pressed roof
Sloped concrete
One layer of bitumen vapor barrier
Concrete slab
2.5cm (1 inch) Heraklith

However, the roof needs renovation, and I have an expert report from a roofing company. The company plans to install:
Thermal insulation made of Styrofoam DAA 100, 160mm (6.3 inches) thick
(I will leave out the rest of the cost estimate)

The existing roof insulation is 6cm (2.4 inches), if I am correctly informed.

The building has two floors.

Oh, and in the energy performance certificate (demand certificate), it states:
Classification H, final energy demand 264.6 kWh
(still with the unrenovated roof, which according to the chimney sweep is a good value for such an old house)

Would this then be generally acceptable with a renovated roof, or is the building structure/insulation of the concrete slab hopelessly outdated?

Best regards

Stefan

Hi again, 160 mm (6.3 inches) of expanded polystyrene insulation meets the legal requirements and will definitely improve the indoor climate. Make sure to do this, especially since you already need to seal the roof.

When it comes to aging, you need to differentiate: the building structure is said to last 100 years, so it is currently about halfway through its lifespan. The insulation and other structural components are designed and approved for about 30 years of service life, while the mechanical systems (heating, etc.) last around 15 years. Accordingly, these components will eventually need replacement. If something breaks, you should upgrade the thermal performance at the same time, so each time you maintain the house, you bring it up to current standards. That way, you keep your house well maintained.

Regarding your roof again: I don’t know if your roofer mentioned it, but for a single- or two-family house, you can get a 10% investment subsidy for your roof insulation if you achieve a U-value of 0.14. Ask your roofer—many can calculate this, and it might not cost more.

Best regards,
Susanne

Hello Susanne,

Thank you for your answers.

A follow-up question: We found out that the 30 cm (12 inch) masonry wall apparently consists of a 24 cm (9.5 inch) outer wall and 6 cm (2.5 inch) internal insulation (we don’t yet know the exact materials).

Was this a standard construction in the past? Are there any issues to be expected today, such as mold growth or similar? Exterior insulation doesn’t last forever either and will need to be replaced. Replacing internal insulation seems to be more complicated...

Thanks and best regards,

Stefan