Hello,
we received a quote for a single-family house built according to the Energy Saving Ordinance from a builder, who offers the following exterior wall construction:
- 17.5 cm (7 inches) aerated concrete
- Mineral fiber insulation mat with a minimum thickness of 14 cm (5.5 inches) according to the thermal protection certificate (thermal conductivity 0.035 W/mK)
- 11.5 cm (4.5 inches) facing brick
What is the evaluation of these materials regarding thermal insulation and soundproofing?
Are there quality differences in this construction as well?
For an additional cost of €2,000, the following upgrades are available:
- 140 mm (5.5 inches) cavity insulation with a thermal conductivity of 0.035 W/mK in the facing brickwork
- 180 mm (7 inches) mineral wool insulation with a thermal conductivity of 0.035 W/mK in the rafter area
- 240 mm (9.5 inches) mineral wool insulation with a thermal conductivity of 0.035 W/mK in the collar beam area
- 100 mm (4 inches) polystyrene rigid foam insulation with a thermal conductivity of 0.035 W/mK under the ground floor screed
With a solar system for domestic hot water preparation, which costs almost €7,000, KfW 70 standard could be achieved.
What do you think about this?
Is the standard specification sufficient, and is the upgrade worth the additional cost?
we received a quote for a single-family house built according to the Energy Saving Ordinance from a builder, who offers the following exterior wall construction:
- 17.5 cm (7 inches) aerated concrete
- Mineral fiber insulation mat with a minimum thickness of 14 cm (5.5 inches) according to the thermal protection certificate (thermal conductivity 0.035 W/mK)
- 11.5 cm (4.5 inches) facing brick
What is the evaluation of these materials regarding thermal insulation and soundproofing?
Are there quality differences in this construction as well?
For an additional cost of €2,000, the following upgrades are available:
- 140 mm (5.5 inches) cavity insulation with a thermal conductivity of 0.035 W/mK in the facing brickwork
- 180 mm (7 inches) mineral wool insulation with a thermal conductivity of 0.035 W/mK in the rafter area
- 240 mm (9.5 inches) mineral wool insulation with a thermal conductivity of 0.035 W/mK in the collar beam area
- 100 mm (4 inches) polystyrene rigid foam insulation with a thermal conductivity of 0.035 W/mK under the ground floor screed
With a solar system for domestic hot water preparation, which costs almost €7,000, KfW 70 standard could be achieved.
What do you think about this?
Is the standard specification sufficient, and is the upgrade worth the additional cost?
Sounds good so far...
That should be included in the initial price... or at least 5cm (2 inches).
There are always quality differences... one manufacturer is good, another is not...
However, I would pay the 2,000 euros and go for a fully insulated house. In my opinion, the price is reasonable.
You can skip the solar system, and instead choose thicker insulation to meet the KfW requirements—unless you prefer heating your water with solar energy.
Häusle77 schrieb:
- 100mm (4 inches) polystyrene rigid foam insulation with a thermal conductivity of 0.035 under the ground floor screed
That should be included in the initial price... or at least 5cm (2 inches).
There are always quality differences... one manufacturer is good, another is not...
However, I would pay the 2,000 euros and go for a fully insulated house. In my opinion, the price is reasonable.
You can skip the solar system, and instead choose thicker insulation to meet the KfW requirements—unless you prefer heating your water with solar energy.
Standard Construction Specifications:
- Below the foundation slab, 25cm (10 inches) of fill sand and a 5cm (2 inches) thick lean concrete blinding layer are installed.
- On the ground floor, a highly insulating 10cm (4 inches) thermal insulation (2-layer with thermal conductivity 0.035 W/mK) is laid, topped with approximately 6cm (2.4 inches) of floating screed.
- On the upper floor, floating screed is installed over 4.0cm (1.6 inches) impact sound insulation and a vapor barrier beneath non-ceramic floor coverings.
- The finished attic space receives high-performance mineral wool insulation as per the energy performance certificate requirements, but at least 180mm (7 inches) thickness (thermal conductivity 0.035 W/mK) with an underside diffusion-retardant membrane.
- On top of the rafters, a vapor-permeable membrane, counter battens, and roof battens are installed.
The windows have a U-value of 1.1 (double glazing with warm edge spacer).
Heating is provided by a gas-fired Vaillant condensing boiler "ecoTec" plus domestic hot water system (VCW).
What do you think? Should I spend an additional €7,000 on a solar system? How long does something like that typically pay off?
The €50,000 KfW loan at 1% interest doesn’t really justify the extra cost for me, especially since an inspector must also be paid (€1,800) for the KfW70 certification.
- Below the foundation slab, 25cm (10 inches) of fill sand and a 5cm (2 inches) thick lean concrete blinding layer are installed.
- On the ground floor, a highly insulating 10cm (4 inches) thermal insulation (2-layer with thermal conductivity 0.035 W/mK) is laid, topped with approximately 6cm (2.4 inches) of floating screed.
- On the upper floor, floating screed is installed over 4.0cm (1.6 inches) impact sound insulation and a vapor barrier beneath non-ceramic floor coverings.
- The finished attic space receives high-performance mineral wool insulation as per the energy performance certificate requirements, but at least 180mm (7 inches) thickness (thermal conductivity 0.035 W/mK) with an underside diffusion-retardant membrane.
- On top of the rafters, a vapor-permeable membrane, counter battens, and roof battens are installed.
The windows have a U-value of 1.1 (double glazing with warm edge spacer).
Heating is provided by a gas-fired Vaillant condensing boiler "ecoTec" plus domestic hot water system (VCW).
What do you think? Should I spend an additional €7,000 on a solar system? How long does something like that typically pay off?
The €50,000 KfW loan at 1% interest doesn’t really justify the extra cost for me, especially since an inspector must also be paid (€1,800) for the KfW70 certification.
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