ᐅ Insulation Under Reinforced Concrete Slab for KfW 55 Standard
Created on: 20 Feb 2018 22:07
T
turbotopo
Hello everyone,
We are going to build a prefabricated house on a concrete slab foundation. Our builder told us that with KFW55 standard, insulation beneath the slab is not required.
Now we are wondering whether we should add it anyway and if it is a worthwhile investment.
The concrete slab:
Reinforced concrete slab as a load-bearing element made of in-situ concrete (c20/25, approx. 15-20cm (6-8 inches) thick, edge reinforced) with reinforcement according to structural requirements.
Costs for the insulation:
120 mm (5 inches) insulation with thermal conductivity class 040 under the slab of the residential building: 3115€
160 mm (6.3 inches) insulation with thermal conductivity class 040 under the slab of the residential building: 4930€
Will these costs ever be recovered through energy savings?
Best regards
We are going to build a prefabricated house on a concrete slab foundation. Our builder told us that with KFW55 standard, insulation beneath the slab is not required.
Now we are wondering whether we should add it anyway and if it is a worthwhile investment.
The concrete slab:
Reinforced concrete slab as a load-bearing element made of in-situ concrete (c20/25, approx. 15-20cm (6-8 inches) thick, edge reinforced) with reinforcement according to structural requirements.
Costs for the insulation:
120 mm (5 inches) insulation with thermal conductivity class 040 under the slab of the residential building: 3115€
160 mm (6.3 inches) insulation with thermal conductivity class 040 under the slab of the residential building: 4930€
Will these costs ever be recovered through energy savings?
Best regards
T
turbotopo21 Feb 2018 22:23OK, then I should first find out exactly what is between the concrete slab and the parquet flooring.
Alternatively, I could also ask the construction company that pours the concrete slab what it would cost directly with them.
Can you explain the advantages to me as a layperson?
Many thanks and best regards
Alternatively, I could also ask the construction company that pours the concrete slab what it would cost directly with them.
Alex85 schrieb:
The price has an extra zero. If there is insulation under the slab, you can save on insulation above it or do a combination of both.
Can you explain the advantages to me as a layperson?
Many thanks and best regards
T
toxicmolotof22 Feb 2018 00:10The advantage is that overall, the insulation needs to be effective. Otherwise, you'll end up with cold feet or, what I find much worse, you’ll be heating the sand beneath the floor.
An air-to-water heat pump relies on good to very good insulation. My question was more about the heat distribution method, meaning underfloor heating or radiators. But that question has already been answered.
An air-to-water heat pump relies on good to very good insulation. My question was more about the heat distribution method, meaning underfloor heating or radiators. But that question has already been answered.
turbotopo schrieb:
ok, then I should first find out exactly what is between the concrete slab and the parquet floor.
Alternatively, I could ask the construction company that pours the slab what it would cost from them directly..
Can you explain the advantages to me as a layperson?
Thanks and best regardsInsulation beneath the slab avoids thermal bridging, which cannot be said for insulation placed only on the slab or a combination of insulation above and below the slab. In my opinion, this is mostly theoretical.
A “disadvantage” of insulating only from below would be that the slab is heated from the building activation perspective—that is, the underfloor heating warms the slab because it isn’t insulated against it.
In the end, you will choose the system that is offered to you at the best price. And that is perfectly fine.
T
turbotopo22 Feb 2018 09:11So above the slab there is 6cm (2.4 inches) of insulation, 2cm (0.8 inches) of fixing panel, and 5.5cm (2.2 inches) of screed.
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