ᐅ KfW55 calculation with or without including the standard thermal bridge allowance?
Created on: 17 Jul 2021 11:32
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fabianbre
Hello everyone,
we are building a detached house with a gable roof. The house will have brick cladding. Our energy consultant provided two options for a KfW55 house.
Option 1) Thermal bridge allowance 0.05, exterior wall insulation 18 cm (7 inches) with thermal conductivity 0.032 W/(m·K), roof insulation 28 cm (11 inches) with thermal conductivity 0.032 W/(m·K)
Option 2) Thermal bridge allowance calculated individually, exterior wall insulation 18 cm (7 inches) with thermal conductivity 0.035 W/(m·K), roof insulation 24 cm (9 inches) with thermal conductivity 0.035 W/(m·K)
Is it because of the method of calculating the thermal bridge allowance that in option 2 a lower insulation thickness and a higher thermal conductivity can be used, or is there a typo?
Thanks and best regards
fabianbre
we are building a detached house with a gable roof. The house will have brick cladding. Our energy consultant provided two options for a KfW55 house.
Option 1) Thermal bridge allowance 0.05, exterior wall insulation 18 cm (7 inches) with thermal conductivity 0.032 W/(m·K), roof insulation 28 cm (11 inches) with thermal conductivity 0.032 W/(m·K)
Option 2) Thermal bridge allowance calculated individually, exterior wall insulation 18 cm (7 inches) with thermal conductivity 0.035 W/(m·K), roof insulation 24 cm (9 inches) with thermal conductivity 0.035 W/(m·K)
Is it because of the method of calculating the thermal bridge allowance that in option 2 a lower insulation thickness and a higher thermal conductivity can be used, or is there a typo?
Thanks and best regards
fabianbre
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nordanney20 Jul 2021 09:19Honestly? Just go with the thicker insulation and enjoy having a better insulated house. The price difference will be marginal (installation costs are the same).
Well, the price for the insulation is definitely much higher (I checked myself two weeks ago), almost a 100% increase. But with this volume, it might only add up to 1000–2000 EUR (approximately 1100–2200 USD), and when you consider the entire house construction, it's basically peanuts.
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nordanney20 Jul 2021 11:48Tolentino schrieb:
Well, the price for insulation is definitely much higher (I checked myself two weeks ago), almost a 100% markup. Someone is trying to rip you off. 18 cm (7 inches) of Neopor with a thermal conductivity of 0.032 W/mK is about 10% more expensive than 18 cm (7 inches) of Neopor with 0.035 W/mK. Then 20 cm (8 inches) with 0.032 W/mK costs another 10% more.
==> current market price (there has actually never been such a big difference before)
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nordanney20 Jul 2021 12:06Tolentino schrieb:
Wasn't there something similar recently regarding PUR/PIR with a thermal conductivity value of 0.023 W/(m·K)?That's right – Smartbau in Nettetal was mentioned. There you can get the 0.023 board for 20% less than the 35 EPS (expanded polystyrene) boards, although it is laminated with aluminum and paper. That's quite impressive. I really like this supplier (or their neighbor, who offers similar prices but also sells different products).Similar topics