Hello everyone,
I currently need to decide on the thickness of our ETICS (External Thermal Insulation Composite System) for the facade. According to the energy-saving regulations, I need at least 12cm (5 inches) on my precast concrete elements.
I have now received quotes for 14cm (5.5 inches), 16cm (6.3 inches), and 18cm (7 inches) as well.
According to the architect, the energy demand differs as follows:
Thickness Final Energy Demand Primary Energy Demand
12 cm (5 inches) 17.70 31.87
14 cm (5.5 inches) 17.66 31.78
16 cm (6.3 inches) 17.04 30.67
18 cm (7 inches) 17.01 30.62
The units are kWh/m²a.
So, what now?
The house has a full basement. Basement and roof insulation are not to be considered here. Geothermal energy will be used as the energy source, and a controlled mechanical ventilation system with heat recovery will be installed. The windows have triple glazing. Overall, about 220 m² (2370 ft²) of living and usable space will be fully heated (attic insulated but not heated).
Do I now have to multiply the difference by the living/usable area, apply my average kWh price, and that will be the additional annual cost? Or am I thinking about this incorrectly?
Thanks and regards,
Markus
I currently need to decide on the thickness of our ETICS (External Thermal Insulation Composite System) for the facade. According to the energy-saving regulations, I need at least 12cm (5 inches) on my precast concrete elements.
I have now received quotes for 14cm (5.5 inches), 16cm (6.3 inches), and 18cm (7 inches) as well.
According to the architect, the energy demand differs as follows:
Thickness Final Energy Demand Primary Energy Demand
12 cm (5 inches) 17.70 31.87
14 cm (5.5 inches) 17.66 31.78
16 cm (6.3 inches) 17.04 30.67
18 cm (7 inches) 17.01 30.62
The units are kWh/m²a.
So, what now?
The house has a full basement. Basement and roof insulation are not to be considered here. Geothermal energy will be used as the energy source, and a controlled mechanical ventilation system with heat recovery will be installed. The windows have triple glazing. Overall, about 220 m² (2370 ft²) of living and usable space will be fully heated (attic insulated but not heated).
Do I now have to multiply the difference by the living/usable area, apply my average kWh price, and that will be the additional annual cost? Or am I thinking about this incorrectly?
Thanks and regards,
Markus
K
Knallkörper18 Mar 2018 02:11-Markus- schrieb:
According to the architect, the energy demand differs as follows
Thickness End energy Primary energy demand
12 cm (5 inches) 17.70 31.87
14 cm (5.5 inches) 17.66 31.78
16 cm (6.3 inches) 17.04 30.67
18 cm (7 inches) 17.01 30.62Hello,
if the insulation is made from the same material in each case, then the numbers cannot be correct. Someone has made a calculation error, or the 16 cm (6.3 inches) and 18 cm (7 inches) insulation is of significantly better quality.
By "significantly better quality," do you mean the "savings" are too high?
I was able to follow the calculation fairly well based on the U-value formulas, and considering the "small" amount of exterior wall surface, the difference seemed realistic to me.
If there are calculation errors here, then the software the architect has been using for several years to prepare energy performance certificates would be incorrect. All other parameters remained the same.
Regards,
-Markus-
I was able to follow the calculation fairly well based on the U-value formulas, and considering the "small" amount of exterior wall surface, the difference seemed realistic to me.
If there are calculation errors here, then the software the architect has been using for several years to prepare energy performance certificates would be incorrect. All other parameters remained the same.
Regards,
-Markus-
K
Knallkörper18 Mar 2018 18:27Sorry, but this mistake is almost obvious. The extrapolation from 12 to 14 to 14 to 16 does not add up. Simple rule of three.
K
Knallkörper18 Mar 2018 18:48However, if all other parameters remain the same, the change in energy demand when increasing the insulation thickness from 12 to 14 cm (5 to 5.5 inches) is roughly the same as when increasing it from 14 to 16 cm (5.5 to 6.3 inches) or from 16 to 18 cm (6.3 to 7 inches).
Knallkörper schrieb:
However, if all other parameters remain the same, the change in energy demand when increasing insulation thickness from 12 to 14 cm (5 to 5.5 inches) is of the same order of magnitude as from 14 to 16 cm (5.5 to 6.3 inches) or 16 to 18 cm (6.3 to 7 inches).However, a building loses energy not only through the walls but also through the floor, roof, windows and doors, thermal bridges, and ventilation.
The original poster should not confuse the calculated primary energy demand with a consumption forecast. Actual consumption also depends, among other things, on the occupants’ behavior.
When considering cost-effectiveness, it is important not only to look at energy costs but also to take into account savings such as lower investment in building services—for example, a smaller heat pump, fewer drilling meters, etc.
Increased insulation can also lead to greater subsidies (KFW, regional programs, climate settlements, etc.). Alternatively, one might insulate so extensively that underfloor heating is no longer necessary (7,000–10,000 € savings -> passive house).
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