Decision on Insulation Thickness (Economic Calculation)

"Paying off" is always such an individual matter.

I would like to be able to assess whether the additional cost (12->14: ~650€, 12->16: ~1300€, 12->18: 2000) pays off or not.

In this context, I would (even if not 100% reasonable) only consider the insulation. The heat pump is fixed, and I did not want to open a complete cost calculation regarding drilling meters now.

So how do I put the above values into perspective?

Regards
Markus

With a view to the heat source and the rather (somehow) rising than falling heating costs, I would take the 18cm.

We were able to achieve KFW55 through the change from 14 to 18cm and a photovoltaic system based on the Energy Saving Ordinance (old before 2016). I'm surprised that this year you are supposed to get by with 12cm to meet the current Energy Saving Ordinance.

What does the rest of the heating (energy) concept look like?

Do you know if you can get by with a smaller size for the heat pump? Could possibly save around 400 euros that way.

We financed without KFW and are therefore not bound to any requirements.

Geothermal energy and controlled residential ventilation. Underfloor heating throughout the whole house. The heat pump is modulating - with the even smaller model, I would be a bit "cowardly" that it might not be enough.

How do I calculate this now. With a naive view on the "decimal places," I would have said 16cm is enough based on gut feeling.

Regards Markus

You have an energy demand per sqm for 12 cm and for 16 cm insulation. You multiply the difference by the area to be insulated and the result is then the difference in heating demand that the heat pump must cover. Let's assume your heat pump has an annual performance factor of 4. Then you divide this heating demand by 4 and multiply it by the amount that one kWh of electricity costs for you.

PS. What kind of heat pump did you choose?

Hi,
honestly, the differences in the values seem very small to me. If the values are correct, the difference is not even 200 kWh/year when comparing 12 cm to 18 cm insulation.

So not more than 200 *0.3/4 = 15 € difference per year?

From a gut feeling, that doesn't quite add up... I would have expected at least 50-100 € savings. However, that still doesn't pay off!

Regards,

Andreas

I find that a bit strange too. The values come from the architect - it could be that he miscalculated.

Thermal conductivity 0.034 W/m*K - thickness as described above. approx. 237m^2 insulation boards

The heat pump is the Buderus WPS 10-1.

If I base it on primary energy demand, I have a difference of 12->16.

31.87 - 30.67 = 1.2
Difference times area - so 225 sqm

1.2*225 = 270.

Assumed performance factor 4
270 / 4 = 67 KWH / year

30 cents / KWH => 20 € / year.

That just doesn’t add up :(

Could the original numbers be correct?
Regards
Markus