ᐅ Single-family house U-values: Good or not so much?

Hi Homebuilding Community,

Are these U-values for our new 110sqm (1,184 sq ft) single-family house considered good or not so much?

Exterior wall: Lambda 0.09 W/mK
Attic ceiling: 0.17 W/m²K
Roof: 0.17 W/m²K
Ground slab: 0.24 W/m²K
Front door: 1.8 W/m²K
Windows: 1.06 W/m²K

What would be the typical energy efficiency category you would roughly assign to these values? KFW 100, 70, 55, or 40?

Good evening,

Nutshell schrieb:

What would be the usual category that you would roughly be classified in with these values? Kfw 100, 70, 55, or 40?[

What are you hoping for, or what has your provider suggested to you?

Regards, Bauexperte

Bauexperte schrieb:
Good evening,


What are you hoping for exactly, or what has your supplier promised you?

Regards, Bauexperte

Good evening to you as well,

I know that the KfW rating is not very meaningful when it comes to actual heating costs. The supplier confirmed a KfW55 standard with these values.
However, that doesn’t necessarily mean the insulation is "good," so I am hoping to get some comparison values to see whether I am doing reasonably well or if the insulation still leaves something to be desired despite the "KfW 55 package."

Nutshell schrieb:

I know that the KfW rating is not really indicative of the actual heating costs; the builder confirmed a KfW55 rating based on these values. However, that doesn’t necessarily mean the insulation is “good,” so I’m hoping to get some comparison values to see if my insulation is fairly decent or if it leaves much to be desired despite the "KfW 55 package."

What makes you say that about the actual heating costs? For me, it has always been that a KfW 55 means the house consumes only 55% of the energy compared to a standard reference building. Your house supplier guarantees you KfW 55, or you ordered it—so in the end, does it really matter how the individual values are distributed?

Hello,

apart from the fact that it would be more than reckless to respond based on the following data

Nutshell schrieb:

Exterior wall: Lambda 0.09 W/mK
Attic ceiling: 0.17 W/m²K
Roof: 0.17 W/m²K
Ground slab: 0.24 W/m²K
Front door: 1.8 W/m²K
Windows: 1.06 W/m²K

I would – subjectively – assume from these figures that it is a standard single-family house, according to the Energy Saving Ordinance.

Nutshell schrieb:

... the provider confirmed a KfW55 with these values.

Based on my experience, this would only work with appropriate technology and only to the extent that it is supported by reliable calculations.

Which heating system has your provider guaranteed you in their offer/contract?

And by the way – as a supplement to my post – the above values don’t say anything about the final efficiency rating of the single-family house. But – if your provider has given you a “written” guarantee to deliver a KfW 55 efficiency house, they are also obliged to do so.

Regards, Bauexperte

Bauexperte schrieb:
Hello,

apart from the fact that it would be more than reckless to comment based on the following data,


I would – subjectively – assume from these data that it is a standard single-family house according to the Energy Saving Ordinance.


In my experience, this would only work with the appropriate technology and only to the extent that it is based on reliable calculations.

What heat generator did your provider commit to in the offer/contract?

And by the way – as a supplement to my post – the above values do not say anything about the final efficiency rating of the single-family house. But – if your provider has given you a "written" assurance that they will deliver a KfW 55 efficiency house, they are obligated to do so.

Regards, Bauexperte

Since a KfW 55 house was ordered turnkey, it is naturally guaranteed in writing ;-)

Heat generator:
Gas condensing boiler: Viessmann Vitodens 300
System control: Vitotronic 200
Solar thermal 5m² (54 ft²): Vitosol 200-F
Solar storage tank: Vitocell 100-W 300 liters (79 gallons)

Technology:
Gas condensing boiler with solar for domestic hot water
Underfloor heating in all rooms
Decentralized ventilation Lunos e² with 90% heat recovery

To clarify the statement about KfW and actual heating costs again:
The primary energy demand depends on the chosen heating system, so it can be artificially “improved” by, for example, calculating with a pellet stove.

I’m not really thrilled that the house is insulated like a standard building according to the Energy Saving Ordinance :/