KFW 70 house and chimney

Hello everyone,

we will soon start building our house. 120 sqm plus living basement. (A total of 160 sqm)
KfW 70 according to the Energy Saving Ordinance 2009 with an air-to-water heat pump.

A chimney for the fireplace is also included.

Now a woman is just looking for the most beautiful fireplaces with 10 KW output, but I am afraid that due to the well-insulated house we will soon have a 160 sqm sauna.

What output is allowed for the fireplace?
Or is my fear unfounded?

Regards Uwe

Good evening Uwe,

we will soon start building our house. 120 m2 plus residential basement. (Total 160 sqm) KFW 70 according to the Energy Saving Ordinance 2009 with air-to-water heat pump.

Do you already have a building permit?

What output is allowed for the chimney?

There should be a thermal protection certificate for the house; ideally a heat load calculation. You should find what you need there.

Rhenish greetings

Actually, with new buildings you can assume that such a chimney is definitely oversized. I would choose one with the lowest possible output. But it becomes difficult to find something under 5KW.

.... we will soon start building our house. 120 m2 plus living basement. (A total of 160 sqm) KFW 70 according to the Energy Saving Ordinance 2009 with air-to-water heat pump......What capacity is the fireplace allowed to have?..

[INDENT] As a smart builder, you surely have adequate system planning/dimensioning, which is especially important for air heat pumps. The heating load calculation shows the room heating load of the installation room. You can use that as a guideline!

....Or is my fear unfounded?

No!

Best regards. [INDENT]

In general, you can assume two things. 10 KW is too much, and the wood stove only heats the room it is in...
Ours has 5 KW and stands right by the door to the living room. But hardly any heat reaches the stairwell without a fan.

A little is recovered through the ventilation system, but for us the stove is just a gimmick if we want it comfortably warm in the evening.
However, if you actually plan to use the stove and want it to take on part of your heating load, you can't avoid having a planner who sizes the thing for you.

Hello,

I also think that 10 kW is probably slightly oversized.

In our new building, a soapstone stove with 5 kW is going into the open living/dining area of about 60 sqm - and even that is more than makes sense according to the heat demand calculation. We should install a stove with a maximum of 4 kW, but finding a stove of that size that we also like was impossible for us...

Regards,

Dirk