ᐅ Calculating the heat demand in kilowatts for a single-family house and how to heat the attic space

Hello!

We are building a solid KfW70 single-family house with 152 sqm (1.5 floors). A staircase already leads to the attic (26 sqm). There is an additional 26 sqm up there, intended initially for storage. However, once we have two children, the attic will be used as a guest/office room. We also want to keep the option of a small bathroom open. The ceiling between the first floor and the attic is wooden. Underfloor heating with an air-to-water heat pump is planned for the ground and first floor.

I have two questions:

1) How many kilowatts should my system have for 152 sqm or 178 sqm? Is there a general rule of thumb?

2) How would you prepare the attic for heating? I keep in mind that it might be used only for storage throughout our lives or only very occasionally as an office/guest room.

Tobiax...

Hello,

Tobiax schrieb:

On the ground floor and first floor, there is underfloor heating planned with an air-to-water heat pump.

I have two questions:

1) How many kW does my system need for 152 sqm (1634 sq ft) or 178 sqm (1915 sq ft)? Is there a rule of thumb?

You should discuss this with your supplier and ask them to include it properly in the heating load calculation. The air-to-water heat pump must definitely be sized larger to account for the potential use of the attic space, even if you might never actually need the higher flow temperature. If you fail to adjust the system accordingly now and later require the additional capacity, you will regret it and only be able to solve it at high cost.

Tobiax schrieb:

2) How would you prepare the attic for heating?

• Adapting the air-to-water heat pump for the attic requires extra heating demand as well as supply and return piping to the floor level at the top edge of the ceiling.
• For future electrical installation, two empty conduit pipes should be installed.
• For the later installation of a shower bathroom in the attic, hot and cold water connections as well as a waste water pipe need to be routed up to the floor level at the top edge of the ceiling.

Best regards

Hello,

Tobiax schrieb:
....So I have 2 questions:
1) How many kW should my system have for 152sqm (1,635 sq ft) and 178sqm (1,916 sq ft)? Is there a rule of thumb?

No, an exact heat load calculation and heating surface design, as well as hydraulic planning, must be carried out. Whether an air-source heat pump is effective at all for this project should be checked beforehand.
Since some uncertainties still exist, if an air-source heat pump is chosen, it should definitely provide full modulation!

Best regards