Calculate heat demand in kW for a single-family house, how to heat the attic

Hello!

We are building a massive Kfw70 single-family house with 152sqm (1.5 floors). A staircase already leads to the attic (26sqm). Here are another 26sqm. These are initially intended to serve as storage space. However, as soon as there are 2 children, the attic will be used as a guest/workroom. We also want to keep the option of a small bathroom open. The ceiling between the 1st floor and the attic is made of wood. Underfloor heating with an air/water heat pump is planned for the ground floor/1st floor.

I therefore have 2 questions:

1) How many kW must my system have for 152sqm or 178sqm? Is there a rule of thumb for this?

2) How would you prepare the attic for heating? I always have in mind that this might be used only as storage space for life or only very rarely as a workroom/guest room.

Tobiax...

Hello,

In the ground floor/1st floor a underfloor heating with air/water heat pump is planned.

I therefore have 2 questions:

1) How many kW must my system have for 152sqm or 178sqm? Is there a rule of thumb?

You should discuss this with your supplier and ask them to consider this accordingly in the heating load calculation. The air-water heat pump must in any case be sized larger for the attic usage case ... even if you will never need the flow temperature. If you fail to adapt the system accordingly and later need the additional space, you will regret it and will only get out of it with high costs.

2) How would you prepare the attic for heating?

[*]The adaptation of the air-water heat pump to the attic requires additional heat demand as well as supply and return lines to the storey up to the top edge of the ceiling.
[*]For the later electrical installation, 2 empty conduits should be laid.
[*]For the later installation of a shower bathroom in the attic, a cold/hot water connection as well as a wastewater pipe must be routed up to the top edge of the ceiling.

Kind regards

Hello,

....I therefore have 2 questions:
1) How many kW must my system have for 152sqm or 178sqm? Is there a rule of thumb?

No, there must be an exact heating load calculation and heating surface design, hydraulics available. Whether an air heat pump is overall even effective here should be checked before.
Since there are still some uncertainties, if air heat pump, it should in any case ensure full modulation!

Best regards