How to best heat a two-family house?

Hello everyone...

I am currently building a two-family house

Basement 96m2, Ground floor 96m2
Upper floor 86m2, Attic approx. 50m2
Underfloor heating everywhere
Southwest orientation
Bims stone insulation clinker
Triple glazing

Suggested by the architect was gas heating + solar buffer tank for hot water basement ground floor + instantaneous water heater for upper floor attic rental planned or gas heating without solar but with heat pump for hot water for basement ground floor + instantaneous water heater for upper floor attic rental planned

Instantaneous water heater because no billing for landlord

I am not a fan of instantaneous water heaters because electricity is getting more expensive even if it is only for the tenant. Heat pump also consumes electricity when the heating element kicks in. Let's say I want the house to be a single-family house eventually, looking towards that also another solution? I am very grateful for tips also with regard to billing for tenants

Best regards totti

Why two systems when one will do?

There are also heat meters for the heating and water meters for the hot water. You just have to come up with a good and fair billing system for the solar share of the hot water. The tenant will hardly contribute to the costs for it, unless you add it to the rent.

The only disadvantage is that it is not all as neatly separated as with instantaneous water heaters.

So I don’t think the idea with the instant water heaters is good. And the argument about the billing is nonsense, you still have to do an operating cost billing anyway because of water and wastewater, insurance, etc. Check with companies in your area that can do the billing for you, and the two heat meters surely won’t weigh that much. And as a tenant, I would consider whether I want to move into an apartment that burns my money on instant water heaters.

Best regards Ronny

..... Heat pumps also consume electricity when the heating element kicks in.

For ground source heat pump systems, no heating element is required for heating operation. In well-designed air source heat pump systems, its share is less than 1% of the annual heating load! Before making any decision, the actual demand (capacity, energy) for heating and hot water should be determined! Apparently, the architect did not inform you about this at all!

Best regards

Hello, thank you very much for the answers

Instant water heaters are also not an option
Billing is really nonsense, the heating costs have to be billed anyway.

Heating demand according to rough calculation based on living area 17kW and they say 30% of that is for hot water, makes 5kW?

I think it comes down to a gas heating system with solar for hot water for the whole house.
What size of buffer tank is recommended? That surely depends on the number of residents?
The number can be variable in a two-family house? Planned is upstairs with 3, downstairs with one?
What I want to say is the heating system must also be suitable for the size of the house.

Best regards, Totti

Hello,

...Heating demand according to rough calculation based on living area 17kW and they say 30% of that is for hot water makes 5kW?

Estimating, guessing, and assuming are poor bases for a cost-effective and energy-efficient heating system.
Here, precise sizing is essential, regardless of the type of heat generator involved. I recently had an example where the energy demand for heating compared to hot water was 91%/9% or 35%/65%.

...What size of buffer tank is recommended? That surely depends on the number of occupants?

Usage conditions also play a major role, especially for hot water. For example, it needs to be checked whether a performance surcharge on the calculated heating load is required for hot water.

Best regards