ᐅ Best way to heat a two-family house?

Hello everyone...

I am currently planning to build a two-family house.

Basement 96m2 (1,033 sq ft), ground floor 96m2 (1,033 sq ft),
upper floor 86m2 (926 sq ft), attic about 50m2 (538 sq ft)
Underfloor heating throughout
Southwest orientation
Aerated concrete insulation with brick veneer
Triple glazing

The architect suggested a gas heating system plus a solar buffer tank for hot water in the basement and ground floor, and electric instantaneous water heaters for the upper floor and attic, which are planned for rental units. Alternatively, a gas heating system without solar but with a heat pump for hot water in basement and ground floor, and electric instantaneous water heaters for the upper floor and attic rental units.

Electric instantaneous water heaters are chosen due to the landlord’s lack of individual utility billing.

I am not a fan of electric instantaneous water heaters because electricity keeps getting more expensive, even if it is only for the tenants. Heat pumps also consume electricity when the heating element kicks in. Let’s say, I want to convert the house into a single-family home at some point; would there be another solution in this regard? I would very much appreciate tips, especially regarding tenant billing.

Best regards,
totti4786

Why use two systems when one is enough?

There are also heat meters for heating and water meters for hot water. You just need to come up with a good and fair billing system for the solar portion of the hot water. Tenants are unlikely to share the costs for that unless it’s added to the rent.

The only downside is that it’s not as clearly separated as with point-of-use water heaters.

I don’t think the idea of using tankless water heaters is a good one. The argument about billing doesn’t make sense because you still have to prepare a utility cost statement anyway, due to water and sewage, insurance, etc. Check with companies in your area that can handle the billing for you, and the two heat meters probably won’t have a significant impact. As a tenant, I would reconsider moving into an apartment where my money is being wasted on tankless water heaters.

Best regards, Ronny

Totti4786 schrieb:
..... Heat pumps also consume electricity when the backup heater activates.

Ground source heat pump systems do not require a backup heater for heating operation. In well-designed air source heat pump systems, the backup heater typically accounts for less than 1% of the annual heating energy! Before making any decisions, the actual demand (capacity, energy) for heating and domestic hot water should be determined! It seems that your architect has not informed you about this at all!

Best regards

Hello, thank you very much for the responses.

Tankless water heaters are not an option either.
The billing system is really nonsense; heating costs have to be billed anyway.

Heating demand according to a rough calculation based on living area is 17 kW (22.8 kBTU), and it is said that 30% of that is for hot water, which makes 5 kW (6.8 kBTU)?

I think it will come down to a gas boiler with solar thermal for hot water for the entire house.
What size buffer tank would you recommend? That probably depends on the number of occupants?
The number of residents can vary in a two-family house. Planned is the top floor with 3 people and the ground floor with one.
What I mean is the heating system must also be suitable for the size of the house.

Best regards,
Totti4786

Hello,

Totti4786 schrieb:
...Heat demand estimated roughly by living area is 17kW, and they say 30% of that is for hot water, so 5kW?

Guessing, assuming, and estimating are not suitable bases for designing an affordable and energy-efficient heating system.
It must be precisely sized, no matter which type of heat generator is used. I recently had an example where the energy demand for heating compared to hot water was 91%/9% or 35%/65%.

Totti4786 schrieb:
...What size of buffer tank is recommended? I guess it depends on the number of occupants?

Usage patterns play a major role, especially for hot water. For example, it needs to be checked whether a performance surcharge for hot water must be added to the calculated heating load.

Best regards