ᐅ Design of a New Heating and Hot Water System for a 1970s Vacation Home

Hello everyone,

I’m really glad to have found this forum and am looking forward to the exchange of ideas.
Regarding the topic, I need a plan for the most cost-effective installation, procurement, and heating cost optimization for a new building following an older standard. So, not a KFW house or similar, since it will probably be considered an extension of an existing building from 1970.
Two residential units will be built near Winterberg.
There, I only need hot water for showers, for two people each, so four in total, who might shower at the same time in the mornings.
The apartments in the house will probably not always be occupied or will be used alternately.
There is no gas connection available. The sun hits the roof from around 10 a.m.
I was thinking of using a domestic hot water heat pump for the hot water… would that be sufficient?
Then I thought about heating with an air conditioning system… does that work? Two units of about 100m² (1,076 sq ft) each. How should the system be designed?
I expect less effort in installation and planning with that.
Would that be manageable? Also, I would like to heat two outdoor jacuzzis… what would be the most cost-effective way to do that?

Looking forward to your opinions….

Saludos Bampa

There is a well-known engineering firm starting with H that offers these types of assessments for single-family homes.

You’re probably right, I’m not looking for specific kW values but want to know what would be the most efficient and cost-effective to install. Pellet stove, domestic hot water heat pump + air conditioning, air-to-water heat pump with solar thermal—how would you approach it? Any other ideas? It’s not a single-family house, but two holiday apartments in one building.

However, I don’t know which engineering firm you are referring to...

Audiobampa schrieb:

Pellet stove, domestic hot water heat pump + air conditioning, air-to-water heat pump with solar thermal – how would you best approach this? Any other ideas?

Since these are holiday apartments that might be vacant at times, I would recommend heating with an air-to-air heat pump, meaning an air conditioning/split system. For hot water, a 50-liter (13-gallon) electric boiler, and for peace of mind, install two small balcony solar power systems or mini photovoltaic units.

Hello everyone,

I have calculated that if I build with brick and have 10% triple glazing, I would need about 22 W per m³ (0.62 BTU per ft³) of heating capacity, and with Ytong blocks about 33 W per m³ (0.92 BTU per ft³). If I want to cover all of that with an air conditioning system... I have about 250 m³ (8,830 ft³) per apartment. There are split units with roughly 7.3 kW (2.1 tons) capacity available—would that be oversized for an air conditioner? Could I choose a smaller unit? The apartment can be imagined like a large garage without room partitions. Two large rooms, one 40 m² (430 ft²) and the other 60 m² (645 ft²), are connected by a 3 to 4 m (10 to 13 feet) wide opening. Where would be the best place to install the air conditioner? In the middle?

Instead of a boiler, could I use an instantaneous water heater (tankless water heater)?

For the pools, I would cover them with pool heat pumps.

I also plan to equip the entire roof with photovoltaic panels to generate enough electricity.

This is the rough plan so far... does this sound reasonable?

The general idea is fine, but the detailed design should be done by a professional, as no one here can calculate it accurately without knowing the specific conditions.
One kW of electricity produces about 3-4 kW of heat or cooling, as is typical for a heat pump.
From March to October, a large photovoltaic system should easily cover this and also be able to charge a car on the side.