Hi everyone,
We are currently building our single-family home, and the shell is basically completed. Now I am working on the quotes for heating/plumbing and would appreciate your assessment regarding the sizing of the heat pump. Due to the KfW funding stop in 2022, we decided not to aim for KfW40 or 55 standards, allowing us more flexibility for DIY work and so on.
The house has three floors and is built on a slope, with the basement partly underground at the rear and exposed on the front side. The heated area in the basement consists of approximately 30m² (323 sq ft) of living space plus stairwell/hall/entrance area, while the remaining areas are unheated: technical room (14m² (150 sq ft)) and an unheated garage (62m² (668 sq ft)).
The ground floor and upper floor are fully heated.
The heated area is around 190–200m² (2045–2153 sq ft).
We have an energy certificate according to GEG2020 with the following data:
- Heated building volume: 876m³ (30,925 cu ft)
- Envelope surface area: 576m² (6,200 sq ft)
- Heated air volume: 666m³ (23,518 cu ft)
- Window area: 66m² (710 sq ft)
- Usable floor area according to the Building Energy Act (Gebäudeenergiegesetz): 280m² (3,014 sq ft)
- Primary energy demand: 44.41 kWh/(m²·a)
- Transmission heat loss coefficient: 0.345 W/(m²·K)
- Transmission heat loss: 6,951 W
- Ventilation heat loss: 5,546 W
- Additional heating load: 6,167 W
- Total heating load: 18,663 W
(Boundary conditions: outdoor temperature -14°C (7°F), indoor temperature 21°C (70°F))
The certification according to GEG2020 was done without controlled mechanical ventilation, but we still plan to install a central controlled mechanical ventilation system.
A few days ago, a heating contractor visited us who seemed very competent and provided a quote on site. He plans to install a Daikin Altherma 3 H HT BG14.
Another heating contractor, who has not yet visited the site, submitted a quote and plans to use a Vaillant Arotherm plus with a two-unit cascade VWL 75/6 A S2.
HB1 – the Daikin contractor – generally offers savings through DIY work, such as laying underfloor heating pipes, drainage pipes, etc.
HB2 – the Vaillant contractor – only allows DIY for laying the underfloor heating pipes; all other work is to be carried out by him.
HB1’s quote is around 50,000 gross including the Daikin heat pump, plumbing (fresh water + wastewater) and so far _without_ controlled mechanical ventilation.
HB2’s quote is about 54,000 gross including the Vaillant heat pump, plumbing (fresh water + wastewater), and controlled mechanical ventilation (Paul Novus 300).
HB2 initially offered a Vaillant 55/6 model (4,000 less expensive), but after a follow-up, corrected the offer to the two-unit cascade 75/6. At first, it seemed strange to me that a significantly smaller heat pump would suffice compared to HB1’s offer. After inquiry, he explained that he calculated with a Vaillant tool and therefore came up with the above two-unit cascade 75/6.
My questions:
- How do you assess the sizing of the heat pump?
- Are there any advantages or disadvantages or known issues with the respective Daikin/Vaillant models?
- How do you generally assess the prices?
- Do you have any other recommendations?
I look forward to your feedback – if you need further information, I’m happy to share 🙂
We are currently building our single-family home, and the shell is basically completed. Now I am working on the quotes for heating/plumbing and would appreciate your assessment regarding the sizing of the heat pump. Due to the KfW funding stop in 2022, we decided not to aim for KfW40 or 55 standards, allowing us more flexibility for DIY work and so on.
The house has three floors and is built on a slope, with the basement partly underground at the rear and exposed on the front side. The heated area in the basement consists of approximately 30m² (323 sq ft) of living space plus stairwell/hall/entrance area, while the remaining areas are unheated: technical room (14m² (150 sq ft)) and an unheated garage (62m² (668 sq ft)).
The ground floor and upper floor are fully heated.
The heated area is around 190–200m² (2045–2153 sq ft).
We have an energy certificate according to GEG2020 with the following data:
- Heated building volume: 876m³ (30,925 cu ft)
- Envelope surface area: 576m² (6,200 sq ft)
- Heated air volume: 666m³ (23,518 cu ft)
- Window area: 66m² (710 sq ft)
- Usable floor area according to the Building Energy Act (Gebäudeenergiegesetz): 280m² (3,014 sq ft)
- Primary energy demand: 44.41 kWh/(m²·a)
- Transmission heat loss coefficient: 0.345 W/(m²·K)
- Transmission heat loss: 6,951 W
- Ventilation heat loss: 5,546 W
- Additional heating load: 6,167 W
- Total heating load: 18,663 W
(Boundary conditions: outdoor temperature -14°C (7°F), indoor temperature 21°C (70°F))
The certification according to GEG2020 was done without controlled mechanical ventilation, but we still plan to install a central controlled mechanical ventilation system.
A few days ago, a heating contractor visited us who seemed very competent and provided a quote on site. He plans to install a Daikin Altherma 3 H HT BG14.
Another heating contractor, who has not yet visited the site, submitted a quote and plans to use a Vaillant Arotherm plus with a two-unit cascade VWL 75/6 A S2.
HB1 – the Daikin contractor – generally offers savings through DIY work, such as laying underfloor heating pipes, drainage pipes, etc.
HB2 – the Vaillant contractor – only allows DIY for laying the underfloor heating pipes; all other work is to be carried out by him.
HB1’s quote is around 50,000 gross including the Daikin heat pump, plumbing (fresh water + wastewater) and so far _without_ controlled mechanical ventilation.
HB2’s quote is about 54,000 gross including the Vaillant heat pump, plumbing (fresh water + wastewater), and controlled mechanical ventilation (Paul Novus 300).
HB2 initially offered a Vaillant 55/6 model (4,000 less expensive), but after a follow-up, corrected the offer to the two-unit cascade 75/6. At first, it seemed strange to me that a significantly smaller heat pump would suffice compared to HB1’s offer. After inquiry, he explained that he calculated with a Vaillant tool and therefore came up with the above two-unit cascade 75/6.
My questions:
- How do you assess the sizing of the heat pump?
- Are there any advantages or disadvantages or known issues with the respective Daikin/Vaillant models?
- How do you generally assess the prices?
- Do you have any other recommendations?
I look forward to your feedback – if you need further information, I’m happy to share 🙂
R
RotorMotor11 Aug 2023 14:26Herdeler schrieb:
Overall, it doesn’t seem too bad to me...?! I didn’t say it was great either, but it’s definitely not ideal for a new build.
It doesn’t seem like you or the heating engineers are very convinced either if they are planning high-temperature heat pumps designed for older buildings.
Herdeler schrieb:
What’s still unclear to me is why the Daikin heat pump in the BAFA list shows different COP values for three different sizes, yet lists the same heating capacity and nominal heating output. On online shops, the nominal heating capacity is the same, but the maximum heating capacity varies depending on the size: Despite the somewhat critical remarks above, the conclusion should be that this simply is not the right heat pump for your new build.
If you want Daikin, then it should be the Altherma 3 R, not the H model.
Herdeler schrieb:
What’s still unclear to me is why the Daikin heat pump in the BAFA list shows different COP values for three different sizes, yet lists the same heating capacity and nominal heating output. On online shops, the nominal heating capacity is the same, but the maximum heating capacity varies depending on the size: I would guess that the units are almost identical in design.
They probably differ only in minor details like the amount of refrigerant or a slightly different valve.
That would make one slightly more efficient, while the other delivers a bit higher peak output...
Herdeler schrieb:
But what exactly do I need to consider when sizing? Which power rating should I use if I trust the heating load calculator from @KarstenausNRW, which gave about 7kW as a first estimate? There are different approaches here. Some size for monovalent operation, meaning the heat pump should cover the heating demand even at the lowest outdoor temperature (design temperature).
Often, slight undersizing is recommended, for example sizing for -5/-7°C (23/19°F) and using the backup electric heater for the remaining load.
Overall, the heat pump should not be selected independently of the design of the heating circuits.
Because not only heating capacity but also pump power, flow rate, temperature spread, etc., all play a role.
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