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 🙂
K
KarstenausNRW10 Aug 2023 13:23Herdeler schrieb:
With controlled residential ventilation, I come to 6700W, without controlled residential ventilation to 8200W. How do you arrive at that? Is it due to the postal code? I used the values from the original post and get different results with the same tool.
xMisterDx schrieb:
Take this to a professional… when you already read here that a heat pump should rather be undersized… maybe, Of course, you let a professional handle this. Heat load calculation from the energy certificate and specifications for supply/return temperature (please aim for around 30/26°C (86/79°F), not higher) and room temperature. Also, a suitable layout plan for the underfloor heating system.
Oh yes, about sizing. It is actually better to choose the smaller rather than the larger option. It has to do with technology, physics, and efficiency. But I guess you don’t really understand that…
RotorMotor schrieb:
That sounds quite reasonable.
What kind of wall construction and other details do you have, that the heating capacity is so low?
Which list are these values from?
Did you perhaps confuse COP with kW?
According to the manufacturer, the VWL 75/6 A still delivers 7 kW heating capacity at -7 degrees Celsius (19°F). The wall construction consists of 36.5 cm (14.4 inches) insulated masonry Bisotherm (Bisoplan 10) with a thermal conductivity (lambda) of 0.1.
The base slab is 24 cm (9.4 inches) thick with 80 mm (3.1 inches) insulation under the screed.
The exterior basement walls are insulated with 12 cm (4.7 inches) Styrodur.
The flat roof is also insulated with 12 cm (4.7 inches) Styrodur.
The values come from the BAFA list:
...and here I wonder why the Daikin units have the same performance ratings in all three sizes?!
K
KarstenausNRW10 Aug 2023 14:16My humble opinion: Anyone who casually offers a heat pump (Daikin) designed as a replacement for old gas and oil heating systems (high heating demand) or for the construction of small residential buildings (i.e., multi-family houses) would be out of the running with me due to a lack of professional expertise. Just saying.
RotorMotor schrieb:
That sounds pretty reasonable already.
What kind of wall construction and so on do you have that the Ht is so poor?
Here are the U-values for the walls:
Bisoplan 10 exterior wall to outside air: 0.257
Concrete basement wall to outside air: 0.27
Concrete basement wall to soil: 0.273
Flat roof: 0.169
Ceiling of unheated garage: 0.289
Ground slab to soil: 0.308
Partition wall inside the house to unheated rooms (garage): 0.47
Windows: 0.9
Overall, none of that seems particularly bad to me...?!
What I haven’t figured out yet is why the Daikin heat pump on the BAFA list shows different COP values for three different unit sizes but lists the same heating capacity and nominal heating capacity. On online shops, the nominal heating capacity is the same, but the maximum heating capacity varies depending on the unit size:
| Altherma 3 H HT BG14 | 7.52 | 5.9 | 9.91 | 9.74 |
| Altherma 3 H HT BG16 | 7.52 | 9.00 | 11.33 | 11.13 |
| Altherma 3 H HT BG18 | 7.52 | 9.00 | 12.74 | 12.52 |
What exactly should I pay attention to during the system design? Which performance figure can I use if I trust the heating load calculator from @KarstenausNRW, which initially gave me about 7 kW?
//Edit: The table doesn’t work for me, so here is a picture:
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