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 🙂
C
Costruttrice10 Aug 2023 11:43I cannot comment on the values, but I recommend getting an independent heating load calculation, especially if you are unsure how to evaluate them. We had this done by an engineering firm; they calculated the heating and mechanical ventilation requirements, including specifying the layout of the underfloor heating and the locations for supply and exhaust air for the mechanical ventilation. We handed this over to the heating contractor, who followed these guidelines.
Thanks for the answers so far! Can you tell me how or with which tool you calculated this heating load, @KarstenausNRW? Using several online rough calculators, I get very different results:
The StiebelEltron calculator shows a heating load of 8kW
The heizleistungsrechner.de calculator shows 2.39kW
The ibo-plan.de calculator shows 14.5kW
The waermepumpe.de calculator shows 4.6kW
I can’t make sense of this either; all were done with quite similar inputs but give such different results... 🙁
And one more question: In the BAFA list, both heating capacity and nominal heating capacity are given:
For example, for an Arotherm, 6.99kW heating capacity at A-7/W35 and 2.77kW nominal heating capacity at A2/W35. How should these two values be interpreted?!
The StiebelEltron calculator shows a heating load of 8kW
The heizleistungsrechner.de calculator shows 2.39kW
The ibo-plan.de calculator shows 14.5kW
The waermepumpe.de calculator shows 4.6kW
I can’t make sense of this either; all were done with quite similar inputs but give such different results... 🙁
And one more question: In the BAFA list, both heating capacity and nominal heating capacity are given:
For example, for an Arotherm, 6.99kW heating capacity at A-7/W35 and 2.77kW nominal heating capacity at A2/W35. How should these two values be interpreted?!
K
KarstenausNRW10 Aug 2023 12:18Check out grabenkollektor.Wärmepumpen-verbrauchsdatenbank.de/Energieeinsparverordnung-heizlast html.
This is a simple yet very accurate tool for initial assessment. It usually matches the results of MEP (mechanical, electrical, and plumbing) planners within about 5%. Deviations mainly result from the final geometry of the house.
A heat pump should preferably be undersized rather than oversized.
This is a simple yet very accurate tool for initial assessment. It usually matches the results of MEP (mechanical, electrical, and plumbing) planners within about 5%. Deviations mainly result from the final geometry of the house.
A heat pump should preferably be undersized rather than oversized.
Thank you, I wasn’t familiar with this version before. This calculator also “once again” gave a different value compared to many other calculators 🙄
With controlled residential ventilation, I get 6700 W, without controlled residential ventilation 8200 W.
Which value (for example from the BAFA list) should be considered the reference? Heating capacity at A-7/W35 or nominal heating capacity at A2/W35?
There are huge differences between the models from the two heating system manufacturers… on top of that, one of them would want to install the aroTHERM in a cascade setup twice…
With controlled residential ventilation, I get 6700 W, without controlled residential ventilation 8200 W.
Which value (for example from the BAFA list) should be considered the reference? Heating capacity at A-7/W35 or nominal heating capacity at A2/W35?
| Model | Heating capacity A2/W35 | Nominal heating capacity A-7/W35 |
| Daikin Altherma 3 H HT | 10.72 kW | 6.87 kW |
| Vaillant aroTHERM plus VWL 75/6 | 6.99 kW | 2.77 kW |
There are huge differences between the models from the two heating system manufacturers… on top of that, one of them would want to install the aroTHERM in a cascade setup twice…
R
RotorMotor10 Aug 2023 13:04Herdeler schrieb:
Thank you, I wasn’t aware of it in this form. This calculator “once again” gave a different number than many other calculators 🙄
With controlled residential ventilation, I arrive at 6700W, without controlled residential ventilation at 8200W.
Which value (for example, from the BAFA list) should be used as the reference? Heat output at A-7/W35 or nominal heat output at A2/W35? That already sounds quite reasonable.
What kind of wall construction and so on do you have, that the heat transfer coefficient is so poor?
Herdeler schrieb:
Model
Heat output A2/W35
Nominal heat output A-7/W35
Daikin Altherma 3 H HT
10.72kW
6.87kW
Vaillant aroTHERM plus VWL 75/6
6.99kW
2.77kW
There are huge differences between the models from the two heating system manufacturers... on top of that, one wants to install two aroTHERM units in cascade... From which list did you get these values?
Did you confuse COP with kW?
According to the manufacturer, the VWL 75/6 A still delivers 7kW heating capacity at -7 degrees Celsius.
X
xMisterDx10 Aug 2023 13:10Take this to a professional... If you already read here that it’s better to undersize a heat pump, that may be true, but then you need the exact heating load, not an estimate. And neither an online tool nor a master plumber can provide that. This is something engineers do...