ᐅ KfW 70 energy standard with Poroton bricks, domestic hot water heat pump, gas heating, and decentralized ventilation system
Created on: 26 Jan 2014 22:12
D
diefamilie1978
Hello experts, homeowners, and friends of energy efficiency,
As a new homeowner (Stuttgart region), I have been focusing strongly on the topic of "energy" for the past few days.
Based on the latest calculations with the architect and structural engineer, a plastered Poroton T8 solid wall (Poroton T8) is fixed. According to the Schlagmann Poroton table, this option with 36.5 bricks meets the KfW 70 requirements.
Triple glazing is also confirmed. The house has a floor area of 220 sqm (2,368 sq ft).
The goal now is to create an optimum for the house’s energy efficiency to achieve KfW 70 without unnecessary financial loss. After the latest energy fair here in the region and initial consultations with building services providers, I see this home energy design as optimal:
1) Domestic hot water heat pump, also supported by photovoltaics, since I will have photovoltaic panels with self-consumption (about 5 kWp from the roof according to the plan)
2) For underfloor heating and peak load in winter, a gas boiler
3) Decentralized ventilation system with heat recovery
Is such a combination sufficient to meet the KfW 70 targets?
If not, where might the weak point in this setup be?
Thanks in advance for any answers or recommendations.
P.S. I removed solar thermal from the plan because, in my case, the payback calculation with photovoltaics and self-consumption is much more attractive.
As a new homeowner (Stuttgart region), I have been focusing strongly on the topic of "energy" for the past few days.
Based on the latest calculations with the architect and structural engineer, a plastered Poroton T8 solid wall (Poroton T8) is fixed. According to the Schlagmann Poroton table, this option with 36.5 bricks meets the KfW 70 requirements.
Triple glazing is also confirmed. The house has a floor area of 220 sqm (2,368 sq ft).
The goal now is to create an optimum for the house’s energy efficiency to achieve KfW 70 without unnecessary financial loss. After the latest energy fair here in the region and initial consultations with building services providers, I see this home energy design as optimal:
1) Domestic hot water heat pump, also supported by photovoltaics, since I will have photovoltaic panels with self-consumption (about 5 kWp from the roof according to the plan)
2) For underfloor heating and peak load in winter, a gas boiler
3) Decentralized ventilation system with heat recovery
Is such a combination sufficient to meet the KfW 70 targets?
If not, where might the weak point in this setup be?
Thanks in advance for any answers or recommendations.
P.S. I removed solar thermal from the plan because, in my case, the payback calculation with photovoltaics and self-consumption is much more attractive.
Well, in that case, the energy consultant really missed the mark...
Since you are planning a gas boiler anyway, the logical conclusion is gas combined with solar (or thicker insulation) and a storage tank...
With the domestic hot water heat pump, you also need the storage tank, so you don’t actually save anything with the proposed setup—in fact, you end up paying more...
Gas + solar + storage costs about 6,000
Domestic hot water heat pump + gas + storage costs about 10,000
Including interest, you can calculate that yourself...
Since you are planning a gas boiler anyway, the logical conclusion is gas combined with solar (or thicker insulation) and a storage tank...
With the domestic hot water heat pump, you also need the storage tank, so you don’t actually save anything with the proposed setup—in fact, you end up paying more...
Gas + solar + storage costs about 6,000
Domestic hot water heat pump + gas + storage costs about 10,000
Including interest, you can calculate that yourself...
K
K.Brodbeck28 Jan 2014 06:02Hello diefamilie1978
Your energy consultant should have calculated that for you already, right?
As others have already mentioned, the weak point is the mix. If you’re already producing your own electricity, why not also use it to supply the heating system? Why pay separately for a gas boiler? I also know of hot water tanks with integrated heat pumps, but those come at an additional cost! Personally, I would consider a decentralized hot water supply with electric instantaneous water heaters—only in combination with rooftop photovoltaics or green electricity.
Solar thermal can still pay off if energy prices continue to rise—but no one really knows how much or if they will rise. It is essentially a good combination with a gas boiler. However, I would choose either photovoltaics or solar thermal, not both.
Good luck!
K.Brodbeck
diefamilie1978 schrieb:
Hello experts, homeowners, and energy efficiency enthusiasts,
As a new homeowner (Stuttgart area), the topic of “energy” has been a major focus in my plans for the past few days.
Based on the latest calculations with my architect and structural engineer, I’ve settled on a plastered Poroton T8 solid wall (Poroton T8). According to the Schlagmann Poroton table, this option with 36.5 cm (14.4 inches) bricks meets the KfW 70 requirements.
Triple glazing is also confirmed. The house has a floor area of 220 m² (2,368 sq ft).
The goal now is to optimize the house’s energy performance to meet KfW 70 standards without unnecessary spending. After attending the latest energy fair here in the region and initial consultations with building services providers, I consider this house energy setup as optimal:
1) Domestic hot water heat pump, also supported by photovoltaics, as I plan to have about 5 kWp photovoltaic capacity on the roof for self-consumption
2) Gas boiler for underfloor heating and peak load during winter
3) Decentralized ventilation system with heat recovery
diefamilie1978 schrieb:
Is this combination sufficient to meet the KfW 70 targets?
Your energy consultant should have calculated that for you already, right?
diefamilie1978 schrieb:
If not, where would the weak point in this setup be?
Thanks in advance for any answers or recommendations.
As others have already mentioned, the weak point is the mix. If you’re already producing your own electricity, why not also use it to supply the heating system? Why pay separately for a gas boiler? I also know of hot water tanks with integrated heat pumps, but those come at an additional cost! Personally, I would consider a decentralized hot water supply with electric instantaneous water heaters—only in combination with rooftop photovoltaics or green electricity.
diefamilie1978 schrieb:
P.S. I dropped solar thermal from the plan because, in my case, the payback calculation with photovoltaics and self-consumption looks much more attractive.
Solar thermal can still pay off if energy prices continue to rise—but no one really knows how much or if they will rise. It is essentially a good combination with a gas boiler. However, I would choose either photovoltaics or solar thermal, not both.
Good luck!
K.Brodbeck
diefamilie1978 schrieb:
...sure, I can now slowly share the first concrete data, but a concept like this was presented to me by an energy consultant.... "Energy consultant" is not a regulated professional title! This field includes insulation or equipment salespeople, simple form fillers, as well as chimney sweeps! Therefore, the person should at least have an engineering degree. It is better if they are a building services engineer and have also qualified in civil engineering (or vice versa)!Best regards
Hello,
Best regards
klblb schrieb:Not a bad approach! I have worked on something similar with self-builders! In terms of consumption costs, it’s like a Passive House, but from a primary energy perspective, it’s closer to the energy saving ordinance standard! ;-)
....Our well-insulated 160 m² (1,722 sq ft) house meets KfW40 standards, more precisely KfW40 with the applied 15% rule. That’s why we don’t need solar thermal systems and get by with a small gas boiler....
klblb schrieb:Just ask me ;-)
... model is not fixed yet
Best regards
@Euro
It only happens every leap year that you praise a concept here 😉 😉
The operating costs of the gas boiler for hot water and heating are around 50 € per month, when simply multiplying the calculated heating demand by the gas prices. I know this is only a rough estimate because practice differs from theory, but the order of magnitude is correct.
The gas boiler will be fully modulating. Buderus manages this quite well in the mentioned power range, if I remember correctly. My energy planner mentioned something about that.
It only happens every leap year that you praise a concept here 😉 😉
The operating costs of the gas boiler for hot water and heating are around 50 € per month, when simply multiplying the calculated heating demand by the gas prices. I know this is only a rough estimate because practice differs from theory, but the order of magnitude is correct.
The gas boiler will be fully modulating. Buderus manages this quite well in the mentioned power range, if I remember correctly. My energy planner mentioned something about that.
What is the actual demand for heating and domestic hot water, and what is the actual annual efficiency for this?
Furthermore, there are significant differences between actual demand and consumption!
Heat pumps can achieve consumption below demand, which makes perfect sense since they utilize free environmental energy. On the other hand, with conventional heat generators such as gas condensing boilers, consumption is always higher than demand 🙂 Strange? ;-)
Regards.
Furthermore, there are significant differences between actual demand and consumption!
Heat pumps can achieve consumption below demand, which makes perfect sense since they utilize free environmental energy. On the other hand, with conventional heat generators such as gas condensing boilers, consumption is always higher than demand 🙂 Strange? ;-)
Regards.
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