Dear heat pump experts and experienced home builders,
I would like to better understand what heat pump capacity we actually need.
Our project:
2 full floors
No basement
148 sqm (1,593 sq ft)
KFW55 standard
In our energy demand calculation, a 6 kW air-to-water heat pump is recommended.
However, the heating load calculation in the plan specifies an 8 kW air-to-air heat pump.
Both calculations seem to follow a standard procedure, as this is a developer project.
Which figures in both documents should I focus on?
To me, 8 kW seems quite high, but this is just a feeling formed by reading here in the forum.
The underfloor heating is already installed, also standard, and the screed has been curing for 4 weeks, waiting for the system to be heated up.
But there is no heat pump installed yet.
The builder would credit us €15,000 if we handle the purchase and installation of the heat pump ourselves.
All these questions are overwhelming us.
Is this even possible? Can we choose a different model or manufacturer?
Is it worthwhile, is €15,000 a reasonable amount?
Is 6 kW enough? ...
We need solid information to stand our ground with the builder.
Help!
Thanks!
I would like to better understand what heat pump capacity we actually need.
Our project:
2 full floors
No basement
148 sqm (1,593 sq ft)
KFW55 standard
In our energy demand calculation, a 6 kW air-to-water heat pump is recommended.
However, the heating load calculation in the plan specifies an 8 kW air-to-air heat pump.
Both calculations seem to follow a standard procedure, as this is a developer project.
Which figures in both documents should I focus on?
To me, 8 kW seems quite high, but this is just a feeling formed by reading here in the forum.
The underfloor heating is already installed, also standard, and the screed has been curing for 4 weeks, waiting for the system to be heated up.
But there is no heat pump installed yet.
The builder would credit us €15,000 if we handle the purchase and installation of the heat pump ourselves.
All these questions are overwhelming us.
Is this even possible? Can we choose a different model or manufacturer?
Is it worthwhile, is €15,000 a reasonable amount?
Is 6 kW enough? ...
We need solid information to stand our ground with the builder.
Help!
Thanks!
face26
Since we are talking about an air-to-water heat pump here, I am referring to Daniel-Sp’s comment that a stratified tank is not required for underfloor heating with a monovalent heat pump. The volume thus refers to the water in the heating pipes, as also specified by the manufacturers.
Of course, according to manufacturers, the systems are monovalent. There are only monovalent and bivalent systems, meaning systems that require either a single heat source or multiple ones. Bivalent systems are essentially hybrid systems because they always require a second backup heater, regardless of whether it is powered by oil, gas, or electricity.
I never spoke about a monoblock system, as this term is meaningless; even a monovalent system can consist of several units.
That the sum of the heating loads can be up to 30% above the calculated building heating load has nothing to do with a safety margin, but with a completely different calculation method. The building heating load from a thermal insulation calculation is not the basis for sizing the generator (heat source), even if some heating engineers represent it that way. Furthermore, KfW calculations do not serve this purpose at all, since KfW has its own rules; therefore, energy performance certificates may not be issued based on these calculations.
The safety margin comes from the heating curves, as each heating engineer designs them so that no one calls in winter around Christmas to complain that the house is not warm enough. However, it must also be said that only the operator or builder can actually set the heating curve, since this requires the lowest and highest outdoor temperatures during the heating period in relation to the indoor temperature settings.
The electric heating element will always consume electricity in a bivalent system because domestic hot water also needs to be heated. Even a tankless water heater operates on the same principle.
This is exactly where the efficiency advantage of a fresh water station in combination with a stratified tank and monovalent systems comes into play.
What you are writing is political philosophy, just like claims that heat pumps are climate neutral and have a primary energy factor of zero.
The kW figures are irrelevant if they are correctly determined; what matters is the actual seasonal performance factor because this relates to efficiency and costs.
Seasonal performance factors above 3 can barely compete with oil heating currently. With rising electricity prices, systems with seasonal performance factors above 4.7 are in demand.
Bivalent systems drop out here, and even monovalent systems reach their limits.
Nothing is truly saved there except, of course, CO₂.
The BEG (Building Energy Act) is being adjusted for good reason, and photovoltaics will completely drop out of BEG subsidies from 2023 onward.
Since we are talking about an air-to-water heat pump here, I am referring to Daniel-Sp’s comment that a stratified tank is not required for underfloor heating with a monovalent heat pump. The volume thus refers to the water in the heating pipes, as also specified by the manufacturers.
Of course, according to manufacturers, the systems are monovalent. There are only monovalent and bivalent systems, meaning systems that require either a single heat source or multiple ones. Bivalent systems are essentially hybrid systems because they always require a second backup heater, regardless of whether it is powered by oil, gas, or electricity.
I never spoke about a monoblock system, as this term is meaningless; even a monovalent system can consist of several units.
That the sum of the heating loads can be up to 30% above the calculated building heating load has nothing to do with a safety margin, but with a completely different calculation method. The building heating load from a thermal insulation calculation is not the basis for sizing the generator (heat source), even if some heating engineers represent it that way. Furthermore, KfW calculations do not serve this purpose at all, since KfW has its own rules; therefore, energy performance certificates may not be issued based on these calculations.
The safety margin comes from the heating curves, as each heating engineer designs them so that no one calls in winter around Christmas to complain that the house is not warm enough. However, it must also be said that only the operator or builder can actually set the heating curve, since this requires the lowest and highest outdoor temperatures during the heating period in relation to the indoor temperature settings.
The electric heating element will always consume electricity in a bivalent system because domestic hot water also needs to be heated. Even a tankless water heater operates on the same principle.
This is exactly where the efficiency advantage of a fresh water station in combination with a stratified tank and monovalent systems comes into play.
What you are writing is political philosophy, just like claims that heat pumps are climate neutral and have a primary energy factor of zero.
The kW figures are irrelevant if they are correctly determined; what matters is the actual seasonal performance factor because this relates to efficiency and costs.
Seasonal performance factors above 3 can barely compete with oil heating currently. With rising electricity prices, systems with seasonal performance factors above 4.7 are in demand.
Bivalent systems drop out here, and even monovalent systems reach their limits.
Nothing is truly saved there except, of course, CO₂.
The BEG (Building Energy Act) is being adjusted for good reason, and photovoltaics will completely drop out of BEG subsidies from 2023 onward.
A
Alessandro12 Dec 2022 10:50I hope you're not a heating engineer 🙁
Edit: A ventilation system is not mandatory for KfW55.
Edit: A ventilation system is not mandatory for KfW55.
D
Daniel-Sp12 Dec 2022 11:02@parcus
Sorry,
except for the statement that the KfW calculation and thermal insulation certificate cannot be used to determine the heating load, I cannot understand any of this....
Sorry,
except for the statement that the KfW calculation and thermal insulation certificate cannot be used to determine the heating load, I cannot understand any of this....
D
Daniel-Sp12 Dec 2022 11:04Alessandro schrieb:
Edit: A ventilation system is not mandatory for KfW55 standard.In 2019, I even built to KfW40 standard without a ventilation system.
parcus schrieb:
Since we’re talking about an air-to-water heat pump here, I’m referring to Daniel-Sp’s comment that a stratified buffer tank is not needed for underfloor heating with a monovalent heat pump. The volume mentioned therefore refers to the water in the heating pipes, as also specified by the manufacturers.Yes, that’s correct. I don’t know what you’re mixing up or think you know here. Do you mean the domestic hot water tank when you say buffer tank? I repeat, I have a heat pump without a stratified buffer tank. I have a simple hot water cylinder to operate the fresh water station. Beyond that, no buffer tanks. I could have replaced the fresh water station with a regular domestic hot water tank as well.
parcus schrieb:
Of course, according to manufacturer specifications, these systems are monovalent. There are only monovalent and bivalent systems—that is, systems that require only one heat source or multiple ones. Strictly speaking, bivalent systems are nothing else than hybrid systems, as they always require a second backup heating source, whether operated with oil, gas, or electricity.This is about system design. I don’t know what your issue is with the term monovalent systems. I’m no expert and don’t have a market overview, but in principle every heat pump has an electric heating element as backup. Including this in the calculations is considered bivalent in the scenario I’m describing here.
parcus schrieb:
I never mentioned a monoblock, since this term is meaningless; a monovalent system can consist of several units.No, but in post #59 you compared monovalent heat pumps with split systems. That’s why I asked. The comparison doesn’t make sense. It’s like saying a hybrid drivetrain is superior to a car with a trailer. It doesn’t hold.
parcus schrieb:
The heating element will always draw electricity in a bivalent system, since domestic hot water must also be heated. A tankless water heater is no different. That’s exactly where efficiency benefits come in with the fresh water station combined with a stratified buffer tank and monovalent systems.That’s simply wrong. I think you’re thinking about this incorrectly. Why should the heating element be required for domestic hot water preparation? Even with a bivalent setup, domestic hot water is normally produced by the heat pump. The only case where the heating element (which is integrated in the heat pump unit itself, not in the tank—maybe that’s your misconception) kicks in is when outdoor temperatures are so low that the heat pump alone can’t cover the heating load. Then the heating element is switched on.
parcus schrieb:
What you write is political philosophy, like the claim that heat pumps are supposedly climate-neutral and have a primary energy factor of zero.All I can say to that is WTF??? I don’t understand what you are trying to tell me or what you are referring to with that. I haven’t philosophized politically at all; I have simply stated facts, completely without judgment.
Daniel-Sp schrieb:
I can’t understand any of thisThe good thing is: I feel the same way, and you don’t have to understand it either. I think it’s (for most people) agreed that the heat pump is too large, and I’m keeping my fingers crossed that you find a better solution somehow.Similar topics