Hello everyone,
My husband and I attended a home exhibition today featuring a local timber house builder (Schleswig-Holstein) and there we learned about the Vestaxx window heating system.
Is there anyone here who has experience with the Vestaxx window heating?
At first, it sounds unusual to have the heating integrated into the windows. For the triple-glazed windows, a nanotechnology-based, invisible layer is applied to the inner surface of the innermost pane, which warms the glass up to 40 degrees Celsius (104°F) via infrared and heats the room. The warmth actually felt very comfortable, and the windows were completely cold on the outside (today’s temperature was below 10 degrees Celsius (50°F)). Allegedly, the Vestaxx window heating transfers 92% of its heat to the room, and the Technical University of Berlin has tested this Vestaxx window heating system and rated it positively. It appears to have been on the market only recently.
Overall, I find this quite interesting. It is significantly cheaper than other heating systems, allows individual control of each room, and unlike underfloor heating, it is very responsive.
Of course, this only makes sense in a low-energy house (the timber builder mainly constructs 40+ standard homes), as the system runs on electricity. In that case, the Vestaxx window heating is said to consume very little power.
This is my impression from the expo; of course, they want to sell the system.
What are your experiences with Vestaxx? Have you heard of this system before? Could it be an alternative to conventional heating? Does it have a future?
My husband and I attended a home exhibition today featuring a local timber house builder (Schleswig-Holstein) and there we learned about the Vestaxx window heating system.
Is there anyone here who has experience with the Vestaxx window heating?
At first, it sounds unusual to have the heating integrated into the windows. For the triple-glazed windows, a nanotechnology-based, invisible layer is applied to the inner surface of the innermost pane, which warms the glass up to 40 degrees Celsius (104°F) via infrared and heats the room. The warmth actually felt very comfortable, and the windows were completely cold on the outside (today’s temperature was below 10 degrees Celsius (50°F)). Allegedly, the Vestaxx window heating transfers 92% of its heat to the room, and the Technical University of Berlin has tested this Vestaxx window heating system and rated it positively. It appears to have been on the market only recently.
Overall, I find this quite interesting. It is significantly cheaper than other heating systems, allows individual control of each room, and unlike underfloor heating, it is very responsive.
Of course, this only makes sense in a low-energy house (the timber builder mainly constructs 40+ standard homes), as the system runs on electricity. In that case, the Vestaxx window heating is said to consume very little power.
This is my impression from the expo; of course, they want to sell the system.
What are your experiences with Vestaxx? Have you heard of this system before? Could it be an alternative to conventional heating? Does it have a future?
R
RotorMotor26 Sep 2022 15:36Convincing yourself that an inefficient heating system is worthwhile by using photovoltaic panels is an "interesting" approach.
Photovoltaic systems are generally always worthwhile. Trying to present an inefficient heating system as more beneficial than another is, with all due respect, not sensible.
Photovoltaic systems are generally always worthwhile. Trying to present an inefficient heating system as more beneficial than another is, with all due respect, not sensible.
Hello Andreas,
I really appreciate that as the system manufacturer you are addressing the open questions and critical comments. I will take a closer look at your data in Excel this evening.
But:
Here, I already wanted to stop reading due to the obvious nonsense. So we are not supposed to trust datasheet figures, but just take your word for it? My heat pump had an annual performance factor of 5 for heating operation over the past 11 months.
If you refer to studies, don’t hide half of the story. The annual performance factor of 2.6 refers, as far as I know, to the Fraunhofer study. But a press release from that study also states:
Furthermore, only 5 (?) of the houses in the study were built in 2005 or later, and in total only 16% of the studied buildings use purely underfloor heating. The rest operate exclusively or partly with radiators.
Therefore, these are by no means comparable to modern KfW55 standard houses, which are the target for the 30 kWh/m² figures referred to.
On one hand, I am told not to believe all brochure figures; on the other, old, unrenovated houses are used as the comparison basis for the annual performance factor.
So heat pump houses combined with photovoltaics are plus-plus energy houses? They produce even more surplus?
For me, this remains a clear “kill your darlings” case in product development, as it only makes sense for absolute passive houses.
I really appreciate that as the system manufacturer you are addressing the open questions and critical comments. I will take a closer look at your data in Excel this evening.
But:
Vestaxx GmbH schrieb:
I would advise not to rely on the numbers from brochures but rather on independent studies from recognized institutes. For air-to-water heat pumps, a typical annual performance factor (APF) of 2.6 is given. Additionally, there is an efficiency rate of 70% (source: TU Berlin - Hermann-Rietschel-Institut), which brings us below 2!
Here, I already wanted to stop reading due to the obvious nonsense. So we are not supposed to trust datasheet figures, but just take your word for it? My heat pump had an annual performance factor of 5 for heating operation over the past 11 months.
If you refer to studies, don’t hide half of the story. The annual performance factor of 2.6 refers, as far as I know, to the Fraunhofer study. But a press release from that study also states:
The average annual performance factors of air-to-water heat pumps at 15 measured systems range between 2.5 and 3.4. A fully renovated building achieved an annual performance factor of 4.1. The annual performance factor describes the ratio of generated heating heat to the electric drive energy used.
Furthermore, only 5 (?) of the houses in the study were built in 2005 or later, and in total only 16% of the studied buildings use purely underfloor heating. The rest operate exclusively or partly with radiators.
Therefore, these are by no means comparable to modern KfW55 standard houses, which are the target for the 30 kWh/m² figures referred to.
On one hand, I am told not to believe all brochure figures; on the other, old, unrenovated houses are used as the comparison basis for the annual performance factor.
Vestaxx GmbH schrieb:
Let’s look at the annual balance: The house produces more energy than it consumes in a year – that’s called a plus-energy house!
So heat pump houses combined with photovoltaics are plus-plus energy houses? They produce even more surplus?
For me, this remains a clear “kill your darlings” case in product development, as it only makes sense for absolute passive houses.
V
Vestaxx GmbH26 Sep 2022 19:09Hello,
Since I have introduced myself, it would be nice if you could also tell us more about yourself.
What do you do professionally and in which industry do you work? Of course, you don’t have to answer.
What I am interested in is where you got your annual performance factor of 5 from, or how you calculated it.
Maybe you could explain that sometime.
However, we can keep the discussion about the annual performance factor brief (study 1 here, study 2 there), because it is actually irrelevant when looking at the full costs. Talking only about the – admittedly low – consumption of a heat pump is not even half the truth.
Example(s):
If you buy a car for 40,000 € that consumes little fuel, you also calculate all costs compared to taxes (depreciation, maintenance, operating costs, etc.) and may apply 30 cents per km.
Or, even better, the example of a photovoltaic system: What does the electricity generated by it cost? -> Investment cost divided by the energy produced over a lifespan of 20 years (photovoltaic systems last up to 40 years or more – but we will leave that aside). This results in an electricity price from the rooftop of about 9 to 11 cents per kWh.
Given the current circumstances, consumers will be very interested in how much a kWh of heat will cost them in the future. That is where our system comes into play. Full costs = investment plus operating and maintenance costs, considered over the lifetime. In our webinar, we explain this in detail and show that even if the electricity supplier was to provide electricity free of charge for the entire lifetime (a dream), the full costs would still be above 1 €/kWh.
Speaking of using a heat pump in a zero-energy house interests me greatly – but I guess that’s not what you meant, right? Talking about a plus-plus energy house in combination (again, investment costs are not considered) sounds nice, but it is not supported by numbers. You’re welcome to provide those figures next time.
I notice you are a heat pump enthusiast, and that’s a good thing – really. I am by no means a heat pump critic (setting aside the annual performance factor and the fact that it is measured at the heat pump output while ignoring distribution losses). From my perspective, heat pumps make sense where specific heating energy demands are fairly high because they help save energy there. But in a nearly zero-energy building with an energy demand (HWB) of around 30 kWh/m²a, you save – let’s say with an annual performance factor of 6 in a 150 m² (1,615 ft²) house – 4,500 : 5 = 3,600 kWh per year.
On the other hand, with a direct electric heating consumption of 4,500 kWh per year, but powered by a photovoltaic system (same investment as with an air-to-water heat pump), you generate 13,500 kWh over the same period – a positive balance of almost 10,000 kWh per year. And every kWh of that is used – either in the house or by a third party somewhere in the grid.
Everyone is free to decide: either not saving 3,600 kWh or rather generating 13,500 kWh.
Have a nice evening.
Best regards
Andreas
Since I have introduced myself, it would be nice if you could also tell us more about yourself.
What do you do professionally and in which industry do you work? Of course, you don’t have to answer.
What I am interested in is where you got your annual performance factor of 5 from, or how you calculated it.
Maybe you could explain that sometime.
However, we can keep the discussion about the annual performance factor brief (study 1 here, study 2 there), because it is actually irrelevant when looking at the full costs. Talking only about the – admittedly low – consumption of a heat pump is not even half the truth.
Example(s):
If you buy a car for 40,000 € that consumes little fuel, you also calculate all costs compared to taxes (depreciation, maintenance, operating costs, etc.) and may apply 30 cents per km.
Or, even better, the example of a photovoltaic system: What does the electricity generated by it cost? -> Investment cost divided by the energy produced over a lifespan of 20 years (photovoltaic systems last up to 40 years or more – but we will leave that aside). This results in an electricity price from the rooftop of about 9 to 11 cents per kWh.
Given the current circumstances, consumers will be very interested in how much a kWh of heat will cost them in the future. That is where our system comes into play. Full costs = investment plus operating and maintenance costs, considered over the lifetime. In our webinar, we explain this in detail and show that even if the electricity supplier was to provide electricity free of charge for the entire lifetime (a dream), the full costs would still be above 1 €/kWh.
Speaking of using a heat pump in a zero-energy house interests me greatly – but I guess that’s not what you meant, right? Talking about a plus-plus energy house in combination (again, investment costs are not considered) sounds nice, but it is not supported by numbers. You’re welcome to provide those figures next time.
I notice you are a heat pump enthusiast, and that’s a good thing – really. I am by no means a heat pump critic (setting aside the annual performance factor and the fact that it is measured at the heat pump output while ignoring distribution losses). From my perspective, heat pumps make sense where specific heating energy demands are fairly high because they help save energy there. But in a nearly zero-energy building with an energy demand (HWB) of around 30 kWh/m²a, you save – let’s say with an annual performance factor of 6 in a 150 m² (1,615 ft²) house – 4,500 : 5 = 3,600 kWh per year.
On the other hand, with a direct electric heating consumption of 4,500 kWh per year, but powered by a photovoltaic system (same investment as with an air-to-water heat pump), you generate 13,500 kWh over the same period – a positive balance of almost 10,000 kWh per year. And every kWh of that is used – either in the house or by a third party somewhere in the grid.
Everyone is free to decide: either not saving 3,600 kWh or rather generating 13,500 kWh.
Have a nice evening.
Best regards
Andreas
V
Vestaxx GmbH26 Sep 2022 19:16... oh, and one more comment on "Kill your Darling":
We are no longer in the product development phase, having completed around 200 projects in total, including many very satisfied customers (I am happy to arrange calls or visits). Some have been using the system through their fifth winter. These are not strictly passive houses but a diverse mix of house types (KfW55, KfW40, and KfW40+).
We are no longer in the product development phase, having completed around 200 projects in total, including many very satisfied customers (I am happy to arrange calls or visits). Some have been using the system through their fifth winter. These are not strictly passive houses but a diverse mix of house types (KfW55, KfW40, and KfW40+).
R
RotorMotor26 Sep 2022 20:22Anyone trying to sell a heating system based on a technology (the photovoltaic system) that has nothing to do with heating probably has few arguments to support the heating system itself. Understandably so, since a COP of 0.92 is clearly much lower than 4 or even higher, which other modern heating systems achieve today.
So once again, the photovoltaic system must be evaluated (because it is not a heating system) and can be financially assessed independently (through loans and similar options), and it will almost always prove worthwhile.
When it comes to heating systems, comparisons can certainly be made: air-to-water heat pump versus direct electric heating, or air-to-water heat pump plus photovoltaic system versus Vestaxx plus photovoltaic system. But the photovoltaic system only provides the environmental input, just like the size and insulation of the house. Unfortunately, making a reliable comparison is especially difficult right now because no one can predict electricity prices. With low electricity costs, I even see potential for direct heating systems.
The environmental balance is also worth considering: the energy required to manufacture and install the systems compared to their energy consumption over their lifetime. However, simply stating that direct heating is cheaper than an air-to-water heat pump, so you can invest in other worthwhile projects, is not very constructive in my opinion.
So once again, the photovoltaic system must be evaluated (because it is not a heating system) and can be financially assessed independently (through loans and similar options), and it will almost always prove worthwhile.
When it comes to heating systems, comparisons can certainly be made: air-to-water heat pump versus direct electric heating, or air-to-water heat pump plus photovoltaic system versus Vestaxx plus photovoltaic system. But the photovoltaic system only provides the environmental input, just like the size and insulation of the house. Unfortunately, making a reliable comparison is especially difficult right now because no one can predict electricity prices. With low electricity costs, I even see potential for direct heating systems.
The environmental balance is also worth considering: the energy required to manufacture and install the systems compared to their energy consumption over their lifetime. However, simply stating that direct heating is cheaper than an air-to-water heat pump, so you can invest in other worthwhile projects, is not very constructive in my opinion.
Vestaxx GmbH schrieb:If that is well known, it should be achieved. According to a large database, the average seasonal performance factor for air-to-water heat pumps in 2021 was 3.73. We are talking about new buildings here; otherwise, I am curious how the calculation for a direct heating system in an older building looks. 😉
I know, many will now again demand a seasonal performance factor of 4.
Vestaxx GmbH schrieb:I couldn’t find that information as stated. Does this apply to new buildings?
Additionally, there is an efficiency of 70% (source: TU Berlin - Hermann-Rietschel-Institut), and we end up below 2!
Vestaxx GmbH schrieb:Here you could already start by saying 1,000 USD more per year at 35 cents per kWh. With an additional cost of 25,000 USD, the payback period for an air-to-water heat pump is 25 years. At 60 cents per kWh, about 14 years. Using photovoltaic electricity at 8.2 cents per kWh, it is 100 years. However, it is safe to say that during winter, when heating is active, hardly any electricity is generated from solar panels. So direct heating benefits very little from photovoltaic systems.
Aha – some will say now. 3,000 kWh more than with a heat pump! I told you!!!
Vestaxx GmbH schrieb:With windows, I understand that losses go outside. But where do the losses of an air-to-water heat pump go? Into the technical room? That is fine—they remain inside the house.
(putting aside the seasonal performance factor and the fact that it is not mentioned that the measurement is taken at the heat pump output and distribution losses are ignored).
Vestaxx GmbH schrieb:It’s really nice to see such enthusiasm for photovoltaic systems, but they simply have nothing to do with heating.
Or better yet, the example of a photovoltaic system: What is the cost per kWh produced? -> investment costs divided by energy produced over a period of 20 years (photovoltaic systems last up to 40 years or longer – but let’s ignore that). This results in a price per kWh from the roof of about 9 to 11 cents.
V
Vestaxx GmbH26 Sep 2022 22:42Anyone trying to sell a heating system based on a technology (the photovoltaic system) that has nothing to do with heating probably has few valid arguments for the heating system itself.
You don’t understand it, or you just don’t want to, so here’s a simple explanation for everyone else:
A house basically has three energy demands that need to be met: heating demand, hot water, and household electricity. To convert this energy, the residents use conversion devices (heating systems) and energy sources. The budget for acquisition is, let’s say, €40,000 (regardless of financing – and you need to explain to us why the costs for the photovoltaic system must be financed separately, but not the costs for the heat pump itself. Yet you don’t respond to questions – unfortunately).
Now, the homeowner can be smart and choose a simple heating system (infrared panels or heating windows WITHOUT maintenance costs). Or they can decide on a highly complex heating system with annual maintenance costs. With the infrared heating system, there is still €30,000 left that can be invested sensibly in an energy generation system. I think this – among many other reasons – is the best argument for a maintenance-free heating system.
I have never denied the low COP of 0.95 (based on recent measurements by TU Berlin) compared to a heat pump with about 4 – but that’s not really the point. A photovoltaic system is not a heating system; it’s an energy generation system. Nowadays, I believe every homeowner would like a large photovoltaic system to reduce dependence on the grid, as it currently is and probably will remain. And – I fully agree – it always pays off!
Air-to-water heat pump versus direct electric heating, or air-to-water heat pump plus photovoltaic system versus Vestaxx plus photovoltaic system. But the photovoltaic system only supplies the environment’s energy, just like the size and insulation of the house. Unfortunately, this comparison is particularly difficult at the moment, as no one can predict electricity prices. At low electricity costs, I even see a chance for direct electric heating systems.
Unfortunately, that’s incorrect. The higher the electricity price, the more important it is to generate as much of your own energy as possible. And I will repeat again: a pure heat pump system has no energy generator if you consider the same budget. But you didn’t properly look at my calculation. Numbers don’t lie, so please comment on the numbers from my first message here in the forum so everyone can follow along.
You can also look at the environmental balance. For example, the energy required to manufacture and install the systems compared to consumption over their lifetime. But I consider the argument that direct electric heating is cheaper than an air-to-water heat pump and so you can invest in other worthwhile things to be unproductive.
Thanks for the opportunity. Then please tell us the CO2 footprint of a heat pump with approximately 2 km (1.24 miles) of piping installed in a house. Regarding our heating glass surface per square meter, I can share: 3 grams of zinc oxide as the heating layer on the glass, 2 m (6.6 feet) of copper tape, and 2 grams of silver conductive adhesive. Compared to a heat pump, that’s about a factor of 10,000 times smaller. And then the photovoltaic yield comes directly from the sun versus electricity for the heat pump from the grid mix. A massive own goal!
And direct electric heating only makes sense in older buildings if the house has been upgraded to new-build standards of insulation beforehand. But I did not raise that topic here and would always advise against it if the house is not insulated.
At this point, one might say, an additional €1,000 per year at €0.35/kWh. At a price difference of €25,000, the payback for an air-to-water heat pump is 25 years.
Now it gets really interesting. So, you calculate 3,000 kWh × €0.35/kWh = €1,000 savings. And with that, the heat pump has paid for itself in 25 years. How do you get a price difference of €25,000? An air-to-water heat pump including everything costs around €40,000 today. And then the simple amortization you calculated without maintenance and repair costs is actually 40 years!!! Unfortunately, most heat pumps don’t last longer than 15 to 20 years. So after 20 years, you have to buy a new heat pump – and not at today’s prices. How you arrive at 8.6 cents (which, by the way, is only the feed-in tariff for electricity fed into the grid, not for electricity used in the house) to reach a 100-year period, you need to explain to us.
With windows, I understand that there are losses to the outside. But where do the losses of an air-to-water heat pump go? Into the utility room? That’s fine because it’s inside the house.
No – not in the utility room, but where the heat is distributed – that is why it’s called distribution losses. So through the floor, with a large surface area toward the colder ground. This is directly comparable to windows via the U-value. We can calculate it anytime, but that is beyond the scope here.
It’s really nice that you are such a fan of photovoltaic systems, but that has nothing to do with heating.
Well, if you consider heating systems don’t require energy, maybe. But unfortunately, heating systems always require energy, and we generate that energy with photovoltaic systems, which is why our heating is also a solar heating system. Because when evaluating a system, you consider all components and not just ignore what you don’t like.
I would find it fair if you would share more about your system with a seasonal performance factor of 5 from the last 11 months and answer my questions. Do the energy calculations for such a house and show us the results. As stated above: numbers are verifiable, and you have said nothing about the full cost calculation. You also don’t seem interested in references from satisfied customers.
It’s actually not worth it, but I am ready to engage with any reasonable argument supported by verifiable numbers.
You don’t understand it, or you just don’t want to, so here’s a simple explanation for everyone else:
A house basically has three energy demands that need to be met: heating demand, hot water, and household electricity. To convert this energy, the residents use conversion devices (heating systems) and energy sources. The budget for acquisition is, let’s say, €40,000 (regardless of financing – and you need to explain to us why the costs for the photovoltaic system must be financed separately, but not the costs for the heat pump itself. Yet you don’t respond to questions – unfortunately).
Now, the homeowner can be smart and choose a simple heating system (infrared panels or heating windows WITHOUT maintenance costs). Or they can decide on a highly complex heating system with annual maintenance costs. With the infrared heating system, there is still €30,000 left that can be invested sensibly in an energy generation system. I think this – among many other reasons – is the best argument for a maintenance-free heating system.
I have never denied the low COP of 0.95 (based on recent measurements by TU Berlin) compared to a heat pump with about 4 – but that’s not really the point. A photovoltaic system is not a heating system; it’s an energy generation system. Nowadays, I believe every homeowner would like a large photovoltaic system to reduce dependence on the grid, as it currently is and probably will remain. And – I fully agree – it always pays off!
Air-to-water heat pump versus direct electric heating, or air-to-water heat pump plus photovoltaic system versus Vestaxx plus photovoltaic system. But the photovoltaic system only supplies the environment’s energy, just like the size and insulation of the house. Unfortunately, this comparison is particularly difficult at the moment, as no one can predict electricity prices. At low electricity costs, I even see a chance for direct electric heating systems.
Unfortunately, that’s incorrect. The higher the electricity price, the more important it is to generate as much of your own energy as possible. And I will repeat again: a pure heat pump system has no energy generator if you consider the same budget. But you didn’t properly look at my calculation. Numbers don’t lie, so please comment on the numbers from my first message here in the forum so everyone can follow along.
You can also look at the environmental balance. For example, the energy required to manufacture and install the systems compared to consumption over their lifetime. But I consider the argument that direct electric heating is cheaper than an air-to-water heat pump and so you can invest in other worthwhile things to be unproductive.
Thanks for the opportunity. Then please tell us the CO2 footprint of a heat pump with approximately 2 km (1.24 miles) of piping installed in a house. Regarding our heating glass surface per square meter, I can share: 3 grams of zinc oxide as the heating layer on the glass, 2 m (6.6 feet) of copper tape, and 2 grams of silver conductive adhesive. Compared to a heat pump, that’s about a factor of 10,000 times smaller. And then the photovoltaic yield comes directly from the sun versus electricity for the heat pump from the grid mix. A massive own goal!
And direct electric heating only makes sense in older buildings if the house has been upgraded to new-build standards of insulation beforehand. But I did not raise that topic here and would always advise against it if the house is not insulated.
At this point, one might say, an additional €1,000 per year at €0.35/kWh. At a price difference of €25,000, the payback for an air-to-water heat pump is 25 years.
Now it gets really interesting. So, you calculate 3,000 kWh × €0.35/kWh = €1,000 savings. And with that, the heat pump has paid for itself in 25 years. How do you get a price difference of €25,000? An air-to-water heat pump including everything costs around €40,000 today. And then the simple amortization you calculated without maintenance and repair costs is actually 40 years!!! Unfortunately, most heat pumps don’t last longer than 15 to 20 years. So after 20 years, you have to buy a new heat pump – and not at today’s prices. How you arrive at 8.6 cents (which, by the way, is only the feed-in tariff for electricity fed into the grid, not for electricity used in the house) to reach a 100-year period, you need to explain to us.
With windows, I understand that there are losses to the outside. But where do the losses of an air-to-water heat pump go? Into the utility room? That’s fine because it’s inside the house.
No – not in the utility room, but where the heat is distributed – that is why it’s called distribution losses. So through the floor, with a large surface area toward the colder ground. This is directly comparable to windows via the U-value. We can calculate it anytime, but that is beyond the scope here.
It’s really nice that you are such a fan of photovoltaic systems, but that has nothing to do with heating.
Well, if you consider heating systems don’t require energy, maybe. But unfortunately, heating systems always require energy, and we generate that energy with photovoltaic systems, which is why our heating is also a solar heating system. Because when evaluating a system, you consider all components and not just ignore what you don’t like.
I would find it fair if you would share more about your system with a seasonal performance factor of 5 from the last 11 months and answer my questions. Do the energy calculations for such a house and show us the results. As stated above: numbers are verifiable, and you have said nothing about the full cost calculation. You also don’t seem interested in references from satisfied customers.
It’s actually not worth it, but I am ready to engage with any reasonable argument supported by verifiable numbers.
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