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?
V
Vestaxx GmbH7 Oct 2022 09:58A brief addition, because I just can’t leave it like that:
I accept a COP of 3.5. This is the efficiency of the air-to-water heat pump under fixed conditions. When varying temperatures come into play over the heating season, it is referred to as the lower annual performance factor (annual performance factor). Both values are measured at the heat pump output. What is NOT included are the distribution losses.
To fairly compare the heat pump with a direct electric heating system, the system efficiency must be used. This was confirmed to me just last week by Prof. Henning from Fraunhofer Freiburg during an association meeting of the Federal Association of Energy Consultants in Fulda. There are also economic findings related to this, which I have mentioned here before.
What always bothers me is that—by whoever—the COP or annual performance factor is stated, giving the customer the positive impression that multiple times the amount of heat energy is obtained from one kilowatt-hour of electricity. However, the customer can never verify this factor without extensive measurement efforts. You only need to consider the heat pump’s supply temperature in relation to the temperature at the interface between the underfloor heating and the occupant, and admit that energy is “lost” on the way from the heat pump to the person.
I accept a COP of 3.5. This is the efficiency of the air-to-water heat pump under fixed conditions. When varying temperatures come into play over the heating season, it is referred to as the lower annual performance factor (annual performance factor). Both values are measured at the heat pump output. What is NOT included are the distribution losses.
To fairly compare the heat pump with a direct electric heating system, the system efficiency must be used. This was confirmed to me just last week by Prof. Henning from Fraunhofer Freiburg during an association meeting of the Federal Association of Energy Consultants in Fulda. There are also economic findings related to this, which I have mentioned here before.
What always bothers me is that—by whoever—the COP or annual performance factor is stated, giving the customer the positive impression that multiple times the amount of heat energy is obtained from one kilowatt-hour of electricity. However, the customer can never verify this factor without extensive measurement efforts. You only need to consider the heat pump’s supply temperature in relation to the temperature at the interface between the underfloor heating and the occupant, and admit that energy is “lost” on the way from the heat pump to the person.
Vestaxx GmbH schrieb:
He just cannot verify the factor—without significant measurement effort. Well, there are many people in this forum alone who have built with an air-to-water heat pump plus underfloor heating, and they can reliably verify this based on their consumption data. This is not just theory; the systems are in active use.
In our new build with an air-to-water heat pump (and photovoltaic system! Shock!), our consumption was about 2350 kWh in one year. Of that, 14% came from the photovoltaic system and 86% from the grid. At that time, our electricity cost was 28 cents per kWh, so even without photovoltaic, our annual cost would have been 2350 x 28¢ = €658.
That translates to just under €54 per month. With that, we kept 153 m² (1645 sq ft) warm (24°C (75°F) indoor temperature, we like it cozy), and hot water and ventilation were also included.
S
stjoob_at7 Oct 2022 11:02It’s relatively straightforward with a heat meter. Usually, a measurement device is already integrated into the heat pump, including electricity consumption monitoring. Otherwise, you can install a heat meter directly after the heat pump for monitoring, and for example, add another one before the underfloor heating manifolds. If the heat pump is located within the conditioned space, there are effectively no distribution losses anymore (it also helps to heat the house).
An annual performance factor (Seasonal Performance Factor, SPF) greater than 3.5 for an air-to-water heat pump is no longer uncommon in new builds. Proper system design and installation are assumed (there is definitely still room for improvement here, and it’s hard to make mistakes with electric direct heating). When considering the annual performance factor, the energy used for domestic hot water preparation from spring to autumn should not be underestimated. Air-to-water heat pumps achieve very high values in this period.
An annual performance factor (Seasonal Performance Factor, SPF) greater than 3.5 for an air-to-water heat pump is no longer uncommon in new builds. Proper system design and installation are assumed (there is definitely still room for improvement here, and it’s hard to make mistakes with electric direct heating). When considering the annual performance factor, the energy used for domestic hot water preparation from spring to autumn should not be underestimated. Air-to-water heat pumps achieve very high values in this period.
V
Vestaxx GmbH7 Oct 2022 11:21kati1337 schrieb:
Well, there are numerous people in this forum alone who have built with an air-to-water heat pump plus underfloor heating, and they can reliably verify this based on their consumption figures. This is not just theory; these systems are already in use.
In our newly built home with an air-to-water heat pump (and photovoltaic system! Shock!), we consumed about 2350 kWh in one year. Of that, 14% came from the photovoltaic system and 86% from the grid. At that time, the price per kWh was still 28 cents, so even without the photovoltaic system, we would have paid 2350 x 28 cents = 658€ per year.
That roughly corresponds to about 54€ per month. With this, we kept 153 m² (24°C (75°F) indoor temperature, we like it cozy) warm, and hot water and ventilation were also included. Yes, that is all correct – but people can only see the consumption figures, not what the house actually consumed net. Or in other words, no one can truly say how much heat actually reached the occupants. At best, you can compare roughly to the heating demand calculated by the energy consultant, but even that is not fully representative because weather conditions and heating behavior remain variables. That’s why everyone is happy about relatively low annual or monthly heating costs, as you described. In a full cost accounting (for references, see the webinar on our homepage – it explains this in detail), the picture looks completely different.
In my personal opinion, the heat pump industry is leading customers by the nose through the ring, and they don’t even notice it.
Vestaxx GmbH schrieb:
Yes, that’s correct – but people can only see the consumption figures, not the actual net energy the house used. Huh? What do you mean by the house’s “net” consumption?
Vestaxx GmbH schrieb:
In other words, no one can really say how much heat actually reached the occupants directly. A thermometer can give a fairly accurate indication of that.
Vestaxx GmbH schrieb:
At best, you can make an approximate comparison to the calculated heating demand from the energy consultant, Who cares? What really matters is the actual cost to me to maintain a comfortable temperature in the house.
Vestaxx GmbH schrieb:
but even that is not representative, because weather conditions and heating behavior are still variables -> You can disregard those variables, since neither the weather nor my heating habits should change depending on the heating system. I don’t suddenly prefer 20°C (68°F) over 24°C (75°F) just because I have a different heating system. And I don’t get a colder winter because of it either.
Vestaxx GmbH schrieb:
so everyone is happy about very low annual or monthly heating costs as you showed. But in the full cost calculation (I refer here to the webinar on our website – it’s explained there in detail) the picture looks completely different. Like what? What are your promised numbers in a full cost comparison based on my example?
Vestaxx GmbH schrieb:
In my personal opinion, the heat pump industry is leading customers by the nose, and they don’t even realize it. And now you’re trying to pull the wool over our eyes here, thinking we won’t notice.
V
Vestaxx GmbH7 Oct 2022 11:32stjoob_at schrieb:
It’s relatively simple with a heat meter. Usually, there is already a measurement device installed in the heat pump, including electricity consumption. Otherwise, you can install a heat meter directly after the heat pump for monitoring and then, for example, add something before the underfloor heating manifolds. If the heat pump is located within the conditioned space, there are essentially no distribution losses anymore (it also heats the house for me).
An annual performance factor (COP) greater than 3.5 for an air-to-water heat pump is no longer uncommon in new buildings. Proper system design and installation are assumed here (there is certainly still potential, and with an electric direct heating system you can hardly make mistakes). You should not underestimate the impact of domestic hot water preparation from spring to autumn on the annual performance factor. Air-to-water heat pumps achieve very high values during this period. Very good points that I fully agree with, except for the suggestion that monitoring is possible with a simple heat meter. Where it is installed—even not at the manifold—we do not want to measure, but rather at the heat transfer point to the occupant. Measuring at that point is extremely difficult.
Also, the argument that waste heat remains inside the house is unfortunately not entirely correct. The underfloor heating system has a large heat sink beneath it—the ground, which we can assume is consistently about 12°C (54°F). The temperature difference (Delta T) to the supply temperature is roughly 28°C (82°F), resulting in a delta T of 16 Kelvin. Considering the floor area and the floor’s U-value (thermal transmittance) to the ground, you can calculate the continuous heat loss to the earth. This loss is often higher than the heat losses through the window glazing.
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