ᐅ Vestaxx window heating – experiences?

Then don’t worry about delivery reliability, the skilled labor shortage, and the resulting rising contractor costs – others might already be.

What do you mean by an honest calculation without photovoltaics? I compare systems with the same initial investment cost. And without photovoltaics, the calculation doesn’t add up. I have already emphasized this several times here. You can only reduce costs if you cut the same amount on the other side of the equation.

So, if only 10 kWp fits on your roof, then treat yourself to a large battery with the remaining budget to increase your self-sufficiency, or invest the money in the bathroom, the kitchen, or a nice vacation.

I have also mentioned several times that heat pumps combined with photovoltaics are of course excellent, but also about 50% more expensive. Those who can afford it – by all means. However, most building families no longer have reserves and have to make compromises.

I just wrote something about infrared panels on the wall today. We are members of the Infrared Association and I support the technology as well. Therefore, I won’t go into detail comparing it to window heating.

Regarding your calculation – 250 € per unit is rather low, or you mean DIY store products from China – then go ahead. The 10,000 € for the heating glass panels is a rough estimate and actually on the high side. I just didn’t want to appear too cheap here, but it still makes financial sense.

You can place the panels wherever you want, and if you rearrange the furniture, just move them – you’ll certainly find a power outlet. 😉 What bothers you about fixed windows? What kind of argument is that? The window surface is the coldest part of the house but becomes the warmest surface in our system – the best comfort class (also posted just today).

The question about the bathroom is relevant again. You can’t get by without additional heaters (towel radiator, heated mirror, or similar) here. This is part of our consulting service for every project. We don’t just sell heated windows but also advise building families beforehand, do the sizing, and later create the individual wiring plans.

By the way, heat pumps with underfloor heating usually aren’t sufficient in the bathroom due to the higher comfort requirements. There’s always an additional heater. This also ensures that your niche is well heated.

Vestaxx GmbH schrieb:

What do you mean by an honest calculation without photovoltaics? I compare systems with the same initial cost. And without photovoltaics, the calculation doesn't add up. But I’ve already emphasized this several times here. You can only cut costs if you reduce the same amount on the other side of the equation.

Then your system can only handle 10 kWp—so use the remaining budget for a large battery to increase your self-sufficiency or invest it in the bathroom, the kitchen, or a nice vacation.

This is exactly what everyone else says. A heating system has to justify itself through heating performance; otherwise, the argument is weak. I would consider it honest if you said, “With 130 sqm (1400 sq ft) and 25 kWh/sqm (8 kBtu/sqft), your heating demand is only about 3200 kWh/year, so efficiency isn’t crucial. You will only recoup the extra cost of a direct heating system after X years.” That is your argument—low initial investment—which can be perfectly adequate. Air heating systems are increasingly common. Two of our future neighbors have them, as does my cousin.

But you only briefly touched on this and prefer to argue in favor of buying the fuel station. Photovoltaics are something you either do because you believe it’s worthwhile or not (or because it is mandatory in Baden-Württemberg). Since the roof produces little electricity in winter anyway, a high energy consumption isn’t a reason to install photovoltaics—especially if the stated system size won’t fit many roofs in the first place. A bigger battery is also no substitute for more installed capacity during winter, as you have to charge it first—especially if your consumption is high due to an inefficient direct heating system.

Vestaxx GmbH schrieb:

Regarding your calculation—€250 per unit is quite low, or are you referring to DIY store products from China? If so, please go ahead. The €10,000 for the heating panels is a rough estimate and probably a bit on the high side. I just didn’t want it to seem too cheap, but it still pays off.

I spent a few minutes looking online, and prices between €100 and €220 per 600W panel appeared. More expensive options didn’t really come up. But with that price difference, there’s definitely room to adjust upward.

Vestaxx GmbH schrieb:

What bothers you about fixed windows?

I can mount a panel wherever I want. For example, in the bathroom case, I would install it below the mirror on the lower wall side so it can shine into the toilet and shower areas. You can’t do that with a window. And if I plan the windows so they provide good light to the room, then the tail is wagging the dog.

Vestaxx GmbH schrieb:

The window area is the coldest surface in the house and becomes the warmest surface in our case.

How cold exactly is a modern triple-glazed window with warm edge spacer? How warm is the adjacent wall? These are genuine questions because I don’t know the answer. But I’m quite sure you can’t simply apply the old logic of “cold windows mean you put radiators underneath” without backing it up with numbers.

Of course, this discussion started off on the wrong foot from the perspective of a window heating system builder.
The correct question should have been:
“Should I invest more money in energy savings or in energy generation?”
This would have excluded half of the options, but the remaining half would still warrant further discussion.
The next question would be:
“Should I invest my money in efficient heat generation or in efficient energy production?”
Again, this narrows it down by half.
With those remaining, one can then discuss opportunities to save costs in plant technology in order to invest more in energy generation.
After that, the remaining different heat transfer systems can be discussed (for example, electric underfloor heating, infrared panels, or window surface heating).
Once this point is reached, the advantages (or disadvantages) can be debated, but the conversation is then among like-minded people, not the majority who have already dropped out earlier.

WilderSueden schrieb:

Exactly what everyone else is saying. A heating system needs to pay for itself through its heating performance; otherwise, the argument is weak. Honestly, I would appreciate it if you said something like, "For 130 m² (1400 ft²) and 25 kWh/m² (7.3 kWh/ft²), your heating demand is only about 3200 kWh/year, so efficiency is not very important. You’ll recover the extra costs of a direct electrical heating system only after several years." That is your argument—the low initial investment—and that can be perfectly reasonable. Air heating systems are now being installed more often. Two of our future neighbors use them, as does my cousin.
However, you only touched on this briefly; you prefer to argue in favor of buying the gas station. A photovoltaic system is something you either do because you think it’s worthwhile or you don’t (or because it is required in Baden-Württemberg). And since solar power production is low in winter anyway, a very high energy consumption is not a strong argument for photovoltaics—not when the given system size doesn’t fit many roofs. Also, a larger battery isn’t a substitute for more installed PV capacity in winter, because you first need to charge it. Especially if your own consumption is high due to an inefficient direct electric heating system.

I searched online for a few minutes and found prices ranging from €100 to €220 for 600 W panels. Significantly more expensive ones did not appear right away. But there is a lot of room for higher prices given this price difference.

I can install a panel wherever I want. In the bathroom example, for instance, I would mount it below the mirror on the inside wall so it can radiate heat into both the toilet and shower areas. That’s not possible with a window. And if I plan windows to effectively warm the room, then the tail is wagging the dog.

How cold is a modern triple-glazed window with warm edge spacer? How warm is the adjacent wall? These are genuine questions because I don’t know the answers. But I’m sure you can’t just apply the old logic “there is cold at the windows, so put radiators underneath” without backing it up with data.

... A heating system needs to pay for itself through the heating system ... — what kind of argument is that? 😡
We are not selling just a heater, but a window heating system combined with photovoltaics and a water-water heat pump.

You start well with your calculation — 3200 kWh — but then you stop. Why not continue the calculation and share it here, as I have? Let’s see together what the result is.

You don’t understand our system and repeatedly point out that photovoltaics don’t produce enough power for heating in winter. Yes, yes, yes, and yes again!

Your remark about the battery is good—I’m also not a fan of batteries in our example because they are not economically viable and don’t really help in summer or winter. I could explain more, but I’m supposed to keep it brief. 😕

What you don’t consider is that you need to buy household electricity all year round (about 3,000 to 4,000 kWh), and the heat pump doesn’t contribute anything extra to that. Yes, the heat pump may save 3,000 kWh per year, but the photovoltaic system produces about five times that annually, and a large portion of it is used directly. Calculate it yourself and you’ll be surprised! Or are you worried you might make an overambitious calculation? 😉

Buy cheap infrared panels and be happy with that—you will already be on what you call an inefficient heating system (direct electric heating) and moving away from the heat pump—congratulations! So far, everything is done correctly. Then forget about the windows as well—that’s fine too. 😉

Placement of radiant heaters:
I already said that an additional heater is always necessary in the bathroom. You can place that wherever you want.

Now to your genuine questions (should I take the rest of your statements less seriously?): 😳
Depending on the insulation, the wall is about 19°C (66°F), and the glass is about 18°C (64°F) (of course, this depends on outside and indoor air temperatures). Buy an infrared thermometer (about €15) and measure for yourself. A normal room (not the bathroom) has about 21°C (70°F) air temperature. With radiant heating, the air temperature can be lowered by up to 3 degrees without reducing comfort. This leads to an 18% reduction in heating energy demand (source: scientific studies).

Perhaps the temptation was to use the buzzword “energy saving” to attract interest.
In this case, that isn’t even accurate.
If the less catchphrase-like phrase “energy production versus energy saving, which makes more sense” had been used, the nitpicking calculations would have been unnecessary.

By the way:
Twenty years ago, I thought it was a good idea to irrigate my garden with a 12 cubic meter (12,000 liters) cistern.
The investment was 6,000 euros.
For a quarter of that amount, I could have drilled a well.
Stormwater discharge fees are 1.50 euros per square meter of sealed surface x 200 square meters = 300 euros for the roof area.
Savings from the well: 4,500 euros
Annual discharge fee: 300 euros
Payback period: 15 years without interest.
Clever??

I just don’t understand why people say heat pump OR photovoltaic.

You should always install photovoltaic systems first, and then decide whether to heat with an air-to-water heat pump, ground-source heat pump, direct electric heating, etc.