Is natural stone heating in combination with a photovoltaic system reasonable?

Hello,

in advance -

Radiant heating in the form of a natural stone heater is, for me, the best form of heating. Healthy, pleasant, unique installation cost and no maintenance or follow-up costs. In combination with photovoltaic systems almost perfect ... also in old buildings; always provided it is massive building fabric.

... where the annual performance factor 3.5 is usually never maintained and actually goes down to 2.8. (Electricity guzzler).

That is not true! Such blanket statements - I always wonder where they come from ... and spread unpleasantly across the country

I have a timber frame house U value 0.14 + triple glazing, the building envelope reaches KfW 55. approx. living area 130m². Now I had a consultant who recommends a natural stone heater, since the building requires little energy.

I hope the system of your Austrian neighbors; all other systems are third or fourth choice.

... If the actual consumption were 60 kWh/m² per year you would end up with 8500 kWh without hot water. so 1800 Euro electricity (that is expensive)

In my opinion you won’t get there, because ...

Is that an oversimplified calculation or does it add up?!

... you want to have a single-family house built in timber frame construction; however, the natural stone heater works like the sun. All solid objects are heated, including your body, and "store" - for a certain period of time and dependent on massive building fabric - the heat produced in this way. The savings therefore result from the natural stone heater itself and the building fabric. Timber frame cannot provide that - the material, described layman’s terms, has no storage potential -, that is why I also think the worst case with you will be higher than €1,800.00/year, if you opt for this system.

The natural stone heater in combination with photovoltaics is unbeatable there - healthy and affordable - where it is installed in a massive constructed house. By the way, it also pays off without photovoltaics, if the heat pump tariff of the utility company is applied and it is used from a KfW 70 - or higher efficiency house.

Kind regards

Hello €uro,

What kind of strange numbers or units are these?

Someone who sells natural stone heaters usually creates the "heat demand calculation" themselves by breaking down each individual room into its components (K-values for exterior/interior walls, windows, floor, ceiling, door) and calculating the expected heat demand (Q-watt) per room based on the individual values. When added together, they then have a number for each room – depending on its use, a higher (bathroom) or lower (utility room) heat demand per sqm is assumed; the sum then results in the calculated "heat demand" for the single-family house.

It is a tedious job – often the K-values for the components of older single-family houses are not so easy to find; therefore, I have always commissioned a planning office with this task (even though I can do it myself); I always like to have a second opinion in hand. It may surprise you, but the heat demand calculated this way regularly matched, and the calculated costs at the energy supplier also corresponded, down to a few pennies. Essential for this manual form of calculation is carefully inquiring about the clients' thermal comfort preferences; otherwise, there is a rude awakening.

Kind regards

Hello construction expert,

...Someone who sells natural stone heaters usually creates the "heat demand calculation" themselves,..... the sum then results in the calculated "heat demand" for the single-family house.

You also apparently have problems with SI units. Heat = Energy (kWh)! Power => (W; kW) Heat demand is equal to energy demand, not power demand! How heating loads are determined in the EU or Germany (national annex) is specified in 12831. If sellers of natural stone heaters do not adhere to this, that is their problem The sum of the room heating loads does not automatically correspond to the standard heating load for the building Apparently these sellers do not consider ventilation heat losses either

...You may be surprised, but the thus calculated heat demand regularly matched and the calculated costs at the utility company also matched, down to a few pennies.

Concrete, comprehensible (not anonymous) examples? Best regards

Hello €uro,

You apparently also have problems with SI units.

That may be ... I’m not an engineer either

Heat demand is equal to energy demand, not power demand!

I never claimed that anywhere; I only wrote that - after a certain calculation procedure - the heat demand, sorry, energy demand, is known.

Concrete, comprehensible (not anonymous) examples?

Yes, certainly

Kind regards

Hello construction expert,

...I never claimed that anywhere; I only wrote that - according to a certain calculation procedure - the heat demand, sorry, energy demand, is known.

Unfortunately, that is wrong! According to the method you described, one arrives at the room heating load (power (W; kW)) or the specific values /m², without taking into account the ventilation heat losses, which would be urgently necessary. How does the inventor of this method now arrive at the annual energy demand (heating)?

...Yes, surely

I would be very interested in these results. You can surely provide me with the figures (calculation, actual energy consumption).

Best regards

Hello €uro,

.. without considering ventilation heat losses, which would be urgently necessary.

I have already written that I am not an engineer and have left the calculations to a planning office. Only - somehow either you or I are missing something. In a natural stone heating system, ventilation heat losses play absolutely no role. The system uses the walls, ceilings, floors ... body - for example, the (massive) walls store the heat for up to 2 hours - the room air is always equally warm or cold; depending on the point of view. I don’t know if you have ever worked with such a system? You can imagine the functioning comparable to a “sunbath” in the mountains. The ambient temperature is minus x° and yet you hardly feel cold. That is why the rooms do not "suffer" as a result of longer ventilation phases either.

I would be very interested in these results. You can surely provide me with the numbers (calculation, actual energy consumption).

I no longer sell this system for several years because I was tired of running into the walls of the big energy suppliers. Accordingly, I also have no contact with my clients from that time. I might still be able to provide you with calculations (they should be found on the tapes of the respective data backups) – whether I still have invoices from the utilities, I dare to doubt – I am glad if I gain a little space every year (analogous to the 10-year retention period). You will have to believe my statements in case of doubt.

Kind regards