ᐅ Buffer tank for basement combined with gas condensing boiler and solar system

Hello everyone,

I am currently planning the heating system for our new single-family home. I will be installing a gas condensing boiler, solar panels on the roof, and a fireplace with a heat exchanger in the living room. So far, so good. Now the question is, what kind of buffer tank should I install in the basement?

I have consulted three heating contractors and received three different opinions.

1.) A 1000 liter (264 gallon) combined storage tank will be installed in the basement. All three heat sources feed their heat into different layers of the tank. The domestic hot water is circulated inside the tank through a stainless steel corrugated pipe and heated on demand via the heat exchanger principle.

2.) Also a combined storage tank, but 800 liters (211 gallons). However, the domestic hot water is stored in a water bladder located in the upper part of the tank.

3.) The fireplace and solar system fill a 300-400 liter (79-106 gallon) tank for domestic hot water. The heating water is heated on demand by the boiler.

Which option is the most sensible?

For your information, we have a combination of underfloor heating and radiators in the house.

Best regards,
Marlon

marlon2468 schrieb:
...I am currently planning the heating system for our new single-family house. I will install a gas condensing boiler, solar panels on the roof, and a fireplace with a heat exchanger in the living room.

This will most likely prove to be uneconomical. Solar thermal systems as well as wood-burning stoves with water heat exchangers usually do not pay off in single-family homes. Although a few kilowatt-hours per year are "harvested," the additional investment costs are generally disproportionate. When using a gas condensing boiler as the heat source, I would always recommend reducing the heat demand (15% rule).
Best regards.

€uro schrieb:
When using a gas condensing boiler as the heat generator, I would always reduce the demand (15% rule).

Best regards.

What do you mean by the 15% rule?

Assuming it is still worthwhile, which option for the buffer tank would be the most sensible?

Regards
Marlon

marlon2468 schrieb:
What do you mean by the 15% rule?

It’s better to improve insulation than to rely on what a solar thermal system would require!

marlon2468 schrieb:
...Assuming it is still worthwhile.

You’re welcome to prove this with your own system. Install heat meters on the solar thermal system and wood stove. Then compare the harvested kWh per year with the demand as well as the investment or financing costs.

marlon2468 schrieb:
...Which option for the buffer tank would be the most sensible?

This needs to be calculated based on specific conditions, including the actual demand for heating and domestic hot water. Alternatively, you could trust a salesperson and hope it somehow works out. However, the likelihood of that is very low. 😉

Best regards.

I probably should have mentioned that my girlfriend will be running a hair salon in the house. Therefore, compared to a typical single-family home, we have a higher need for hot water, which is also evenly distributed throughout the day, provided there is sunlight.

marlon2468 schrieb:
I probably should have mentioned that my girlfriend will run a hair salon in the house. Therefore, compared to a typical single-family home, we have a higher demand for hot water, which is also evenly distributed throughout the day, even when there is sunlight.

This is not a minor detail, but a decisive factor!

Best regards