Hello everyone,
We are going to build a townhouse with 160 sqm (1,722 sq ft) plus a basement (https://www.hausbau-forum.de/threads/grundriss-stadtvilla-160qm-bitte-um-tipps.30018/). We are two adults, a 6-year-old daughter, and a baby on the way. We all enjoy long, comfortably warm baths or showers.
Our construction contract includes two possible heating systems in the price. I don't want to start a fundamental debate here about whether an air-to-water heat pump or gas/solar is better. Maybe someone has some insight and can give us advice on what might be more suitable for OUR building project and OUR family situation. I also have some specific questions...
(P.S.: Underfloor heating will be installed throughout the house except in the utility room. We also want a fireplace.)
1. Gas condensing boiler with hot water storage tank (manufacturer Wolf, 4–8 kW, with 300 l (79 gallons) storage volume). Domestic hot water supply is central without circulation pipes. 2–3 flat solar collectors included.
- Is 300 l (79 gallons) enough for us "warm water lovers," or will we run out of hot water by the end of the day?
- What exactly is meant by circulation pipes?
- Are 2–3 flat solar collectors sufficient? Our acquaintances are also four people and have 12.
OR:
2. Air-to-water heat pump (manufacturer Rotex HPSU Compact, 4–8 kW) with outdoor and indoor units. One energy storage tank with 300 l (79 gallons) storage volume.
- Does anyone have experience with this device regarding noise levels?
- I once read that when using an air-to-water heat pump, it is advisable to install a photovoltaic system as well, but that can be quite expensive, right?
Since we want a fireplace, the idea came up to combine a water-bearing wood stove with gas/solar and install a combined storage tank (or stratified storage tank?). What additional costs would that involve? Does anyone have experience with that?
What would you recommend? Thanks in advance!
We are going to build a townhouse with 160 sqm (1,722 sq ft) plus a basement (https://www.hausbau-forum.de/threads/grundriss-stadtvilla-160qm-bitte-um-tipps.30018/). We are two adults, a 6-year-old daughter, and a baby on the way. We all enjoy long, comfortably warm baths or showers.
Our construction contract includes two possible heating systems in the price. I don't want to start a fundamental debate here about whether an air-to-water heat pump or gas/solar is better. Maybe someone has some insight and can give us advice on what might be more suitable for OUR building project and OUR family situation. I also have some specific questions...
(P.S.: Underfloor heating will be installed throughout the house except in the utility room. We also want a fireplace.)
1. Gas condensing boiler with hot water storage tank (manufacturer Wolf, 4–8 kW, with 300 l (79 gallons) storage volume). Domestic hot water supply is central without circulation pipes. 2–3 flat solar collectors included.
- Is 300 l (79 gallons) enough for us "warm water lovers," or will we run out of hot water by the end of the day?
- What exactly is meant by circulation pipes?
- Are 2–3 flat solar collectors sufficient? Our acquaintances are also four people and have 12.
OR:
2. Air-to-water heat pump (manufacturer Rotex HPSU Compact, 4–8 kW) with outdoor and indoor units. One energy storage tank with 300 l (79 gallons) storage volume.
- Does anyone have experience with this device regarding noise levels?
- I once read that when using an air-to-water heat pump, it is advisable to install a photovoltaic system as well, but that can be quite expensive, right?
Since we want a fireplace, the idea came up to combine a water-bearing wood stove with gas/solar and install a combined storage tank (or stratified storage tank?). What additional costs would that involve? Does anyone have experience with that?
What would you recommend? Thanks in advance!
B
Bauherrin9226 Feb 2019 12:21Thank you for your assessment @Lumpi_LE
Does anyone have experience with a combined gas-solar-fireplace system?
Does anyone have experience with a combined gas-solar-fireplace system?
G
Grobmutant26 Feb 2019 14:32We also considered installing a water-heated fireplace. The conclusion was that it will likely never be cost-effective. Even a stove installer advised against it, since the initial expenses (stove, piping, pressure monitor, labor costs, etc.) are unlikely to be recovered.
For it to be worthwhile, you would need very cheap wood and, above all, run the stove/fireplace for a long time. However, in a new build, this would probably result in the living room overheating.
The stove installer’s recommendation for a new build: Choose a small stove/fireplace with low heating output and without any unnecessary features.
For it to be worthwhile, you would need very cheap wood and, above all, run the stove/fireplace for a long time. However, in a new build, this would probably result in the living room overheating.
The stove installer’s recommendation for a new build: Choose a small stove/fireplace with low heating output and without any unnecessary features.
B
Bauherrin9228 Feb 2019 10:19Quick question for clarification: Does the solar system also support the heating? Or is it only used for heating the water? Is the heat generated in summer stored in any way to be used during winter?
Obstlerbaum schrieb:
Circulation pipes can be omitted in a single-family house, which means it takes about 5 instead of 2 seconds for hot water to reach the tap. One less component that can break.
I can’t really confirm that... we have circulation pipes in the kitchen and the upstairs bathroom, with the pump running on a timer. Warm water arrives quickly there. But if the pump is off and we want water from the kitchen (about ten meters (33 feet) of pipe), it takes quite a while.
In the downstairs bathroom, we didn’t install a circulation line. The plumber said, "The room is right next to the utility room, so the supply line is very short, we don’t need one." But there it doesn’t take 5 seconds, more like 10+ seconds... and that’s pretty annoying.
Bauherrin92 schrieb:
Quick question for clarification: Does solar also support the heating system? Or is it only used to heat the water? Is the heat from summer somehow stored for use in winter? Solar is used to heat water for bathing and similar purposes. The sun’s position allows this to cover 100% of the demand from late February to late October. Otherwise, the gas heating system has to provide additional support. Solar assistance for heating is possible but not cost-effective when comparing expenses and savings.
No long-term heat storage is involved. Either you use the hot water, or the energy is effectively lost.
K.
Regarding circulation pipes:
This is simply a comfort issue. If you want hot water immediately at the tap at all times or during peak usage, a circulation system makes sense. If the house is very well designed with relatively short hot water pipes, you might be able to do without it. However, in most cases, the water does not arrive immediately anyway. Due to our house layout, the main shower is about 15 meters (50 feet) of pipe length from the hot water storage tank. If I shower at an unusual time, it takes almost a minute until the hot water finally arrives.
With a 300-liter (79-gallon) hot water storage tank, you don’t have to worry about running out of hot water when using gas. Even if you completely drain it, it can be set to reheat automatically once a certain temperature is reached, which the gas boiler handles quite quickly.
Regarding solar:
From an economic perspective, it doesn’t make much sense. A solar thermal system for hot water costs at least €4,000–5,000 (euros) upfront. With annual savings of around €150–200, you can easily calculate the payback period. However, the law requires some form of renewable energy if you still want to heat with gas, and solar thermal systems are usually the first option.
Are you getting a ventilation system? It might be possible to cover the renewable energy share through heat recovery from the ventilation system, allowing you to dispense with solar despite using gas, but you would need to run the numbers. That’s how we solved it, as a mechanical ventilation with heat recovery was already planned. Heating is done only with gas, without solar or a stove.
This is simply a comfort issue. If you want hot water immediately at the tap at all times or during peak usage, a circulation system makes sense. If the house is very well designed with relatively short hot water pipes, you might be able to do without it. However, in most cases, the water does not arrive immediately anyway. Due to our house layout, the main shower is about 15 meters (50 feet) of pipe length from the hot water storage tank. If I shower at an unusual time, it takes almost a minute until the hot water finally arrives.
With a 300-liter (79-gallon) hot water storage tank, you don’t have to worry about running out of hot water when using gas. Even if you completely drain it, it can be set to reheat automatically once a certain temperature is reached, which the gas boiler handles quite quickly.
Regarding solar:
From an economic perspective, it doesn’t make much sense. A solar thermal system for hot water costs at least €4,000–5,000 (euros) upfront. With annual savings of around €150–200, you can easily calculate the payback period. However, the law requires some form of renewable energy if you still want to heat with gas, and solar thermal systems are usually the first option.
Are you getting a ventilation system? It might be possible to cover the renewable energy share through heat recovery from the ventilation system, allowing you to dispense with solar despite using gas, but you would need to run the numbers. That’s how we solved it, as a mechanical ventilation with heat recovery was already planned. Heating is done only with gas, without solar or a stove.
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