Hello everyone,
I have a question regarding a heating system renovation. I am new here and hope this is the right place for my inquiry.
We are currently planning to modernize our heating system. Our house was built in 1995, conventional construction, Poroton bricks, underfloor heating, about 220m² (2,368 sq ft).
We are currently heating with oil (consumption about 4000 liters/year (1057 gallons)), without a condensing boiler.
We are refinancing at the moment and would like to remove the oil heating system to get rid of the oil tanks and later convert the gained space into living areas.
As options, gas or a geothermal heat pump have emerged. Air-to-water heat pumps are not an option since we do not want an outdoor unit. Gas could be connected to the house for under 2000 euros, the investment is manageable, but it would still mean relying on a fossil fuel. According to our quotes, converting to gas would cost around 16,000 euros.
Geothermal would be possible for us. Our neighbor has a borehole of about 100 meters (328 feet). I do not know the details. According to our quotes, we expect costs around 35,000 euros. The drilling company offered a borehole with 3 x 45 meters (3 x 148 feet), 3 x 15 kW.
Now, I have no idea how to evaluate this borehole or if it is sufficient. It confuses me that the neighbor only has the one borehole, which goes significantly deeper.
In principle, we are also unsure whether the considerably higher investment will ever pay off (apart from the gas dependency). Our neighbor uses about 50-60 euros of electricity per month for his heat pump but has a low-energy house with a ventilation system. We have generally left out subsidies for now. The region of Hesse offers discounted electricity tariffs for heat pumps.
Perhaps someone can give us an assessment to help us with our decision-making. We would really appreciate it.
Best regards
Christian Kumpf
I have a question regarding a heating system renovation. I am new here and hope this is the right place for my inquiry.
We are currently planning to modernize our heating system. Our house was built in 1995, conventional construction, Poroton bricks, underfloor heating, about 220m² (2,368 sq ft).
We are currently heating with oil (consumption about 4000 liters/year (1057 gallons)), without a condensing boiler.
We are refinancing at the moment and would like to remove the oil heating system to get rid of the oil tanks and later convert the gained space into living areas.
As options, gas or a geothermal heat pump have emerged. Air-to-water heat pumps are not an option since we do not want an outdoor unit. Gas could be connected to the house for under 2000 euros, the investment is manageable, but it would still mean relying on a fossil fuel. According to our quotes, converting to gas would cost around 16,000 euros.
Geothermal would be possible for us. Our neighbor has a borehole of about 100 meters (328 feet). I do not know the details. According to our quotes, we expect costs around 35,000 euros. The drilling company offered a borehole with 3 x 45 meters (3 x 148 feet), 3 x 15 kW.
Now, I have no idea how to evaluate this borehole or if it is sufficient. It confuses me that the neighbor only has the one borehole, which goes significantly deeper.
In principle, we are also unsure whether the considerably higher investment will ever pay off (apart from the gas dependency). Our neighbor uses about 50-60 euros of electricity per month for his heat pump but has a low-energy house with a ventilation system. We have generally left out subsidies for now. The region of Hesse offers discounted electricity tariffs for heat pumps.
Perhaps someone can give us an assessment to help us with our decision-making. We would really appreciate it.
Best regards
Christian Kumpf
dertill schrieb:
If you want to be independent and self-sufficient, build a passive house with sufficient photovoltaic panels, a garden for self-supply, and a chicken coop Gladly 🙂 but unfortunately, there are no suitable plots for that here...
smurf26579 schrieb:
This probably speaks in favor of a proper gas heating system... Probably... but not certain. The following points need to be considered.
1. 4000 liters (1057 gallons) of oil for a household of four suggests a heating load of about 14 kW. That is roughly 64 W/m² and almost double what a house compliant with today’s energy saving regulations achieves. Whether it is actually 14 kW is doubtful. Most likely, the oil system was or has been operated very inefficiently.
2. For efficient operation of a heat pump, the required supply water temperatures are crucial. With underfloor heating, conditions are relatively favorable. Some heat pump users even manage to run them very efficiently with radiators. With underfloor heating that operates at supply temperatures below 40°C (104°F), this should be easily possible. However, you need to engage properly with the technology. That means no electric backup heaters, no buffer tank, proper hydraulic balancing, and an optimal heating curve.
If the current underfloor heating cannot achieve supply temperatures below 40°C (104°F), it is worth considering improving the insulation standards. This has two effects:
- Lowering the required supply temperatures (making the system suitable for a heat pump)
- Reducing the overall heat demand.
3. If supply temperatures indicate that a ground source heat pump could be an option, it is advisable to research the concept of a trench collector. In new builds, this can be installed very cost-effectively. After subsidies, it can even outperform an air source heat pump. For existing buildings, it is somewhat more challenging but definitely feasible. Getting informed certainly doesn’t hurt.
4. Gas has the advantage that you don’t have to worry about the points mentioned above. On the other hand, you should consider whether there is a risk that fossil fuels might face significantly higher costs in the near future, for example through CO2 taxes.
Regards, Nika
S
smurf2657931 Mar 2019 20:49gnika77 schrieb:
Probably... but not certain... The following points should be considered.
1. 4000 liters (about 1057 gallons) of oil for a 4-person household indicate a heating load of around 14 kW. That equates to about 64 W/m² (6 W/ft²), which is almost double what a house built to current energy-saving standards would require. Whether it is really 14 kW is doubtful. Most likely, the oil heating system has been operated very inefficiently so far.
2. For efficient operation of a heat pump, the required supply temperatures are especially important. Underfloor heating provides quite good conditions for this. Some heat pump users manage to operate a heat pump even with radiators extremely efficiently. With underfloor heating, which typically reaches supply temperatures below 40°C (104°F), it should be no problem. However, you need to pay attention to the technology: no electric backup heater (ERR), no buffer tank, hydraulic balancing, and an optimal heating curve.
If the current underfloor heating system cannot achieve supply temperatures below 40°C (104°F), improvements in the insulation standard should be considered. This has two effects:
- Lowering the supply temperatures (making it suitable for a heat pump)
- Reducing the heating demand
3. If, based on possible supply temperatures, a ground-source heat pump is an option, it is recommended to research the concept of the “loop trench collector” (ring trench collector). In new builds, this can be installed extremely cost-effectively. After factoring in subsidies, it can even be more advantageous than an air-source heat pump. For existing buildings, it is somewhat more difficult but still feasible. Getting informed can only help.
4. Gas has the advantage that one does not have to worry much about the points mentioned above. On the other hand, it is worth considering whether there is a risk that fossil fuels will face significantly higher charges in the near future, for example in the form of CO2 taxes.
Best regards, NikaThank you very much for the great feedback!
(also to everyone else)
Our supply temperature is about 30°C (86°F) – although we do have radiators running at 60°C (140°F) supply temperature, but in fact only one radiator is in use – the one in the bathroom.
The loop trench collector sounds very interesting, but our garden is mostly built up and landscaped, so unfortunately this option is not possible.
The 4000 liters (about 1057 gallons) of oil is more of an estimate – but 3500 liters (about 924 gallons) is certainly closer to the real consumption.
Gas is probably the cheapest option, but somehow we don’t feel comfortable investing in this type of fuel.
Good luck!
smurf26579 schrieb:
Our supply temperature is about 30°C (86°F) – we do have radiators running at 60°C (140°F) supply temperature, but only one of them is actually in use – the one in the bathroom.Is the 30°C (86°F) supply temperature independent of the outdoor temperature? Or do you have 30°C (86°F) supply at 10°C (50°F) outside, and more like 40-45°C (104-113°F) supply when it’s -10°C (14°F) outside?
When switching the heating system to any type (gas condensing, oil condensing, pellet with condensing, or heat pump), lower the bathroom supply temperature to match the rest of the system. Right now, because of the bathroom radiator, you always have 60°C (140°F) supply temperature (or whatever the highest temperature in the heating circuit is) for everything. The rest is just mixed down. With your old oil boiler, that doesn’t really matter since it doesn’t use condensing technology. But with a new system, the average heating medium temperature should be as low as possible, and 25/60 is definitely higher than 25/35.
S
smurf265791 Apr 2019 09:00dertill schrieb:
Is the 30 degrees (30°C / 86°F) independent of the outside temperature? Or do you have 30°C (86°F) supply temperature at 10°C (50°F) outside, but closer to 40-45°C (104-113°F) supply when it’s -10°C (14°F) outside?
When switching the heating system to anything (gas condensing, oil condensing, pellet with condensing, or heat pump), lower the supply temperature in the bathroom to match the level of the rest of the circuit. Right now, because of the bathroom radiator, you always have 60°C (140°F) or the highest temperature in the heating circuit in the supply line for everything. The rest is then mixed down. With your old oil boiler, it doesn’t really matter since it doesn’t use condensing technology anyway. But with a new system, the average heat carrier temperature should be as low as possible, and 25/60 is much higher than 25/35.So the supply temperature is always around 30°C (86°F).
Thanks for the tip about the bathroom radiator – it’s not running continuously, though. I’ll have to check where to adjust this in the heating system menu. Of course, providing energy at 60°C (140°F) costs more.
By the way, there was an error in my initial post – the boreholes for the heat pump are not 3 x 45 m (3 x 148 ft), but rather 3 x 90 m (3 x 295 ft) or 2 x 135 m (2 x 443 ft) deep...
Can you really do without passive cooling? Or is the effect in summer so pleasant that the €900 (plus tax) extra cost would be worth it in our case?
H
hampshire1 Apr 2019 09:55Bookstar schrieb:
No second thought, of course gas because it is much cheaper and more reliable technology No second thought. Of course, without fossil fuels if technically feasible.
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