ᐅ Heating System Upgrade for Existing Buildings – Condensing Boiler / Air-to-Water Heat Pump / Air Source Heat Pump
Created on: 9 Apr 2022 10:12
C
Chrizz72
Hello dear forum,
I am new here and this is my first post. I would be very grateful if anyone could help me with my question/problem.
Starting point:
We are about to buy a single-family house (built in 1959/60; living area approx. 170sqm (1830 sq ft) – 65sqm (700 sq ft) first floor, 65sqm (700 sq ft) second floor, 40sqm (430 sq ft) attic). The windows were replaced in 2005 (Uw-value 1.2), we will reroof and insulate the roof (U-value 0.14), possibly also insulate the basement ceiling – everything else is still in the “original condition.” Four of us will live in the house (2 adults + 2 children). The attic will be converted into living space. There is an old gas boiler (not condensing) in the basement and old cast iron radiators throughout the house. Additionally, we will renew the electrical system and renovate all the floors.
The key question now is: What heating system should we choose?
Since the house was previously occupied only by an elderly lady, there is no reliable data to estimate our future heating demand. Naturally, we would prefer to move away from fossil fuels and install an air-to-water heat pump combined with underfloor heating and photovoltaic panels (without subsidies, this would definitely cost about 65K) – however, this would exceed our budget. Without photovoltaic, I am also quite worried that the electricity costs could skyrocket. As a compromise, we have now focused on the following option: installation of a gas condensing boiler for heating and a domestic hot water heat pump (DHW HP) for hot water production – the ability to reduce the condensing boiler’s use during warmer months seems very attractive. Besides the cost aspect (which is completely acceptable to us, both initially and ongoing), the sustainability aspect also plays a role here (of course, a DHW HP alone is not a huge lever). At the same time, we are thinking about switching to underfloor heating on the ground floor and low-temperature radiators on the first and second floors. The idea behind this is to create an infrastructure that would allow us to switch to a heat pump fairly easily in the future. We would also gain reliable data regarding heat and heating demand. We wouldn’t have to install photovoltaic on the roof immediately but could add it later, either gradually or all at once.
How do you assess my approach? Does it sound realistic and reasonable to you, especially considering the current context (war, energy transition/costs, etc.)? I understand there is no perfect solution, but I would like to make a well-informed decision that makes economic and ecological sense in the short and long term. Maybe there are alternatives I haven’t considered yet.
A little about me: I am unfortunately not very skilled technically and have very little experience. However, I have noticed that I can quite quickly get to grips with unfamiliar topics and have a steeper learning curve than expected 🙂
I look forward to your feedback.
Best regards,
Christian
I am new here and this is my first post. I would be very grateful if anyone could help me with my question/problem.
Starting point:
We are about to buy a single-family house (built in 1959/60; living area approx. 170sqm (1830 sq ft) – 65sqm (700 sq ft) first floor, 65sqm (700 sq ft) second floor, 40sqm (430 sq ft) attic). The windows were replaced in 2005 (Uw-value 1.2), we will reroof and insulate the roof (U-value 0.14), possibly also insulate the basement ceiling – everything else is still in the “original condition.” Four of us will live in the house (2 adults + 2 children). The attic will be converted into living space. There is an old gas boiler (not condensing) in the basement and old cast iron radiators throughout the house. Additionally, we will renew the electrical system and renovate all the floors.
The key question now is: What heating system should we choose?
Since the house was previously occupied only by an elderly lady, there is no reliable data to estimate our future heating demand. Naturally, we would prefer to move away from fossil fuels and install an air-to-water heat pump combined with underfloor heating and photovoltaic panels (without subsidies, this would definitely cost about 65K) – however, this would exceed our budget. Without photovoltaic, I am also quite worried that the electricity costs could skyrocket. As a compromise, we have now focused on the following option: installation of a gas condensing boiler for heating and a domestic hot water heat pump (DHW HP) for hot water production – the ability to reduce the condensing boiler’s use during warmer months seems very attractive. Besides the cost aspect (which is completely acceptable to us, both initially and ongoing), the sustainability aspect also plays a role here (of course, a DHW HP alone is not a huge lever). At the same time, we are thinking about switching to underfloor heating on the ground floor and low-temperature radiators on the first and second floors. The idea behind this is to create an infrastructure that would allow us to switch to a heat pump fairly easily in the future. We would also gain reliable data regarding heat and heating demand. We wouldn’t have to install photovoltaic on the roof immediately but could add it later, either gradually or all at once.
How do you assess my approach? Does it sound realistic and reasonable to you, especially considering the current context (war, energy transition/costs, etc.)? I understand there is no perfect solution, but I would like to make a well-informed decision that makes economic and ecological sense in the short and long term. Maybe there are alternatives I haven’t considered yet.
A little about me: I am unfortunately not very skilled technically and have very little experience. However, I have noticed that I can quite quickly get to grips with unfamiliar topics and have a steeper learning curve than expected 🙂
I look forward to your feedback.
Best regards,
Christian
i_b_n_a_n schrieb:
And what about the photovoltaic system (the only investment that really pays off, especially in combination with a heat pump) later on? No, the interest rates are still low, so it makes sense to install it together with the new roof (good photovoltaic = full roof) if it is financially feasible. I would definitely only do it at the expense of other renovation costs or work. Whether it's even financially feasible, I still have to check...
D
Deliverer9 Apr 2022 13:35Photovoltaics should be considered entirely independently. It is a (very worthwhile) investment, one that pays off even if financed (KfW). However, it has nothing to do with the rest. The small amount of electricity it can supply for heating is not critical.
There are no alternatives to heat pumps (even if some think otherwise). Your task now is to make the heat pump and yourself as comfortable as possible.
There are no alternatives to heat pumps (even if some think otherwise). Your task now is to make the heat pump and yourself as comfortable as possible.
B
Benutzer2009 Apr 2022 14:03Chrizz72 schrieb:
So you mean that if there is no photovoltaic system, it definitely needs to be calculated. In your experience, it would probably show that it is economically justifiable. Sounds good to me. How much would such a calculation cost? Can a qualified energy consultant do it as well? Even with a photovoltaic system, the calculation is necessary. The room-by-room heating load calculation including underfloor heating design should NOT be done by the energy consultant, but by the planning office. It might cost around 150-200€. For example, Büro Heckmann.
Thank you for your replies. Now it is up to us to make a decision. Basically, many people recommend the same: a heat pump, ideally combined with photovoltaic panels.
I have one more question: based on the room-by-room heating load calculation, can the heating contractor select and adjust the appropriate heat pump as well as underfloor heating and/or low-temperature radiators accordingly? The energy consultant could then double-check this (based on the offer or similar) and handle the applications, for example with BAFA?
I have one more question: based on the room-by-room heating load calculation, can the heating contractor select and adjust the appropriate heat pump as well as underfloor heating and/or low-temperature radiators accordingly? The energy consultant could then double-check this (based on the offer or similar) and handle the applications, for example with BAFA?
D
Deliverer10 Apr 2022 11:47In theory, yes. In practice, most heating engineers and energy consultants are not very reliable. But basically, you are right... Self-monitoring is recommended. In the end, these are just numbers you can add up.
You can submit the Bafa applications yourself. I wouldn’t pay anyone for that.
Addendum: If you combine radiators and underfloor heating, you should ensure that the radiators are calculated to have the same flow temperature as the underfloor heating. You do NOT want to use a mixing valve.
Also: The maximum heating load determines the size of the heat pump. No extra allowances for peace of mind or domestic hot water preparation.
You can submit the Bafa applications yourself. I wouldn’t pay anyone for that.
Addendum: If you combine radiators and underfloor heating, you should ensure that the radiators are calculated to have the same flow temperature as the underfloor heating. You do NOT want to use a mixing valve.
Also: The maximum heating load determines the size of the heat pump. No extra allowances for peace of mind or domestic hot water preparation.
B
Benutzer20010 Apr 2022 11:51Chrizz72 schrieb:
I have one more question: Based on the room-by-room heating load calculation, can the HVAC installer select and configure the appropriate heat pump as well as underfloor heating and/or low-temperature radiators? Then the energy consultant could review it again (based on the offer or similar) and submit applications, for example, to BAFA? You should also have the underfloor heating planned by a professional. They will design it to achieve the lowest possible supply temperature. The HVAC installer might say, "We’ve always done it that way." And the energy consultant is an advisor and not necessarily a technically skilled person.
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