First of all, I want to clarify that my goal is not to save the world (sorry, my bad), but solely to reduce heating costs! I have been calculating back and forth for some time now but unfortunately can’t come to an optimal conclusion.
So here’s my attempt to use collective intelligence. Perhaps someone has already considered the same issues.
My house (old, 25cm (10 inches) Ytong blocks) could be improved in terms of U-value by adding a brick-style polystyrene cladding, or I could install a heat pump. Currently, I am heating with oil but could switch to gas. Oil heating still has a certain grandfathering protection for a while, but it’s likely that I will face problems with oil in the future.
Switching to gas would cost me about $8,000, the heat pump around $15,000. The polystyrene (or similar) cladding would indeed lower heating costs, but when I asked for information, no one could really tell me by what percentage my costs would drop if I improved the U-value (currently 0.35 for 25cm (10 inches) Ytong) by a factor X through additional insulation.
Are there tables or simple rough calculations that could help me decide without having to take another university-level math course first?
Thanks in advance for any information from someone who, like me, does not want to wait for the climate transition that will supposedly bring us winter temperatures of +15°C (59°F). 😉
So here’s my attempt to use collective intelligence. Perhaps someone has already considered the same issues.
My house (old, 25cm (10 inches) Ytong blocks) could be improved in terms of U-value by adding a brick-style polystyrene cladding, or I could install a heat pump. Currently, I am heating with oil but could switch to gas. Oil heating still has a certain grandfathering protection for a while, but it’s likely that I will face problems with oil in the future.
Switching to gas would cost me about $8,000, the heat pump around $15,000. The polystyrene (or similar) cladding would indeed lower heating costs, but when I asked for information, no one could really tell me by what percentage my costs would drop if I improved the U-value (currently 0.35 for 25cm (10 inches) Ytong) by a factor X through additional insulation.
Are there tables or simple rough calculations that could help me decide without having to take another university-level math course first?
Thanks in advance for any information from someone who, like me, does not want to wait for the climate transition that will supposedly bring us winter temperatures of +15°C (59°F). 😉
Höhlenmensch30 Nov 2021 11:52Thank you for the responses. I already suspected that it wouldn’t be easy to get a concise statement.
The tip about consulting an energy advisor is certainly valid, but from past conversations I’ve had some experiences that have made me “consultation resistant” Beratungsresistent!
Warning, this is a subjective experience!
I won’t go into detail here, since there are obviously accurate advisors, but many (especially the cheaper ones) are effectively “pushy salespeople” who tend to emphasize problems, want to make plans, measure the heating room, etc., to justify the consulting effort and then offer proposals that are usually company-specific for commission reasons.
After some time-consuming research, I have found that heat pumps are good for the environment but unfortunately don’t have much of a positive impact on my heating costs, so I will probably switch from oil to gas instead of to a heat pump.
(A small additional remark: it is relatively easy to import heat pumps from China yourself. Not everything from the Far East is junk, you just have to take some care, and the components are surprisingly cheaper, so you can do without subsidies—if you get any at all.)
The currently sharply increased gas price does make me think a lot about the future, which is why I’ve still researched Chinese heat pumps online.
Regarding the topic, as mentioned, 25cm Ytong (10 inches) / 120m² (1,292 ft²) / underfloor heating / annual oil consumption about 2000 liters (530 gallons).
The values are unfortunately not cleanly reproducible because I haven’t insulated the basement ceiling. As a result, some heat radiates downwards, and I end up heating the basement (fully cellared) as well.
As I said, consultation resistant, since all experts warned against this approach.
In practice, however, it has proven effective, as the basement can be used comfortably without radiators or installation. However, my floor heating supply temperature is not 35°C (95°F) but 50°C (122°F) in severe cold, but as mentioned, I indirectly heat the basement a little this way.
Apologies if I want to simplify this.
At the above-mentioned 25cm Ytong with U-value 0.35, my oil consumption is about 2000 liters (530 gallons).
Since the best savings potential is insulation, I intend to install additional external insulation. According to my research, a thickness of 6cm (2.4 inches) is reasonable in terms of price and efficiency (I understand more is better, but the efficiency curve flattens out beyond that).
The insulation panel would be made of polyurethane and have a U-value of 0.21.
Question: What is the effective combined U-value when combining the 0.35 value of the masonry and the 0.21 insulation panel?
The value should improve. When I asked companies, I was repeatedly referred to “complicated advanced mathematical calculations,” which I find hard to understand.
If I had the new “combined value,” I could compare it to my oil usage and roughly estimate how much I might save.
Even if it’s not exact, that’s really all I care about!
Before investing, I want to know what it will bring me.
For example, if I save about $200 per year, that’s $2,000 over 10 years and may not be proportional to the investment. (Yes, I know nothing is too expensive for the environment.)
Sorry for the lengthy text, but I think it’s clear what I’m aiming at!?
The tip about consulting an energy advisor is certainly valid, but from past conversations I’ve had some experiences that have made me “consultation resistant” Beratungsresistent!
Warning, this is a subjective experience!
I won’t go into detail here, since there are obviously accurate advisors, but many (especially the cheaper ones) are effectively “pushy salespeople” who tend to emphasize problems, want to make plans, measure the heating room, etc., to justify the consulting effort and then offer proposals that are usually company-specific for commission reasons.
After some time-consuming research, I have found that heat pumps are good for the environment but unfortunately don’t have much of a positive impact on my heating costs, so I will probably switch from oil to gas instead of to a heat pump.
(A small additional remark: it is relatively easy to import heat pumps from China yourself. Not everything from the Far East is junk, you just have to take some care, and the components are surprisingly cheaper, so you can do without subsidies—if you get any at all.)
The currently sharply increased gas price does make me think a lot about the future, which is why I’ve still researched Chinese heat pumps online.
Regarding the topic, as mentioned, 25cm Ytong (10 inches) / 120m² (1,292 ft²) / underfloor heating / annual oil consumption about 2000 liters (530 gallons).
The values are unfortunately not cleanly reproducible because I haven’t insulated the basement ceiling. As a result, some heat radiates downwards, and I end up heating the basement (fully cellared) as well.
As I said, consultation resistant, since all experts warned against this approach.
In practice, however, it has proven effective, as the basement can be used comfortably without radiators or installation. However, my floor heating supply temperature is not 35°C (95°F) but 50°C (122°F) in severe cold, but as mentioned, I indirectly heat the basement a little this way.
Apologies if I want to simplify this.
At the above-mentioned 25cm Ytong with U-value 0.35, my oil consumption is about 2000 liters (530 gallons).
Since the best savings potential is insulation, I intend to install additional external insulation. According to my research, a thickness of 6cm (2.4 inches) is reasonable in terms of price and efficiency (I understand more is better, but the efficiency curve flattens out beyond that).
The insulation panel would be made of polyurethane and have a U-value of 0.21.
Question: What is the effective combined U-value when combining the 0.35 value of the masonry and the 0.21 insulation panel?
The value should improve. When I asked companies, I was repeatedly referred to “complicated advanced mathematical calculations,” which I find hard to understand.
If I had the new “combined value,” I could compare it to my oil usage and roughly estimate how much I might save.
Even if it’s not exact, that’s really all I care about!
Before investing, I want to know what it will bring me.
For example, if I save about $200 per year, that’s $2,000 over 10 years and may not be proportional to the investment. (Yes, I know nothing is too expensive for the environment.)
Sorry for the lengthy text, but I think it’s clear what I’m aiming at!?
O
Oetzberger30 Nov 2021 12:02Just do the calculations yourself using tools like ubakus and TGA BIM. What the energy consultant does is not rocket science. You can compare affordable self-installed Panasonic heat pumps and gas systems with a few Excel calculations. Underfloor heating sounds like a good idea to start with.
B
Benutzer20030 Nov 2021 12:07Höhlenmensch schrieb:
After some time-consuming research, I’ve found that heat pumps are good for the environment but unfortunately don’t reduce my heating costs very much, so I would probably switch from oil to gas instead of to a heat pump. It depends on a) where the electricity for the heat pump comes from and b) how much electricity you use. Without improving the building’s energy efficiency, gas will likely perform similarly (although gas is generally more environmentally friendly than oil).
Höhlenmensch schrieb:
(A small side note: you can also relatively easily import heat pumps from China yourself. Look into Panasonic monoblocks. They are highly efficient with reasonable costs (a 5kW monoblock costs around €3,000 (about $3,200) from a German dealer).
Höhlenmensch schrieb:
Regarding the topic: as mentioned, 25cm Ytong /120m²/ underfloor heating / annual oil consumption around 2,000 liters
The numbers aren’t perfectly reliable since I haven’t insulated the basement ceiling. So some heat escapes downwards and also heats the basement (fully basemented). You should consider insulating the basement ceiling. It’s the easiest and most cost-effective way to save energy. My house is also uninsulated on the outside, but the windows are new and both the top floor ceiling and basement ceiling are insulated. At slightly below freezing temperatures, 30 degrees Celsius (86°F) supply temperature from the heat pump is sufficient.
Höhlenmensch schrieb:
Apologies if I want to simplify it anyway.
I now have, with the aforementioned 25cm Ytong and U-value of 0.35, an oil consumption of about 2,000 liters.
Since the best saving potential is insulation, I plan to add an external insulation layer. Based on my research, a thickness of 6 cm is reasonable in terms of cost and efficiency (I know more is better, but the efficiency gains tend to flatten out). Use tools like Ubakus to calculate U-values. Remember that adding more insulation accounts for only a fraction of the total costs. The overall fixed costs matter most. You should definitely insulate the basement as well.
Höhlenmensch schrieb:
The cladding is made of polyurethane and has a U-value of 0.21 What kind of insulation is this with those values? That’s new to me.
Höhlenmensch1 Dec 2021 18:59Regarding:
1. 😉 Electricity comes from my socket.
Joking aside—I already have 4000 kWh (4000 kWh) annually.
After thorough research and comparing notes with an acquaintance, I’ve ruled out photovoltaics. I’m located at 53° north latitude, and my gable roof faces west! Even our top expert from the Technical University of Berlin (you can watch Quaschning’s lecture on YouTube) raised a cautionary flag when it’s considered only from a cost perspective.
For everyone with a heat pump—may the upcoming winters stay warm. The aforementioned acquaintance installed a special meter that shows how often and how long the auxiliary heating rods kick in—the power in watts is known—and realized that the 5°C (41°F) limit is somewhat optimistic.
Luckily, I don’t have a new build but an existing property.
Our world-saving "legislators" may not view the extra costs of the energy-saving regulation as significant, but since all new builds are supposed to have photovoltaics by 2025, I do wonder who will pay for that.
2. Thanks for the tip—I checked it out, but the “affordable” units are all in the low 5 kW (5 kW) range, which won’t cover my needs for 120 m² (1300 ft²).
China was just a suggestion (Alibaba) that I’m still researching (shipping costs), but they do offer units with up to 80°C (176°F) flow temperature. I’m skeptical about that as well and am currently in correspondence.
3. Regarding basement insulation, I already mentioned that contrary to the commonly promoted opinion, I didn’t plan any special insulation back then (only slag as a weight to reduce ceiling vibration). This has proven effective over the years despite experts’ opinions. The heat from the underfloor heating mainly rises due to convection, and I don’t consider the downward heat loss as a loss but rather a gain. I use the basement rooms and am glad they stay sufficiently warm without additional heating installations!
Of course, anyone who uses the basement just as a cellar (cooling wine bottles—Rothschild Chateau Lafite southern exposure 😉 delicious!) should pay attention to good insulation.
Almost everyone I know uses their basements for hobbies, office, children’s rooms, etc., and also heats them additionally.
4. Thanks also for the calculator and software tips I looked into—unfortunately, they all calculate only a single U-value, and I haven’t yet managed to combine two values (insulation U1 0.35 // + insulation U2 0.21) for a more precise estimate.
5. The 0.21 W/(m²·K) polyurethane corresponds to the 6 cm (2.4 inches) version from the company Boegerfassaden (insulation overlay with brick design).
It looks good visually with the brick design, and you don’t have to plaster over the insulation! However, it is somewhat expensive.
One neighbor applied this insulation and told me he saves about 250 liters (about 66 gallons) of oil per year (~15%) on his 100 m² (1076 ft²) house.
Roughly scaled up to my house, that translates to just over 200 in savings annually.
So, in practice, the savings claimed by insulation vendors should be viewed with caution.
Even if I assume savings of 250–300, over 10 years that is 3,000.
That doesn’t seem like a great return on investment considering the cost of insulation and its installation.
Sorry if I’m judging this only financially and not in terms of environmental benefits.
I’ll keep a low profile for now and continue researching how much shipping costs for heat pumps from China to Germany “free delivery” really are.
Hopefully, the winter will be WARM!
1. 😉 Electricity comes from my socket.
Joking aside—I already have 4000 kWh (4000 kWh) annually.
After thorough research and comparing notes with an acquaintance, I’ve ruled out photovoltaics. I’m located at 53° north latitude, and my gable roof faces west! Even our top expert from the Technical University of Berlin (you can watch Quaschning’s lecture on YouTube) raised a cautionary flag when it’s considered only from a cost perspective.
For everyone with a heat pump—may the upcoming winters stay warm. The aforementioned acquaintance installed a special meter that shows how often and how long the auxiliary heating rods kick in—the power in watts is known—and realized that the 5°C (41°F) limit is somewhat optimistic.
Luckily, I don’t have a new build but an existing property.
Our world-saving "legislators" may not view the extra costs of the energy-saving regulation as significant, but since all new builds are supposed to have photovoltaics by 2025, I do wonder who will pay for that.
2. Thanks for the tip—I checked it out, but the “affordable” units are all in the low 5 kW (5 kW) range, which won’t cover my needs for 120 m² (1300 ft²).
China was just a suggestion (Alibaba) that I’m still researching (shipping costs), but they do offer units with up to 80°C (176°F) flow temperature. I’m skeptical about that as well and am currently in correspondence.
3. Regarding basement insulation, I already mentioned that contrary to the commonly promoted opinion, I didn’t plan any special insulation back then (only slag as a weight to reduce ceiling vibration). This has proven effective over the years despite experts’ opinions. The heat from the underfloor heating mainly rises due to convection, and I don’t consider the downward heat loss as a loss but rather a gain. I use the basement rooms and am glad they stay sufficiently warm without additional heating installations!
Of course, anyone who uses the basement just as a cellar (cooling wine bottles—Rothschild Chateau Lafite southern exposure 😉 delicious!) should pay attention to good insulation.
Almost everyone I know uses their basements for hobbies, office, children’s rooms, etc., and also heats them additionally.
4. Thanks also for the calculator and software tips I looked into—unfortunately, they all calculate only a single U-value, and I haven’t yet managed to combine two values (insulation U1 0.35 // + insulation U2 0.21) for a more precise estimate.
5. The 0.21 W/(m²·K) polyurethane corresponds to the 6 cm (2.4 inches) version from the company Boegerfassaden (insulation overlay with brick design).
It looks good visually with the brick design, and you don’t have to plaster over the insulation! However, it is somewhat expensive.
One neighbor applied this insulation and told me he saves about 250 liters (about 66 gallons) of oil per year (~15%) on his 100 m² (1076 ft²) house.
Roughly scaled up to my house, that translates to just over 200 in savings annually.
So, in practice, the savings claimed by insulation vendors should be viewed with caution.
Even if I assume savings of 250–300, over 10 years that is 3,000.
That doesn’t seem like a great return on investment considering the cost of insulation and its installation.
Sorry if I’m judging this only financially and not in terms of environmental benefits.
I’ll keep a low profile for now and continue researching how much shipping costs for heat pumps from China to Germany “free delivery” really are.
Hopefully, the winter will be WARM!
O
Oetzberger1 Dec 2021 19:11Höhlenmensch schrieb:
4. Thanks also for the calculator program recommendations, which I have checked out. Unfortunately, they all only calculate the single "U-value," and I was not able to determine the combination of two values (insulation U1 0.35 // + insulation U2 0.21). If you have the time and interest, then simulate everything using TGA Tools BIM.
RotorMotor schrieb:
I would recommend involving an energy consultant in your project.
Without proper calculations, the tables won’t help you much.
And without knowing your heating system, it’s impossible to advise what would be more effective!
Currently, both insulation and heat pumps are heavily subsidized, whether as individual measures or as a complete package with KfW level support. But you can.
Tell me your annual oil consumption, living area in m2 (square meters), the volume of heated space in m3 (cubic meters), and the age of your oil heating system. Hydronic balancing done? Possibly known supply temperatures?
Underfloor heating or radiators?
Based on these data, a sizing can be planned with 90-95% accuracy. The remaining 5-10% is only worth it ecologically, not economically.
Economics seems to be your priority.
edit: just reading the thread now, never mind...
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