Hello,
I am currently wondering how it would be practically possible to follow the ideal sequence for building a house in order to maintain the most accurate cost-effectiveness for the various components within the agreed budget.
Many homeowners always ask themselves, "Is this worth it?" But unfortunately, the answer usually comes much later, after the damage has already been done.
For me, the heating load calculation (HLB) provides a key answer regarding the cost-effectiveness of a house or its components. However, this calculation is usually only done once all components are already decided or even built. For prefab home suppliers/general contractors, it is probably even more expensive to maintain this kind of flexibility.
We have about €10,000 (around $11,000) left that we want to invest wisely. The first idea was to improve the masonry from T9 (unfilled) to T7 (filled). This should save real money later on. Assuming we have a quote from the mason with a €4,000 (about $4,400) surcharge compared to the T9. Basically, only the HLB can tell me approximately how many years it will take for the saved heating costs to offset this extra cost. I am aware that this also depends on how efficiently my heating system converts electricity into heat, how cold it will be in the coming years, and so on. But you can still get a rough estimate. Not to forget that the investment will also incur interest costs, which will have a compounding effect over the years of repayment. But all of this can theoretically be calculated.
So, would it be helpful to have the HLB done in advance and analyze different values along with the corresponding costs? Which, incidentally, is not cheap to commission itself... and I believe that is the main reason why this is not usually done in practice, right?
I am currently wondering how it would be practically possible to follow the ideal sequence for building a house in order to maintain the most accurate cost-effectiveness for the various components within the agreed budget.
Many homeowners always ask themselves, "Is this worth it?" But unfortunately, the answer usually comes much later, after the damage has already been done.
For me, the heating load calculation (HLB) provides a key answer regarding the cost-effectiveness of a house or its components. However, this calculation is usually only done once all components are already decided or even built. For prefab home suppliers/general contractors, it is probably even more expensive to maintain this kind of flexibility.
We have about €10,000 (around $11,000) left that we want to invest wisely. The first idea was to improve the masonry from T9 (unfilled) to T7 (filled). This should save real money later on. Assuming we have a quote from the mason with a €4,000 (about $4,400) surcharge compared to the T9. Basically, only the HLB can tell me approximately how many years it will take for the saved heating costs to offset this extra cost. I am aware that this also depends on how efficiently my heating system converts electricity into heat, how cold it will be in the coming years, and so on. But you can still get a rough estimate. Not to forget that the investment will also incur interest costs, which will have a compounding effect over the years of repayment. But all of this can theoretically be calculated.
So, would it be helpful to have the HLB done in advance and analyze different values along with the corresponding costs? Which, incidentally, is not cheap to commission itself... and I believe that is the main reason why this is not usually done in practice, right?
These individual measures are quite ineffective. A house needs a coherent energy concept, meaning you should set the desired standard and then have it developed by a professional.
If you really want to spend the money upfront, a mechanical ventilation system with heat recovery is probably the most reasonable option. While it doesn't offer financial benefits, it at least provides a perceived improvement in comfort.
Otherwise, in my opinion, the most economical investment by far is making extra loan repayments or early repayment.
But believe me, your 20,000 buffer will be gone in the end! Especially if you haven’t properly planned your garden (carport, paving, planting, etc.).
If you really want to spend the money upfront, a mechanical ventilation system with heat recovery is probably the most reasonable option. While it doesn't offer financial benefits, it at least provides a perceived improvement in comfort.
Otherwise, in my opinion, the most economical investment by far is making extra loan repayments or early repayment.
But believe me, your 20,000 buffer will be gone in the end! Especially if you haven’t properly planned your garden (carport, paving, planting, etc.).
Everything is planned. I just mentioned that it could also be done later.
The real challenge is finding someone who truly knows what they’re doing and isn’t just trying to make money off me.
You could also approach it from the other end… that is, define a specific heating technology and capacity first and then design the house accordingly. For example, if I want to use a 5kW (17,000 BTU) air-to-water heat pump, I need certain U-values to achieve a suitably low heat load.
Ultimately, for me, the key factor is cost-effectiveness. Savings on heating systems and electricity need to be proportional to the investment in insulation. Payback time — 10 years? 15 years?
And this is probably what every homeowner should do. Whoever designs the house and provides the thermal performance certificate should be asked about the economic feasibility of the project. It’s important for the homeowner to ensure that financing, maintenance, and the lifespan of the building components are taken into account. If it’s only about comfort, that’s a completely different matter.
I’m curious how my architect will respond when I ask these questions and what arguments he will have. One thing is certain: I want to see numbers. I’m not interested in anecdotal experience, I’ve heard that far too often.
Who else has approached it this way? Who has just built a KfW xy standard house because it was recommended and because it seems logical that insulation and better financing rates save money? Step forward 😀
I just remembered my conversation with Viebrockhaus when I said I only wanted to build according to the 2014 Energy Saving Ordinance… “We only build from KfW 55 standard upwards… unfortunately, we can’t help you.” So does that mean everyone who builds with Viebrockhaus will be uneconomical for the next 10-15 years?
The real challenge is finding someone who truly knows what they’re doing and isn’t just trying to make money off me.
You could also approach it from the other end… that is, define a specific heating technology and capacity first and then design the house accordingly. For example, if I want to use a 5kW (17,000 BTU) air-to-water heat pump, I need certain U-values to achieve a suitably low heat load.
Ultimately, for me, the key factor is cost-effectiveness. Savings on heating systems and electricity need to be proportional to the investment in insulation. Payback time — 10 years? 15 years?
And this is probably what every homeowner should do. Whoever designs the house and provides the thermal performance certificate should be asked about the economic feasibility of the project. It’s important for the homeowner to ensure that financing, maintenance, and the lifespan of the building components are taken into account. If it’s only about comfort, that’s a completely different matter.
I’m curious how my architect will respond when I ask these questions and what arguments he will have. One thing is certain: I want to see numbers. I’m not interested in anecdotal experience, I’ve heard that far too often.
Who else has approached it this way? Who has just built a KfW xy standard house because it was recommended and because it seems logical that insulation and better financing rates save money? Step forward 😀
I just remembered my conversation with Viebrockhaus when I said I only wanted to build according to the 2014 Energy Saving Ordinance… “We only build from KfW 55 standard upwards… unfortunately, we can’t help you.” So does that mean everyone who builds with Viebrockhaus will be uneconomical for the next 10-15 years?
As already mentioned, building economically is still not feasible. There is no real return on investment; costs can only be reduced or postponed.
You are simply considering which additional investment will save you more money in the long run than you put in. However, you generally do not get anything back.
So just set a timeframe, for example, a measure should "pay for itself" within a certain period (e.g., 15 years). Then you can calculate how much energy you are estimated to save (values such as heating degree days can be found online for your region) and decide if it suits you or not. Regardless of all the math and physics, it will only be an estimate (there is no 100% calculation; otherwise, you would need to know every single screw). Therefore, this aspect can also be overstated; the calculations are only meaningful if the results are substantial—heating costs cannot be calculated to the exact dollar, as user behavior, weather, and other factors play a significant role.
The thermal performance of insulation is inversely proportional to its thickness, meaning it quickly stops making "sense" to add even more insulation. To halve the heat loss through a wall, for instance, the insulation thickness must be doubled (doubling the cost), but you only save half of the consumption costs. If these costs are already low, the savings quickly become disproportionate to the expenses. High energy efficiency standards like KfW or passive houses are more a matter of conscience, as the standard is already so high that there isn't much left to save.
Furthermore, comfort should not be forgotten. For me, a pellet heating system combined with omitting the controlled ventilation system (whose heat recovery at best reduces losses) might have been more "economical." However, I do not want to miss the comfort of controlled ventilation and the heat pump. These provide almost effortless operation with consistently good air quality and comfortable temperatures.
On paper, I have KfW-70, because in my view, anything more was not worthwhile. I did not even attempt to reach KfW-55. The building services were already nearly compliant, and the insulation almost met the standard, but the costs for the effort (consultants, etc.) would have consumed the KfW bonus. In actual consumption, there would have been hardly any noticeable difference.
You are simply considering which additional investment will save you more money in the long run than you put in. However, you generally do not get anything back.
So just set a timeframe, for example, a measure should "pay for itself" within a certain period (e.g., 15 years). Then you can calculate how much energy you are estimated to save (values such as heating degree days can be found online for your region) and decide if it suits you or not. Regardless of all the math and physics, it will only be an estimate (there is no 100% calculation; otherwise, you would need to know every single screw). Therefore, this aspect can also be overstated; the calculations are only meaningful if the results are substantial—heating costs cannot be calculated to the exact dollar, as user behavior, weather, and other factors play a significant role.
The thermal performance of insulation is inversely proportional to its thickness, meaning it quickly stops making "sense" to add even more insulation. To halve the heat loss through a wall, for instance, the insulation thickness must be doubled (doubling the cost), but you only save half of the consumption costs. If these costs are already low, the savings quickly become disproportionate to the expenses. High energy efficiency standards like KfW or passive houses are more a matter of conscience, as the standard is already so high that there isn't much left to save.
Furthermore, comfort should not be forgotten. For me, a pellet heating system combined with omitting the controlled ventilation system (whose heat recovery at best reduces losses) might have been more "economical." However, I do not want to miss the comfort of controlled ventilation and the heat pump. These provide almost effortless operation with consistently good air quality and comfortable temperatures.
On paper, I have KfW-70, because in my view, anything more was not worthwhile. I did not even attempt to reach KfW-55. The building services were already nearly compliant, and the insulation almost met the standard, but the costs for the effort (consultants, etc.) would have consumed the KfW bonus. In actual consumption, there would have been hardly any noticeable difference.
Tichu78 schrieb:
With an average annual performance factor of 2.5, that's 140 kWh electricity consumption per year. At €0.27 / kWh, that results in almost €40 savings per year.
Where is the calculation error?As already mentioned here, you calculated everything correctly. Saving heat through the walls is generally quite difficult because only a small percentage (about 15-20%) of the heat is lost through them. Windows and the roof would be more suitable areas to focus on, although it might not be cost-effective either.
Personally, I am still considering a 42.5 cm (17 inches) wall, mainly because it should offer an advantage as heat protection in summer (keyword: thermal phase shift). Additionally, it provides slightly better sound insulation and deeper window sills (which is not to everyone's taste). Of course, this depends on the additional cost. It is also important to keep in mind that the interior dimensions of the house will be correspondingly smaller or you will need to plan for a slightly larger footprint.
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