ᐅ Is it worth investing in insulation beyond the standard requirements for new construction?
Created on: 8 Jul 2015 19:25
G
Grym
Concepts like these from the prefab house provider Kampa initially sound quite good, and there are many people in forums who believe that nowadays you shouldn’t build a house with a U-value above 0.15.
On the other hand, when you calculate the raw numbers, I struggle to understand how insulation beyond what is necessary can actually be cost-effective.
Let’s take a 140-150 sqm (1500-1600 sq ft) house with 1.5 stories as an example. This would have an exterior wall surface area of about 170 sqm (1830 sq ft) (excluding roof, top floor ceiling, foundation slab, and windows, with a relatively high knee wall as we plan).
The local provider, in a standard case, offers a U-value of 0.21, while Kampa advertises 0.11. According to a U-value calculator, the local provider’s wall consumes 16 kWh/m² per year, and the 0.11 U-value leads to 7 kWh/m² per year. Calculated over the surface area, that’s 2,720 kWh versus 1,190 kWh. With an air-to-water heat pump with an annual performance factor of 4.1 (yes, these are available for about 4,000 EUR – greetings to the purple forum), this equates to 663 kWh_el versus 290 kWh_el. So, you save about 373 kWh just from the exterior wall construction. Variant A: standard solid construction and Variant B: passive house wall. In strict monetary terms, that’s about 93.25 EUR per year or 7.77 EUR monthly installments.
Over 20 years, the difference adds up to 1,865 EUR. In 20 years!!!
Of course, additional savings come from insulating the foundation slab, roof, and better windows in a passive house, but those also require separate higher investments.
On the other hand, a photovoltaic self-consumption system can save a lot, especially during transitional seasons (self-generated electricity costs less than half compared to grid electricity). This is particularly true for an energy-saving standard house, which benefits significantly from PV power during these periods, unlike a KFW40-level house where heating is mostly needed only in the coldest winter months.
The question in the end is: is it even worth it, or is the current energy-saving regulation standard already so strict that the economic feasibility has long been exceeded?
There’s also a bit of a question between timber frame prefab houses versus solid construction. Only with a timber frame prefab house can you achieve a high insulation value for the exterior facade with a reasonably manageable wall thickness (in cm). In my opinion, this is the only advantage of a timber frame prefab house compared to solid construction.
On the other hand, when you calculate the raw numbers, I struggle to understand how insulation beyond what is necessary can actually be cost-effective.
Let’s take a 140-150 sqm (1500-1600 sq ft) house with 1.5 stories as an example. This would have an exterior wall surface area of about 170 sqm (1830 sq ft) (excluding roof, top floor ceiling, foundation slab, and windows, with a relatively high knee wall as we plan).
The local provider, in a standard case, offers a U-value of 0.21, while Kampa advertises 0.11. According to a U-value calculator, the local provider’s wall consumes 16 kWh/m² per year, and the 0.11 U-value leads to 7 kWh/m² per year. Calculated over the surface area, that’s 2,720 kWh versus 1,190 kWh. With an air-to-water heat pump with an annual performance factor of 4.1 (yes, these are available for about 4,000 EUR – greetings to the purple forum), this equates to 663 kWh_el versus 290 kWh_el. So, you save about 373 kWh just from the exterior wall construction. Variant A: standard solid construction and Variant B: passive house wall. In strict monetary terms, that’s about 93.25 EUR per year or 7.77 EUR monthly installments.
Over 20 years, the difference adds up to 1,865 EUR. In 20 years!!!
Of course, additional savings come from insulating the foundation slab, roof, and better windows in a passive house, but those also require separate higher investments.
On the other hand, a photovoltaic self-consumption system can save a lot, especially during transitional seasons (self-generated electricity costs less than half compared to grid electricity). This is particularly true for an energy-saving standard house, which benefits significantly from PV power during these periods, unlike a KFW40-level house where heating is mostly needed only in the coldest winter months.
The question in the end is: is it even worth it, or is the current energy-saving regulation standard already so strict that the economic feasibility has long been exceeded?
There’s also a bit of a question between timber frame prefab houses versus solid construction. Only with a timber frame prefab house can you achieve a high insulation value for the exterior facade with a reasonably manageable wall thickness (in cm). In my opinion, this is the only advantage of a timber frame prefab house compared to solid construction.
It’s not unreasonable – 40 million households in Germany, let’s say half of them have heating systems. Your 20% (over 30% in new buildings) of that equals 4 million heat pumps. Each with a modest 2 kW demand results in a short-term total of 8,000 megawatts or 8 gigawatts of potential decentralized energy consumption... more than ten gas power plants. Control systems can also be quickly developed for older heat pumps. Altogether, this is enough to have a noticeable impact.
Just throwing some numbers into the discussion...
Of course, it’s not a cure-all, but it’s part of the energy puzzle.
Just throwing some numbers into the discussion...
Of course, it’s not a cure-all, but it’s part of the energy puzzle.
Now we are getting closer to the point.
We can now generate several times more wind power, so the wind-to-gas idea is not that far-fetched after all. There are simply many more options to store and use gas than just using heat pumps as buffer storage.
This will certainly change or shift in the future, but heat pumps can only remain a small yet valuable puzzle piece in the long term...
We can now generate several times more wind power, so the wind-to-gas idea is not that far-fetched after all. There are simply many more options to store and use gas than just using heat pumps as buffer storage.
This will certainly change or shift in the future, but heat pumps can only remain a small yet valuable puzzle piece in the long term...
D
DerBjoern12 Aug 2015 07:50@Frank78
The conversion to methane gas using the Power-to-Gas method currently achieves an efficiency of around 70%. It is certainly not a cure-all solution, but it can be one possible component. The heat pump with a battery you mentioned is still far from being a viable solution. Considering the additional costs for heat pumps, you need to have a certain level of consumption for it to pay off. Batteries are only now reaching break-even in terms of cost-effectiveness. There is still a long way to go.
Another issue is that solar power is mainly available in summer, whereas heat pumps typically have their highest energy demand in winter.
As I said, Power-to-Gas can still be one piece of the puzzle.
The conversion to methane gas using the Power-to-Gas method currently achieves an efficiency of around 70%. It is certainly not a cure-all solution, but it can be one possible component. The heat pump with a battery you mentioned is still far from being a viable solution. Considering the additional costs for heat pumps, you need to have a certain level of consumption for it to pay off. Batteries are only now reaching break-even in terms of cost-effectiveness. There is still a long way to go.
Another issue is that solar power is mainly available in summer, whereas heat pumps typically have their highest energy demand in winter.
As I said, Power-to-Gas can still be one piece of the puzzle.
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