ᐅ Is a gas condensing boiler without solar thermal system sufficient for a KfW 70 standard?
Created on: 7 Mar 2013 10:54
J
James
Dear forum community,
I have already posted some information and read a lot about heat pumps and related topics. We are planning to build (with solid construction) and have signed the contract with our developer. The plans are completed, and the application for the KfW loan has been prepared (the loan has already been approved, but I still need to provide the proof).
The architect calculated a yearly primary energy demand of 36.2 kWh/(m²a) (11.5 kBtu/(ft²·yr)).
We want to use a heat pump for heating and hot water (IWS, ground-source heat pump, including controlled ventilation with heat recovery up to 90% (90 percent)).
The windows are double-glazed, and the exterior walls, including the bricks, insulation, and cladding, are about 44 cm (17 inches) thick in total.
The architect included a solar thermal system for hot water preparation in the calculations. However, we do not want this system, and he said: Then KfW 70 will not be achieved! 😕 🙁
He argued that the heat pump consumes electricity, which is negative.
If we were to install a gas condensing boiler (but no solar thermal system), KfW 70 would be reached.
I actually expected that with the heat pump, ventilation, heat recovery, and overall insulation, we would at least meet KfW 70, possibly even KfW 55.
I am quite frustrated about this right now...
🙁
I have already posted some information and read a lot about heat pumps and related topics. We are planning to build (with solid construction) and have signed the contract with our developer. The plans are completed, and the application for the KfW loan has been prepared (the loan has already been approved, but I still need to provide the proof).
The architect calculated a yearly primary energy demand of 36.2 kWh/(m²a) (11.5 kBtu/(ft²·yr)).
We want to use a heat pump for heating and hot water (IWS, ground-source heat pump, including controlled ventilation with heat recovery up to 90% (90 percent)).
The windows are double-glazed, and the exterior walls, including the bricks, insulation, and cladding, are about 44 cm (17 inches) thick in total.
The architect included a solar thermal system for hot water preparation in the calculations. However, we do not want this system, and he said: Then KfW 70 will not be achieved! 😕 🙁
He argued that the heat pump consumes electricity, which is negative.
If we were to install a gas condensing boiler (but no solar thermal system), KfW 70 would be reached.
I actually expected that with the heat pump, ventilation, heat recovery, and overall insulation, we would at least meet KfW 70, possibly even KfW 55.
I am quite frustrated about this right now...
🙁
Hello,
Best regards.
hanpetz schrieb:Hopefully, this is a mild climate location. Pay close attention to precise planning and sizing, especially when selecting manufacturers and equipment!
...So we are currently working on a KfW 70 house. We have no solar panels, no photovoltaics. But an air-to-water heat pump...
hanpetz schrieb:In general, it is beneficial if the U-values of the exterior walls and windows are not too far apart, to avoid large differences in surface temperatures (which can cause a cold draft feeling, especially with very large window areas). On the other hand, windows are usually the “weak point” regarding condensation. This is not necessarily a bad thing! A problematic combination would be poorly or non-insulated exterior walls combined with very well-insulated windows.
...And you have to make sure that the insulation thickness matches the windows, so they don’t sweat.
Best regards.
James, you know that the KfW Bank is now paying closer attention to what qualifies for funding and what doesn’t?
We are currently in discussions with a general contractor.
Originally, we only wanted to build according to the Energy Saving Ordinance requirements, but now we have reached Efficiency 70. Our contractor’s technical advisor says that Efficiency 70 is just a temporary solution.
I had to give him a yellow card for that. :p
According to him, you should either build according to the Energy Saving Ordinance or go straight for Efficiency 55, which is considered the standard. 🙄
You should be aware that any improvement in efficiency standards requires additional investment.
And due to rising construction costs, you should have an expert calculate when which energy-saving measures will pay off for you over the years.
We are currently in discussions with a general contractor.
Originally, we only wanted to build according to the Energy Saving Ordinance requirements, but now we have reached Efficiency 70. Our contractor’s technical advisor says that Efficiency 70 is just a temporary solution.
I had to give him a yellow card for that. :p
According to him, you should either build according to the Energy Saving Ordinance or go straight for Efficiency 55, which is considered the standard. 🙄
You should be aware that any improvement in efficiency standards requires additional investment.
And due to rising construction costs, you should have an expert calculate when which energy-saving measures will pay off for you over the years.
vokono schrieb:
...And due to rising construction costs, you should have a professional calculate when which energy-saving measures will pay off for you over the years. Correct. Unfortunately, most people think they can do it themselves. Just a little browsing on the internet, and the problem is solved. 😕 In reality, this is a very complex topic that even many professionals struggle with. Moreover, the pursuit of supposed "funding incentives" often leads to misguided investments. The latter is even more likely when proper planning and sizing are neglected and instead, flowery sales pitches are trusted.Best regards
Hello.
I’m only now getting the chance to clarify everything.
I had a call with the architect, and it turned out: Even without solar thermal systems and using just a (ground-source) heat pump, meeting KfW 70 standards is not a problem.
The annual primary energy demand would even allow for KfW 55, but the heat transmission loss is too high for that.
We also can’t easily reduce that loss enough to make it work. Insulation under the slab and Y-TONG blocks instead of Poroton are still not sufficient. Therefore, the investment would likely exceed 4,000 euros.
From homeowners who have built with our general contractor so far, as well as from heat pump owners, I’ve only heard positive feedback, so I believe we are on a good track.
I’m only now getting the chance to clarify everything.
I had a call with the architect, and it turned out: Even without solar thermal systems and using just a (ground-source) heat pump, meeting KfW 70 standards is not a problem.
The annual primary energy demand would even allow for KfW 55, but the heat transmission loss is too high for that.
We also can’t easily reduce that loss enough to make it work. Insulation under the slab and Y-TONG blocks instead of Poroton are still not sufficient. Therefore, the investment would likely exceed 4,000 euros.
From homeowners who have built with our general contractor so far, as well as from heat pump owners, I’ve only heard positive feedback, so I believe we are on a good track.
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