Thermal insulation, Energy Saving Ordinance, KFW 70 / 55 / 40 - Your experiences

In our conversation this week, a construction company informed us that with a monolithic construction method, which we personally also intend to pursue, the requirements for KFW55 funding can result in an additional investment of around €20,000. This estimate does not even consider the stone and window side (as there would hardly be any differences here), but solely to achieve the required points regarding heating, etc.

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when I read this from you now, that would probably not be the case. We are not yet that far in the current preliminary planning phase regarding the point allocations for KFW, etc., so I cannot really assess the two statements at this time. Currently, we are wondering whether the KFW interest rate with KFW55, the additional expenses compared to the construction method according to the 2016 Energy Saving Ordinance (old KFW70), and the costs of the energy consultant, etc., really stand in relation.

As mentioned above, a construction company informed us that the additional costs are not in relation to the savings from the better building envelope / heating, etc.

Regards, Andreas

@ I was also talking about "indication," that's simply my personal impression. Besides, there are also plenty of residential buildings constructed in solid brickwork without external insulation. However, these are different developers/investors, and that is also a subjective impression; you can simply tell who builds cheaply and quickly aiming for higher returns and who builds sustainably and with quality. It may be that all this can be disproved if one presents the energy concepts and structural calculations, etc., but if I were looking for a condominium, I would rather move into the brick house. That's just how it is.

@Häuselbau3r One must, of course, consider the overall concept. We had a turnkey KFW70 offered according to the old Energy Saving Ordinance 2014 (building application was still submitted in 2015, so we could have built according to the Energy Saving Ordinance 2014!). Even then, it was clear to me: I wanted a central controlled residential ventilation system with heat recovery (=additional cost approx. 10-12k€), which would not have been necessary for this house. After signing the contract, we went to an independent energy consultation (district office) and had everything checked. They advised us to consider an upgrade to KFW55 because with the heat pump, good windows, and basement insulation, we were already very close, and the loan subsidies would become interesting. Said and done, we had an additional charge calculated, which amounted to about 9,000€ (floor slab insulation, W08 bricks, a few minor things with the plaster etc. because of the brick). Then we had a new energy calculation done and were able to meet the Energy Saving Ordinance 2016 with KFW55. After hours of profitability calculations and playing around with several financing models (financing was not yet finalized), I decided that overall it was more economical to go with KFW55 according to the Energy Saving Ordinance 2016.

Overall, including the controlled residential ventilation, you can assume an additional cost of about 20k€.

Your construction company is a joke... I rather think that there is little experience with other building materials or even worse/bad sources for them and therefore you want to put people off with the price (even understandable, since special building physics requests for larger GÜs certainly initially mean high additional costs, as often the whole concept fails) To clarify: our heating including drilling did not cost 20k€ - it is even suitable for a passive house purely based on the primary energy factor. , I agree with you about the return, just want to say that it is not always everything black and white / good and bad. The brick with a U-value of 0.08 has little to do with a solid piece of eternity - it is just very heavily perforated; still of course a great natural building material in itself

Your construction company is useless... I rather think that there is little experience with other building materials or rather poorer sources for them, and that's why they want to discourage you with the price (even understandable, since special building physics requirements for larger GÜs certainly initially mean high additional costs, as often the whole concept fails) To clarify: our heating including drilling didn't cost 20,000€ - it's even suitable for a passive house purely from the primary energy factor standpoint.

Was that referring to my post, which was meant for Manuel, or ?

The construction company has been building what is requested for over 50 years. Whether it's, as with acquaintances of ours, to KFW 55 or even higher standards, or just according to the 2016 Energy Saving Ordinance standard. So let's leave aside the comment about being useless.

But your example is exactly appropriate... as is Manuel’s example with the controlled residential ventilation. I could certainly imagine building with controlled residential ventilation or it was planned as such until now (also for health reasons in the family regarding allergies like hay fever, grasses, pollen, etc.). But that it would be absolutely necessary for a house built to the 2016 Energy Saving Ordinance standard due to ventilation behavior and airtight envelopes is nonsense (one shouldn’t be out of the house 200 days a year anyway).

Thus, one always compares one thing (the benefits derived from it) with the disadvantage, which will surely primarily be the cost factor. Normally, no one has money left over to say I have this and that, but economically it doesn’t really pay off, right?

why did you decide on controlled residential ventilation, or was it clear to you that it would be installed, if I may ask so casually? Apparently, this was regardless of whether it was built to KFW standard or not.

Regards, Andreas

Was referring to you - Oh I see.. yes sure - if you didn't have a controlled residential ventilation system in the plan, it naturally becomes correspondingly more expensive; but then you have a controlled residential ventilation system, which not only affects heating costs but also represents a major comfort factor - attributing it only to the "heating" is somewhat short-sighted; it would be like equating an Opel Corsa and a 5 Series BMW just because they both get you from A to B.

why did you choose the controlled residential ventilation system, or was it clear to you that it would be installed, if I may ask so bluntly? Apparently, this was independent of whether it was built according to KFW or not.

Regards Andreas

My reasons for a controlled residential ventilation system are:
- Fresh air in the bedrooms without opening the windows at night (I find this a huge comfort advantage! I'm really looking forward to it because I almost always fall backwards out of the room when I get up to use the toilet in the morning and come back to the bedroom - I am hoping for better sleep thanks to the fresh air!)
- No need for daily, multiple ventilation (especially if you are away for a few days, I think it’s important that everything doesn’t just “stagnate” inside)
- No constant window open (“stuffy”), window closed (“I’m cold”) when you have guests
- Energy saving, especially in winter, and at least minimal cooling effect in summer (made possible by a ground heat exchanger – although you shouldn’t expect too much effect)
- No fear of mold, especially in humid rooms

I am simply convinced by the technology and benefits of a controlled residential ventilation system. And only with a central controlled ventilation system. New build and decentralized doesn’t fit for me: too many failure points (fans), many filters (one for each room), and then this hole in every room. The central system will be more expensive, but also less conspicuous and hopefully easier to maintain.

I don’t even want to say that the controlled residential ventilation system would have been necessary for the KFW55 house. As we know, it’s all a mixed calculation of primary energy, energy efficiency, and building material.
Without the controlled residential ventilation system, we would have needed extras in materials again.
Thanks to the controlled residential ventilation system, we reach the minimum requirements relatively easily in my opinion, and that was the reason why we chose KFW55.