Oh, thanks for the answers
: we also had a thicker monolithic stone at the beginning during the consultation. The energy saving ordinance would still be possible with 36.5 aerated concrete. Not with Poroton anymore, so definitely take it thicker. A narrow wall with ETICS has the advantage that you lose little interior space because the external insulation is applied on the outside. (10x10m foundation slab gives 91.7m² living space with a 42.5cm stone, 96.5m² with a 17.5cm stone - so almost 10m² over two floors).
: He suggests that to still meet the 2016 energy saving ordinance with a gas condensing boiler + 10m² solar thermal. Alternatively, 6cm XPS under the foundation slab. Gas boiler including solar would cost about the same as the Rotex HpSu air-water heat pump. But the additional insulation costs are quite hefty in terms of amortizing the extra expenses with gas, since that would be in addition to the gas heating. XPS would "only" cost 1800, but I don’t know if I want to take that risk.
: No idea, collar beam roof, 24cm mineral wool, why would he give a worse value than actually exists?
: Your hint ultimately leads further (if the figures are roughly correct). With an air-water heat pump, I would come to about 3000 kWh p/a according to my rough calculations (seasonal performance factor 2.1 is realistic with panel radiators supply temperature 45° - please no discussion, I want it that way! - and extremely drafty high altitude location on the Swabian Alb at about 600m above sea level - it won’t be more than that), so electricity for about 750 euros. With the gas system I would probably come to 6000 kWh minus solar thermal 1500 kWh = 4500 kWh, so about 260 euros.
Savings roughly 500 p/a with additional costs of 9,000 (gas tank, connection, chimney sweep etc.).
Add another 100 savings through insulation, so 600 p/a. Probably still not a good idea.
Looking forward to opinions on this
michael
Phew, the statement about aerated concrete and Poroton really hurts me. Such a general statement misses the point completely.
You have to achieve a certain "energy efficiency" with your entire house. That has nothing to do with the exterior wall or insulation individually. What matters is the bottom line. I bet that a Poroton T9 is usable and a Poroton T7 even more so.
Then you just have to invest more in controlled ventilation or renewable heating technology.
Are you aware of how many extra costs you have to meet the energy saving ordinance with a gas condensing boiler? As far as I know, a renewable share with solar on the roof is necessary just for the gas condensing boiler. You can meet the energy saving ordinance much easier with a heat pump and much less insulation madness, which costs you a lot of money.
Could it be that your "consultant" is interested in selling you something? I would be very skeptical! I am missing the arguments and the comparison with other alternatives including pros and cons.
Choosing gas could be just as right or wrong as a heat pump or even pellets, etc. Since no one knows how prices will develop in the future.
My arguments for an air-water heat pump:
Investment costs within range (gas presumably cheaper)
Electricity as a source, which can be generated from all resources. Even from the photovoltaics on my roof with a home battery.
Underfloor heating with low supply temperature ~30-35°
Savings on chimney -> more living space
Low maintenance
Positive in the energy saving ordinance calculation -> lower costs to meet the energy saving ordinance
Think about which arguments are understandable TO YOU and educate yourself.
We have Poroton T9, 10cm XPS floor insulation, 22cm insulation between rafters, and standard windows ~Uw=0.8. That is enough to comply with the 2014 energy saving ordinance for now. How it would be with the 2016 energy saving ordinance ... no idea. Many think we are building an old house ... which is also true, since this standard was already built 10-15 years ago. But it is affordable and still nice.
I have tried to calculate and find people to calculate for me. The costs exceed any benefit. So it is not economical. Trust your common sense and listen to various opinions. Everyone is right and wrong. Filter out what seems reasonable to you and decide. You have to pay and live in the house.
The worst thing for me about the whole matter is the fear of making a wrong decision. Admitting not having listened to Fritz or Peter, who said build KFW 55 or 40 ... buy controlled ventilation, otherwise you will get mold, etc. You surely know the arguments.
It is easy for outsiders to say "Buy the best stone, the best insulation, the best technology, the best of the best, etc..." They don’t have to pay for it.
Oh yes ... listen to your gut feeling, which has helped us very well so far with general contractor/architect, financial advisor, structural engineer, surveyor, soil expert, shell builder, and earthworks!
