ᐅ Poroton 36.5 or 42.5 with perlite or mineral wool insulation

Hello everyone,
we are uncertain whether to go with a monolithic KfW40 or just KfW55 standard.
That means choosing between the Poroton T7 36.5cm (14.4 inches) or the 42.5cm (16.7 inches) insulated brick.

We are also undecided between using perlite or mineral wool insulation. I hope to get some input based on experience. The building contractor is not giving clear advice, with different opinions on which is better or worse.
Since we are building two residential units, we will receive double KfW subsidies, so the repayment grant is a strong argument in favor of KfW40 and the 42.5cm (16.7 inches) brick.

On the other hand, there is the actual loss of space with the 42.5cm (16.7 inches) brick compared to the 36.5cm (14.4 inches) one, and the fear that heating costs with the 36.5cm (14.4 inches) brick might become overwhelming after a few years.

We definitely want a solar system, which again supports going for the KfW40+ standard and the 42.5cm (16.7 inches) brick.

We look forward to your opinions.

Both options are good and work well. KfW40 is more expensive but receives better subsidies. Whether it is worth it (also considering the space consumed by thicker walls) is something only you can decide.

Freiburger2020 schrieb:

and the fear that heating costs with the 36.5cm (14.4 inches) block will overwhelm us after a few years.

LOL. Depending on ventilation and heating habits, one family can have significantly higher heating costs in KfW40 than another family in KfW55. That’s why the KfW classification is completely unsuitable for this.

Freiburger2020 schrieb:

We wanted a solar system anyway, which again would argue for KfW40+ subsidies and the 42.5cm (16.7 inches) block

Then just do that if your budget allows.

Hello,
would the Poroton T7 36.5 also be available in a filled version? The unfilled ones are so delicate that I would be very concerned about sound insulation.

I also spent a long time thinking about this back then. From today’s perspective, I consider this issue to be greatly overrated. Nowadays, I would simply build with 17 or 24 cm (7 or 9.5 inches) sand-lime brick and add external thermal insulation (ETICS) on the outside. Soundproofing and summer heat protection are much more important than saving a few percent on heating costs.

Best regards,

Andreas

Regarding heating costs ........ we chose a 36.5cm (14.4 inches) wall thickness, and with plaster, the total masonry thickness comes to about 40cm (15.7 inches). The house is a bungalow measuring 9 x 13 meters (29.5 x 42.7 feet) with a flat roof and a concrete ceiling, not a wooden roof structure, and 24cm (9.4 inches) of EPS insulation on top. We have a Bosch Junkers heat pump system, Package Compress 7000i AW CS 775, CS7000iAW IRM, 6kW, 120 liters (32 gallons). Heating costs for electricity are approximately 750.00 euros per year.

https://www.hausbau-forum.de/threads/energieeinsparung-durch-bessere-steine.33668/

andimann schrieb:

Hello,
is the Poroton T7 36.5 also available as a filled version? The unfilled ones are so delicate that I would be very concerned about sound insulation.

I also spent a long time thinking about this back then. In hindsight, I consider this issue greatly overrated. Today, I would just build with 17 or 24 cm (7 or 9.5 inches) sand-lime bricks and an external thermal insulation composite system (ETICS) on the outside. Sound insulation and protection against heat in summer are much more important than saving those last few percent on heating costs.

Best regards,

Andreas

Yes, the block is always filled, whether 36.5 or 42.5 cm (14.5 or 16.75 inches). Otherwise, it would not be possible to meet the KfW 40 standard monolithically. Besides, this is an attached house where sound insulation is particularly important. The neighbor’s house is only 6 meters (20 feet) away.