New building: Which insulation is appropriate?

Hello,

even though there have already been similar questions here, I will open a new topic.

We are planning a new build and are now in the process of comparing the insulation in the exterior walls, basement, roof, etc.

We want to build solid with a double-shell masonry made of aerated concrete.

The construction companies all insulate the exterior wall with mineral wool in a thickness of 8 to 14 cm, WLG 035.

For the roof insulation, there is always an insulation between the rafters of 20-24 cm WLG 035. And in the attic, the roof is only insulated if a conversion is desired. However, if it is financially feasible for us, we also want to have this insulated.

Now the first question: can you recommend insulation with mineral wool? And if so, which thickness should one choose, and should one demand a WLG 032???
Of course, better insulation is better. But what really makes sense when I compare investment costs to possible heating savings?

Then we also consulted a civil engineer who individually plans and has houses built. He had a crisis when given the information from the housebuilding companies.
He recommends insulation with polyurethane boards of WLS 024 and 20-24 cm thickness.
For the roof, he recommends a complete rafter insulation with the same material.

Then our exterior wall would have, instead of a U-value of perhaps 0.16 - 0.18 with good mineral wool insulation, a U-value of 0.10- 0.12 with polyurethane (according to info brochure).

Of course, that would be better, but according to his calculation, the house would cost us at least €50,000 more and would no longer be financially feasible for us.

We really want to think this through carefully and do everything as properly and sensibly as possible and would be very, very grateful for professional answers!

Maya

Hello Maya,

We really want to think it through carefully and do everything as properly and sensibly as possible and would be very, very grateful for your expert answers!

What is your primary goal when building the house? Why does it have to be a double-shell masonry? Why as much insulation as possible? What is your thought behind everything?

Kind regards

Hello,

it is difficult to say in such general terms how you should insulate your house. The building must be considered as a whole construct. This includes the building technology (insulation of the building envelope) as well as the system technology (heating, ventilation, etc.). Both must be coordinated and fit together in order to be economical.

So be sure to get a planner on board. Preferably an independent one who does not just want to sell something because it is currently trendy.

Then we also consulted a civil engineer who designs and has houses built individually. He had a crisis with the information from the house construction companies.
He recommends insulation with polyurethane panels of WLS 024 and 20-24 cm thickness.

Stick polyurethane panels to the exterior walls and then cover them?

For the roof he recommends complete counter-batten insulation with the same material.

expensive...expensive....expensive....and really doesn’t make sense. I see no advantage of counter-batten insulation

Regards

Hello!

Of course that would be better, but according to his estimate the house would cost us at least €50,000 more and would no longer be affordable for us.

If it is not affordable for you, then it is off the table anyway. A good planner is also characterized by orienting themselves from the outset to the set budget of the builders.

On the topic: €50,000 additional cost ONLY for the insulation - or as the total extra cost for the custom-designed house?

I don’t know how big you want to build, etc... Do you already have a rough idea of what energy demand you want to achieve?

Regards
Peter

Hello,

...Of course, better insulation is better. But what really makes sense when I compare investment costs to possible heating savings?

Long-term savings in heating costs are only sustainable through investments. The extent of effort one should actually undertake can be determined with an economic efficiency calculation. It does not always have to be a certified PH right away. It is certain that the prices of all energy sources will rise significantly in the future. The best energy is always the one that is not needed, i.e., demand reduction!
E.Curb has already described it: building, system technology, climate location, and user behavior form a complex unit and should only be considered meaningfully as a whole.

best regards

Hello

and thank you very much for the first replies.

Then I will respond to them as best as I can:

We are planning a house with about 150 m2 and a basement.
Heating system: gas condensing boiler plus solar for water and heating, water-bearing fireplace, underfloor heating, controlled ventilation system with heat recovery.

The goal of our insulation: to keep energy consumption low, and not to risk mold formation due to thermal bridges, etc. Overall a solid house with a good balance of insulation and heating, etc.

So you find the polyurethane insulation on the roof not very sensible?
But isn’t an over-rafter insulation better than a between-rafter insulation? What are possibly the advantages and disadvantages?

Yes, the polyurethane boards are supposed to go on the exterior wall, where otherwise the mineral wool would go + cladding.

This particular structural engineer also does this type of roof insulation for house modernizations. Is it possibly more sensible there or not? (Acquaintances want to possibly modernize with him).

The €50,000 are already considered total costs, whereby the house won’t really look different or better than through a developer and will also be smaller.
There, we made the same specifications for technology and equipment.

A brick-clad pointed dormer, which we like (I know, energetically not sensible, but one still wants to like it, right?), he priced at at least €9,000...

I look forward to your comments...