New building: Which insulation is appropriate?

He recommends insulation with polyurethane panels of WLS 024 and 20-24 cm thickness

Is it supposed to be a passive house?
Also, I would be interested to know how the cavity distance of 20 cm is supposed to be bridged. There are approvals for cavity anchors > 150mm, but that also has to be paid for. Everything has to be in proportion and for a solid house that is somewhat exaggerated.

Yes, the polyurethane panels are apparently supposed to go on the exterior wall, where otherwise the mineral wool would go + facing.

You can use PUR as core insulation, but I'm not exactly a fan of it. Keyword costs and building physics. PUR is somehow not open to diffusion enough for me.

So you find the polyurethane insulation on the roof not very sensible? But isn't an insulation above the rafters better than insulation between the rafters? What are possible advantages and disadvantages?

... and again the costs. For a renovation that might still make sense in few cases, emphasis on few, but in new construction? I can avoid the thermal bridge at the rafters differently.

Best regards

Hello E.Curb,

Should it be a passive house?

No, actually a KfW 70 house, since we want a gas heating system, but with a SENSIBLE, possibly better insulation - without overdoing it.

I would also be interested to know how the cavity distance of 20cm should be bridged. There are approvals for cavity wall ties > 150mm, but that also has to be paid for. Everything has to be in proportion, and for a solid house that is a bit over the top.

-- I don't know that either now. He just presented his ideas to us and was very "shocked" by the two-shell masonry construction of the local developers, along the lines of...: I was insulating like that 10 years ago.

What is to be made of that? Which insulation: thickness and thermal conductivity value (WLG) is good and sensible for a 150 m2 single-family house? How thick should the perimeter insulation around the basement be?

...and again the costs. For a renovation, that may still be sensible in a few cases, emphasis on few, but for new construction? I can avoid the thermal bridge caused by rafters in other ways.

How can thermal bridges be avoided in between-rafter insulation, or what should we pay attention to when dealing with providers?

My parents want to have a house from the 1970s modernized, about 110 m2. The roof needs to be redone (tiles), and it should be insulated at the same time, which has not been the case so far. Also wall insulation with foam, new windows and front door, new heating system (from oil to gas plus solar). However, this is supposed to cost around €100,000 for the small house, and the two of them are almost losing interest already.

...

Hi,

No, actually a KfW 70 house, since we want a gas heating system, but with a SENSIBLE, possibly better insulation - without overdoing it.

For a KFW 70 house, an insulation thickness of 200mm with WLG 024 is excessive. I estimate you will achieve a U-value around 0.1 W/m²K. That is passive house level!

What do you think about that? Which insulation: thickness and WLG is good and reasonable for a 150 m2 single-family house? How thick should the perimeter insulation around the basement be?

If you have a certain budget and the requirement for a KFW 70 house, then your planner can best answer this question for you.

How can thermal bridges be avoided in the insulation between rafters?

Insulation under the rafters or an underlay board (e.g. Gutex).

Regards

Hello,

For a KFW 70 house, an insulation thickness of 200mm with WLG 024 is exaggerated. I estimate you will achieve a U-value of around 0.1 W/m²K. That is a Passive House!

Yes, that is clear to me now as well. But would that really be so bad? It would certainly be quite a bit more expensive.

If you have a certain budget and the requirement of a KFW 70 house, your planner can best answer this question for you

We actually wanted to work with a developer. However, they first specify their standard insulation and don't really tell you how much more also makes sense, or I just don't necessarily trust their statements.
That's why it would be nice to know how much wall, basement, and roof insulation is really sensible and also stands in a realistic ratio between investment costs and energy savings.


Best regards Maya

Hello,

But would that be so bad? It would certainly be a lot more expensive.

No, of course that wouldn’t be bad. But you yourself said that you don’t want to exaggerate.
Why don’t you build a passive house? (the question is really meant seriously)

We actually wanted to work with a developer. But they first specify their standard insulation and don’t really say how much more would make sense, or I don’t necessarily trust their statements.

If you don’t trust them, why don’t you build with an architect?

That’s why it would be nice to know how much wall, basement, and roof insulation really makes sense and is also in a real ratio to the energy savings in terms of investment costs.

see above

Regards

Hello Maya,

no offense – but at times your statements read like the “who is who” of internet knowledge. Invest some time and maybe also money and find a seller or an architect who knows what they are talking about. The advantage is that internet statements will no longer scare you because you learn to distinguish truth from lies.

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

It is true that for KfW 70 – if you want to work with a gas condensing boiler – you need a controlled supply/exhaust air system with heat recovery. I would skip the hydronic fireplace because, firstly, it is quite expensive, secondly, an additional water circuit passes through your new walls, and thirdly, the efficiency is based more on belief than on knowledge. Besides, it is not so easy to reconcile controlled supply/exhaust air ventilation with this system.

Regarding controlled supply/exhaust air ventilation – as far as I know, you cannot banish this system to the basement, where most builders would like it to be, because it requires a lot of space. Opposite outlets – for supply and exhaust air – must also be created, which is not feasible in a basement. Therefore, enough space must be planned on the ground floor. Why don’t you include an air-to-water heat pump in your considerations? It is also unproblematic in the north.

Our insulation goal: to keep energy consumption low, to avoid mold growth due to thermal bridges, etc. Overall a solid house with a good mix of insulation and heating, etc. chosen.

Mold does not arise from thermal bridges but where houses are built so tightly – the current and upcoming Energy Saving Ordinance unfortunately does not make this any easier – that, for example, regular ventilation is insufficient.

E.Curb has already given you the right answers regarding the roof/insulation; the same applies to €uro concerning his area of expertise.

The construction engineer you described also seems to want to extend his field of activity to new buildings; according to the motto “nothing is too difficult for the engineer.” You write “Overall a solid house with a good mix of insulation and heating, etc. chosen.” To make things a bit more transparent: how much money do you intend to spend on the house? It is probably in the range of TEUR 230 and up _without_ any frills as the engineer envisages.

Kind regards