Insulation of attic and masonry for bungalow

Hello everyone,

I hope there is someone here who can help me...

We are close to signing the contract for our new construction project. We are building an angled bungalow with 120 sqm on the ground floor. Since a roof pitch of 40° is specified according to the development plan, we have decided to convert a 20 sqm room in the attic. The rest of the attic space will be used as storage. This area will also be insulated.

Now we have since had a consultation with the Bauherren-Schutzbund, who pointed out some things to us. Unfortunately, these again cause considerable additional costs, so I would like to know what you think of them. Are they really necessary or is it also sufficient to build one "level" lower? Specifically, I have the following questions:

1. The base slab and strip foundations are made of reinforced concrete, insulated with extruded polystyrene rigid foam board WLG 035. Now the Bauherren-Schutzbund recommended that the insulation under the slab should be load-bearing, approved perimeter insulation, e.g. CS 5000. Also, lateral perimeter insulation (edge insulation) is important. We are now being offered edge insulation in the slab area (omission of insulation under the slab, but 18 cm floor buildup) and masonry insulation with moisture-resistant PUR rigid foam insulation thickness 14 cm, WLG 024. Additional cost: €4,900

2. The Bauherren-Schutzbund recommends that the surfaces (walls and door) of the upper hallway (separation from the storage area in the attic) be particularly well insulated and that attention be paid to a drop seal on the hallway door to the storage room in order to prevent heat from the ground floor from entering the storage room. We have now been offered to achieve airtightness with a climate membrane sd = 0.2 - 5.0 m, brand Isover Vario KM. Additional cost: €1,100

3. We were told that the front door is still not particularly well insulated nowadays, in contrast to the masonry. In the offer we have a door 2.01 m, costing €3,200. Alternatively, an aluminum front door "Cotherm", thickness 10 cm, has now been offered. Additional cost: €3,000

4. Lastly, a question about the roof truss and the wood used. Our roof truss is offered as standard made of wood grade S10. The Bauherren-Schutzbund has now recommended that we use structural solid wood. Additional cost: €1,620

So, that’s it for now. I would be very grateful if there were a well-founded opinion here on what would be best for us, although I have to say that I am already aware that the above-mentioned design changes represent an improvement over the standard. I just want to know if they are absolutely necessary and sensible. I do not want to save in the wrong place!

A thousand thanks for your help!!
Unfortunately very uninformed Shikara

Hello,

....We have now been to a consultation at the Bauherren-Schutzbund, who pointed out some things to us. Unfortunately, these again cause considerable additional costs, so I would like to know what you think about them. Are they absolutely necessary or is it also sufficient to build one number "less"?

Often many roads lead to Rome ;) What is more valuable must also cost more, otherwise it would be pointless. Generally, with a given budget, it makes more sense to choose a slightly smaller built-up area and use the freed-up funds to realize quality.

.
1. The base slab and strip foundations are made of reinforced concrete, insulation with extruded polystyrene rigid foam board WLG 035. Now the Bauherren-Schutzbund recommended that the insulation under the base should be a load-bearing, approved perimeter insulation, e.g., CS 5000.

This saves x m³ of exterior wall with the same clear room height. However, it must be certainly ensured that water does not negate the insulation effect.

Furthermore, a lateral perimeter insulation (edge insulation) is important. We are now being offered edge insulation in the base slab area (omission of insulation under the base, but 18 cm floor construction) and masonry insulation with moisture-resistant PUR rigid foam insulation d=14 cm, WLG 024. Additional costs: €4,900

Not every insulation sold is necessarily essential. ;) For this, the energy balances would have to be calculated.

....
3. We were told that the front door is still not particularly well insulated these days, in contrast to the masonry. We have a door 2.01 m in the offer, which costs €3,200. Alternatively, an aluminum front door "Cotherm," d=10 cm, was offered to us. Additional costs: €3,000

Costs are often determined by appearance. What is trendy, however, does not have to be energetically better. Here attention must be paid to a low U-value of the entire door.

....4. Lastly, a question about the roof truss and the wood used. Our roof truss is standardly made of wood quality class S10 in the offer. The Bauherren-Schutzbund has now recommended using glued laminated timber (Konstruktionsvollholz). Additional costs: €1,620

The roof truss essentially has a structural function. KVH is not necessarily required for this.
Since this will presumably be built with a general contractor (GU/GÜ), I recommend having the building services planning (heating, hot water generation, ventilation, etc.) carried out by an independent planner. Otherwise, there is a risk of ending up with a somewhat inefficient system. It is not uncommon to find glaring errors already in the energy saving ordinance documentation.
Overall, it is advisable to have the construction accompanied by an external party.

Best regards.

Hello,

...Now we have since had a consultation with the Bauherren-Schutzbund, who pointed out a few things to us. Unfortunately, these again cause considerable additional costs...

...as a supplement to €uro's response – the Bauherren-Schutzbund is certainly a good point of contact to review contractual conditions; briefly the framework conditions.

Regarding the trades of the execution, the statements of the ladies and gentlemen – similar to those of consumer advice – must be evaluated in a differentiated way. They have each undergone training based on the "statements" of so-called experts for federal and state levels and thereby unsettle – I assume unintentionally – most potential builders. However, it is the case that sometimes "less" results in "more," so I would, in your place, consult an independent construction manager (addresses can be found plenty on the internet or through the frequently mentioned places here) or an expert based on the information in your BB. He will be able to answer the statements from the BB with those of the Bauherren-Schutzbund to your satisfaction and take away your feeling of fear (which is completely normal when building for the first time) of making an "irreversible" decision.

Kind regards

@€uro and construction expert
Thank you very much for your answers. I can see, it’s not so easy after all. But I didn’t expect it to be. We have already talked to so many professionals and those who believe they are professionals that my head is starting to spin. Unfortunately, we now have to get moving because we have scheduled the start of construction for 01.04. The building expert from the Bauherren-Schutzbund will also accompany our construction as an external party. Everything else is too uncertain for me, as neither my husband nor I have the time and qualifications to check everything thoroughly. The building expert is also an architect and gives a very competent impression. Let’s hope that we made a good choice with him.
Thank you again for your answers!
It will work out *g*
Best regards
Shikara