ᐅ Solid wood (milled solid timber) or timber frame – concrete offers, tips

Hello,

Happy New Year!
And this is my first post here.
We have been struggling for a while to decide between the two remaining contractors. To make a decision, I would like to gather some opinions.

From the beginning, only timber construction was an option for us, with an emphasis on ecological and healthy building methods. We requested quotes from six companies and have now narrowed it down to two. The offer is for a shell-and-core house: same floor plan, wooden windows, design for controlled mechanical ventilation and underfloor heating. Heating, plumbing, and electrical work are not included here – these will be contracted separately or done by ourselves.

Here is a brief overview of our options:

Offer A – Solid Wood Wall (MHM)
- Exterior walls: 100 mm (4 inches) wood fiber insulation + 205 mm (8 inches) solid wood wall
- Interior walls: 115 or 160 mm (4.5 or 6.3 inches) solid wood wall
- Finished with gypsum board panels
Advantages:
- Ecological, no chemical treatment of the solid wood wall
- Good protection against summer heat
- The company appears somewhat more reliable and professional than Offer B. Offer B would not still be under consideration if we had serious doubts.
Disadvantages:
- Approximately 8–10% more expensive than Offer B
- Not passive house standard (KfW40 equivalent) by default, since the exterior wall has a U-value of 0.22. Exact calculation only after contract award; additional costs might be needed to achieve KfW40 (controlled ventilation and photovoltaics are planned). I am skeptical about the stated U-value after deeper research (“effective U-value,” phase shift, etc.).
- More relevant for us is the subsidy: Our financier cannot confirm yet whether the KfW funding is worthwhile without a detailed calculation.
- Especially for the electrical trade (DIY work): precise upfront planning is necessary. Deviations later on during installation would require more effort inside the walls.

Regarding the massive, vapor-retarder-free, and chemical-free walls (as far as I can judge, leaving aside the wood fiber board on the exterior), this is our favorite. For winter insulation properties, I am still unsure. The simple U-value makes the wall appear rather poor, but various studies conclude that reality is different and actual energy costs are significantly lower than calculated.

Offer B – Timber Frame Construction
- Exterior wall: 60 mm (2.4 inches) wood fiber board, 60/260 mm (2.4/10 inches) KVH studs with cellulose insulation (Isocell), 15 mm (0.6 inches) OSB board, 12.5 mm (0.5 inches) gypsum fiber board
- Interior walls: 12.5 mm (0.5 inches) Fermacell, 120 or 160 mm (4.7 or 6.3 inches) KVH duo studs, 12.5 mm (0.5 inches) Fermacell. Insulated by us with jute.
Advantages:
- Very ecological, no foil/vapor barrier, no polystyrene insulation
- U-value of 0.14. KfW40 equivalent “standard,” with controlled ventilation and photovoltaics plus battery, also KfW40 plus possible
- Continuous cable duct (no separate installation level), so DIY electrical work probably more flexible than with solid wood construction
- About 8–10% cheaper, not counting any potential KfW subsidies
Disadvantages:
- Insulation materials jute and cellulose: Not necessarily as ecological and healthy as often marketed; may contain borates, polyethylene terephthalate, etc.
- Walls are naturally less straightforward for hanging objects compared to solid wood

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We have already discussed this with friends and received very different opinions such as:
1) MHM: Poor U-value, not even passive house standard, and also more expensive? Definitely not!
2) MHM: Only 10% more expensive? That’s definitely worth it to me for this maximally healthy and ecological building method!

My opinion is somewhere in between: With equal pricing, I would choose solid wood wall and accept not meeting KfW40. For our financing, those 10% are significant but somehow manageable.

I now look forward to your assessments and subjective opinions.
Is there anything missing in my information that you would like to know?

Thank you very much!

As long as the solid wood wall is not left exposed or covered with drywall, it is easy to install additional cables and sockets.

Summer thermal insulation that provides better insulation also reduces the amount of heat passing through the wall. However, the effectiveness of the shading has a greater impact on thermal protection.

If you prefer solid wood but find it too expensive, consider using timber stud interior walls instead. Possibly as a DIY project. Having the general contractor install timber studs instead of solid wood would have saved us a bit more than 10,000, plus additional savings from doing some of the work ourselves.

Choose whichever option suits you better and fits your budget. The 100€ difference in heating costs, KfW subsidies, and U-values will not matter much in the long run. With a well-designed heating system and technology, you will save more than with better walls.

Thermal insulation: Properly shaded windows and more mass in the house through solid wood help here. The phase shift is often overestimated. Shade the roof as much as possible with photovoltaic panels.

Thank you for your answers!

I still have a few questions regarding the Energy Saving Ordinance / KfW calculation – I might be overthinking some of these points. Since we plan to carry out some work ourselves and contract individual trades, I’m not entirely sure how the documentation and applications for potential KfW and BAFA subsidies need to be organized in this case. Would we need to handle everything ourselves?

• My understanding of the process: Our general contractor (GC) calculates the primary energy demand based on our plans, including the basement, planned heating system, etc. From this, the energy performance certificate and the KfW standard are determined. At this stage, we can decide whether we want to make further optimizations. Is that correct?
• The basement is planned to be built by us as self-performed work, based on the GC’s design. Since this is self-performance: How is it demonstrated that the building strictly follows the approved plans? Can the GC, who is not physically involved in building the basement, act as the required expert through agreements or site supervision?
• Same principle with the ground-source heat pump: If we install the collectors ourselves and the heating contractor’s responsibility begins at the distribution manifold, will the heating contractor provide the necessary documents for KfW/BAFA subsidies, which I can then submit?
• Are there defined target average U-values for the building envelope that must not be exceeded for the different KfW standards? Or is the U-value initially just one factor within the overall calculation?
• If the basement is not used as living space and therefore is not insulated accordingly (except for the basement ceiling) and is separated from the dwelling by a door: Does this negatively affect the Energy Saving Ordinance calculation? Or is only the basement ceiling considered in the calculation?
• Is a ground-source (water-to-water) heat pump generally more favorable in the Energy Saving Ordinance calculation compared to an air-to-water heat pump? Can this be expressed in approximate figures?

Thank you very much!

flowschi schrieb:

Hello,

happy new year!
And my first post here.
We have been struggling for a while to decide between the two remaining builders. To make a decision, I would like to gather some opinions.

From the start, only timber construction was an option for us, as an ecological and healthy building method is important. We requested quotes from six companies and have now narrowed it down to two. Both offer a shell-and-core house: same floor plan, wooden windows, design including controlled mechanical ventilation and underfloor heating. Heating, plumbing, and electrical work are not considered here—they will be done separately or as self-performed work.

Here is a brief summary of our options:

Offer A – Solid Timber Wall (MHM)
- Exterior walls: 100 mm (4 inches) wood fiber insulation + 205 mm (8 inches) solid timber wall
- Interior walls: 115 or 160 mm (4.5 or 6.3 inches) solid timber wall
- Wall lining with plasterboard

Advantages:
- Ecological, no chemical treatment of MHM
- Good summer heat protection
- The company seems somewhat more reliable and professional than Offer B. Offer B would not be in the running if we had serious doubts.

Disadvantages:
- About 8–10% more expensive than Offer B
- Not standard KfW 40 (energy standard), since the exterior wall has a U-value of 0.22. Exact calculation only after contract award, with additional costs it may be possible to reach KfW 40 (planned controlled ventilation and photovoltaics). I am skeptical about this U-value, having studied “effective U-value” and thermal phase shift more deeply.
- My main concern is the subsidy: Our financer cannot yet say if the KfW funding will be worth it without a concrete calculation.
- Especially for the electrical trade (self-performed): Requires precise planning in advance. Later deviations in routing will mean more effort to install in the walls.

Regarding the solid, foil-free, and chemical-free walls (as far as I can tell, except maybe the wood fiber board outside), this is our favorite. For the insulation performance in winter, I am not quite certain. The simple U-value seems to underestimate the real performance, while various studies conclude that reality is different and actual energy costs are much lower than calculated.

Offer B – Timber Frame Construction
- Exterior wall: 60 mm (2.4 inches) wood fiber board, 60/260 mm (2.4/10 inches) structural timber studs insulated with cellulose, 15 mm (0.6 inches) OSB board, 12.5 mm (0.5 inches) gypsum fiberboard
- Interior walls: 12.5 mm (0.5 inches) fiber gypsum board, 120 mm (4.7 inches) or 160 mm (6.3 inches) structural timber, 12.5 mm (0.5 inches) fiber gypsum board. Insulation with jute by self-performance.

Advantages:
- Very ecological, no foil/vapor barrier, no polystyrene insulation
- U-value 0.14. KfW 40 “standard,” with controlled mechanical ventilation and photovoltaics + battery potentially reaching KfW 40 plus.
- Continuous cable trunking (no separate installation layer), self-performed electrical work likely somewhat more flexible than with solid timber
- About 8–10% cheaper, without factoring in any potential KfW funding

Disadvantages:
- Insulation materials jute and cellulose: not necessarily as ecological and healthy as marketed. May contain additives like boron salts, polyethylene terephthalate...
- Walls are naturally less suitable for hanging items compared to solid timber

---

We have already discussed this with friends and acquaintances and received quite different opinions, such as:
1) MHM: Poor U-value, no KfW 40, and also more expensive? No way!
2) MHM: Only 10% more expensive? That healthy and ecological building method is definitely worth that to me!

My opinion is somewhat in between: with equal prices, I would choose MHM and forego KfW 40. For our financing, these 10% do matter, but it is somehow possible.

I look forward to your assessment and also subjective opinions.
Is there any information missing that you would need?

Thank you!

Hello, what are the prices of your two offers?
Thanks

Heinziii schrieb:

Hello, what price range are you looking at for your two quotes?
Thanks

For the mentioned construction options with about 153/155 sqm (MHM has 305 mm (12 inches) exterior wall, studs 355 mm (14 inches)):

Stud frame: 195k including material delivery / drywall interior finish
MHM: 210k excluding material / drywall interior finish

There are a few minor differences here and there, but overall they are comparable down to the last thousand.