Flat Pack Technology Technical Manifesto
The design of buildings with extreme temperature and humidity conditions (Finnish saunas, steam rooms, commercial spas) is governed by the laws of thermodynamics and building climatology. The traditional approach—delivering prefabricated modular structures assembled in a workshop—has two critical vulnerabilities: the high cost of transporting "air" (the interior volume of the module) and the risk of damage to the geometric parameters of the frame due to dynamic and vibration loads during crane handling and lifting.
The Flat Pack engineering solution (pressed prefabricated kit) transforms production from volume logistics to mass logistics. It is a precision-cut and labeled set of components, manufactured on CNC equipment with precise dimensional tolerances.
This approach allows us to completely eliminate the limitations of hard-to-reach locations, optimize export logistics by 4-5 times, and ensure step-by-step instrumental quality control of each hidden component directly at the construction site.
The Anatomy of a Hidden Marriage: What's Buried in Prefabricated Modules (A Pig in a Poke)
When purchasing a prefabricated sauna from a third-party manufacturer, the customer sees only two layers: the exterior decorative finish (façade) and the interior lining of the steam room. The space inside the wall structure remains inaccessible for inspection. Based on our eight years of experience auditing third-party structures, in 82% of cases, hidden defects in the prefabricated walls lead to structural failure within just two to three years of use.
What's hidden in a closed wall pie (Defect Analysis):
|
Name of the unit/material |
Technological defect in finished modules |
Consequences for the design |
|
Hydro- and vapor insulation |
Use of thin construction films or foil-coated polyethylene foam instead of kraft-based aluminum foil. |
At high temperatures, polyethylene decomposes, releases toxic phenolic compounds, loses its tightness and allows steam to pass into the insulation. |
|
Thermal insulation layer |
Installation of rolled glass wool or low-density slag with a high content of phenol-formaldehyde resins. |
Under the influence of vibrations during transportation, the cotton wool sags downwards, forming continuous cold bridges in the upper part of the wall. |
|
Internal power frame |
The use of raw pine of natural moisture content, sewn on both sides with films without a ventilation gap. |
The trapped moisture, when exposed to heat, turns the frame into an incubator for Coniophora puteana fungi . After 1.5–2 years, the holding capacity decreases. |
The physics of pie destruction when the seal is broken:
If the vapor barrier is damaged or installed without sealing the seams with heat-resistant aluminum tape, moisture diffuses into the mineral wool due to the pressure difference. As the temperature inside the wall drops, the dew point is reached , and the vapor condenses, turning into water.
Increasing the moisture content of mineral wool reduces its thermal insulation properties (thermal conductivity) . Water becomes a heat conductor, the sauna's heat loss increases exponentially, and the frame begins to rot.
The Flat Pack format completely eliminates these risks . The client or installation supervisor accepts the elements layer by layer. Every frame post, every roll of foil, every basalt wool slab, and every interior paneling lamella is installed openly. The possibility of concealing a defect or using substandard material is zero.
The Real Limitations of Flat Pack Technology (Honest Technical Analysis)
Flat Pack technology isn't a one-size-fits-all solution for all construction conditions. For clarity, we highlight three key limitations that engineers must consider before ordering a kit.
1. High requirements for the qualifications of performers (for independent collection)
Even though all parts are marked and the joints are pre-cut at the factory, assembling Flat Packs requires basic knowledge of timber construction and strict adherence to process charts. An error in self-adhesive application of the vapor barrier or improper installation of sealing tapes in the corner joints of the frame can negate the advantages of factory-cut parts. If the customer lacks experience with measuring instruments (laser levels, angle gauges) and hand tools, self-assembly of large structures is not recommended without the assistance of a factory installation supervisor.
2. Depending on the weather conditions at the site
Unlike modular assembly in a workshop, where a constant microclimate is maintained, Flat Pack installation takes place outdoors or under temporary awnings. Although thermally modified wood has extremely low hygroscopicity (deep thermal modification reduces water absorption by 3-5 times), prolonged direct exposure of exposed mineral wool insulation to intense precipitation during installation is unacceptable. Assembly of the load-bearing frame and roofing must be performed on dry days, or protective awnings should be provided over the construction site.
3. Time costs for locations
A prefabricated modular unit is mounted on the foundation in 2-4 hours using a crane, after which it is ready for use. Assembly of a Flat Pack kit of a similar size takes 3 to 7 working days, depending on the size of the team (2-3 people are optimal) and the complexity of the architecture. If commissioning "today" is critical, a Flat Pack kit is inferior to a prefabricated module in terms of final assembly speed.
4. Flat Pack production process at the plant
The production of a durable thermosauna begins not with a machine, but with the physical and chemical transformation of the wood structure itself. Below is a step-by-step process flow chart of the process that each chip of the future Flat Pack construction kit undergoes in our workshops.
Scheme of the industrial cycle of production of the kit:
|
Production stage |
Technological process and conditions |
Physical and technical result of the element |
|
Step 1: Convection Drying |
Heating of lumber (pine, ash, linden) in a chamber. |
Reduction of free and bound moisture in the wood structure to the indicator. |
|
Step 2: Thermal modification |
Heating in a water vapor environment without access to oxygen. |
Destruction of hemicellulose (sugars). Humidity levels stabilize. The wood does not rot, shrink, or release resin. |
|
Step 3: Four-sided profiling |
Processing of workpieces on a Weinig milling line (Germany) . |
Formation of precision tongue and groove locks with class tolerances and surface roughness. |
|
Step 4: Trimming and laser marking |
Cutting of frame and sheathing elements on the optimization line using CNC drawings. |
Each part receives a stable code (eg K1-S3-L12 ), which clearly corresponds to the assembly diagram. |
|
Step 5: Vacuum preservation |
Sorting, stacking on pallets with polystyrene foam, binding with PP tapes. |
Sealed packaging of the pack in heat-shrinkable PVC film to protect against moisture during logistics. |
Comparative engineering and economic analysis of alternatives
To objectively assess the effectiveness of the Flat Pack format, we will compare it using key parameters with two common technologies on the market: traditional on-site construction from raw boards (hand-made) and delivery of a prefabricated, prefabricated module.
Comparative table of characteristics of construction technologies:
|
Comparison parameter |
Classic on-site construction (Green board) |
Ready-made volumetric module (factory assembly) |
Flat Pack Technology (Thermowood, CNC) |
|
Geometric stability of the frame |
Low. Shrinkage, cracks, door/window distortions. |
High, but there is a risk of deformation of the geometry during crane lifting. |
Absolutely. Shrinkage. Geometry is stable for decades. |
|
Thermal conductivity coefficient of the wall ( |
High due to high wood moisture content). |
Average. |
Minimal , due to the porous structure of thermally modified wood. |
|
Quality control of hidden works |
Depends on the honesty of the team on site (human factor). |
It is impossible without destroying the finished product’s cladding. |
100% visual control of each layer by the customer during installation. |
|
Logistics costs (per 1000 km) |
High (you need to transport timber, insulation, films, and fasteners from different bases separately). |
Maximum (payment for oversized lowboy and truck crane). |
Minimal. The kit takes up 4-5 times less space. Standard truck/container. |
|
Risk of biological damage (mold) |
High. Requires regular chemical treatment with antiseptics. |
Average. It depends on the quality of the ventilation gap. |
Zero. Thermowood is devoid of polysaccharides and does not support fungal growth. |
)
Real Case: Exporting Flat Packs to a Dealer in Stuttgart, Germany
Object: Commercial spa-sauna with panoramic glazing and a built-in IBAAT dousing system.
Client: Official dealer in Germany, specializing in the development of wellness areas in hotel complexes.
Calculation of logistics and economic effect:
During the transportation of the object in the form of a ready-made volumetric module, two critical engineering and logistical problems arose:
- The height of the module, including the lowboy platform, exceeded the permitted European clearance for standard tunnels and bridges. A special route and police escort were required, increasing the cost of delivery along the standard Zhytomyr-Stuttgart route.
Logistics scheme for cargo optimization:
|
Transportation parameters |
Option "Ready-made volumetric module" |
Factory Flat Pack Option |
|
Type of transport used |
Specialized low-deck oversized lowboy. |
Standard tarpaulin truck (loaded with Euro pallets) |
|
Cargo volume / Number of pieces |
1 module (behind a closed air circuit) |
5 Euro pallets in tight stacking |
|
Method of unloading at the location |
Heavy truck crane |
Conventional forklift + manual loading of elements through the slot |
The cargo was cleared through customs at the Zhitomir plant and received a EUR.1 certificate , which exempted the German dealer from paying import duties.
Pure cost-effectiveness: Using Flat Pack technology at this facility saved the client only on delivery and installation costs, completely eliminating the architectural risks of damage to the hotel's facades and landscaping.
Technical FAQ (Questions from Engineers and Dealers)
1. What type of tool is required to assemble the Flat Pack kit on site?
For professional installation, the minimum set includes: a laser level (360 degrees), a cordless screwdriver with a torque of at least (2 units), a miter saw with a clean cut for wood, a construction stapler, a pneumatic gun for finishing studs (recommended for capsules), a Torx bit and heat-resistant sealant.
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