The Okto.green Building System

Built
different.
By design.

Every component in a Nest home is part of an engineered system — not a collection of standard building materials assembled on site. This is what makes the difference between a house and a system.

E −9
Energy positive · always
40
Working days to assemble
±1500
Recycled PET bottles · Nest 1.0
6
vs. standard timber frame
Engineering choices

Six improvements over standard timber frame

Every choice in the Okto.green Building System is a deliberate improvement over the conventional platform timber frame. This is not a standard house with better insulation. It is a different structural logic.

01
Kerto LVL floor structure
Engineered laminated veneer lumber — no knots, no natural defects, uniform strength over the full length. LVL resists warping and shrinking under moisture changes. A Kerto-Ripa floor weighs ±34 kg/m² versus 675 kg/m² for reinforced concrete — 20× lighter, without compromising span or load capacity.
vs. solid timber joists
02
Glulam at every element joint
Glued laminated timber at every joint of the OKTO Green insulation system. Stresses are distributed across laminations, so there are no weak points from knots or grain slope. It stays dimensionally stable under the tight tolerances of prefab assembly, and it is produced from younger, faster-growing timber than large solid beams.
vs. solid sawn timber
03
Insulated wall elements — not stud infill
Load-bearing insulated wall elements replace the repeating timber studs of a standard frame. There is no thermal bridge at every stud. The elements settle ±2 mm per floor versus 15 mm for conventional timber frame, which reduces post-completion cracking, joint movement and callbacks. Each element is both structure and insulation in one.
vs. CLS stud frame with mineral wool
04
Dry construction above foundation
Above the concrete slab, everything is dry construction. No masonry, no plaster, no waiting for materials to dry or cure. Light assembly on site — no tower cranes, no heavy trucks, no large production halls. The full workflow has been engineered for a 3-person team in 40 working days.
vs. block & render or brick & plaster
05
BLUE PIR insulation
The insulation core in every wall panel and roof layer is BLUE PIR — produced from recycled PET bottles in Belgium. Thermal resistance Rd 6.05 m²K/W. U-value 0.17 W/m²K. Fire classification REI 60. The same material forms a continuous thermal envelope from wall base to roof edge — no interface, no gap, no bridge.
vs. mineral wool between studs
06
Custom metal connectors
Purpose-engineered, reinforced steel connectors at the critical junctions of the structure: from the concrete foundation and the thermal break block to the LVL intermediate floor. These are not standard hardware-store brackets. They are repeatable, precision connections developed for this system and checked against the plans of every project.
vs. standard joist hangers
Build-up

Seven elements. No shortcuts.

From roof to foundation, every element of a Nest home has a defined function. The numbers match the drawing.

1
Flat roof
One-piece EPDM membrane on BLUE PIR insulation. The same recycled-PET core as the walls, forming one continuous thermal envelope.
2
Intermediate floor
Kerto LVL beams and I-joists on an LVL ring beam (63 × 300 mm), joined with reinforced steel connectors. Dimensionally stable, knot-free, about 20× lighter than a concrete floor for the same span.
3
Facade
The finish is either thermally modified timber boards (22 mm) or dark ceramic brick slips. It sits on a ventilated cavity with double 44 mm battens, behind which runs a continuous air and water barrier membrane.
4
OKTO Green insulation system
Load-bearing insulated wall elements: 15 mm OSB + 140 mm BLUE PIR + 15 mm OSB. Each element is one piece, up to 5.8 m high across both floors, with glulam at every element joint. Rd 6.05 m²K/W · U 0.17 W/m²K · REI 60. The blue core is recycled PET.
5
Bottom plate
42 × 138 mm timber plate, anchored 33 cm deep into the concrete with M16 anchor bolts.
6
Plinth (optional)
YTONG blocks with an EPDM damp-proof layer, as a thermal break between concrete and timber.
7
Foundation
23 cm concrete slab with frost edge.
Exploded view of a Nest 1.0 home, numbered 1 to 7: flat roof, intermediate floor, facade, OKTO Green insulation system, bottom plate, optional plinth and foundation.
BLUE PIR — Recycled PET insulation

The blue that
counts.

The insulation core in every wall panel and roof layer is BLUE PIR — produced from recycled PET bottles, manufactured in Belgium. The number you see on the right is what sits inside the walls of your home. Verified against supplier specification. No certification claim — just a fact.

Thermal resistance Rd 6.05 m²K/W
U-value 0.17 W/m²K
Fire classification REI 60
Thickness — wall panels 140 mm PIR core
Production Belgium
Calculation basis: 28.5 kg PET per 250 m² at 140 mm · Supplier specification · 500 ml reference bottle (35 g) · Source: supplier mail
Nest 1.0 · 471 m² BLUE PIR total
0
recycled PET bottles in walls & roof
Nest 2.0 · 538 m² BLUE PIR total
0
recycled PET bottles in walls & roof
Measured energy performance

E −9. Every time.

E −9 is not a target — it is the reference value the Okto.green Building System is designed to achieve on every project. Below the E-level norm by more than 100%. The numbers below are from the EPB studies for Watou (Nest 1.0) and Handzame (Nest 2.0).

Nest 1.0 · Watou EPB
E-level — primary energy E −9
Max. allowed E 30 · 130% below norm
S-level — building envelope S 21
Max. S 28 · 25% below norm
Overheating risk 4,580 Kh
Max. 6,500 Kh · 30% below norm
Nest 2.0 · Handzame EPB
E-level — primary energy E −9
Max. allowed E 30 · 130% below norm
S-level — building envelope S 21
Max. S 28 · 25% below norm
Overheating risk 4,580 Kh
Max. 6,500 Kh · 30% below norm

See it
being built.

Four active projects in West Flanders — building permits, subdivisions, first pilot under construction.

View active projects Become a regional partner