Spruce Windows - λ 0.11 W/m·K, Highest Efficiency

Spruce Wooden windows – Thermal Conductivity 0.11 W/m·K

Spruce (Picea abies) is one of our primary stock species, with the best thermal coefficient in our range at λ 0.11 W/m·K. It is the reference species for nZEB and PHPP calculations, supporting low frame U-values. In Romanian joinery the popular term “fir windows” almost always refers to spruce; if you were searching for fir, you have come to the right page.

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Density 405 kg/m³

Lightweight

λ 0.11 W/m·K

Best thermal performance

Janka 1,680 N

Moderate hardness

The Thermal Reference – Light, Stable, and Efficient

Spruce delivers the lowest thermal conductivity available in our range, which makes it one of the reference species for nZEB and PHPP calculations. At 405 kg/m³ it is also the lightest, reducing stress on the hinges and making large sashes easier to operate. Multi-layer lamination and a correct industrial finish give this softwood a reliable service life that depends on finishing and maintenance.

Technical Data – Spruce

Property

Value

Density

405 kg/m³

Janka Hardness

1,680 N

Bending Strength

63 MPa

Modulus of Elasticity

9.7 GPa

Compressive Strength

35.5 MPa

Radial Shrinkage

3.9 %

Tangential Shrinkage

8.2 %

Volumetric Shrinkage

12.9 %

Thermal Conductivity (λ)

0.11 W/m·K

Natural Durability Class

4 (poor – 5‑10 years untreated)

What these figures mean for joinery: at 405 kg/m³, a spruce sash is the lightest in our range, reducing hinge stress. λ 0.11 W/m·K delivers the lowest frame U-value. Radial shrinkage of 3.9% ensures good dimensional stability, and multi-layer lamination removes the natural tendency to warp. Janka 1 680 N is low but irrelevant for window profiles; for thresholds, oak is the correct choice.

Performance in Windows

Spruce is the thermal benchmark of our entire range – light, precise, and very well suited to nZEB requirements.

1

Thermal

λ 0.11 W/m·K – the best in our range. A spruce frame can contribute to a low frame Uf; exact compliance with nZEB and PHPP requirements is verified for the complete window configuration. Full thermal data is supplied on request.

2

Processing

Spruce machines efficiently on our CNC lines. Its uniform fibre, low hardness, and Class I wood quality keep production fast and precise – the reason it ties with Nordic pine for the shortest lead time in our range.

3

Finish

Spruce takes RAL/NCS opaque paints and translucent stains equally well. Its natural off‑white colour is neutral, giving uniform coverage without extra primer. Under a clear stain the grain is subtle – elegant but not dramatic.

Long‑term Performance

With a factory finish, spruce’s low natural durability is fully compensated – the key is disciplined maintenance.

Natural Durability

Class 4 – untreated spruce degrades within 5‑10 years. A 3‑4 layer Remmers factory finish completely transforms this, sealing the fibre against water and UV for decades.

Dimensional Stability

Radial shrinkage is only 3.9%, and the characteristic spiral grain distributes stresses evenly. Multi‑layer lamination significantly reduces the risk of warping or twisting and improves dimensional stability.

Maintenance

A cleaning and re‑coating every 7‑10 years is all that is needed. With this simple routine, a spruce window can serve structurally for decades.

Only Class I joinery‑grade spruce is used – free of large knots and resin pockets. The wood is not construction‑grade, ensuring a clean finish and predictable long‑term behaviour.

Advantages of Spruce

Advantages

  • λ 0.11 W/m·K – the best thermal coefficient in the range, contributing to a low frame Uf
  • Lightweight sash (405 kg/m³) – less stress on hinges, easier operation
  • Permanent stock – shortest lead time (6‑12 weeks), identical to Nordic pine
  • Excellent CNC processability – high precision, fast production
  • FSC available on request; neutral base for any RAL/NCS opaque or stain finish

Disadvantages

  • Natural Durability Class 4 – finish is mandatory, no exceptions
  • Janka 1 680 N – marks on impact; not suitable for high‑traffic thresholds
  • Subtle grain under stains – lacks the visual impact of oak or meranti
  • Distinctive odour during processing – disappears after finishing
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Comparison with Other Essences

Where spruce stands among our core softwood and hardwood options.

Spruce vs Nordic Pine

Both are in permanent stock at the same cost. Spruce wins thermally (λ 0.11 vs 0.13); Nordic pine has better moisture resistance and a more noticeable grain. For an opaque RAL finish the choice is purely technical: spruce for the lowest Uf, pine if moisture resistance matters.

Spruce vs Meranti

Spruce wins on λ (0.11 vs 0.13) and cost. Meranti has a more stable radial shrinkage and a tropical appearance under stains. For an opaque nZEB window, spruce is the logical choice; meranti is selected when a warm translucent finish is required.

Spruce vs Oak

Spruce has a huge thermal advantage (λ 0.11 vs 0.18). Oak wins on hardness, durability, and grain character. For high‑traffic doors or visible‑grain projects, oak is the choice; for standard nZEB windows, spruce is the cost‑effective thermal benchmark.

Appearance and Colour

Off‑white with a subtle yellow or light reddish‑brown tint. The characteristic spiral grain is visible during processing but disappears under the finished surface. Narrow annual rings give a uniform appearance free of large knots. Under opaque RAL paint the coverage is perfect; under translucent stains the tone is light and elegant – honest wood, not a spectacle.

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Availability & SM WOOD Execution

Key Details

  • Permanent stock – available on all series: IV68, IV78, IV92, D68, D78, D92, wood‑aluminium, internal doors, shutters.
  • Shortest lead time: IV78 6‑10 weeks; other series 8‑12 weeks. Urgent orders can be discussed.
  • FSC available on request – lead time discussed at quoting.
  • Cost comparable to Nordic pine – the most budget‑friendly species in our range.
Contact us for Spruce availability
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Price depends on the series, dimensions, and finish – request a free quotation. For B2B projects, we supply complete PHPP data (Uf, Uw, Ug, g‑value, psi‑spacer) on request.

When Spruce is the Right Choice – and When It Isn’t

Spruce is the right choice when:

  • The project has nZEB or PHPP requirements and the lowest λ in the range is preferred – λ 0.11 W/m·K is the best in our range.
  • Budget and lead time are priorities – spruce is in permanent stock and costs the same as Nordic pine.
  • The finish is an opaque RAL colour – spruce gives the same visual result as any other species.
  • FSC certification is a contractual requirement – spruce can be supplied FSC on request.

Spruce is NOT the right choice when:

  • The design calls for a dramatic wood grain under a translucent stain – oak or meranti are far more expressive.
  • High‑traffic sills or thresholds are required – Janka 1 680 N will mark; oak is the correct choice.
  • The client wants a visually premium species – spruce is technically excellent but not a visual showpiece.

Frequently Asked Questions

Not technically, but in practice almost always yes. Fir (Abies alba) and spruce (Picea abies) are different species. In Romanian joinery, the popular term “fir windows” (ferestre din brad) almost always means spruce. We produce spruce – if you were looking for laminated fir windows, this is the right product.

Thermal conductivity depends on density – denser wood conducts more heat. Spruce (405 kg/m³, λ 0.11 W/m·K) is less than half as conductive as oak (675 kg/m³, λ 0.18 W/m·K). For the same 78 mm profile, a spruce frame loses significantly less heat than an oak frame.

Uw 0.81 W/m²K for the standard size of 1230×1480 mm with triple glazing Ug 0.6 W/m²K. For small windows (615×740 mm), Uw rises to 0.96 W/m²K. Complete PHPP data – Uf, Ug, g‑value, psi‑spacer, dB – are available on request.

Yes. 2,000+ RAL and NCS colours are available, including dual interior/exterior painting. The opaque finish completely covers the grain – spruce, pine, or meranti underneath makes no difference visually.

Simple solid spruce warps with humidity changes – it twists, jams, or leaves gaps. Laminating in 3 or more layers with perpendicular grains eliminates this structural problem. We do not manufacture windows from simple solid wood.

On request. Standard spruce stock is not FSC. FSC orders are discussed during quoting – the timeline is slightly longer than current stock.

With 3‑4 layers of Remmers applied in the factory and a maintenance check every 7‑10 years, the structure stays serviceable for decades. Without maintenance, degradation becomes visible much sooner on exposed areas.

Contact and Quote

SC SM WOOD PRODCOM SRL – manufacturer of laminated wooden windows and doors, including Spruce joinery from permanent stock.
Floresti, Ferma 9, Hala 8A, 407280, Cluj

  • www.smwoodprodcom.ro
  • Spruce windows and doors – in permanent stock, 6‑12 week delivery
  • Laminated wood IV78/IV92 series – complementary profiles
  • FSC certified wood available on request
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