Does engineered wood still count as carbon-negative if it’s landfilled after demolition?

No. The stored biogenic carbon is gradually released as methane and CO₂ in a landfill. Design for reuse, recycling, or clean combustion is essential to keep the negative balance credible.

Which PCR should I use for a new composite siding that blends wood and mineral fillers?

Start with EN 15804-aligned Construction Products PCR (version 1.3 or newer). A good LCA partner will also check which PCR your direct competitors followed so your numbers remain comparable.

Can I reuse a fiber cement EPD from our Asian plant for North American bids?

Probably not. EPDs are location-specific because energy grids and transport routes drive results. You’ll need a separate declaration or a multi-plant EPD that includes U.S. data.

How long does producing a siding EPD typically take?

With streamlined data collection and an experienced verifier you can publish in six to eight months; traditional timelines often exceed a year.

Does LP SmartSide’s carbon-negative claim hold up under EN 15804 +A2 rules?

Yes. The EPD subtracts biogenic CO₂ that remains sequestered for the declared 50-year service life and applies the latest A2 characterization factors. Third-party verifiers accepted the approach in 2021, although some European certifiers still prefer to show biogenic uptake separately.

Can fiber-cement earn carbon credits by recarbonation at end of life?

Partially. James Hardie’s 2023 Australian EPD includes recarbonation in module C, trimming about 3 kg CO₂e / m². The U.S. version has not modeled this yet, so project teams must take care before claiming the benefit.

Fiber Cement or Engineered Wood: Carbon Showdown in Siding

Why carbon math on the façade matters

Project teams chasing LEED v5 and municipal Buy-Clean rules now get scored on every kilogram of CO₂e. Exterior cladding sits at eye level on those spreadsheets because one square foot of siding wraps big areas fast. Miss the target here and you spend the rest of the bill of materials scrambling for reductions.

Reading a siding EPD in 90 seconds

Most declarations use a declared unit of 1 m² cradle-to-gate. Skip to the A1-A3 table: that line shows the manufacturing footprint before site waste or transport. Watch for biogenic carbon reporting rules; engineered wood will list stored carbon (negative numbers) on a separate row, while mineral-based products list only emissions.

Fiber cement: solid but carbon heavy

James Hardie’s U.S. cladding EPD puts HardiePlank at roughly 10 kg CO₂e/m² cradle-to-gate (International EPD, 2022). Nichiha’s new U.S. plant declarations land in the same ballpark, with incremental drops promised after a kiln fuel switch later this year (Nichiha, 2024). Both makers have public roadmaps to cut thirty-plus percent by 2030, yet today the chemistry of Portland cement keeps numbers stubborn.

Engineered wood: smart or smartly marketed?

LP SmartSide’s ASTM-verified EPD shows -8 kg CO₂e/m² after biogenic storage is counted, claiming the siding locks away ten times the carbon of fiber cement while emitting 59 percent less in production (LP, 2024). The catch: if panels end life in a landfill, most of that carbon slowly re-enters the atmosphere. Design for deconstruction or clean combustion is key, yet rarely guaranteed.

Service life: warranty vs. weather

James Hardie offers a 30-year non-prorated substrate warranty (James Hardie, 2025).
LP backs SmartSide with a 50-year prorated warranty that drops to partial coverage after year five (LP, 2025).
Nichiha lists 15- to 30-year coverage depending on product lines (Nichiha FAQs, 2025).

Field studies show fiber cement trim in coastal zones often outlasts roofs, while engineered wood may require repainting sooner in humid climates. Carbon payback evaporates if panels need early replacement; durability still rules the scoreboard.

Durability trade-offs you can’t ignore

Fiber cement shrugs off termites, flame, and hail up to 1.75 inches. It does, however, crack if installers skip gap joints. Engineered wood resists impact and flexes without breaking, yet remains vulnerable to fungal decay when cuts are left unsealed. Your installer training budget suddenly looks like a decarbonization tactic.

How to get an apples-to-apples LCA

Pick the same reference service life (30 or 60 years).
Model realistic maintenance: repaint cycles every 10 years for wood, every 15 for fiber cement.
Choose identical end-of-life scenarios: landfill vs. energy recovery changes wood dramatically.
Audit biogenic carbon rules in the PCR used; some subtract storage only in A1-A3, others across the full life cycle.

A solid consultant will run these sensitivities in a day; fighting over spreadsheet versions for weeks is a luxury no bid team has.

What specifiers ask in 2025 RFQs

“Show me your third-party EPD and explain your plan to cut it in half within five years.” The answer has to include concrete numbers, not just marketing copy, becuase owners now benchmark against EC3 median values released each quarter (Building Transparency, 2025).

Bottom line for manufacturers

If your catalog sits in the gray zone between these two materials, you need a verified EPD yesterday. Without transparent data the market assumes the worst, and tougher carbon caps loom in states like New York and California. Get your credentials sorted so the only debate left is color palette.