diff --git a/scripts/iso/README.md b/scripts/iso/README.md
index 1b117c6..7905e43 100644
--- a/scripts/iso/README.md
+++ b/scripts/iso/README.md
@@ -42,9 +42,9 @@ scripts/iso/build-felhom-iso.sh \
 ```
 > On the DooPlex build server (180) the felhom working dirs were moved off the SSD to
 > `/mnt/5_hdd/felhom.eu/` (2026-07-18): the input PVE ISO lives at
-> `/mnt/5_hdd/felhom.eu/drill/proxmox-ve_9.2-1.iso` and ISO output goes to
-> `/mnt/5_hdd/felhom.eu/felhom-iso/out`. The script's built-in `--out` default is still `$HOME/felhom-iso/out`
-> (portable) — **always pass `--out` explicitly on 180** so nothing regrows the SSD.
+> `/mnt/5_hdd/felhom.eu/drill/proxmox-ve_9.2-1.iso`. The script's `--out` **default is now
+> `/mnt/5_hdd/felhom.eu/felhom-iso/out`** (override with `$FELHOM_ISO_OUT` on other hosts), so on 180 you
+> can omit `--out` entirely and output still lands on the HDD, never the SSD.
 
 Output: `felhom-pve-<pvever>-v<isover>-<profile>.iso` + `.sha256` + `.manifest.txt`.
 
diff --git a/scripts/iso/build-felhom-iso.sh b/scripts/iso/build-felhom-iso.sh
index cb60d57..7757694 100644
--- a/scripts/iso/build-felhom-iso.sh
+++ b/scripts/iso/build-felhom-iso.sh
@@ -47,7 +47,7 @@ log_success() { echo -e "${GREEN}[OK]${NC} $1"; }
 log_dry()     { echo -e "${CYAN}[DRY-RUN]${NC} $1"; }
 die()         { log_error "$1"; exit 1; }
 
-PVE_ISO=""; ISO_SHA256=""; PROFILE=""; BOOTSTRAP_ENV=""; OUT_DIR="${HOME}/felhom-iso/out"; PVE_VERSION=""; DRY_RUN=false
+PVE_ISO=""; ISO_SHA256=""; PROFILE=""; BOOTSTRAP_ENV=""; OUT_DIR="${FELHOM_ISO_OUT:-/mnt/5_hdd/felhom.eu/felhom-iso/out}"; PVE_VERSION=""; DRY_RUN=false
 LOADER_CLI=""   # --loader override; empty = fall back to the profile, then the shim default.
 PAIRING=false   # --pairing: build the GENERIC secret-free ISO (slice C); no --bootstrap-env.
 usage() {
@@ -72,7 +72,8 @@ Options:
                          shim = stock MS-signed chain (Secure Boot OK on compliant firmware).
                          mkimage = monolithic grub-mkimage loader for cheap AMI boards that can't boot
                          the ISO's GRUB from USB (F1). UNSIGNED -> the target board needs Secure Boot OFF.
-  --out DIR             output directory (default: \$HOME/felhom-iso/out)
+  --out DIR             output directory (default: the DooPlex build root
+                        /mnt/5_hdd/felhom.eu/felhom-iso/out; override via \$FELHOM_ISO_OUT for other hosts)
   --pve-version VER     override PVE version tag (default: parsed from the ISO filename)
   --dry-run             print the steps without producing an ISO
   -h, --help            this help