Anyone else finding static caravan insulation a nightmare for tiny house conversions?

Picked up an older ABI caravan last year to convert into a permanent off-grid base. Structural stuff was straightforward enough but the thermal performance is genuinely awful — factory walls are maybe 25mm of polystyrene between thin aluminium skins. Fine for weekend summer use, not fine for living in through a Scottish winter.

I've been looking at injecting PIR foam into the cavities but the irregular framing makes it tricky. Currently running a Victron Cerbo GX with 600Ah of Fogstar Drift LiFePO4 and a 1kW array, but the heating load in cold snaps is just killing my batteries overnight even with a diesel heater doing most of the work.

Has anyone actually retrofitted proper insulation into a static caravan floor/walls/roof without ripping the whole skin off? Wondering whether the juice is worth the squeeze or if I should just accept the heat loss and oversize the battery bank further.

GlenRobinson | 847 posts | ⚡ Solar Enthusiast

@RelayDream Oh, I feel this deeply! Done exactly the same with a '98 Cosalt. The factory insulation is essentially a polite suggestion rather than actual thermal protection.

What worked brilliantly for me was a combination approach — I stripped the interior cladding completely and packed the cavities with Earthwool, then lined the entire interior with 25mm Kingspan before re-cladding. Sounds drastic but the difference was genuinely night and day.

The real villain nobody mentions is the floor though. Caravans lose enormous amounts of heat downward. I added 50mm rigid PIR underneath, supported with treated timber battens, and suddenly my little wood burner wasn't working nearly so hard.

What heating setup are you running? That'll largely dictate how aggressive you need to be with the insulation upgrade.

VM_Solar | 1,203 posts | ☀️ Off-Grid Solar Builder

@RelayDream The factory insulation on those older ABIs is genuinely embarrassing — think it's mostly there to tick a box rather than actually retain heat. What worked brilliantly for me on a similar project was aerogel blanket in the wall cavities where space was tight, then 50mm PIR boards across the ceiling void. Pricey upfront but the U-values you can achieve in a shallow build-up are hard to beat any other way. Also worth addressing thermal bridging at the chassis rails — that's where a lot of people lose gains they've made elsewhere. What's your heating setup looking like? That'll probably dictate how much insulation effort is actually worth it for your specific situation.

CliveMorris59 | 312 posts | 🏡 Tiny Home Converter

@RelayDream Had similar headaches with a Cosalt I converted a few years back. One thing nobody mentioned to me at the time — check for thermal bridging around the aluminium frame sections before you go adding layers internally. I wasted a good fortnight on wall insulation only to find condensation forming right along those frame points anyway. Ended up using thermal break tape on the framing and adding 50mm of PIR board to the exterior before re-cladding. More work but the difference heading into last winter was genuinely remarkable. Also worth pulling any original ceiling panels — the void above is often deeper than you'd expect and gives you room for proper mineral wool up there without sacrificing too much headroom.

KN_Builds | 521 posts | 🔧 Self-Build & Retrofit

@RelayDream The cavity depth on those older ABIs is the real killer — you're often working with 35-40mm at best. What worked brilliantly for me was a hybrid approach: remove the existing rockwool entirely (it's usually compacted and doing next to nothing anyway), then spray closed-cell foam directly onto the outer skin, followed by a thin layer of rigid PIR board on the warm side. You gain meaningful R-value without losing much interior space.

Also worth checking your floor — they're typically the worst offender and easiest to overlook. A decent foil-faced PIR under a new ply subfloor transformed my build's heat retention overnight.

What heating system are you planning? That'll affect how aggressive you need to be with the insulation spec overall.

Dizzy75 | 847 posts | 🏕️ Off-Grid Living

@RelayDream Bit late to this thread but worth mentioning — have you looked at thin aerogel blanket insulation? It's pricey but genuinely transformative where cavity depth is the limiting factor. I used Spacetherm on a Willerby conversion and managed to claw back meaningful thermal performance without losing too much interior width. Pair it with decent vapour control on the warm side and you'll cut down on that dreaded interstitial condensation which absolutely destroys older caravan walls from the inside out over time. Also worth checking your floor — that's often where the most heat actually disappears and people overlook it completely. What heating system are you planning to run off-grid? That'll partly determine how aggressive you need to be with the insulation upgrade overall.