Anyone else find their garden office gets unbearably hot in summer even with insulation?

Mine's a static caravan so basically a tin can with delusions of grandeur, and yes, absolutely roasting by 10am even with 50mm insulation throughout.

Ended up going down the rabbit hole of phase change material boards behind the wall panels — the idea being they absorb heat as they melt (at a molecular level, not literally dripping down your walls) and release it at night. Mixed results if I'm honest, but it has taken the edge off the worst days.

What actually made the most difference though:

• External solar shading over the south-facing windows — cheap awning from Amazon, embarrassingly effective
• Switched my Victron MPPT and inverter to a external battery box rather than inside the van, those things kick out proper heat
• A small 12v fan running constantly to stop the air going stagnant

The insulation trap is real by the way — people think more insulation = cooler, but it just stores the heat rather than reflects it. A radiant barrier on the roof cavity is what you actually want for summer. Foil-faced PIR does double duty on that front.

Anyone tried those evaporative coolers? Curious whether they're actually useful in the UK or whether our humid summers just laugh at them.

@LutonBuild mate, you're speaking my language — I've got both a garden office and a static caravan, so I'm suffering in stereo every July.

The phase change materials route is genuinely interesting but pricey. What actually shifted things for me was combining reflective foil sarking on the roof (the stuff normally used under slates) with a small 12V DC fan running off my Victron system to create cross-ventilation at night. Basically pre-cools the thermal mass before the day starts.

The static caravan is harder because the roof is essentially a biscuit tin — I've seen people fit external "cool roof" coatings with decent results. Rubbershield-type stuff reflects a surprising amount of solar gain before it even becomes heat.

What orientation is yours? South-facing roof is obviously the worst offender, but it's also prime real estate for panels, which creates a lovely moral dilemma.

@LutonBuild phase change materials are interesting but honestly for a static the bigger win is usually just blocking solar gain in the first place. Reflective window film made a massive difference to mine — cheap and easy.

Also worth checking if your roof has any air gap. Static roofs often have zero ventilation cavity so heat just builds up with nowhere to go. A simple solar-powered roof vent fan sorted it for me — runs off a small panel, no wiring needed, and kicks in exactly when you need it most.

Not a silver bullet but combined with the film my setup went from "actively hostile" to "bearable" by mid-morning. PCM might be interesting for thermal mass but I'd nail the basics first before spending serious money.

@LutonBuild static caravans are heat sinks by design, no amount of PCM wizardry fixes that fundamental problem.

My cabin's timber frame so slightly better but still gets grim July/August. What actually moved the needle for me was a reflective bubble wrap layer under the metal roof — cheap, stupid simple, dramatic difference.

Also worth checking your ventilation ridge. Most static vans have them but they're often blocked or sealed by previous owners trying to keep rain out.

@LDVSolar is right about solar gain being the main culprit though. External roller blinds or even just whitewashing the south-facing windows for summer sorted more than any insulation upgrade I did.

PCM is genuinely interesting tech but the payback vs cost doesn't stack up unless you're already doing a full refurb. Fix the basics first.

@GrumpyBuilder fair point but my van conversion taught me that where you put your insulation matters as much as how much — reflective foil under the roof skin before any PCM or wool does more work than people expect, basically a free win before you spend a penny on fancy materials.

@LutonBuild have you considered a simple external shade sail over the roof? Dead cheap, doesn't require rewiring your entire build, and I knocked about 8°C off my cabin peak temp with one from B&Q that cost less than a tank of diesel.

PCM is genuinely interesting tech but feels like treating the symptom rather than the cause — stop the heat getting in before you start storing it.

@NaeClue is onto something massive there. In my van build I made the classic mistake of insulating the walls but leaving thermal bridges everywhere at the ribs — basically had cold (or in summer, hot) rails conducting straight through.

@LutonBuild for a static, I'd look hard at external insulation over internal if you can stomach the faff. Keeps the thermal mass on the inside working for you rather than against you.

Also — and nobody's mentioned this — ventilation strategy matters as much as insulation spec. I've got a Victron-monitored setup in my garden office and the temperature logs clearly show that passive cross-ventilation drops peak temps by 4-5°C before you even touch active cooling.

PCM is genuinely interesting tech but @GrumpyBuilder's scepticism is warranted until the price per m² comes down significantly.