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

Yeah this is the bane of my life every July/August. My place faces south-west which is brilliant for the solar panels but absolutely lethal by 3pm.

Few things that actually made a difference for me:

• External blinds not internal ones — massive difference, stops heat entering in the first place rather than just blocking light once it's already cooking the glass
• Got a small 12v fan running off my Victron setup, basically free to run and keeps air moving
• Planted a fast-growing climber along the south-facing wall last autumn — won't see proper benefit til next summer but fingers crossed

The insulation thing is a bit of a trap isn't it. Great in winter, basically turns the place into a thermos in summer. Mine's well insulated and it just holds heat once it builds up. Opening windows in the morning before it gets warm helps massively, then close everything up around 11ish.

Considering a mini-split but the install cost is painful and I'm not sure I want to be running it off battery. Anyone actually done this off-grid? What size system are you running?

Also curious whether anyone's tried those radiative cooling roof paints — seen a few mentions of them but no proper reviews from anyone who's actually used one in the UK climate. Feels like it might be a bit of a gimmick but open to being wrong.

What's everyone else doing? Feels like this doesn't get talked about enough compared to heating in winter.

@PeakVanLifer mate, a south-west facing shepherd's hut is basically a slow cooker with wifi — external reflective window film was the single best £40 I ever spent, cuts the solar gain dramatically without murdering your panel output like internal blinds do.

Ha, @LochLover's slow cooker description is painfully accurate!

One thing nobody's mentioned yet — thermal mass can actually work against you in a garden office compared to a brick building. Because these structures heat up so quickly, you want to be ventilating aggressively in the early morning before temperatures climb, then sealing everything shut by around 10am. Counterintuitive but it works.

I also fitted a small solar-powered roof vent (basically a bathroom extractor with a dedicated tiny panel) which runs hardest exactly when the sun is worst. Costs nothing to run and shifted the peak temperature in mine by a good 4-5°C.

The other game-changer was external blinds rather than internal — stops heat entering in the first place rather than trying to deal with it once it's already through the glass.

Ran a cable to my garden office last summer, nearly fried myself in the process — and I mean that literally, it was 34°C in there by 2pm.

What sorted it for me was a basic 12V ceiling fan running off the solar system. Dead simple, pulls almost nothing, and just moving the air around made a massive difference before I even touched

@PeakVanLifer south-west facing is the worst combination isn't it — you get the full afternoon blast right when you're trying to actually concentrate.

One thing that's made a genuine difference for me is a 12V DC ceiling fan wired directly off the battery bank — no inverter losses, runs almost for free on a sunny day when you need it most, and moves enough air to make the heat bearable even if it doesn't reduce the temperature massively.

Also worth looking at external solar shading rather than internal blinds. Internal blinds let the heat through the glass first before blocking it. A simple bamboo roller blind or even a bit of shade sail fixed outside the window cuts the solar gain significantly before it enters the space. Dead cheap too compared to proper glazing upgrades.

Different angle from someone who's dealt with this in a van rather than a garden office — thermal bridging through the structure is often the silent killer. Even with decent insulation, if your frame is steel or aluminium, you're essentially running a radiator around the perimeter.

In a van conversion context I tackled this with a continuous layer of 10mm Kooltherm before anything else goes on — breaks the bridge completely. Same principle would apply to a garden office, particularly around any metal fixings or window frames.

Also worth checking: is your insulation actually performing, or has moisture compromised it? Mineral wool especially loses significant R-value when damp. If it was fitted without a proper vapour barrier on the warm side, that could be quietly sabotaging everything — and no amount of ventilation fixes degraded insulation.