Controls · Blinds and shading
Most of the cooling job, done before any cooling kit.
A south-facing window on a clear August afternoon delivers roughly the same heat into a room as a small electric heater running continuously. Stopping the heat before it arrives is almost always cheaper, quieter and longer-lived than removing it afterwards. The control layer is what makes the stopping happen at the right time.
August afternoon, blinds manual, everyone at work
A heatwave afternoon in an empty house; the manual blinds nobody is home to close, and the west-facing bedroom quietly climbing past 28°C.
External shading first, internal shading second.
External shutters, awnings and brise-soleil intercept solar heat before it crosses the glass and reach roughly three times the effective cooling reduction of an internal blind. Internal blinds and curtains still help, particularly when paired with a night-purge ventilation strategy, but they are managing heat that has already entered the room.
This site's full argument for external shading lives in the Cooling ecosystem; the Controls angle is narrower. Whatever shading you specify, the control layer decides whether it operates at the moments that matter.
Same afternoon; external shading on a sun-position trigger
Same house, same afternoon, external shading on a sun-position trigger; closed at 1pm, ready to reopen after sunset for a night purge.
What the control layer adds.
Automation earns its keep on south and west-facing rooms and on rooflights; on the rest of the house the case is weaker.
Sun-position or thermostat trigger
- Strength
- Closes external shading at the moment the room would otherwise begin to overheat, without anyone being home; opens again after sunset for night purge.
- Trade-off
- Wind sensors are not optional on awnings; retractable fabric that saves you in July is a sail in October.
- Best for
- South and west-facing rooms in households where nobody is home mid-afternoon.
Smart curtain tracks (thermal-lined)
- Strength
- Winter comfort upgrade; dusk-triggered closes cut evening heat loss materially through single glazing.
- Trade-off
- Only useful with proper thermal linings; sheer curtains on a smart track are decoration.
- Best for
- Older houses with single or thin double glazing where curtain quality is doing real work.
Rooflight actuators
- Strength
- Rooflights are the single biggest overheating risk in most extensions; motorised blinds tied to a sun-position or temperature trigger stop the problem at source.
- Trade-off
- Retrofit motorisation is expensive and awkward; ideally specified at the rooflight order stage.
- Best for
- Rear extensions, loft conversions, and any room with a Velux facing east or west.
Verdict
Blinds and shading, honestly assessed.
Automate external shading on any south or west-facing room that overheats or has a rooflight; leave internal blinds and curtains manual unless thermal-lined curtains on a dusk schedule are genuinely worth the electronics.
A single motorised external roller on the worst bedroom window commonly halves peak solar gain and pays for itself in avoided cooling capital and running cost within a few summers. Add sun-position triggering and it stops needing to be remembered.
Automated internal blinds on rooms that already have good external shading are usually gadget territory; manual is fine. The control layer earns its keep where the shading is doing real cooling work and where nobody is home to operate it.
What it gives you
- Cuts peak solar gain by roughly 60 to 70 per cent on a west-facing bedroom.
- Shrinks or removes the case for active cooling in most UK homes.
- Doubles as a winter comfort measure when paired with thermal curtains on a dusk trigger.
What it costs you
- External motorised systems need wiring and wind sensors.
- Retrofit rooflight actuators are awkward and expensive.
- Interior gadgets that do not shrink real cooling load are not worth the electronics.
Why we think thisOpenClose
Reasoning
The three-to-one external:internal shading ratio comes from CIBSE TM52 and TM59 design shading factors, which UK mechanical engineers use to size cooling loads for homes and schools. The rooflight overheating risk figure follows CIBSE TM52 rooflight orientation guidance and Zero Carbon Hub overheating research.
Cost bands reflect UK installer quotes in 2026; single-window motorised external roller shutters at £500 to £1,800 depending on wind sensing, smart curtain tracks at £250 to £500 per opening, and retrofit rooflight actuators at £300 to £600 per unit.
Assumptions
- The room has enough solar exposure for shading to be doing real work; north-facing rooms rarely benefit.
- Wind sensors are specified on any external retractable fabric; they are not optional.
- Automation is genuinely commissioned; a smart shutter left on manual is worse than a good manual one.
Sources
If this were our house
If this were our house with a west-facing bedroom and a rooflight in the kitchen extension, we would motorise those two windows first and leave the rest of the house on manual.
- 1Fit a motorised external roller on the worst west-facing bedroom window with a sun-position trigger and a wind sensor.
- 2Motorise the rooflight blind in the kitchen extension on a temperature trigger; it removes the single biggest summer overheating source most extensions have.
- 3Leave interior blinds and curtains manual unless a dusk-triggered thermal curtain track genuinely improves winter comfort in a specific room.
On a listed or conservation frontage the external shading conversation changes; internal blinds plus night purge is the honest fallback.