Local Shutter InstallersHeat · Season
Approved Document O and existing houses
Updated
Approved Document O in England is about overheating in new residential buildings, and external shading is one of the strategies designers use. It is not a form you file because you fancy a shutter on a 2014 extension.
What the glass admits
The worked opening for Approved Document O and existing houses is 4.2 m wide by 2.35 m high, 9.87 square metres of glass. This figure puts 545 watts per square metre on the pane and uses a g-value of 0.63, about 3389 watts into the room if the curtain is up. An opaque external shutter, taken as stopping 80 percent of that gain while it is fully down, leaves about 678 watts and keeps about 2711 watts out. That is a noon figure for comparison. An internal blind does not get the same reduction. For Approved Document O and existing houses, use the noon figure to compare two openings on the same house, then let a measured survey replace the figure.
An internal blind does not get that reduction, because the energy has already crossed the glass.
The hot part of the day
It does explain why new homes with a lot of glass keep running into the same complaint.
Dusk in January
Winter figure for Approved Document O and existing houses: glass at 1.2 W/m2K, 9.87 square metres, a 12 degree inside-outside gap and eight night hours. The bare pane is about 1.14 kWh a night on that crude sum. A closed shutter cutting about 18 percent of the flow leaves 0.93 kWh and saves about 0.20 kWh a night, only while it is down. Open it when you want winter sun.
Leave it if
Stop Approved Document O and existing houses if the solar panel would sit in a soffit with no sky, and the quote has no wired alternative. A photograph is not a manufacturing size.
Leeds is only a setting for Approved Document O and existing houses. The streets there are not the product.
How to use the figure
The 4.2 by 2.35 metre opening inside Approved Document O and existing houses is there so a quote has something to disagree with. If the tape gives a different size, the tape wins.
The example drive is a belt, and the illustration is £5,885. A belt, a wired motor and a solar motor can share a curtain and still be different jobs. Compare those lines, not a single bold total.
What the survey still has to write down
For Approved Document O and existing houses, ask where the box lands, what colour reference will be ordered, and how the curtain opens when the motor is dead. Those three answers move the job more than a rounded price.
Leave the lantern, the side light and the next elevation off the order unless they are drawn. Approved Document O and existing houses covers one kind of opening. The house may have three.
When I would not order yet
Approved Document O and existing houses should wait if the opening is an escape door with no way to raise a dead motor, or if the front is the elevation a conservation area was drawn to protect.
A photograph is not a manufacturing size. Two quotes for Approved Document O and existing houses only compare when the slat, the box and the drive are the same kind of thing.
Questions worth asking the fitter
Is the price on this page a quote?
No. £5,885 illustrates Approved Document O and existing houses for a 4.2 by 2.35 metre opening with a belt, at September 2026 rates. Your survey replaces it.
Does the shutter cover every pane?
It covers the opening it is built for. Here that example is 9.87 square metres. A roof lantern, a side light or the next elevation is another line.
What if planning is unclear?
Do not pay the factory for Approved Document O and existing houses until a listed building, a conservation front, a flat or a shopfront has a written answer. Ordinary rear walls on houses are sometimes simpler.
What should two quotes share?
The same openings, the same slat type, and the same drive. Approved Document O and existing houses uses a belt in the example so you can see how much the motor choice moves £5,885.