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Discussion Starter #1
Say I buy a property that has a South East facing rear roof (standard 45 degree pitched roof). If I wanted to get a dormer loft conversion (the type that gives a relatively flat roof with a max height of the highest point of the roof (the ridge line). Is it possible to get a solar panel installation on that? The loft conversion has not been done yet so I'm in the fortunately position to be able to consider a loft conversion with solar PV solution from the outset (assuming it is even possible).

Thoughts?

Thanks in advance
 

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South facing roof is the ideal for installing PV's. If you are installing a dormer then you have to make sure the panels are not covering that area.
I would do the conversion first and then the PV's so you don't risk the builder to damage them.
PV panels are standard size so unless you have enough area for them to be installed within the edges of the roof you should be fine.
Installers won't install a panel underneath the window for safety reasons. But they will be able to advise you when they perform the survey.
 

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Discussion Starter #3
I mean does anyone know if it's possible to put PV panels on top of the dormer (flat-ish) roof? I know it won't be the optimum angle as it'll be almost flat but hoping that it can still be worthwhile doing.

So something like this:
 

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You can fit PV's on a surface with pretty much any inclination and even on a flat one.
It all depends on how much you will have to spend as additional cost for the supporting structure.
This assuming the roof will handle the extra weight.

Nobody better than the installer's surveyor to advise you.
 

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I mean does anyone know if it's possible to put PV panels on top of the dormer (flat-ish) roof? I know it won't be the optimum angle as it'll be almost flat but hoping that it can still be worthwhile doing.
You will need planning permission if above the highest point of the building (usually the ridge). If exposed to the wind you will also need a positive connection, e.g. bolting them down to the roof (the ones you show appear to be relying on ballast).

You can't install panels flat, but whatever solar mountings you use will induce the minimum angle required (usually about 5 degrees).
 

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Flattish panels like that may need regular cleaning, say at the start of summer. Bird poo, leaves & dust are likely to accumulate, and the run-off of rainwater might not be fast enough to wash them for you. My panels have been on a 25 degree pitched roof for 4 years, and when I've washed them down with hosepipe spray & wiper on a long stick I've not been able to detect any increase in output, so I reckon mine are effectively self-cleaning.
 

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Our roof was designed to have dormers but we deliberately avoided flat rooves and specified them as S facing with 17.5deg slope. At the time, solar panels would have had a four hundred year payback so preparing for them wasn't a consideration.

Since then we've installed solar panels on the roof and they've been working fine (and long since paid for themselves thanks to FIT). In fact, for max generation at Summer Solstice you'd really need a 30deg slope so ours are probably a bit better than a so-called conventional 45deg roof.

Another approach for a S facing dormer window would be to have a gabled roof above it with panels E-facing and W-facing.
 

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East & West facing works very well, IF you have enough panels such that there are times when you can't use all the electricity they produce. Let me explain - fit a 4kW system on a "perfect" South-facing roof at say 45 degrees and you'll get near-as-dammit 4 kW on that perfect June day around noon. Chances are there are many days you don't need 4kW at that time of day, so end up exporting most of it. You won't have got much electricity when the sun was reasonably up at 8 a.m. and the washing machine went on, so might well have imported a lot then. You won't have much electricity as sunset approaches, as again the sun will be at a very shallow angle to them. You might have got a much better fit of panels-to-usage had you put those same 4kW of panels 50-50 on East-West sloping roofs instead. Your max output at midday would only be around 3kW in June/July, but you would see a far faster rise the moment the sun's up.

My panels are all East facing (10 degrees North of that actually) - I'd wanted to use the West facing slope as was predicted to get a few kWh more p.a., but wife vetoed that as was visible from road = Ugly. Turns out that East was a better fit! E.g. today my panels woke up at 6 a.m. producing 32W, at 7 440W, at 8 1680W, at 9 2200W, and then it's pretty flat until noon when it's 2000W and starting to tail down slowly. So the ramp-up at sunrise is very quick, with pretty-much full power by 9 am! By 1:30 p.m. its dropped to 800W as the sun has effectively set on these panels, then slowly decreases to 500W at 4:15 and shutdown at 6:30.

I'd have got a better fit if these panels were split 50-50, as I'd be getting a rapid rise to just over 1 kW by 9 a.m., then a gentle rise to 2 kW at noon, then a slow fall to 1 kW close to sunset, which would typically be much better suited to say charging Ev at 6A = 1.4kW all day long.

The very most I get from this East-facing 25-degree slope set is 3kW, usually around 10:30-11 on that perfect June day.

(I have actually boosted my generation with a shallow-angle South-facing triplet on garden shed roof to top-up to nearer 4 kW max, but the figures above exclude this group.)
 

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AFAIK all residential solar installations on flat roofs require planning permission. Also, they are often free-standing and not attached to the roof so require ballast to hold in place. Solar on flat roofs is not ideal.
 

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AFAIK all residential solar installations on flat roofs require planning permission. Also, they are often free-standing and not attached to the roof so require ballast to hold in place. Solar on flat roofs is not ideal.
I'm not aware of any requirement to get planning permission for flat roofs, beyond what I outline above. The majority of flat roof installations are free standing with ballast, but where wind loading is likely high you can use positive connections (e.g. bolt through a bitumen roof and then cover the fixing with new bitumen).
 
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