Solar PV - in roof or on roof?

Pinklepurr

We have recently been quoted for Solar PV panels and have decided on a company we are happy with and a price which is competitive. One thing we remain undecided about is whether it is better to go for on roof or in roof option. The in roof option will cost us £500 more but my OH feels quite strongly that this will look aesthetically more pleasing and reduce the weight on the roof dramatically. I don't know either way and wonder if it would be a waste of money - solar panels never look pretty! However, I do wonder if the extra weight on the roof is something we seriously need to consider.

We have a 3 storey home and were advised by the developers when buying that the roof is only designed to take the weight of snow and therefore we could not use the limited loft space for storage. I am wondering if we would need to consult a structural engineer if we were to go with the on roof option.

It would be interesting to hear from others who have gone for the in roof option.

Thanks

nigelpm

Am I missing the point here?

Surely, you will still have the weight bearing down on the roof and loft structure whether they are on the roof or in the roof.

Al1x

Do you mean having solar panels instead of tiles/slate rather than on top of them?

Pinklepurr

Yes, by in roof I mean they will remove the tiles and inset the panels in the roof, rather than sitting them on top of the tiles.

WestonDave

The in roof option is exactly that - you take the tiles/slates off and fit them instead of them as a roof covering. I've never personally seen a roof with that done with the big 250W panels but I've seen one with "solar slates" and that looks the dogs wotsits - other than the slight gloss to the solar ones compared to the matt finish of the (new) slates its hard to see where the solar ones are. That was on a new build house though so there was presumably a saving in buying the traditional slates that went towards what I guess would be the higher costs of the slate style panels.


In theory if you don't have the slates/tiles and panels then you save the weight of the slates/tiles and just have the panels rather than both. That said as I understand it the panels are not that heavy - probably around 25kg for a traditional panel spread over a number of joists - that compares to the point weight of 70kg ish standing on one joist if you go in the roof space which may cause structural concerns.

Martyn1981

Only a minor issue, but worth considering, in-roof systems are slightly less efficient than on-roof, as they get less cooling/air flow. I think the difference is about 5%.

Try it yourself on PVGIS, free standing v's building integrated.

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

As stated, panels are only about 20kg each, and the weight is spread thinly. However, a good installer will check the roof structure, and if necessary add extra supports, as some of the more modern roofs only have a thin margin of error. Unlike good old belt and braces roofs with 8by4 purlings.

Have fun.

Mart.

theboylard

Personally I'd be concerned about the builder saying that you cant use the loft space as it won't take any extra weight?!

What have they scrimped on to make the roof space so fragile?

nigelpm

theboylard wrote: »

Personally I'd be concerned about the builder saying that you cant use the loft space as it won't take any extra weight?!

What have they scrimped on to make the roof space so fragile?

Indeed and if this is the case what will happen when the installers have to stand on the roof to put the panels in.

ed110220

Pinklepurr wrote: »

We have recently been quoted for Solar PV panels and have decided on a company we are happy with and a price which is competitive. One thing we remain undecided about is whether it is better to go for on roof or in roof option. The in roof option will cost us £500 more but my OH feels quite strongly that this will look aesthetically more pleasing and reduce the weight on the roof dramatically. I don't know either way and wonder if it would be a waste of money - solar panels never look pretty! However, I do wonder if the extra weight on the roof is something we seriously need to consider.

We have a 3 storey home and were advised by the developers when buying that the roof is only designed to take the weight of snow and therefore we could not use the limited loft space for storage. I am wondering if we would need to consult a structural engineer if we were to go with the on roof option.

It would be interesting to hear from others who have gone for the in roof option.

Thanks

Aesthetics are all opinion - I find a lot of things commonly found on homes much more unappealing than solar - untidy exterior plumbing, TV antennas, satellite dishes and wiring; mismatched replacement windows, tacked on porches that don't match the house style etc etc. Solar is new though and I bet in a few years people will hardly notice it because it's become so familiar.

Personally I prefer the idea of keeping the solar panels and roof covering separate. Solar panels should last a long time, but roofs should last longer. Ours is 65 years and only now getting to the end of its life. If down the line a panel fails it's probably going to be a lot simpler to sort out if it's on the roof rather than being in/part of the roof.

Just my two cents.

As for the roof strength, is this a new house? Lofts aren't normally designed to take a lot of weight (compared with habitable floors), so the developers might just be covering themselves. I imagine they mean you can keep the things people typically store in lofts like Christmas decorations, old slides and other bits and pieces, just not big items of furniture.

Ed

MFW_ASAP

We live in a listed building that is also in a conservation area. We've asked for permission to put solar on an outbuilding and they are allowing in-roof solar.

We're looking at Viridian solar panels:
http://www.viridiansolar.co.uk/Products_Solar_Panels_for_Pitched_Roof_Installation.htm

They do look much better than the ones that sit on the roof of a house, but there is a reduction in efficiency because the wind cannot get under them to cool them down. Personally I would rather see a reduction in efficiency than a reduction in kerb appeal, as I think on-roof solar panels are really ugly, but beauty is in the eye of the beholder.

lstar337

MFW_ASAP wrote: »

We live in a listed building that is also in a conservation area. We've asked for permission to put solar on an outbuilding and they are allowing in-roof solar.

We're looking at Viridian solar panels:
http://www.viridiansolar.co.uk/Products_Solar_Panels_for_Pitched_Roof_Installation.htm

They do look much better than the ones that sit on the roof of a house, but there is a reduction in efficiency because the wind cannot get under them to cool them down. Personally I would rather see a reduction in efficiency than a reduction in kerb appeal, as I think on-roof solar panels are really ugly, but beauty is in the eye of the beholder.

They hardly look any different!

The only ones that look really different are the solar tiles.