How to Get What you Want and not Get What You’re Given
Damn right, too! These materials have a huge impact on the overall appearance of the house and should be defined carefully to preserve the integrity of the design, and the quality and sale-ability of the finished product.
Which makes it all the more surprising to find in developers’ design packages a great big rectangle drawn on the roof labelled “solar by others” or “solar by specialist installer”.
Surely you know that once you hand over your beautiful, carefully considered design to a Quantity Surveyor, if your specification does not nail down the materials you’re looking for, then the words “solar by others” might as well say: “solar – the cheapest you can find, no I honestly don’t care what it looks like – yes, I know I was really fussy about the exact make and model of cavity closer, but really, just get what you want for the solar – it’s not like anyone will notice it’s there.”
It doesn’t all look this good. Image credit: ARPower
Solar PV is becoming more and more common on roofs. Incentivised by Feed in Tariffs, more than 800,000 households have now chosen to install solar as a retrofit. Building regulations in Scotland have made solar the norm on new homes and planning conditions in many local authorities (including zero carbon homes in London) also mean new homes are more likely than ever to need solar.
With the coming shift towards electric transport – (the speed of which I predict will take policy makers and energy companies completely by surprise), economies of scale for battery manufacture will drive the availability of cost effective electricity storage, and make solar an even more compelling feature of a mainstream home.
What you Need to Know
Here are the choices you face, starting with those that have the greatest impact on ‘kerb appeal’.
1. Panel Layout
The number one impact on the overall look of the building is the layout of panels on the roof. Early design engagement with solar specialists means that cluttered designs fitted around other roofing features can be avoided. Higher power panels can be selected to achieve energy goals in the most aesthetically balanced way. See also this guidance on panel design by the Campaign to Protect Rural England.
2. Frame colour.
Solar panel frames are most commonly either silver or black. Both have a protective anodised surface finish, but a silver (natural) colour avoids the dyeing process needed to make a black frame so is slightly cheaper. In most (but not all) situations black frames are considered the most discreet and harmonious choice.
3. Mounting System.
Panels can be mounted on metal racking above the tiles or slates or conventional roof covering, or they can be sunk into the roof covering (roof integrated), replacing the conventional roof covering and looking more like an intended part of the building design and less like a ‘bolt-on’. Many systems use a ‘top clamp’ arrangement to hold down the panels to the framing, but some systems have hidden fixings, resulting in a less cluttered finish above the plane of the panels.
Roof integrated systems with visible clamps (top) and invisible fixings (bottom)
5. Cell Type.Polycrystalline cells are sometimes a similar price to mono crystalline cells, but in times of over-supply often seem to fall further and faster. Right now modules based on polycrystalline cells are around 10% lower in cost than those based on mono crystalline cells. In general poly cells will look a bit bluer than mono, and may have little more colour variation across and between panels , but modern cell production technologies can mean that nowadays they rarely show the crystalline pattern that used to be so characteristic of this type of panel.
(More information on the differences between polycrystalline and monocrystalline cells can be found in this blog).
6. Cell Interconnections.Some manufacturers hide the bus-bars (silver strips at the top and bottom edges of the panel that electrically connect the cells together, but obviously this also adds cost. Some panels have cells with rear face connections so there’s no silver lines visible on the top face of the panel.
How About Just Asking For Roof Integrated Solar?
I took the pictures below at the same site and they show two phases of the same development. The specification called only for “in-roof solar”, opening the door to the silver-framed installations in the lower image which meet the letter, if perhaps not the spirit, of the specification.
Both are roof integrated solar
For something that has such a big impact on the way a building looks, surely it’s time for designers to take control of the solar they get, rather than giving the commercial team carte-blanche to go with the cheapest option offered. Unfortunately there’s no substitute for carefully choosing and specifying the product you want, just like you do for other building materials.