Your questions and our answers

  • SRT .... Solar roof tile
  • SRT PVI.... Solar roof tile photovoltaic installation (roof integrated)
  • CPVI.... conventional photovoltaic installation (roof mounted)
  • SRT classic... brown colour for presavation order protected buildings
  • SRT trend... blue colour for modern architecture
  • SSB... Solar Switch Box
  • EPC... Electric power company
  • PV... photovoltaic
Q: I live in a pretty house, which I like very much and want to buy a photovoltaic installation. All the companies offer CPVI only which turn my houses roof into an ugly blue glass wall. What shall I do?
Just install a SRT classic. SRT in the STEPdesign keep the original aspect of your roof. You must not pay your commitment for a clean environment with an ugly aspect of your house. You can even improve the look of your house when arranging the SRT into different groups.
Q: What does STEPdesign mean ?
STEPdesign is the design of the SRT. The original roof structure and colour remain. The SRT PVI is integrated perfectly into the existing roof. The look of your home is improved by the architectural accent of the SRT PVI.
Q: Does the SRT need more space on the roof than CPVI ?
Not really, since nearly every roof has venting tiles, skylights, chimneys etc. which are an obstacle for a CPVI, but not for the SRT, so the additional space is neglectable. 96 SRT form a PVI with lkWp.
Q: The building authority forbids a CPVI, since my house is listed under protection order. What shall I do ?
A SRT PVI classic can be installed on every building, which is listed under a preservation order (example: preserved school in Berlin)
Q: Do I have to get building permission from the building authority for my SRT PVI.
No. Since you only exchange roof tiles and do not change either the appearance or the statics of the roof, a building permit is not necessary. This does not apply, if your house is listed under a preservation order, you then must get a permission from the protection authority, which should be in most cases issued problem-free.
Q: I have a house with an older roof, which looks like a rollercoaster. Do I have to restore the roof, which is required for any CPVI and how much is it?
With the installation of a SRT PVI there is no need to restore or repair the roof, since the SRT have about 2/3 of the weight of the original roof tiles and fit seamlessly into the roofs landscape and also look beautiful when finished and not inclined as a CPVI.
Q: How can I save money when buying a SRT PVI?
You can save money, when you do a part of the planning by yourself. Study the installation instructions pages carefully, then fix the position of the PV installation by counting the tiles on your roof and avoiding places with shadows during a day. You can even try different arrangements of the strings to improve the look of the SRT PVI.
Q: How long does the roofer need for the installation of the SRT PVI ?
An experienced roofer team needs approximately 3 hours for a SRT PVI with lkWp size to install. Add one hour to install a crane when the house has more than 1 storey and another hour to remove the old tiles. Normally a 2 kWp installation can be completed in one day.
Q: I have always problems with coordinating craftsmen, for a CPVI I need a roofer, a plumber and an electrician on site at the same time!
The installation of a SRT PVI is flexible. The electrician and roofer can work independently from each other. Once the roofer has laid the tiles and connected everything correctly (8 red LED lamps light up in the SSB), the electrician can start his task connecting the SSB to the inverter and grid. The simultaneous presence of roofer and electrician is no longer necessary
Q: My roofer fears for his saftey when connecting the SRT! as there is constant solar electricity produced.
As long as the SSB is not opened and the SRT PVI is not connected to the inverter or the grid, there is only a harmless safety voltage produced, like e.g. on a model railway (under 75 VDC!!!) Therefore you do not need an electrician when laying or connecting the SRT.
Q: The SRT is made from plastic. What is the lifetime of the material ?
The SRT have the same material guarantee as the original roof tiles.
Q: The SRT is made from plastic. Is there a danger of fracturing?
The SRT show a substantially higher breaking strength like the original roof tiles.
Q: What do the SRT consist of?
The SRT consist of recycled plastic, which start a second life cycle with this product.
Q: Can I collect and use the rain water, which flows over the SRT PVI?
The SRT does not release any dangerous material to the environment. The SRT are naturally PVC free, and yes you can collect the rain water as with any other normal roof.
Q: There is no SRT available in the model of my roof tiles according to the internet page "models". What can I do?
Find out the manufacturer of your original roof tiles and ask them, when they will add the SRT in the STEPdesign to their product range. We need approximately 3 months from the first contact with the roof tile manufacturer to the first delivery.
Q: How much is a SRT PVI?
A SRT PVI costs about the same as a professional mounted CPVI. You will get the same electrical output together with many advantages and with a beautiful look.
Q: Where can I buy a SRT PVI ?
Ask your roofer. He will know the manufacturer of the SRT, he knows your roof and your roof tile model and he normally co-operates with an electrician, who is responsible for the connection of the SRT PVI to the grid.
Q: Can I hire my personal electrician for the electrical installation
You can hire any electrician of your choice, who knows how to install a PVI. The electrician is strictly independent to the roofer.
Q: Where can I get subsedies for my PVI ?
The mayor or your government will inform you about the actual governmental and European subsedies for PVI. Your electrician will inform you about the actual power selling possibilities to your local EPC. Our country representative will support you to find out the right adresses.
Q: What is an island and a grid connected application ?
In an island application there is no grid available, you need a storage battery for bad weather and nocturnal hours. Typical applications: Mountain hill farm, weekend house, hunting chalet, international space station.
A grid connected application delivers power direct to the grid with a special inverter. As you are connected to the grid, no battery is required. In Europe most PV installations are grid connected.
Q: Why does one lkWp SRT PVI consist of 8 strings with 12 SRT per string ?
There are 2 reasons:

The 12 SRT produce a safety voltage under 75VDC during the installation only, like a model railway. As this voltage is harmless, the roofer is allowed to connect the SRT during laying the roof and to connect the strings to the SSB.

A characteristic of PV systems is that the weakest element determines the power output. A CPVI which is connected in series fails totally when just one element or a connector fails. In a SRT PVI always 2 strings run parallel, so if one element or a connector fails, 50% of the output is still available. You also see immediately if a string has failed if any of the red indication lamps is off.
Q: I am a roofer and want to sell SRT. How should I start ?
You know the roofs of your home town, because you will have made most of them in the past. Select suitable roof examples near your company ( use the roof check ) and offer the SRT to their owners. These people should be opinion leaders in your home town. One of them will certainly acquire a SRT PVI, because these people are ready to invest into a clean environment. Make advertising with the first installation in the local press and place your company name on the site. You will see that the interested people will come to you to get a SRT PVI. The best start is certainly to install a SRT PVI on your own roof to have a demonstration object. You can train your workers on the job without time pressure. You can choose an electrician without stress with whom you will cooperate on future installations and check out all the necessary information about the local authorities, local EPC and subsedies. You are a solar expert already, when you meet your first customer. In our experience your customer will ask you if you have a SRT PVI on your roof already. If you can say yes, then the customer will normally buy the SRT PVI.
Q: Do the SRT get hot in summertime and loose output power?
The SRT is designed as a frame. The PV elements are cooled by the air convection of the ventilated roof. Thus the power decrease is moderate in summertime.
Q: Do I have to install a lightning protection for the SRT PVI?
No, a SRT PVI is a ROOF INTEGRATED SYSTEM. All cables are inside the roof and the POLYMATRIX plastic material is a perfect isolator.

CPVI show metallic elements and the cabling runs on the roof. Therefore these elements are mandatory for CPVI and not longer necessary for SRT PVI:
  • lightning protection.
  • earthing cable with 16mm2 minimum from the roof to the ground
  • house earthing device.
As the strings are very small in area, no significant induced voltage is produced by an indirect lightning strike.
CPVI have a large string area, which leads to a high induced voltage and are very sensible to indirect lightning strikes. Therefore these elements are mandatory for CPVI and not longer necessary for SRT PVI:
  • over voltage protection device under the roof
  • earthing cable with 16mm2 minimum from the roof to the ground
  • over voltage protection before the inverter*)
  • house earthing device

*) Modern inverters are equipped with an over voltage protection inside. An extra over voltage protection device is only recommended if the house is located in an area with a high lightning storms frequency.
Q: Why must I fix the SRT to the roof ?
You must fix the SRT to the roof because the surface of plastic is very smooth and you would dislodge the SRT when you climb on them. We recommend standard roofers screws 4,0x50mm with a standard roof. The hooking of snow stoppers is possible even after the fixing. The fixing of the SRT prevent the pushing up of the SRT , when roofers climb on a roof. This could damage the hidden cabling. On the otherhand climbing on the SRT is possible.
Q: The cable seems very small to me!
The cable is a high tech product. It is double isolated, ( which is necessary for protection class II) , free from PVC, size 2mm2 , strong enough, high tensile strength and nearly bite proof from vermin. Conventional rubber isolated cables only LOOK larger. Vermin like them. Also the connectors are in use in billion numbers on earth.
Q: Is POLYMATRIX really ecological?
POLYMATRIX consists of collected and sorted packing material garbage, which are styrene free PVC. As an alternative to the primitive burn and disposal of plastics and waste materials, the process to produce POLYMATRIX recovers the ash produced by waste management process and in turn provides the raw materials to produce a SRT. A very good of example of recycling.
POLYMATRIX is also one of the few building materials certified as ECOLOGICAL.
Q: What happens to the SRT, if my house burns?
There are flame resistant roof materials (concrete, clay/tone, slate, metal) and flammable materials (reeds, wood, bitumen, plastic). Plastics burn, as do the majority of plastics consisting of hydrocarbon elements.
In Europe general fire regulations apply: Inflammable roof materials must be steady against spreading fires and radiant heat. The SRT POLYMATRIX fulfills all these demands. In addition they do not produce poisonous gases, as they are PVC free and like other plastics do not melt or drip.
Summary: If the neighboring house should burn, then there is no danger by radiant heat or spreading fire. If the house should burn from the inside out, then its roof timbers and its isolation and all roof covering systems (flame resistant or not) are all totally destroyed.

Q: The PV part of the SRT consists of so few cells. Is that a disadvantage?
Exactly the opposite. Each SRT contains 8 solar cells with a so-called bypass diode

In case of shading of one or several PV cells - the so-called " Hot Spot effect " - the bypass diode redirects the electricity by bridging the shaded cells.

If no bypass diode was used, the electricity would flow through the shaded cells and cause damage by the heat, which occurs by the electrical resistance of the cells.

Normal PV installations use bypass diodes every 18 - 24 cells, which are all brigded in the case of a single shaded cell and fail to produce current. With the SRT only 8 cells are bridged , which increases current production.

Q: I have converted my attic and want to mount the SSB on the wall outside. Is this possible?

The SSB are designed to withstand humid conditions inside a room. When mounted outside the SSB should be protected from the weather where possible.

Water can enter through the cable inlet, condensation can also collect inside. We recommend before you mount the SSB, drill a few small drainage holes in the base of the SSB approximately 3mm wide.

Make regular maintenance checks.
Don't forget to remove the housing screws of the SSB to prevent unqualified entry, you may also consider placing a "warning electricity!" sign on or near the SSB.

Constantly updated