Green Roof & Solar Panels

Why: Because our bedroom gets really hot in the summer. A green roof might help. Solar panels too, and of course will give us sustainable energy.

The questions I want answered:

How much does a green roof help with heat?

Not really clear from websites. But do all say that is has this effect and also keeps in the heat in the winter.

Best info here (Living Roofs). Heat under roof is not 32, but 17 C.

How much does a green roof costs? Could I get the neighbour(s) involved?

This website (GroenDak) looks best. Here is an instruction on how to put it on the roof yourself.

Costs are €41 per m2 (DIY)

Roof is m2 (or m2 if only our own part)

How much do solar panels cost? How does long does it to earn them back?

Based on zonnepanelen.net website calculator (which first gobbles up your email and then wants more).

3200 kWh per year energy based on 12 panels.

That is very good, our usage is 1700 kWh or lower.

Size of panel is 165- or 196x99cm (so about 2m2).

€60 euro per month savings/money earned (guesstimate).

Based on GroenDak website, costs are around €2500 for 8 panels.

Can I combine both?

Coolblue says no (for green roof and installing solar panels).

Is there a subsidie available?

This one for green roofs Rotterdam. (links to this page)