Felix Mildner

August 18, 2022, 3:14 pm | Read time: 5 minutes

A solar system on the roof or rather plants? With a solar green roof, property owners don’t have to choose. This model combines both and even offers advantages over a pure photovoltaic solution. The cooling effect of the greenery helps maintain the efficiency of the solar panels even on hot days. However, a solar green roof is not suitable for every house roof.

Who benefits from a solar green roof?

A solar green roof is generally only suitable for flat roofs–such as on bungalows or garages, according to the Consumer Center NRW in Düsseldorf. On the other hand, the photovoltaic modules on the green flat roof do not need to be screwed into the roof structure. It is sufficient to weigh down their base plates with plant substrate.

Also interesting: Is a solar system on the balcony worthwhile for generating your own electricity?

How much weight must the roof support?

According to the Consumer Center NRW, those planning should expect the following weights: 80 to 180 kilograms per square meter for the plants in a wet state, plus 25 kilograms for the solar technology. If there are doubts about the roof’s load-bearing capacity, a structural engineer should be consulted.

Also interesting: Innovative materials for roof covering

More on the topic

Suitable Species The Best Plants for Sandy Soil

Long Blooming Period 6 Flowers You Can Still Plant on Your Balcony in Late Summer

Which plants are suitable for green roofing?

Numerous low-growing, drought-resistant plants are suitable for a solar green roof, which can also help cool the building’s interior on hot days–a heat protection measure. Additionally, the roof greenery provides food for many insects, contributing to biodiversity, according to the Consumer Center NRW. The following sedum plants are recommended by experts. They should be planted on a substrate layer of at least 10-12 cm.

• White Stonecrop (Sedum Album): Sunny location, Bloom: June – August, Flower color: White, Growth height: 5–10 cm
• Common Houseleek (Sempervivum tectorum): Sunny location, Bloom: July – August, Flower color: Light red, Growth height: 5-30 cm
• Carline Thistle (Carlina vulgaris): Sunny location, Bloom: July – September, Flower color: Golden yellow, Growth height: 15-40 cm
• Bulbous Buttercup (Ranunculus bulbosus): Sunny location, Bloom: May – July, Flower color: Yellow, Growth height: 10-40 cm (Caution: Plant sap contains substances that can cause skin irritation)
• Reflexed Stonecrop (Sedum reflexum): Sunny location, Bloom: July on upright shoots, Flower color: Yellow, Growth height: 20-25 cm
• Spring Cinquefoil (Potentilla neumanniana): Sunny to partially shaded location, Bloom: May – June, Flower color: Yellow, Growth height: 5-10 cm
• Wild Thyme (Thymus serpyllum): Dry location in full sun, requires some time to establish, Bloom: June – August, Flower color: Pink, Growth height: 5-10 cm
• Large-flowered Self-heal (Prunella grandiflora): Sunny location, Bloom: June – August, Flower color: Dark violet to purple violet, Growth height: 10-20 cm
• Harebell (Campanula rotundifolia): Sunny to partially shaded location, Bloom: June – September, Flower color: Blue – Light blue, Growth height: 20-60 cm
• Wall Germander (Teucrium chamaedrys): Sunny location, Bloom: July – August, Flower color: Purple pink, Growth height: 20-25 cm
• Branched St Bernard’s Lily (Anthericum ramosum): Sunny location, Bloom: June – August, Flower color: White, Growth height: 20-60 cm
• Mouse-ear Hawkweed (Hieracium pilosella): Sunny location, Bloom: May – September, Flower color: Light yellow, Growth height: 10-20 cm
• Carthusian Pink (Dianthus carthusianorum): Sunny location, Bloom: June – September, Flower color: Purple red, Growth height 15-40 cm
• Pussytoes (Antennaria dioica): Sunny location, Bloom: May – June, Flower color in male plants: Pure white, Light yellow or Soft pink, in female plants: Bright pink or Purple, Growth height: 5-50 cm
• Common Rock-rose (Helianthemum nummularium): Sunny location, Bloom: June – September, Flower color: Yellow, Growth height: 10-30 cm
• Oregano (Origanum vulgare): Sunny location, Bloom: July – September, Flower color: Light pink-violet, Growth height: 30-50 cm
• Chives (Allium schoenoprasum): Sunny to partially shaded location, Bloom: June – August, Flower color: Pink, Growth height: 10-40 cm
• Biting Stonecrop (Sedum acre): Sunny location, Bloom: June – July, Flower color: Yellow, Growth height: 5-10 cm,
• Little Mouse-ear Chickweed (Cerastium semidecandrum): Sunny location, Bloom: March – June, Flower color: White, Growth height: 3-20 cm
• Maiden Pink (Dianthus deltoides): Sunny location, Bloom: June – August, Flower color: Pink, Growth height 6-8 cm
• Sand Everlasting (Helichrysum arenarium): Sunny location, Bloom: July – August, Flower color: Golden yellow, Growth height: 20-30 cm
• Sheep’s-bit (Jasione montana): Sunny location, Bloom: July – August, Flower color: Blue, Growth height: 10-40 cm
• Bladder Campion (Silene vulgaris): Sunny location, Bloom: June – July, Flower color: White, Growth height: 10-40 cm
• Burnet Saxifrage (Pimpinella saxifraga): Sunny location, Bloom: June – September, Flower color: White/Pink, Growth height 20-50 cm
• Meadow Saxifrage (Saxifraga granulata): Sunny location, Bloom: June – September, Flower color: White, Growth height 15-40 cm
• Meadow Clary (Salvia pratensis): Sunny location, Bloom: May – August, Flower color: Violet, Growth height: 20-40 cm
• Cheddar Pink (Petrorhagia saxifraga): Sunny location, Bloom: June – September, Flower color: Pink, Growth height 10-30 cm
• Tassel Hyacinth (Muscari comosum): Sunny location, Bloom: May – June, Flower color: Blue violet, Growth height 30-70 cm

Tip: Hire two specialized companies

It is advised to coordinate hiring a specialized company for solar technology and another for green roofing for a solar green roof. There are subsidies available for both solar energy use and green roofing, according to Düsseldorf. Here you can learn more about subsidies for green roofs.

with material from dpa