Everything you need to know about green roofs

Perhaps the main appeal of log cabin living is the sense of being closer to nature, at one with the surrounding environment in a building that blends effortlessly into the landscape. And most people can picture a log cabin such as this. But, fewer people have stopped to think about the roof and how this can take your cabin even further towards disappearing into its environs. In some parts of the world, particularly Scandinavia, green roofs have been used for centuries and in this article we explore everything you need to know about green roof systems, also known as living roofs or sedum roofs.

Green roofs have been used in Scandinavian log cabins for centuries

Why choose a green roof?

There are many distinct benefits to choosing a green roof system over a steel, tile or shingle roof and some of them are surprising.

• A well maintained green roof system acts as additional insulation for your cabin, helping regulate both temperature and noise. Slow evaporation of rainwater acts as a cooling mechanism during warmer months, whereas the additional biomass of the living roof plants themselves help keep the cabin warmer in winter. This complements the other thermal efficiency benefits of building with logs further reducing energy consumption and costs.

• The projected impacts of climate change include longer, hotter summers, heavier rainfall and stronger winds. It has been demonstrated that green roofs are more resilient to all of these than some more commonplace roofing materials and actively protect your underlying structure from UV radiation and mechanical damage from the elements. At the same time, a green roof does not reflect heat back into the atmosphere - a significant problem in urban areas where abundant concrete, glass and other materials do just that.

• A healthy living roof absorbs a significant proportion of the rainwater that falls on it, reducing run-off into stormwater discharge channels, easing pressure on rivers & drainage systems and complementing the natural water cycle.

• A biodiverse green roof will in time become a thriving microhabitat for a wide variety of insects and pollinators which in turn help attract and support bird and amphibian populations. If you’re looking to be at one with nature, a truly living roof can add significant enjoyment to your new log cabin as well as helping it blend into its surroundings.

• Finally, if designed in from the outset, a green roof can form an additional recreational space for the owners or residents of the cabin. Imagine sitting on a green sedum roof on a warm summer’s day reading a book or watching the bees buzz busily around you. Bliss!

With so many environmental benefits to a green roof system, it is unsurprising perhaps that many planning officers look very favourably upon them when considering your application. If your local planning office has specific biodiversity plans or targets, then a living roof may help you progress through the application process so it is certainly worth doing your research and looking closer at this roofing option.

A green roof can help your log cabin blend into its surroundings

How do costs compare vs other roofing options?

The initial outlay for a sedum roof is higher than other more standard roofing options such as steel or shingle as it may require additional structural considerations (calculated to saturation weight) and the installation of the green roof system itself, but overall is cheaper than a slate roof. However, with minimal maintenance and additional energy efficiency benefits, a green roof can start to pay for itself as soon as it is established, reducing the running costs of your log cabin in the mid and longer term.

Are green roofs good for wildlife?

Yes, absolutely! Generally speaking, the more plant species a green roof accommodates the more diverse a range of wildlife it will be able to support. First and foremost, insects, beetles and butterflies will be attracted to a healthy green roof, often in significant numbers, and they in turn attract foraging wildlife and birds such as goldfinches, starlings and wagtails. Additionally, given relative quiet, a living roof may even attract ground-nesting birds such as skylarks, plovers, and lapwings.

With wildlife populations under pressure from pesticides and habitat loss due to farming and urbanisation, even a relatively small area of green roof can be of significant benefit to a local bee and insect numbers and may even help species return to areas from where they have previously been lost. For you as the owner, a green roof and these little visitors they attract bring year-round interest, reward and well-being benefits that conventional roof types simply do not offer.

Goldfinches will be attracted by the insects on a green roof

What are intensive and extensive green roofs?

Quite simply, an intensive green roof is one that is designed for active use as a recreational or leisure space, whereas an extensive system is designed primarily for the simple ecological reasons for having a natural roof.

A true intensive green roof can include trees, walkways, seating areas and significant landscaping. For that reason intensive green roofs lend themselves to flat roofs in particular and are most commonly seen on some office spaces, museum tops and other public buildings.

By contrast, extensive green roofs are constructed using low maintenance, low-growing plants such as sedums, succulents and some herbs and wildflowers. They are designed to accommodate plants that thrive in thin (lightweight), nutrient-poor soils, are xerophytic (drought-resistant) and can withstand exposed locations. Your green roof will be exposed to wind, frost, summer sun, snow and rainfall and not all plants will survive such challenging and changeable conditions.

We can design and work with both intensive and extensive roofs although the latter is the most common with log cabins. It is also possible to retrofit a green roof if you decide further down the line that you would prefer a living roof system although some additional structural work may be required to accommodate the increased weight that comes with a green roof.

Which plants are best for a green roof?

Not all plants will take to the thin substrate and exposed conditions of a green roof, but some plants are perfectly adapted for these growing conditions.

• Sedums - these low-growing plants have a long flowering season and produce both nectar and pollen during spring and summer which are great for attracting butterflies and bees. They also tend to spread rapidly and form a dense, low carpet, often of strikingly beautiful colours.

• Hawkbits, related to the cornflower, attract butterflies, bees and a number of species of beetle as well as producing beautiful flowers in themselves.

• Vetches, trefoils and Viper’s bugloss are also loved by bees, butterflies and other insects and make great additions to a green roof.

• If you need to go lightweight, mosses and sedums are your best option but can be interspersed with alpine flowers to add variety and interest.

• To further increase biodiversity and habitat, fallen logs and branches can be added to encourage lichens and fungi as well as hiding places for insects and food for xylophagous creatures.
  

Sedums are perfectly suited to the exposed conditions of a green roof

How to maintain green roofs

For the most part, green roofs, particularly extensive green roofs, require very little maintenance and once established will be largely self sufficient. During the initial stages of growth the young plants may require regular watering particularly during the growing months until they have developed sufficient root systems and the roof has reached a level of water saturation.

As your green roof evolves, you may need to replace patches where plants have not taken, replace substrate lost to wind, weed out self-seeded and other unwanted plants and water from time to time. Additionally, slow-release fertiliser should be applied during the spring to ensure healthy growth throughout peak growing season, you may need to remove debris such as dead leaves and other organic matter, and gutters and drainage systems need to be kept clear. It is recommended therefore that safe access to a green roof is designed into your plans, so this is something to discuss with us.

We love installing a sedum green roof and watching the cabin begin to merge with its surroundings, and feedback from clients who have gone down this route is that they love the additional wildlife their green roof attracts. So with environmental, financial and aesthetic benefits, a green roof is a fantastic option and should certainly feature on your list of things to consider when planning a new log cabin.