4 Tips for Cold-Weather Green Roof Design & Maintenance

Green roofs offer business owners many benefits. Not only are they beneficial for the environment, but they also provide great insulation that can potentially help lower building heating and cooling costs. However, if you own a business in Minnesota or another area of the country that experiences cold, snowy winters, then you may think that a green roof is not right for your business, because many plants simply cannot survive harsh winter weather.

The truth is that green roofs are great options in even the coldest areas of the country when they are properly designed and maintained. 

Read on to learn four tips for designing and maintaining a green roof that thrives in even the harshest winter weather. 

Choose the Right Plants

One important way to increase the chance that your green roof will thrive during even the coldest winters is to choose the right plants. Some plants are hardier than others, which means they tend to survive adverse weather conditions, such as freezing temperatures and drought conditions, that less hardy plants cannot. 

Succulent plants are great options for cold-weather green roofs, because these plants store large amounts of water in their leaves that they can then utilize during periods of drought. A few succulent plants commonly planted on green roofs include  sedum sarmentosum , or gold moss stonecrop;  sempervivum ; and aloe vera. 

While many grass species are easily killed by cold temperatures and drought, a  few  are hardy enough to be planted on a cold-weather green roof. Blue sedge and Bowles’ golden sedge are two grass species that can withstand harsh weather conditions. Blue sedge is blue in color, while Bowles’ golden sedge is yellow. 

A flowering, grass-like plant called  Ophiopogon japonicas  or mondo grass and juniper shrubs are additional great plant options for installation on cold-weather green roofs due to their tolerance to extremely cold temperatures. 

For the best chance of survival, only mature plants should be installed on a cold-weather green roof and seedlings should be avoided due to their fragile nature. Ideally, these plants should be pre-grown locally outdoors during the winter. 

Install a Thick Layer of Growing Medium

A typical green roof is composed of several layers. Underneath the plant layer lies a layer of growing medium. This medium acts as a lightweight substitute for traditional garden soil by providing plants nutrients and absorbing water when it rains, which the plant roots can then soak up to stay hydrated. 

When designing a green roof in a cold climate, this layer of growing medium should be relatively thick. A thicker layer of growing medium absorbs more water when it rains and when snow melts than a thinner layer does to help plants stay hydrated during the winter months. In addition, this additional growing medium acts as insulation to help keep plant roots from freezing during the cold winter months. 

Take Steps to Prevent Growing Medium Erosion

When your green roof is subjected to strong winds during the harsh winter, the growing medium can erode. Growing medium erosion is a form of green roof damage that can jeopardize the health of your plants and reduce your roof’s ability to insulate your building properly. 

To prevent wind erosion, ensure your green roof has plant coverage of about 85 percent or more. This high plant coverage shields your growing medium from strong winds. The installation of erosion control blankets or netting just below the surface of your growing medium can also prevent growing media erosion caused by high winds. 

Finally, when snow falls on the surface of your green roof, never remove it unless its weight begins to exceed your roof’s weight load capacity. This snow helps protect the growing medium underneath it from erosion and insulates the plants on your roof to protect them from the harsh winter elements. 

Perform Bi-Annual Roof Maintenance

All green roofs need to be maintained properly to optimize roof performance and the health of plants. Ideally, maintenance should be performed bi-annually during the fall and spring seasons. 

In the fall, all leaves and other loose debris should be removed from the roof, and any weeds that have sprouted should be pulled. Your roof’s drainage system should also be inspected to ensure water is draining from your roof properly.

In addition, while proper irrigation of your green roof is essential year-round, it is especially important during the fall season. Plants that are well-hydrated and in optimal health before winter arrives are more likely to survive an especially long, harsh winter. 

When springtime arrives, your roof should be inspected for growing medium erosion and new growing medium should be added where necessary. Any plants that did not survive the winter should also be removed and replaced with healthy plants. 

If you live in an area of the country that experiences long, cold, snowy winters, then you may think that a green roof is not right for your business building. However, green roofs can and do perform very well in cold climates when they are designed carefully and maintained properly. Contact the commercial roof experts at Berwald Roofing & Sheet Metal for design and installation of a  commercial green roof  today.

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