Green roofs can diffuse heat that would otherwise be absorbed through your roof in warmer months and act as an added layer of insulation when it’s chilly outside. Often considered to be one of the most sustainable styles of roof for this reason—and also because a living roof can be a habitat for bees and other pollinators—green roofs can also be a charming addition to your home simply for the way they look. Installing a traditional green roof, however, can cost almost twice as much as a standard roof. Instead, consider modular options for a green roof, which makes the upgrade more affordable as well as friendlier for a DIY enthusiast.
A green or living roof is a roof that's surfaced with soil and plants instead of shingles or tiles. Systems for installing green roofs vary, but usually consist of creating a moisture barrier to keep water from getting inside and including some kind of barrier to prevent plants from growing down through the roof into your home. Then, soil, drainage medium, and plants can be added in layers or as modular units like those for a green roof. The whole system has to be compatible with the load capacity of your roof in mind, which is why you should always consult a roofing contractor or a structural engineer before trying a green roof.
A modular green roof system costs between $10 and $30 per square foot, as compared to a built-in green roof, which averages between $20 and $35 per square foot. (The average cost to install a traditional roof is between $4.35 and $11 per square foot.) While modular systems can still be twice as expensive as a regular roof, they are a significant savings as compared to built-in-place alternatives.
A green roof can save as much as 25% on cooling costs during warmer months and in winter can reduce energy costs on the top floor of your home by up to 12%. Green roofs also reduce runoff water from your roof by around 65%, which can improve moisture conditions around your home and help to prevent water from collecting near your foundation. When planted with the right varieties of plants for your area, green roofs can also help improve biodiversity and attract pollinators.
Since modular green roofs come in smaller sections that snap together to form a grid on your roof, the system can be simpler to install than built-in systems that require lots of assembly on site. A simpler installation helps to lower the cost of a modular green roof as well as having some elements that are DIY-friendly. Although you’ll need help from a professional for prepping your roof for modular trays, the planting of the trays and some of the installation can be a DIY project.
A modular green roof also has the benefit of simpler maintenance, as most modular green roof systems allow sections to be removed and brought to the ground for maintenance or replanting, rather than requiring planting to take place on the roof. If you’re an ambitious DIYer and feel capable of getting the modules to and from the roof, you could do this type of maintenance yourself, but in general, it’s a good idea to hire a professional to perform maintenance including weeding about once per year.
Because green roofs add weight to your home, you need to make sure that a green roof can be supported by your home’s structure. In addition to the engineering portion, keeping your green roof in place over the long term means it needs to be properly attached, whether it’s modular or built in place. Prepping for the installation to ensure proper drainage, proper weight distribution, and irrigation if necessary are all considerations that make this a job best left to the professionals unless you’re very skilled and familiar with engineering schematics as well as permitting requirements.
Modular green roofing systems usually don’t work on a roof with a slope of more than 20 or 30%, so they aren’t a good fit for many peaked roofs. In addition to needing a gradually sloped or flat roof, modular roofing systems won’t likely last as long as their built-in counterparts. Although a built-in green roof might last as long as the building it’s attached to, a modular green roof will likely only last around 30 years. While there can be significant savings over the long term through longevity, reduced maintenance costs, and energy savings by installing a modular green roof, the upfront cost can be twice as much as a regular shingle roof.
