Climate change adaptation

Here Comes the Rain Again

Methods to Increase Comfort and Safety at Our Homes - Precipitation

09-01-2022

 

In this blog we focus on strategies to improve the efficiency of water and plumbing systems to respond to an increase in water supply from extreme precipitation events. These strategies aim to keep away or reduce the amount of water touching critical indoor elements, protect your house and local water supply sources from water runoff, prevent sewage backing, and maintain clean potable water for your family.

Blog Content:

  • Forget the Past, Focus on the Future
  • Drainage Capacity and Flood Damage Prevention 
  • Clean Water
  • Waterproofing
  • Final Thoughts
  • References

 

Forget the Past, Focus on the Future

Similar to building codes and standards, people rely on historical data and experiences to plan and design their house systems. At eampact, we believe it is necessary to consider future predictions and extreme events to build sustainable and resilient homes. 

Have you ever heard of network peak times? It’s when the streaming stalls or completely stops during the best part of your Friday night movie or in the middle of the Super Bowl. When many people stream simultaneously, the network slows down. Similarly, when everyone’s AC is on to ease the heat, it may cause power outages during a hot afternoon. Network service providers design networks not for steady-state or routine traffic loads, but those peak-time traffic events.

If we design and build our homes based on historical data or normal climate conditions, we may encounter undesired disturbances, or in extreme events, unwanted disasters as a result of heavy wind and rain.

Water management systems, including retention and detention ponds, are sized using past precipitation data and current definitions of 50 or 100-year storm events. Heavy precipitation events may overwhelm water management systems more frequently in the future. 

Plumbing solutions used to be straightforward. But today, the increasing frequency of droughts, floods, and extreme weather conditions, remind us to eliminate water and energy waste. Luckily, technology and creativity bring solutions to better preserve, circulate and utilize water and the energy associated with water.

Note that this blog discusses the main strategies to cope with precipitation and extreme precipitation but does not attempt to cover all solutions for managing floods. We discuss these in our blog dedicated to flooding.

 

Drainage Capacity and Flood Damage Prevention 

Oversized Roof Drainage

This strategy allows a roof system to shed larger rainwater volumes than is required by code. Roof leaders, gutters, downspouts, and drains are all sized to the maximum rain rate recorded in historical data. Increasing the diameter of piping or the size of gutters can help prevent ponding and roof damage in the event of severe precipitation. This strategy was often used while retrofitting urban structures in the UK to store excess flows. Further stricter runoff restrictions were recommended for all new developments to incrementally reduce the stormwater runoff entering the system over time.

Elevation

Elevating an entire house is a costly project and is suitable for houses that are located in high flood risk zones. Many countries have flood maps that determine which locations are flood-prone, and in many cases in the U.S, states and local municipalities have granular data on flood risks as well as corresponding building codes. 

It is recommended to hire an expert that is familiar with the local risks and codes to properly design and build your house to protect it against excess precipitation and floods.

Here are additional sources of information from FEMA (Federal Emergency Management Agency) to familiarize yourself with the basics:

 

Green Roofs: 

Green roofs on buildings are a relatively new trend and they should be considered thoughtfully. These are roofs covered with vegetation that is planted over a waterproof membrane. The prime intent in roof design and construction should be to drain water quickly from the roof and away from the house as much as possible. A green roof’s primary objective is to reduce the rate and quantity of stormwater from the roof surface by capturing it first. 

Green roofs have the capacity to capture excess rainwater and reduce or delay stormwater runoff. This strategy may help prevent roof-top runoff water from getting into other areas of the house and its surroundings. Careful and accurate design and construction are crucial to be effective and not overburden the roof or create water damage over time.

There are other benefits to green roofs such as reducing solar gain and preventing overheating in buildings by adding thermal mass and insulation to the roof and even reducing the urban heat island effect. 

Green roofs reduce the roof’s temperature by absorbing heat into their thermal mass and by the evaporation of moisture (as long as they do not dry out). Lastly, planting green on roofs can definitely be a beautiful design element, as long as they are designed properly. 

Here are examples of green roofs installers to inspire:

 

Rain Gardens:

Rain gardens are a solution to prevent water runoff that also improves the water quality in the community. A rain garden is a garden of native plants planted after observing where rainwater flows in the yard following a massive rain. By digging a ditch or creating a small barrier/slope, and planting the right plants, you can help stop excess rainwater from running off and damaging your property, or overwhelming the local sewer system and water reservoirs. 

According to the Groundwater Foundation, “rain gardens are effective in removing up to 90% of nutrients and chemicals and up to 80% of sediments from the rainwater runoff. Compared to a conventional lawn, rain gardens allow for 30% more water to soak into the ground…” and since “...rain gardens will drain within 12-48 hours, they prevent the breeding of mosquitoes.”

For further reading about rain gardens, visit

 

Clean Water

Sewage Backflow Preventer: 

This strategy may help prevent sewage from backing up into a building from increased precipitation and/or floods. A sewage backflow preventer allows wastewater to flow out in one direction by restricting the flow from reversing back into the building. Sewage backflow preventers can be of several types from simple check valves to more complex spring-loaded relief valves. 

Water Filtration Systems

What is water runoff and why do we need to protect our homes from it? Excessive precipitation may cause water runoff. When massive rain falls on buildings, industrial machinery, factories, roads, parking lots, and other surfaces that do not allow the water to infiltrate into the ground, this creates water runoff. The runoff produced will keep traveling above ground until it finds the nearest river, lake, bay, or water reservoir. This water may contain harmful substances, which it carries to water supply sources, such as heavy metals, oils, pesticides, bacteria, and other chemicals.

While most states and municipalities have methods to treat such water, during excessive precipitation those systems may not perform well.

There are many home filtering solutions ranging from several dollars to a little shy of $2,000 for an initial installation followed by yearly costs of filter replacements (that can average anywhere between $100 to $400 a year). 

 

Waterproofing

Eaves and Gables

While eaves and gables contribute to the aesthetics of a house, they actually serve multiple purposes. In the context of precipitation, the key function of eaves is to keep rainwater or melting ice/snow, off and away from the siding walls of the house. Together with preventive roof sheathing and underlayment, eaves help prevent water from entering the house at the seams where the roof meets the wall. Gable overhangs have the same functionality and help reduce the amount of rain that hits the exterior end wall of the home.

Since eaves, and especially gables, are vulnerable components during high-wind events, the art is to get their length and width right, add proper sheathing, and strengthen them and the gutters attached to them.

Window & Door Flashing:

Flashing is another important strategy to prevent water from entering your walls, floors, and roof. There are different areas and methods to apply flashing, but the most common are on windows and doors that expose your foundation to water through the joints where the frame meets the wall (the “opening”). 

Since building codes and product manufacturer installation guides do not provide holistic coverage, an experienced contractor can help properly install flashing. Discuss with your contractor the use of top, side, bottom, and corner caps (e.g. sheet metal strips, aluminum, or vinyl), self-adherent/flexible flashing (e.g. tape), and sealants/liquid flashing (e.g. silicon).

Water Resistive Materials: 

The main concept here is to take advantage of building materials that can thoroughly dry out, resulting in minimal damage and preventing decay and mold growth. Examples of water-resistive materials are preservative-treated wood framing (with environmentally friendly treatments like borate), and fiberglass-faced drywall rather than paper-faced drywall. Newer materials such as fiber cement products, and certain types of metals and plastics also resist water damage.

Beyond choosing the right materials that can dry quickly, it is crucial to properly design the house to allow interior and exterior surfaces to dry. Depending on the climate zone, the temperatures inside and outside the house, the humidity, the insulation, and airtightness applied, may differ. You should allow vapor, precipitation, melting snow, and ice to dry quickly to prevent damage and risk to health and aggravation that may be recurring if not done correctly. 

The solution is to hire professionals and make sure they walk you through the design and material choices they make, as well as how the house system will behave during normal conditions(per your climate zone and during/after extreme events such as an atmospheric river.

Back to materials, there are green-friendly options that we encourage exploring. Here are some to get inspired by:

  • Preservative-treated Wood (With Borate-Based Treatments)

Preservative-treated wood is resistant to water, fungal, and insect damage (e.g. termites). Its durability makes it an excellent low-maintenance material with a minimal environmental impact as it reduces the need for frequent forest harvesting. 

Though not suitable for all climate zones, Borate-based treatments are a safer alternative to ACQ-treated wood. In 2004, the EPA reached an agreement to end the sale of CCA-treated wood for most wood-based products due to its toxic nature. Today, commonly used wood products are often treated with alkaline copper quaternary (ACQ) as an alternative. However, ACQ may have some risks associated with its copper substance. 

Once again, be sure to consult with an expert before making a decision since different treatments behave differently in various climate zones.

  • Fiberglass-faced Drywall

Paper-faced drywalls are more common and affordable but they pose a risk in wet and humid areas as they can develop mold. Using mold-resistant drywall such as fiberglass-faced drywall may be more expensive up-front but it will provide longevity and resilience.

While wood is commonly used for sidings, today you can find various types of sidings such as aluminum, vinyl, stone, brick, stucco, or fiber cement. We consider the latter an eco-friendly alternative, however, there are a few considerations to take into account: it absorbs moisture, upfront costs may be high, and it requires ongoing treatment after its installation.

Before choosing an alternative for sidings make sure that they are well suited for your climate zone.

Enhanced Roof Access:

Sometimes the best solutions are straightforward such as simply being aware and proactive. This strategy allows for regular inspection of the roof membrane to prevent rain, wind, and/or moisture damage. Many buildings have only limited access to the roof through a hatch. This may discourage routine inspections of the roof’s membrane, flashing, and drainage systems. As an example, where applicable, a full man door to the roof will allow easy access to the roof for inspections, provide safety for the occupants, and in the event of a wildfire, may allow firefighting equipment to access the roof to prevent the ignition from embers. 

 

Final Thoughts

It is important to make our homes waterproof to withstand excess precipitation and to perform routine inspections and clean the property's foundation, basement, exterior walls, gutters, and waterspouts, and of course, the roof and attic. These are fundamental activities to ensure our house is well maintained and able to withstand normal and extreme weather events while keeping its occupants safe and comfortable.

Here is a summary of solutions that can further contribute to the resilience of your house and keep your family safe and comfortable during and after extreme precipitation events:

  • Green roofs
  • Rain gardens
  • Oversized drainage
  • House elevation
  • Sewage backflow preventers
  • Water filtration systems 
  • Extended eaves and gables
  • Proper window and door flashing
  • Water-resistant materials
  • Enhanced roof access

 

KEEP COOL. BUILD RESILIENCE. EAMPACT.

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