World's First (Note 1): Development of Water Damage Resistant Housing

Ichijo Co., Ltd.

Publication date	November 11, 2021(Posted on October 24, 2022)
Sector	Natural Disasters / Coastal Areas

Company Overview

Climate Change Impacts

In the case of housing, laws and regulations regarding “earthquake resistance” and “fire resistance” have been organized over the years, and the technology and performance have improved accordingly. However, the reality is that not much progress has been made in the development of technology for “flood resistance.” The torrential rains and floods caused by climate change are beginning to exceed the conventional flood control scenarios, and flood damage is no longer a "disaster within a limited area.” It is therefore imperative for Japan and similarly endangered countries to "adapt" to this climate change and to develop innovative technologies to prepare for flood damage.

Adaptation Initiatives

Through repeated experiments conducted in collaboration with the National Research Institute for Earth Science and Disaster Resilience, we have developed the world's first Flood-Resistant Homes, a home that can withstand water damage.

In a typical house, there are several points that are vulnerable to flood damage. We identified them as hazard points and classified them into four categories: inundation, backflow, submersion, and buoyancy, to take countermeasures (Figure 1).

Point 1: Elimination of gaps where water can enter to prevent inundation

A float valve was installed on the inside the ventilation port that normally draws outside air into the underfloor. When water comes in, the valve floats to cover the opening and prevent the water from infiltrating into the underfloor. When the water recedes, the valve drops to its original position so the vent will function again (Figure 2). The walls have also been waterproofed to prevent water from entering while maintaining moisture permeability, and the entrance door has been made watertight by integrating the wall and door frame to eliminate gaps and also by using door seals. In addition, tempered glass is used for the window to withstand high water pressure (Note 2).

Point 2: Automatic drain blockage to prevent backflow

The backflow prevention valves used in the underfloor drains are normally used with the valves open. When the water level rises due to flooding, and sewage flows backwards, the valve automatically closes to prevent sewage overflow.

Point 3: Securing lifelines to prevent submersion

The components and circuit boards for the power system of the electric water heater are located on the upper part of the main unit. This was developed in collaboration with a specialized manufacturer so that even if the main unit is partially submerged, it can still operate and the water in the tank can be used for domestic purposes. The outdoor units of air conditioners, exterior power outlets, solar power inverters, and power storage batteries are also located on specific stands at a height that is less likely to be submerged.

Point 4: Innovative buoyancy measures to prevent the houses from being washed away

Two types of buoyancy countermeasures have been developed to meet the needs of customers and residential areas. The first is the "standard method," which uses water as a weight to protect the houses from buoyancy forces; water is drawn in from the underfloor before it reaches the level where the house will float, and the weight of the water will resist buoyancy (Note 3). The other type is the "floating and mooring the home method," which protects the house itself by making it float. Like a ship moored at a harbor, the house is connected to anchored poles at the four corners of the property. Even if the house becomes completely submerged by flooding, the damage will be minimized by deliberately floating the house, and the house will be protected from submersion and runoff.

Effects / Expected Benefits

In October 2020, a full-scale experiment was conducted at a large-scale rainfall test facility in the National Research Institute for Earth Science and Disaster Resilience. We constructed our Flood-Resistant Home (floating type) and a house with standard specifications in the test facility using approximately 3,000 tons of water to simulate torrential rain and flood damage (Figure 3). While the water kept flowing into each room through the underfloor ventilation openings, front doors, and windows in the standard house, the Flood-Resistant Home suffered no damage under the floor or inside the house (Figure 4).

By promoting the spread of the Flood-Resistant Homes, the project aims to: facilitate disaster recovery operations, realize an early transition from evacuation shelters to homes, and mitigate the damage cost of houses by more than 160 billion yen per year (costed by the annual average of 30,000 houses that are damaged by climate change risks), and reduce flood waste by 50,000 tons per year.

The development and production of the Flood-Resistant Homes has received high public recognition; we received the Japan Resilience Award 2021 Semi-Grand Prix Gold Prize (Corporate and Industrial Category) and was selected as the first recipient of the Minister of the Environment's Award for Climate Change Action (Development and Production Category/Adaptation Field) sponsored by the Ministry of the Environment.