Hitachi Cable is pleased to announce that it is expanding its waterproof sheet business by providing waterproof sheets for rooftop greenery. The Company has been selling "Hitachi Sarnaroof" via a partnership with Sarnafil International AG (Headquarters: Switzerland; see company outline) since 1994, and its solid reputation for weatherproofing plus its root-resistant qualities make "Hitachi Sarnaroof" ideal for rooftop greenery.

Big cities have been shown to function as "heat islands," retaining more heat than their surrounding suburbs. Rooftop greenery is an increasingly popular method to address this problem. In addition, rooftop greenery allows buildings to be more energy efficient, improves scenery, and can be used as a sanctuary from day-to-day city life.

The advantages of rooftop greenery noted above has caused Tokyo to revise the Tokyo Nature Preservation and Recovery Ordinance. Starting in April of this year, 30% of usable roof space in public facilities larger than 250 m2 that are under construction or renovation must be covered by rooftop greenery. In addition, 20% of the usable roof space in private facilities larger than 1,000 m2 that are under construction or renovation must be covered by rooftop greenery. The City Greenery Protection Law was revised in May of this year to allow a 50% reduction of fixed assets taxes for 5 years when rooftop greenery is installed on buildings in conformity with local government-approved improvement plans. The rooftop greenery movement is gaining legal backing as well.

While rooftop greenery is positive step for a variety of reasons, building owners worry that root growth could lead to water leaks. This has raised demand for more reliable waterproofing.

"Hitachi Sarnaroof" is ideal for this job. This product is first and foremost a waterproof sheet used on roofs, but it also possesses highly reliable root-resistant qualities for use with rooftop greenery and biotopes (spaces where small plants grow). Based on Sarnaroof's strong record in such environmentally advanced nations as Switzerland and Germany, Hitachi Cable has been supplying waterproof lining to domestic building projects for many years. However, we anticipate a dramatic increase in the demand for rooftop greenery, so we are making preparations that will enhance our ability to produce and distribute waterproof lining for rooftop greenery.

"Hitachi Sarnaroof" possesses the following advantages:

1) A strong record of root resistance

In Europe, where rooftop greenery is common, there are many different tests*1 for evaluating the tree and plant root resistance of waterproof sheets. "Sarnaroof" has achieved zero penetration in each of these tests.

*1Waterproof sheet root resistance tests(DIN 4062, SIA 280)

Plant root resistance tests: Investigations are done 6-8 weeks after lupines are planted to check for root penetration

Tree root resistance tests: Trees with strong roots were planted (e.g.; elms, poplars, wild thistles), and after four years investigations are done to check for root penetration

2) Lightweight

Using our lining means no root-resistance sheet and protective concrete are necessary. This means that rooftop greenery can even be installed on roofs that have weight limits.

3) Reliable weatherproofing

"Hitachi Sarnaroof" is made of a vinyl chloride layer 1.2 to 2 mm thick. A special compound means that there is little plasticizer dispersal. Because heat bonding is used instead of solder, joints are tightly sealed and the resulting sheet is highly weatherproof.

We also produce flexible non-chloride olefin products that are environment-friendly under the name "Hitachi Sarnaroof T."

4) Two different installation methods

There are two different waterproof system installation. One is a general method for use when rooftop greenery consists of smaller plants. The other is the double layer waterproofing system installation method used for small and medium-sized trees and other large-scale greenery (for only our vinyl chloride sheets.).

5) High reliability and easy repair using the double layer waterproofing system installation method

The double layer waterproofing installation method consists of a "Hitachi Sarnaroof" sheet being installed on the roof, after which an embossed1 "Hitachi Sarnaroof" sheet is laid over this sheet. The top layer is heat bonded to the bottom layer in 50 m2 block units, forming individual blocks. The process is complete when a special injection pipe is affixed to each block. This method allows a numerical assessment of how watertight the lower sheet and the joints are. This is important because these are places where waterproofing problems are likely to crop up. These numerical assessments are made using applied pressure tests and vacuum tests.

Should there be a leak after the sheets have been installed, a vacuum test makes it possible to easily determine which block the leak is in. Once this is known, an injection pipe can be used to inject waterproofing material between the two waterproofing layers in the relevant block. In other words, fixing leaks is quite simple. This means that temporarily removing a large amount of soil and reinstalling the entire system is not necessary. Moreover, this system should last for more than 10 years.

Applied Pressure Test: First, a leak detector is attached to a joint. Then an air compressor is used to apply pressure between the two sheets to ensure that there is no blistering.

Vacuum test: A vacuum pipe is used to lower pressure to 380mmHG. If, after 5 minutes, the pressure has increased by 76 mmHG, then the test was successful.

Outline of Sarnafil International AG

Address: Industriestrasse, CH-6060 Sarnen, Switzerland
Founded: 1958
Capital: 27.8 billion yen (CHF 397.1 million)
Sales: 47 billion yen (CHF 672.4 million) as of fiscal 1999
Employees: 2,100

Sarnafil summary:

Sarnafil developed vinyl chloride waterproofing sheets in 1964. Since then, products have been designed using a variety of bonding methods, including mechanical fastening and total surface bonding. At present, more than 300 million m2 of these highly reliable waterproof sheets are being used in projects all around the world.

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Explanation of terms:

1. Embossed "Hitachi Sarnaroof"

The vacuum test for detecting water leaks cannot be performed properly if sheets are smooth and completely attached to one another. In order to ensure that the test can be done properly, an embossed sheet is used.