Architectural Record – August 2019

115

CONTINUING EDUCATION

EDUCATIONAL-ADVERTISEMENT

Joto-Vent System USA, Inc. was established in Redmond, Washinton, in 2017 and is the U.S. subsidiary of Joto Techno Co., Ltd., a leader of

residential building materials in Japan. Joto-Vent System USA, Inc. is introducing the Joto-Vent System, a continuous perimeter foundation

vent, which has been used in Japan for 40 years and is the standard method of crawlspace ventilation there. http://www.joto-vent.com

Continues at ce.architecturalrecord.com

Kathy Price-Robinson writes about building and

architecture with a focus on adapting to climate

change. http://www.kathyprice.com

With every catastrophic disaster, building codes and practices tend
to change. After the Kobe Earthquake in 1995 destroyed more than
400,000 buildings, the use of perimeter venting systems increased.

This house has a continuous perimeter vent system for crawl-space

ventilation. The absence of vent holes in the foundation is a preferred

aesthetic by some architects.

and are more susceptible to damage. The second
reason is that with the perimeter venting system
the sill plate is separated from the founda-
tion and so it won’t decompose, which aided
in supporting a long-term structurally sound
fou ndat ion.”
In the two decades following the Kobe
Earthquake, adoption of the perimeter venting
system has skyrocketed. One company alone
has provided perimeter venting systems to more
than 4.5 million new Japanese homes.

A SLEEK AESTHETIC
A final consideration is the sleek elegance of
this venting system, allowing complete passive
crawl-space ventilation with just a thin and
nearly unnoticeable presence, and without the
common—and some would say unsightly—
large openings currently cut into foundations or
rim joists every 8 feet or so to allow for airf low.
For architects, engineers, and builders in
North America, however, while those holes cut
into the foundation or rim joist ventilation may
be ugly and even detrimental to the integrity of
the foundation, the practice continues because
“it’s the way things have always been done.”
Erik de Buhr, an owner and builder in
Eugene, Oregon, and founder and co-executive
director of a nonprofit that helps solve home-
lessness, sought out the new venting system as a
solution to a design problem.

“While designing our house, I realized that

our stem wall was going to be too short to use

the standard plastic crawl-space vents,” he says,

adding that he “wasn’t looking forward to using

them anyway because, in my opinion, the vent

boxes detract from the clean exterior look of the

house and don’t do a very good job.”

So the questions arise: Is the conventional

box venting method the only way to go? Is it

the best way? Is there a better way? This course

examines this innovative manner of passively

venting a crawl space evenly and unobtrusively

around the entire perimeter, and compares it

with the traditional method of box vent open-

ings to which most have become accustomed.

Let the designer or builder be the judge.

We begin with why crawl space ventilation is

so critically important.

HOW AND WHY MOISTURE BUILDS UP

IN CRAWL SPACES

Providing ventilation under a raised foundation

house is as old as the North American building

trade itself. While some homes are built over

basements, or more recently on grade-level con-

crete slabs, there are plenty of locations and soils

and climates where separating the foundation of

the home from the ground is the best design.

Consider raised homes built for centuries in

the Northwest or Southeast of North America.

Pilings set deep in the ground provide anchors

for the raised foundation. While the tempera-

ture at the surface of the ground varies widely

depending on season and climate, the tempera-

ture becomes less changeable and more moderate

below the surface. This relatively warm below-

surface ground temperature produces moisture,

and this is the reason for the building practice

of a raised foundation built up on a crawl space.

While the soil below alternately gets wet, dries

out, freezes, or unfreezes, the foundation raised

above it remains unaffected. And with air f low-

ing freely underneath the house, natural breezes

carry away ground moisture. The raised design

also allows easy access to plumbing, electrical,

and mechanicals under the f loor.

As building practices changed, the pilings on

which the foundation sat became a reinforced

and poured concrete foundation wall on which

the foundation sat. To create the necessary

airf low to keep moisture from accumulating,

the code required holes in the foundation wall to

allow air to freely move in and out of the crawl

space. Screens or louvers were also required to

prevent rodent intrusions.