Onix Tubing Installation Manual

page 16 Watts Radiant: Onix Installation Manual
a room were 10,000 BTUs and the
windows were single pane and had a
total heat loss of 6700 BTUs. The
Heat Loss Report would reflect this
unusually high heat loss area and a
decision to install double pane win-
dows might be made to help make this
room more energy efficient.
Applications
As construction materials improve,
installation details change. It would be
impossible to try to fit all possible
construction scenarios into this manu-
al. Because of this, only the most com-
mon applications are discussed. Each
contains examples and techniques for
the most popular variations.
Should a project call for a construction
detail not mentioned in this manual,
please feel free to contact Watts
Radiant for design assistance.
Frame Floors
Introduction
Of all the radiant applications, frame
floors offer the most installation flexi-
bility. Over 80% of all residential radi-
ant projects have at least one form of a
frame installation. Of these, the
Staple-Up
™
application is the most
common.
Frame floor projects allow for easy
installation of a radiant system, for
new construction or renovation. Even
though some installation details vary
from application to application, basic
design considerations remain the same.
The most important goal is to make
sure the Onix is in direct contact with
the subfloor.
The second most important detail for a
Staple-Up
™
application is to properly
install foil-faced batt insulation below
the tubing. If a non-foil-faced insula-
tion is used,
the system may operate
with a 25% loss of maximum heat
output and some (smaller) loss of effi-
ciency.
Other insulation can be used
instead of a fiberglass batt, however,
certain cautions need to be observed.
1. Tight seal. One of the largest areas
of heat loss with any underfloor
application is convective loss
through the band joists and other
perimeter areas. The tighter the
joist cavity, the better the system
will perform.
2. Foil Face. The foil on the
insulation will ensure most of the
heat and energy coming from the
tubing is reflected up to the sub-
floor where it is distributed. The
foil also spreads the heat out over
the subfloor. This in turn reduces
what has been called thermal strip-
ing.
3. Air Gap. A 2"–4" air gap is neces-
sary between the tubing and the
insulation. This air gap helps
increase the effective R-value of
the insulation while fully optimiz-
ing the ability of the foil insulation.
The main goal is to keep the tubing
from coming into contact with the
insulation. If contact is made, ener-
gy is no longer reflected upwards,
but rather, is conducted downward.
This can reduce the effective heat-
ing of the floor by 10% to 20%,
depending on the load conditions
and thickness of insulation.
4. R-Value. As a rule of thumb, an R-
Value of at least 4 times higher
than the floor is desired. For most
indoor conditions, an R-13, or a
3-1/2" batt should be used. When
installing over an unheated area,
exposed area or crawlspace, a
minimum R-19 or 6" batt should
be used.
Design Parameters
With any new or renovation project, it
is important to know the layers used in
the floor construction. As these layers
Frame Floors
Foil Faced
Joist
Sub Floor
Supply/Return Manifolds
Typical Staple-Up Application
Insulation