Note: Common to all diagrams is the barrier between the
slab and foundation or outside block wall. This is very
important to prevent the slab from conducting directly
to the outside.
Vapor barrier is optional, Electro Industries always
recommends because we've seen problems with too much moisture
coming through the floor. However, the insulation board
may be adequate in many areas.
The peripheral insulation is significantly more important
than the insulation under the slab. The key factor is
keeping the heat energy from escaping horizontally. Heat
energy will not go down more than about 18" to 24"
and becomes stable at that point.
Slab thermostats can be added at any time using Electro
Industries' electronic sensor. Sensor can easily be drilled
in with a 1/4" hole at a surface sensing point.
Reference sand bed technique, the domestic plumbing and
drain system can actually be in the sand above the tube/insulation
board. Often this simplifies the basic plumbing task and
allows simpler concrete installation techniques.
The rule of thumb and most common installation is 12"
on centers, with perhaps the outside first row or two
being closer. This is adequate for basic heating and basic
heat loss requirements.
However, in the case of ETS storage (again depending
upon the charge time versus storage time) the heating
source needs to be oversized by a factor of 1.2 to 1.5
to make sure the energy can be "pumped into"
the storage bed during the shorter off-peak hours. If
this is the case spacing also needs to apply to the multiplier.
In many cases 12" spacing just simply will not provide
enough tubing surface area to "pump in" the
required energy during a typical 12-hour charge time.
Electro Industries recommends 9" spacing or the installer
go through the actual calculations to make sure the tubing
can indeed produce adequate square foot Btu's for the
storage recharge requirement.