APPENDIX H
RADIANT HEAT INSTALLATIONS
With radiant heat, the heat source is directly beneath
the flooring, so the flooring may dry out faster than a similar floor in a home with a conventional heating system.
Wood flooring can be installed over radiant heat as long as you understand radiant heat and how it can impact wood
flooring, what precautions to take, and what type of wood flooring to use.
Types of wood flooring that are best suited-for radiant heat subfloor are products
that possess improved dimensional stability such as:
•
Engineered wood flooring is more dimensionally stable than solid wood flooring.
• Certain species are known for their inherent dimensional stability such as
North American oak, American cherry, American walnut and others. Denser species such as maple and Brazilian cherry
are less stable.
• Quartersawn and rift-sawn
wood flooring is more dimensionally stable in width than plain sawn wood flooring.
• Narrow boards are more dimensionally stable than wide boards.
GENERAL RADIANT HEAT INSTALLATION GUIDELINES
• To minimize the effect that rapid changes in
temperature will have on the moisture content of the wood floor, NWFA recommends that an outside thermostat be installed.
If one is not present, suggest to your customer that this should be considered. Unlike conventional heating systems,
which switch on as needed, radiant systems work most effectively and with less trauma to the wood floor if the heating
process is gradual, based on small incremental increases in relation to the outside temperature.
• Subfloors should have proper moisture tests according to the moisture
testing procedures outlined in Chapter 3.
•
The essential requirement in proper applications of wood flooring over radiant heated systems is to avoid penetration
of the heating element. Radiant-heated subfloor systems can be concrete, wood or a combination of both. The type
of subfloor as described in the previous chapters determines subfloor preparation.
• If the subfloor is concrete and it has cured, turn the heat on, regardless
of season, and leave it on for at least 5-6 days to drive out residual moisture before installation of the wood
flooring. Some installation systems, particularly glue-down applications, require the heat to be reduced or even
turned off before installation of the flooring begins, so the adhesive does not cure excessively.
• With water-heated radiant-heat systems, a pressure test must
be performed and documented by a qualified plumber or the system installer prior to beginning the installation of the wood
flooring.
• If flooring materials that conduct heat
at different rates are on the same circuit or heating zone, check with the HVAC mechanical engineer before proceeding.
Copyright 2007 National Wood Flooring Association 21 Revised March
2007
Appendix H – Radiant Heat Installations
•
Radiant heat is dry heat. A humidification system may be necessary to maintain wood flooring in its comfort zone.
The following installation
and subfloor systems can be used successfully over radiant heat:
• 1. Glue-down, engineered or solid parquet
•
2. Floating engineered
• 3. Direct-nail,
solid wood or engineered wood flooring to wood subfloor
•
4. Solid T&G floor direct-nail to sleepers
•
5. Single layer of plywood on sleepers
• 6. Double
plywood floating subfloor
• 7. Loose-lay single
layer of 3⁄4” plywood cut in 16” planks staggered with 1⁄2” gap between laid perpendicular to
wood direction
GLUE-DOWN, ENGINEERED
OR SOLID PARQUET
NOTE: Follow manufacturer’s
installation instructions.
Adhesive
Engineered flooring
Install over approved subfloor. Refer
to Chapter 7, Parquet Installation and Chapter 8, Engineered Flooring Installation.
• Use an adhesive approved by the manufacturer.
• The heating system has to
be turned off before installation.
• The maximum allowable subfloor surface temperature is 85° F (29.44°
C). • Expect some heating season shrinkage.
Radient slab Radiant slab
Copyright 2007 National
Wood Flooring Association 22 Revised March 2007
Appendix H – Radiant Heat Installations
DIRECT NAIL, SOLID WOOD OR ENGINEERED
TO WOOD SUBFLOOR
NOTE: Follow manufacturer’s installation
instructions.
• Install over approved subfloor.
Refer to Chapter 8, Engineered Flooring Installation, and Chapter 9, Solid Strip & Plank Installation.
• Always check for subfloor moisture. See Chapter 3, Moisture Requirements
and Moisture Testing.
• Solid wood must be properly
acclimated to normal living conditions.
• All other
installation procedures are the same as outlined in Chapter 8, Engineered Flooring Installation, and Chapter 9, Solid Strip
& Plank Installation.
• Be sure fasteners are
not so long as to penetrate heating elements. • Maximum subfloor surface temperature-85° F (29.44° C).
Copyright 2007 National Wood Flooring Association 23 Revised March
2007
Appendix H – Radiant Heat Installations
SOLID T & G FLOOR DIRECT NAIL TO SLEEPERS
NOTE: Follow manufacturer’s installation instructions.
• The use of solid wood flooring 4 inches and wider is not recommended over sleepers. •
Solid wood must be properly acclimated.
• Cannot use shorts.
• Maximum subfloor surface temperature
- 85° F (29.44° C)
Vapor barrier 2x4 sleeper
wood flooring
Radiant tube Subfloor
3/4-in. solid Blind-nail flooring
SINGLE LAYER OF PLYWOOD ON SLEEPERS
NOTE: Follow manufacturer’s installation instructions.
Vapor 3/4-in. ACX or barrier 2x4 sleeper CDX plywood
Radiant tube
Blind-nail flooring to subfloor
• Solid
wood must be properly acclimated.
• Maximum subfloor surface temperature-85° F (29.44° C)
Copyright 2007 National Wood Flooring Association 24 Revised
March 2007
DOUBLE PLYWOOD
NOTE: Follow manufacturer’s
installation instructions.
1/2-in. ACX or 3/4-in. solid screw, nail or Vapor barrier Adhesive CDX plywood wood flooring staple 12" o.c.
• Solid wood must be properly acclimated.
• Maximum subfloor surface temperature - 85°
F (29.44° C)
FLOATING ENGINEERED
NOTE: Follow manufacturer’s installation instructions.
Recommended Glued Engineered Foam
vapor barrier joint flooring
• Install over approved
subfloor. Refer to Chapter 8, Engineered Flooring Installation.
• A 6 mil or better polyethylene vapor retarder should be installed over concrete subfloors. In some
cases, this may be part of the flooring underlayment.
•
A foam or resilient underlayment recommended by the flooring manufacturer must be installed prior to application
of the wood flooring.
• Use an adhesive
approved by the manufacturer for side and/or end joints. • Maximum subfloor surface temperature-85° F (29.44°
C).
Appendix
H – Radiant Heat Installations
Copyright 2007 National Wood Flooring Association 25 Revised March 2007