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Flooring 101 Home Floor Care and Repairs Problems Cautions for Radiant Installations

Cautions for Radiant Installations

TIPS for Installing a Radiant Heat Floor  p1                   
Installing Hardwood over radiant heat is slightly different from laying a typical Hardwood floor. It is important to have good communication and understanding with the radiant heat system designer. It is critical that everyone is notified of any work pertaining to installation, especially if specifications are changed. 
To ensure a superior end product, pay attention to the following factors before, during and after installation: Floor Temperature, Sub-floor, installation/routing of the system, Climate Controls, Moisture Content and *floor type.
Floor Temperature  - Provide the radiant heat system designer with the area dimensions, sub-floor style, wood floor selection and the desired temperature of each room. This will give her/him the information needed to calculate the necessary system supply water temperature. Do not allow the surface temperature of the finished flooring to exceed 85 F.
Operation - New radiant systems have control valves and other features that prevent the system from rapidly heating the floor. Older systems may or may not have these regulators. It is imperative that the user gradually increases the heat when the system is utilized. Rapid or sustained over heating may result in the bottom of the flooring shrinking faster than the top of the flooring causing cracking and possible delamination of Engineered boards. A faulty regulator or thermostat can even lead to surface blister damage.
Sub-floor - Work with the system designer to choose the option that best meets both of your needs. The heat system designer is responsible for the sub-floor installation, but you will want to be familiar with some styles. Direct contact of the tubing with the flooring is not recommended. Some sort of protective insulation is highly recommended. The following are five sub-floor options for radiant heat.
1. Stapled To Sub-floor - This is a common method. The water tubes are stapled onto the elevated sub-floor. Insulation is placed under the tubing. 
2. Sandwich Over Frame Floor - An approach used when you don't have access under the existing floor or when the underside of the floor can't be used, such as a second story over beamed ceilings. The tubing is laid onto the existing sub-floor. Furring strips (sleepers), that are somewhat higher than the tubing, are glued to the existing sub-floor. A new sub-floor is installed onto the furring strips. The new flooring is then installed onto the new sub-floor. 
3. Masonry Filled Sandwich Over Frame Floor with Fiberglass Insulation - This method provides fire resistance, sound dampening and thermal mass of a thin slab. Insulation is placed under the existing sub-floor. Fiberglass insulation is placed under the sub-floor. Furring strips are attached to the existing sub-floor, somewhat higher than the tubing. Concrete mix or gypsum covers the tubing. A new sub-floor is attached to the furring strips and the new flooring is installed onto the sub-floor. 
4. Masonry Filled Sandwich Over Frame Floor with Foam Insulation -This is another method used when access under the existing floor is impossible. It also offers fire resistance, sound dampening and thermal mass. A rigid insulation is placed between the sub-floor and the tubing. Furring strips are attached to the existing sub-floor. A concrete mix or gypsum covers the tubing. A new sub-floor is attached to the furring strips onto which the flooring is installed. 
5. Glue Down - Insure that the heating system is operating correctly and has been turned on for a minimum of 72 hours. Acclimate the flooring, outside of the box and plastic, until it reaches a moisture balance with the indoor climate. Use 100% urethane adhesives approved for radiant heat, and follow their directions as to trowel size and application. 

 *Installation                         P 2
 Consult the systems design to determine the tube network layout so you will know where the tubes are before you nail down the floor. It is best to have the tubing or heating spaced evenly between the sleepers, cover the sleepers with a minimum of 5/8" plywood, for proper heat transfer omit the felt or paper liner, nail the flooring onto the plywood at 8"-10" intervals. When the heating circuits are crossed over the center of a joist cavity, the system designer can use nail plates to protect the radiant circuits from being punctured.
Climate Controls  - The following climate controls should be operational before the flooring is installed to minimize expansion and contraction during and after installation:
Mechanical Humidity Control - The HVAC system should have mechanical humidity control. This will ensure stable relative humidity levels, thereby keeping the equilibrium moisture content of the flooring stable.
Heat Transfer Point Control - The system designer should install a set point control that will monitor the flooring's temperature. This set point control should either reduce the system temperature or temporarily cycle the system off to prevent over heating the flooring in case of equipment malfunction.
Exterior Thermostat - This is recommended to protect the perimeter of the system from condensation absorption during the spring and fall when rapid temperature changes may occur.
Moisture Content  - Once the sub-floor, heating system and climate controls have been installed and before bringing in the wood to acclimate, the heating system should be allowed to run for a minimum of 72 hours to further dry any hidden pockets of moisture or balance-out the dwelling's moisture content. Follow the Flooring Installation instructions for installing the floor. Know the moisture content of the sub-floor and the flooring, as this will have a profound effect on the end result of the installation. In this way, even wider boards can be used for radiant application you must however ensure the moisture content is dry 6-9% before installation, if not wider boards can gap dramatically. Do not install the flooring over green concrete or wet plywood. The flooring will pick up excess moisture from its environment.
Concrete Slab - The slab should be well aged before installation. Never install the flooring over concrete until the floor heating systems has been used to remove any residual moisture from the slab. A simple but less accurate method to determine the presence of excessive slab moisture is to tape a 4' x 4' section of plastic sheeting to the slab and turn on the heat. If moisture droplets appear under the plastic, heat the slab further. Repeat this test until no moisture is visible
Plywood Sub-Floor - Turn on the heating system to acclimate the plywood and bring the room to the proper relative humidity. Plywood is recommended for sub-floor material in radiant heat installations. Radiant heat companies do not recommend particle board sub-floors.
The flooring should be removed from plastic wrapped boxes and stacked in the room to acclimate the core to the room environment. Once the flooring reaches the desired moisture content (typically 3 to 7 days), you are now ready to install the flooring. 
In an effort to prevent shock to the flooring, do not store flooring in a garage, on bare cement floors or out buildings. In addition, it is highly recommended to use moisture meters to establish moisture values before installation.

 Floating floors are perfect for Radiant heat applications                                                                  - The following are some guidelines for floating engineered or laminate floors:
1.Acclimate the flooring outside of the boxes for 3-7 days in the final, humidity controlled, environment in which the flooring is to be installed. 
2.When installing over concrete, a vapor barrier (minimum 6-8 mil polyfilm) MUST BE used to prevent moisture migration to the flooring. Ensure that the vapor barrier seams are overlapped and taped and is continued 1 1/2 to 2 inches up all walls. Repair any damage to the vapor barrier before covering with flooring. 
3.Follow the manufactures guideline for expansion breaks required.
4.Use a high-density pad underlayment pad 
5. Use engineered or laminate flooring approved for radiant heat applications                            
6. Do not allow the surface temperature of the finished flooring to exceed 85 F. Follow manufacturer's instructions.

It is necessary to control Moisture or humidity within the work area to prevent expansion or shrinking of the floor. Maintain humidity between 30%-50% 

*Some species are more stable for radiant heat application than others are. See our "FLOODING 101" for recommended styles, species and related topics.

Technical & Installation  02/2016

Flooring 101 Home Floor Care and Repairs Problems Cautions for Radiant Installations