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IM-PR 566442 1114 (Design Manual)

1.4 Panel coverings

Like insulation, a radiant panel’s covering (e.g.,

gypsum for walls; carpet, tile or hardwoods for

floors) also affects its ability to deliver heat to a

conditioned space. Coverings with lower R-values

provide less resistance to the radiation of heat from

the panel into the conditioned space. Coverings

with higher R-values will require higher supply

temperatures or flow rates to deliver the same

amount of heat to a space. To optimize water

temperatures and promote efficient heat transfer,

minimize the R-value of floor coverings and

substrates (e.g., padding). Appendix G contains a

table of R-values for various panel coverings. To

determine the total R-value of a panel covering, add

the R-values of its individual components.

1.4.1 Hardwoods

Use of hardwood flooring over radiant hydronic

heating can be done successfully, provided

proper consideration is given to the selection and

installation of the hardwood. Detailed instructions

for installation of hardwood flooring products

over radiant floors are typically provided by

manufacturers and should be closely followed.

Generally speaking, there are four major

considerations for selection and installation of

hardwood floors over radiant hydronic heat:

1. Dimensional stability

2. Floor surface temperatures

3. Moisture

4. Subfloor

Dimensional stability

In general, floors with higher dimensional stability

will hold up better under a greater range of

temperatures and moisture levels. To choose a

dimensionally stable hardwood floor that will remain

attractive during the operation of radiant heating,

consider the following:

• Milling: Quartersawn are preferable to

plainsawn due to tendency to expand

vertically instead of horizontally.

• Width: Select narrower boards over

wider boards for less shrinking and

swelling. Quartersawn wideplank flooring

is acceptable, provided you consult the

wholesaler or mill where it was produced to

ensure proper storing and drying.

• Engineered products: More plies = greater

stability. Typically higher stability than solid

plank products, though exceptions may

exist for reclaimed woods that have a tighter

pattern of growth rings. Thin profiles and

lower R-values for some engineered products

versus solid plank products can improve heat

transfer to the room.

• Parquet products: Small pieces in these

floors generally result in less expansion and

contraction.

• Techniques to make gaps between boards

less obvious: strong grain patterns, beveled

edges, distressed finishes, dark colors.

• Species: Oak, walnut, ash, most soft woods

and teak have a reputation for stability;

hickory, beech, maple, Australian cypress

and bamboo are less stable.

Floor surface temperatures

For many builders, a reluctance to install hardwood

floors over radiant heat stems from problems

associated with incorrect control of the floor

surface temperatures. However, modern insulation

and building techniques allow a radiant floor to stay

cooler than the floor of the average sunroom while

satisfying the room’s heat load. When specifying

a hardwood floor, the floor surface temperature

should not exceed the lesser of manufacturer

recommendations, or 85°F or as otherwise

specified by local governing bodies. For CSA

requirements see Section 1.4.2.

Also be careful when using multiple or high

R-value area rugs over hardwood flooring. Your

radiant heating system must be designed with this

additional R-value taken into account in order to

perform properly. If the system was designed for

bare wood flooring, adding area rugs may lead to a

situation where heat output is diminished.

(CSA B214 Clause 14.2.1)

Floor surface temperatures shall not exceed

(a) 25°C (77°F) in areas where prolonged

foot contact with the oor is likely;

(b) 31°C (88°F) in dwellings or commercial

space;

swimming pools and foyers; and

(d) 35°C (95°F) in radiant panel perimeter

areas, i.e., up to 0.8 m (2.5 ft) from

outside walls.

1.4.2 Floor surface temperatures