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Radiant Floor Heating

Additional reading

The health effects of installed infloor heating systems operating at excessive floor surface temperatures.
Part I & Part II
Thermal Environments


Click here to see the options available to conditions floors to your thermal satisfaction.

 


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2014 Radiant Flooring Guide
The Radiant Flooring Guide is the intellectual property of the Radiant Professionals Alliance, Published by BNP Media


Order hardcopy or view online version

  

Recommended floor temperatures for bare feet and for those wearing shoes: For additional support visit our visitor services page.

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Humans appreciate floors temperatures that are controlled to above 66˚F (19˚C) in cooling and below 84˚F (29˚C) in heating. When floors are conditioned within this range most people wearing normal footwear will enjoy having their feet on the floor. Based on research, 74˚F - 77˚F (23˚C - 25˚C) is a condition where the least amount of people will complain (appx. 6%) or the most amount of people will be satisfied (94%) (see below for comments on bare feet). This range is for people occupying spaces for 15 minutes or longer (ref.: ASHRAE Std. 55).


Figure 1. Recommended range of floor temperatures for those wearing normal footwear.[1] Bookmark and Share


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Figure 2. Floor temps for bare feet on different floor coverings. [2] Click table for larger image. Bookmark and Share

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Figure 3. Relationship between heating flux and surface temperatures at various operative temperatures. Click image for larger view. Bookmark and Share



Why do some floor coverings feel cooler or warmer even though they can be at the very same temperature. Courtesy of minutephysics. Bookmark and Share

Contact coefficient

 

One method of describing the influence of flooring on bare feet is by using the contact coefficient (b) which integrates flooring characteristics into a numerical value written as;
 

       b = √k р c 

where  

       k = conductivity

       p =density

       c = specific heat

Note how the higher the contact coefficient of the floor the more effective it will be at drawing heat out of the feet. Likewise the higher the contact coefficient the lower the fluid temperature required for heating and cooling all other elements being equal.

Contact coefficient for various floor coverings based on conductivity, density and specific heat

Flooring

Contact coefficient, b ( kCal/m2 hr0.5 C)

Steel

180

Concrete

25

Linoleum,

9

Oak wood

7

Pine wood

4

Cork

2

source: Fanger, P.O., Thermal Comfort: Analysis and Applications in Environmental Engineering, McGraw-Hill Book Company, 1970

From ASHRAE Handbooks: 

“The most extensive studies of the influence of floor temperature on feet comfort were performed by Olesen (1977a, 1977b), who, based on his own experiments and reanalysis of the data from Nevins and Flinner (1958), Nevins et al. (1964), and Nevins and Feyerherm (1967), recorded the following results. For floors occupied by people with bare feet (in swimming halls, gymnasiums, dressing rooms, bathrooms, and bedrooms), flooring material is important. Ranges for some typical floor materials are as follows: 

Textiles (rugs) 70˚F to 82˚F
Pine floor 72.5˚F to 82˚F
Oak floor 76˚F to 82˚F
Hard linoleum 75˚F to 82˚F
Concrete 79˚F to 83˚F 

To save energy, flooring materials with a low contact coefficient (cork, wood, carpets), radiant heated floors, or floor heating systems can be used to eliminate the desire for higher ambient temperatures caused by cold feet. These recommendations should also be followed in schools, where children often play directly on the floor. For floors occupied by people with normal indoor footwear, flooring material is insignificant. Olesen (1977b) found an optimal temperature of 77˚F for sedentary and 73.5˚F for standing or walking persons. At the optimal temperature, 6% of the occupants felt warm or cold discomfort in the feet. Figure 10 shows the relationship between floor temperature and percentage of dissatisfied, combining data from experiments with seated and standing subjects. In all experiments, the subjects were in thermal neutrality; thus, the percentage of dissatisfied is only related to the discomfort due to cold or warm feet. No significant difference in floor temperature was preferred by females and males.”

Note: In addition to ASHRAE Standard 55, the following also provide guidance to floor temperatures:

  • Radiant Panel Associations Guidelines to Panel Heating

  • Canadian Standards Association B214, Hydronic Heating Installation Standards

  • ISO 7730:2005 - Ergonomics of the thermal environment -- Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria


  1. (Adapted from ANSI/ASHRAE Standard 55 -2010, Thermal Environmental Conditions for Human Occupancy) (Copyright 2012, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Reprinted by permission from ASHRAE Standard 55-2010. This material may not be copied nor distributed in either paper or digital form without ASHRAE’s permission).

  2. Olesen, B.W., Thermal comfort requirements for floors occupied by people with bare feet, ASHRAE Transactions No. 2451, 1977, pp. 41–57 (ref.: Table 5) (available as a special archive request via ASHRAE Bookstore)

  3. Chrenko, F.A., The Effects of the Temperatures of the Floor Surface and of the air on Thermal Sensations and the Skin Temperature of the Feet, British Journal Industrial Medicine, 1957 January; 14(1): 13–21.

  4. Estimation of Comfort Conditions, The British Medical Journal, August 15, 1936
     


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