NBSIR 77-1263 DO NOT REM

Radiant Heating in Seamless

Flooring - A Feasibility Study

P. G. Campbell

M. A. Post

M. Godette

W. E. Roberts

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

July 1977

Final Report

Prepared for Office of Policy Development and Research

Division of Energy, Building Technology and Standards

Department of Housing and Urban Development

Washington, D. C. 20410

NBSIR 77-1263

RAIDANT HEATING IN SEAMLESS

FLOORING - A FEASIBILITY STUDY

P. G. Campbell

M. A. Post

M. Godette

W. E. Roberts

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

July 1977

Final Report

Prepared for Office of Policy Development and Research

Division of Energy, Building Technology and Standards

Department of Housing and Urban Development

Washington, D. C. 20410

U S. DEPARTMENT OF COMMERCE. Juanita M. Kreps. Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director
H,

.

"• ' v
TABLE OF CONTENTS

Page

A. INTRODUCE1 ION 1

B. OBJECTIVES 2 C. LITERATURE SURVEY 2 C.l Seamless Flooring 2 C.2 Radiant Heating Elements 3 C. 3 Radiant Panel-Seamless Flooring System. 4 C. 4 Summary 4 D. PERFORMANCE TESTS 4 D. 1 Materials Selection 6 D.2 Performance Tests on Seamless Flooring Systems..,, 9 D. 2 , 1 Abrasion Resistance 9 D

2 . 2 Resistance to Elevated Temperature 9 D . 2 . 3 Inpact Resistance 10

D. 2 . 4 Stain Resistance 10

D.2. 5 Flammability of Seamless Flooring Systems 10

D.2.6 Resistance to Moisture and Elevated Tanperature 10

D. 3 Performance Tests on Radiant Panels 10

D.3.1 Preparation of Radiant Panels... 10

D.3.2 Surface Temperature Characteristics of the Radiant Panels 11

D.4 Performance Tests on the Radiant Panel-Seamless Flooring System., 11

D. 5 Performance Tests on a Large Radiant Panel-Seamless Flooring System 12

E. RESULTS AND DISCUSSION 12

E. l Seamless Flooring Systems 12

E. 2 Radiant Panel Tests 13

E. 3 Radiant Panel-Seamless Flooring System. 13

E. 4 Larger Panel Tests 16

E.5 Cost Effectiveness of Radiant Panel-Seamless Flooring System.,,.. 22

F. SUMMARY 23

G. ACKNOWLEDGMENTS 24

H. REFERENCES 25

APPENDIX A - Identification of Areas for Future Research and Development 26

iii

Radiant Heating in Seamless Flooring - A Feasibility Study

P. G. Campbell, M. A. Post, M. Godette and W. E. Roberts

The purpose of this study was to determine the feasibility of using

radiant heating in seamless flooring as a supplemental heating source in

housing units. The resistance of twenty seamless flooring systems to

abrasion, flow, impact, flame, stain, moisture and elevated temperature were evaluated using laboratory tests. Power requirements and the

magnitude and 'uniformity of surface tenperatures of nine electrical heating

elements , functioning as radiant heating panels, were experimentally determined and evaluated. The radiant heating panels were coated with selected

seamless flooring systems and the performance characteristics of the

radiant panel-seamless flooring system were evaluated. The report contains

a summary of test results demonstrating the feasibility of the radiant

panel-seamless flooring system and the identification of areas for future

research.

Key words: Electrical heating elements; materials performance; radiant

panel-seamless flooring system; seamless flooring; temperature characteristics.

A. INTRODUCTION

The problems of energy conservation are of rational concern. They are also of importance

to the Maintenance Engineering Branch of Housing Management (HUD) since much energy is used

in the public housing which they maintain. Many public housing units have a disproportionate

share of the elderly and the very young and adequate tenperatures are especially important

for these occupants. Overall, the availability of adequate and economical heating sources has a direct bearing on the health and comfort of all housing occupants.

A novel approach to the supplemental heating of housing units is through electrical

heating elements in a seamless flooring system, A possible advantage of radiant heating is

•that its use may permit the reduction of ambient tenperatures without causing discomfort to

housing occupants. In addition, it is expected that the low operating temperatures should

lead to safe and durable heating systems. However, there are a number of questions about

the use of radiant heaters in seamless flooring installations which need to be answered

before their use can be recommended. These concern 1) cost effectiveness, 2) safety, and

3) compatibility between the seamless flooring and the heating element. These questions were addressed in the project described in this report.

1
B. OBJECTIVES

The objectives of the report are as follows:

1. to prepare a literature survey on the feasibility of a radiant panel-seamless

flooring system.

2. to prepare and evaluate the performance of a small-scale laboratory system

constructed from coirmercially available seamless flooring systems and radiant

heating components

.

3. to recommend heating components and flooring finishes which are likely to

provide an effective heating system.

4. if the radiant heating concept is feasible, to identify and recommend areas

for future research and development.

C. LITERATURE SURVEY

The survey of the literature applicable to the radiant panel-seamless flooring system was divided into three broad categories 1) seamless flooring, 2) radiant heating elements,

and 3) the radiant panel-seamless flooring system. Sources of information included the

1974 Directory and Buying Guide Issue of Flooring , the Association of Seamless Applicators

(ASA) , National Association of Decorative Architectural Finishes (NADAF) , the Seamless

Systems Manufacturers' Committee of the National Paint and Coating Association (NPCA)

,

National Electrical Manufacturers Association (NEMA) , Underwriters' Laboratories (U.L.),

Electrical Research Association (ERA-UK) , and the Emerson Electrical Institute. In addition,

the following computer data bases were utilized: Chemical Abstracts, NTIS, Compendex, and

NAL/Cain.

C. 1 Seamless Flooring

The modem seamless flooring system was developed in Germany in the 1940 's and introduced

into the U.S.A. in the early 1960's [1]. These systems are used in apartments, homes,

hospitals, schools, offices, cafeterias, and nuclear plants [2, 3] . The advantages of

using seamless flooring include easy maintenance, abrasion, impact and chemical resistance,

moisture resistance, and the availability of a wide variety of decorative patterns [2, 3, 4]

.

2
The floor coating may be based on urethane, epoxy, polyester, or acrylic resins or in

various resin combinations . Aggregates such as vinyl chips, metallic chips, quartz, and

marble may be embedded into the base coat for decorative purposes. While such systems have

been installed over many substrates, e.g., concrete, plywood, and vinyl tile, careful

preparation of the substrate is essential for successful installation. Detailed instructions for substrate preparation are given in the Association of Seamless Applicators Handbook for Seamless Flooring [5] as well as in the descriptive literature provided by manufacturers of seamless flooring components. The many polymeric types of seamless flooring

(listed as monolithic flooring) are listed in the 1973 Directory and Buying Guide Issue of

Flooring [6] .

C.2 Radiant Heating Elements

Radiant heaters transfer radiant energy in the infrared range to objects and surfaces

in the line of sight from the radiation source. Radiant electrical heaters may be placed

in two broad categories, a) low intensity heaters which operate at temperatures less than

500°F (260°C) and b) high intensity heaters which operate at temperatures greater than

500°F (260°C) [7] . Low intensity radiant heaters include ceiling cable, cable (or panels)

in the floor, ceiling panels, and wall panels; their heating elements consist of electrical

resistive wires, films, or ribbons. High intensity heaters are beyond the scope of this

project, but examples are quartz lamp heaters, infrared lamps, open-wire ribbon and glass

panel heaters.

With few exceptions, building code authorities in the U.S.A. require that electrical

wiring and equipment in buildings, including radiant heating cable and panel installations,

comply with applicable provisions of the National Electric Code (NEC) . The NEC does not

permit heating cables in walls; heating cables are permitted on dry board, in plaster and on concrete ceilings. The NEC permits both panels and cables to be installed in floors,

provided they are in poured concrete or masonry 18]

.

Protection must be provided against electric shock, fire hazards, contact with electrical

conductors, and the effects of mechanical abuse, corrosion, and vibration. Innovations in

electrical systems would have to be approved by NEC before any use beyond the prototype

stage. The use of safety devices such as ground fault circuit interrupters and the use of

voltages less than 40V might be required.

The U.L. Electrical Appliance and Utilization list was used to identify manufacturers

of electrical radiant heating cables and panels 19] . Electrical radiant heating floor

systems are used extensively in Europe and the Electrical Research Association (ERA) list

of radiant heating sources was utilized to identify foreign manufacturers. In addition,

innovative heating elements included a conductive nonwoven graphite fabric, polyesterlaminated heating elements and conductive paints.

3
C.3 Radiant Panel-Seamless Flooring System

The literature surveyed showed the radiant panel-seamless flooring system to be

innovative. However, Salter [10] has described a quick response system generally called

the "under floor coverings heating method" which utilizes electric cable floor heating and

where the quick response system reaches acceptable temperature wnthin 20 minutes after the

power is turned on. It has apparently been used with other floor coverings such as rugs,

wood parquetry, and vinyl tile. Figure 1 is an adaptation of a Salter drawing relating to

radiant heating in flooring and the potential use of seamless flooring as part of the

system.

An Australian study [11] investigated the physiological aspects of electrical radiant

heat. Among their conclusions were the following: 1) in order for the human body bo be

comfortable, the body should not lose heat to the environment, 2) special thermal sensitivities of the body are related primarily bo the head and feet, 3) extended heating of the

head by radiation leads to discomfort and possible distress, 4) the feet and legs become

colder as the ambient temperature falls below 60°F (16°C) because of restriction of blood

flow to the legs and the feet are likely to feel uncomfortable if ambient conditions exceed 80 °F

(27°C) . The studv concluded that the rate at which heat is released from a heated floor should

be such that the floor temperatures are a little below 80 °F (27°C)

.

C. 4 Summary

The literature survey of seamless flooring systems indicated that these systems are

available in a wide variety of compositions of base coat, glaze coat, finish coat, and the

decorative aggregates. While the majority of systems utilize polyurethane resins in the

finish coat, other systems included water-thinned urethane, epoxy, acrylic, and moistureresistant solvent-thinned urethane resins.

The review of the literature on heating elements for potential use in a radiant panelseamless flooring system indicated that no data on cost-effectiveness studies were available.

An innovative electrical system would have to be approved by the National Electric Code

(NEC) for any use beyond a prototype study. At present, NEC only approves electrical

radiant heating elements buried six inches in a concrete slab.

D. PERFORMANCE TESTS

The evaluation of the seamless flooring system involved test methods and procedures

which would simulate conditions encountered in use in public and other housing. The test

procedures used were generally modified from ones given in Military Specification MIL-D-3134F,

"Deck Covering Materials," Federal Specification TT-C-001685, "Coating System - Decorative

4
Figure 1.

RADIANT

HEATING

IN

SEAMLESS

FLOORING

a.

ccooaoo

ccoo

_J

Lt_

lx! f—

lx! CCooo 5
and Protective, Seamless," in relevant ASTM standards or in Fed. Test Method Std. No. 141a.

Tests included abrasion resistance, resistance to elevated temperature (flow or slip) , impact

resistance, stain resistance, flammability and heat stability. Since the radiant panelseamless flooring system would be expected to be used with ground fault circuit interrupters

and at voltages less than 40V, electrical shock measurements were not determined. However,

these measurements would be expected to be included in any acceptance tests.

While seamless floorings (monolithic flooring) have been used since the early 1960's,

their suitability as coatings for radiant heating elements have not been established. In this

phase of the study, the performance of the radiant heating panel was studied separately and

in conjunction with seamless flooring coating systems. Voltage and power requirements,

surface temperatures and uniformity of heat distribution, and their effect on the seamless

flooring resins were of concern in studying the radiant heating panels.

Each seamless floor system was prepared using the procedure recommended by the manufacturer.

However, every system fits into the ASA-PFU-S category, and thus, the thickness of each system

was 35 mil (0.889 mm) minimum as described in ASA "1973-74 Specifications Handbook for

Seamless Flooring."

The steel panels used as substrate for many of the performance tests were from Type R,

Q-Panels, 0.032 in (0.813 mm), cold rolled, low carbon steel (ASTM D609, Type 1-B) . The

plywood panels used as substrate for the performance testing of the radiant heating elements were 3/4 in x 24 in x 24 in (19 mm x 609 mm x 609 mm) conforming to Exterior AC Grade,

Species Group 1 (Voluntary Product Standard PS 1-74) , American National Standard

A 199.1-1974)

.

D.l Materials Selection

The seamless flooring systems used in this feasibility study were selected to give a wide range of generic resin types, e.g., urethane, acrylic; but none of the systems was

specifically designed to be heated for any length of time or for use with heating elements.

Also, the heating elements used in the study were designed for ceiling and wall use rather

than for use on floors.

The materials used in the performance tests described here are listed by numerical key given:* as follows and the order of application for each system is *

* Certain commercial equipment, instruments, or materials are identified in this paper in

order to adequately specify the experimental procedure. Ino case does such identification imply recommendation or endorsement by the National Bureau of Standards, nor does it

imply that the material or equipment identified is necessarily the best available for the

purpose.

6
System Manufacturer

#1 A. Epoxy base coat

B. Epoxy resin glaze

C. Granules

D. Epoxy sealer

#2 A. Epoxy base coat

B. Vinyl chips

C. Polyurethane glaze

#3 A. Epoxy base coat

B. Seal coat

C. Vinyl chips

D. Epoxy glaze

#4 A. Epoxy base coat

B. Seal coat

C. Vinyl chips

D. Urethane glaze

#5 A. Epoxy base coat

B. Granules

C. Epoxy top coat

#6 A. Acrylic base coat

B. Vinyl chips

C. Acrylic top coat

#7 A. Urethane base

B. Urethane top coat

#8 A. Epoxy base

B. Vinyl chips

C. Epoxy seal

D. Epoxy glaze

#9 A. Epoxy base

B. Vinyl chips

C. Urethane top coat

#10 A. Epoxy base

B. Granules

C. Epoxy top coat

#11A A. Urethane base coat

B. Urethane top coat

#11B A. Epoxy base coat

B. Urethane top coat

General Polymers Corp.

3925 Huston Avenue

Cincinnati, OH 45212

General Polymers Corp.

3925 Huston Avenue

Cincinnati, OH 45212

General Polymers Corp.

3925 Huston Avenue

Cincinnati, OH 45212

General Polymers Corp.

3925 Huston Avenue

Cincinnati, OH 45212

Lehn & Fink Industrial Products

Division

Sterling Drug, Inc. Montvale , NJ 07645

Zurock , Inc

.

7300 Natural Bridge

St. Louis, MO 63121

Wilmington Chemical Corp.

Pyles Lane

Wilmington, DE 19899

Dur-A-Flex, Inc

.

100 Meadow Street

Hartford, CT 06114

Cambridge Tile Mfg. Company

P.O. Box 71

Cincinnati, OH 45215

Cambridge Tile Mfg. Company

P.O. Box 71

Cincinnati, OH 45215

M-R Plastics & Coatings Inc. 11460 Dorsett Road

Maryland Heights, MO 63043

M-R Plastics & Coatings Inc. 11460 Dorsett Road

Maryland Heights, MO 63043

7
#12

#13

#14

#15

#16

#17

#18

*#19

#20

A. Urethane base coat

B. Vinyl chips

C. Urethane glaze coat

A. Epoxy base coat

B. Vinyl chips

C. Epoxy top coat

A. Epoxy base coat

B. Vinyl chips

C. Epoxy-acrylic glaze coat

A. Epoxy base coat

B. Vinyl chips

C. Epoxy glaze coat

A. Epoxy base coat

B . Vinyl chips

C . Urethane glaze

D. Urethane glaze with UV filter

A. Epoxy base coat

B. Granules

C . Urethane glaze

D. Urethane glaze with UV filter

A. Epoxy base coat

B. Epoxy intermediate coat

C . Vinyl chips

D. Urethane top coat

A. Epoxy base coat

B. Modified urethane top coat

A. Epoxy base coat

B. Vinyl chips

C. Sealer coat

D. Epoxy top coat.

Southern Imperial Coatings

Corp.

16362 Chef Menteur Highway

New Orleans, LA 70129

McDevco Inc. 27692 Camino Capistrano

Laguna Niguel, CA 92677

Key Laboratories

1181 Baskins Road

Largo, FL 33540

Readco Industries, Inc. Ash Street

Reading, MA 01867

Peterson Chemical Corp.

704 South River Street

Sheboygan, WI 53081

Peterson Chemical Corp.

704 South River Street

Sheboygan, WI 53081

Acme Chemicals & Insulation

Company

Div. of Allied Products Corp.

P.O. Box 1404

New Haven, CT 06505

Mobay Plastics & Coatings Div

Mobay Chemical Corp.

Penn Lincoln Parkway West

Pittsburgh, PA 15205

General Polymers Corp.

3925 Huston Avenue

Cincinnati, OH 45212

The decorative chips or aggregates used were those supplied by the manufacturer.

The identifications and descriptions of the heating elements are as follows:

Number Description Manufacturer

H-l Conductive nonwoven graphite fabric Union Carbide Corp.

Parma Technical Center

P.O. Box 6116

Cleveland, OH 44101

* Available in pilot plant quantities.

8
H-2 Acrylic conductive paint Chomerics

77 Dragon Court

Wbburn, MA 01801

H-3 Epoxy conductive paint Chomerics

77 Dragon Court

Woburn, MA 01801

H-4 Acrylic conductive paint Hunterlec-USA

P.O. Box 53

Markham, VA 22643

H-5 Vinyl-coated heating element Electric-Heat Company

Johnson City, TN 37601

H-6 Copper mesh over vinyl-coated

heating cable

Berko Electric Mfg. Corp.

Michigan City, IN 46360

*H-7 Polyester-laminated heating

element

E.O. DuPont de Nemours

1007 Market Street

Wilmington, DE 19898

H-8 Prefabricated metal radiant

heating ceiling panel

Berko Electric Mfg. Corp.

Michigan City, IN 46360

**H-9 Foil elements in resinimpregnated glass cloth

Cooperheat

3345A Newport Boulevard

Newport Beach, CA 92663.

Performance Tests on Seamless Flooring Systems

D.2.1 Abrasion Resistance . The method for the determination of the abrasion resistance was

that described in Method 6192, Fed. Test Method Std. No. 141a. The 20 coating systems were

each applied on 4 in x 4 in (100 mm x 100 mm) steel panels with center hole and samples were made in triplicate. For each abrasion resistance determination a load of 1,000 g and

abrasive calibrase wheels, No. CS-17, were used with the Taber Abraser. Specimens were

abraded for 1000 cycles and the weight loss was recorded to 0.1 mg.

D.2.2 Resistance to Elevated Tanperature . The procedure used for the measurement of flow

or slip was that described in 4. 7. 5.1 of MIL-D-3134F. For each of the 20 seamless floorings,

the carplete system was applied to a steel panel (6 in x 2 in (150 run x 50 irm) ) , cured,

scribed, and placed vertically in an oven at 158°F (70°C) for 5 hours. The difference

between the scribe mark and reference edge before and after heating is a measure of flew or

slip. The measurements were taken to 0.0001 in (0.0025 nm) .

Available in pilot plant quantities.

Designed for use without additional coating.

9

**
D.2.3 Impact Resistance . The method for the determination of the impact resistance was

that described in ASTM D2794, Resistance of Organic Coatings to the Effects of Rapid

Deformation (Impact) . Each coating system was applied to a steel panel and the impact

tests were performed with the coated side up. The largest impact at which failure did not

occur was determined.

D.2.4 Stain Resistance . The method used for the determination of stain release of the

seamless flooring was, generally, that described in ASTM D1308, Effect of Household Chemicals on Clear and Pigmented Organic Finishes. Glass rings, 1 in I.D., 1/2 in height (25.4 mm

I.D., 12.7 mm) were sealed to the surface with a polyurethane sealer. After curing of the

sealer for 24 hours, 1 ml of the stain was placed in the sealed ring and the ring was

covered immediately with a watch glass. After 16 hours, the watch glass was removed, the

stains were washed off and any alteration to the surface was noted. The following stains were used: detergent, i.e. 5% Ivory Flakes, amyl acetate; acetone; coffee; mustard; tea; Mercurochrome; shoe polish; felt tip marker.

D.2.5 Flammability of Seamless Flooring Systems . The procedure used for the determination

of the flammability was, generally, that described in ASTM D635, Flammability of SelfSupporting Plastics. Test specimens were 5 in by 1/2 in (127 mm x 12.7 irm) and were

approximately 35 mils in thickness of the seamless flooring system beomg tested. The

results were reported as rate of flame spread.

D.2.6 Resistance to Moisture and Elevated Temperature . The procedure for the measurement

of resistance to moisture was modified frcm that described in 4.7.7 of MIL-D-3134F. Each

seamless flooring system was applied to a steel panel and the panels were cured for 48

hours. The coated panels were then immersed in distilled water for 48 hours. Immediately

after immersion, the panels were exposed to an oven temperature of 158 °F (70°C) for 5 hours. The samples were examined for evidence of cracking or other failure.

D. 3 Performance Tests on Radiant Panels

D.3.1 Preparation of Radiant Panels . Since the heating elements differed markedly,

descriptions for the preparation of the radiant panels (3/4 in x 24 in x 24 in (0.02 m x

0.6 m x 0.6m)) follow:

The conductive fabric (H-l) was furnished as part of a roll. The fabric was spread over the plywood panel and copper strips (10 mil x 2 in x 24 in (0.0025 m x 0.05 m x 0.6m)) were used as electrodes. The copper strips were stapled at opposite ends of the panel. It

should be noted that the fabric was extremely fragile.

10
The conductive paints (H-2, H-3, and H-4) were applied to the plywood panel in accordance

with the manufacturer's directions. Copper electrodes, as described previously, were

affixed at opposite ends of the panel.

The conductive heating cables (H-5, H-6) were each placed in parallel channels routed in

the plywood panel since it was desired to keep the surface as flat as possible. The "S" pattern for the routed channel was approximately 3/16 in (5 mm) deep, 2 in (50 mm) on center

and 1 in (25 mm) from the edges of the panel. Aluminum foil 0.001 in (0.025 mm) was used to cover the panel.

The polyester laminated heating element (H-7) of approximately 1/8 in thickness was a self-contained unit consisting of conductive material and aluminum electrodes laminated

between 2 layers of plastic. The prefabricated metal heating panel (H-8) had heating

cables spaced 2 inches apart underneath the metal skin. This system was fabricated for use on ceilings and was used in this study as a uniform substrate to monitor the performance of

the seamless flooring coatings applied to the outer metal skin. The heating panel (H-9) was also prefabricated, but it consisted of a heating element (wire) encased in fiberglass

polyester resin.

D.3.2 Surface Temperature Characteristics of the Radiant Panels . The purpose of this test was to produce a panel surface temperature of approximately 80°F (27°C) and to measure the

temperature uniformity of the radiant panels both uncoated and coated with the seamless

flooring system.

A variable step-dcwn transformer was used to control the applied voltage. A voltmeter

and ohmeter were used to measure the applied voltage and the approximate power consumption

of the resistive heating circuit.

Surface temperatures were measured by using a digital surface pyrometer and uniformity

of temperature was measured by scanning the surface with an infrared television camera. Use of a camera attachment to record the television image afforded a permanent record of

the surface temperature uniformity.

D.4 Performance Tests on the Radiant Panel-Seamless Flooring System

After the surface temperature characteristics and pcwer requirements of the nine

uncoated radiant panels were obtained, quarters of each of the panels were coated with four

of the more premising seamless flooring systems (lib, 17, 19, and 20) applied in 1 sq ft

sections. Temperature and pcwer measurements were repeated on the systems

.

11
Based on the overall performance tests, the radiant panel-seamless flooring systems

with the heating elements H-2 and H-4 were chosen to be heated continuously for one month

at 40 volts. Impact (ASTM D2794) , 60° gloss (method 6101, F.T.M.S. No. 141) , and color

difference (method 6123, F.T.M.S. No. 141) measurements were made on the coatings.

D. 5 Performance Tests on a Large Radiant Panel-Seamless Flooring System

The conductive paints (H-2 and H-4) ware applied to plywood panels (3/4 in x 48 in x

96 in (0.02 m x 1.2 m x 2.4 m) )

.

Copper strips (10 mil x 2 in x 48 in (0.00254 m x 0.05 m

x 1.2 m) ) were used as electrodes and were stapled at opposite ends of the panels

.

The surface characteristics of the radiant panels were determined as per D.3.2. After

the surface temperatures and energy requirements were obtained, the panel coated with the

conductive paint H-4 was coated with the seamless flooring system 20. Temperature and

power measurements were repeated on the system.

E. RESULTS AND DISCUSSION

E.l Seamless Flooring Systems

The performance characteristics of the seamless flooring systems are tabulated in

table 1 for abrasion and stain resistance, flow, impact resistance, flame resistance, and

resistance to moisture and elevated temperatures

.

Definite differences in the abrasion resistance of the various systems can be seen in

table 1. There were more systems with urethane topcoats (Nos. 2, 4, 11a, lib, 15, 17, 19)

than with epoxy topcoats (Nos. 5, 10, 13, 20) that had a weight loss of less than 0.1 g per 1000 cycles. However, there were more urethane systems under consideration. Also, the

decorative chips may have had an effect on the abrasion resistance of the systems tested.

The resistance to flow or slip of all systems was high, with only one system (No. 18)

having a movement of as much as 0.006 in (0.0152 mm) under the test exposures.

The impact resistances of the seamless flooring systems were greater than those of the

vinyl tiles. However, the urethane systems seemed to have greater impact resistances than

the epoxy systems, e.g. most epoxy systems were less than 40 inch pounds (4.5 Nm) . The

seamless flooring systems were more resistant to stains than vinyl tiles, but acetone and

amyl acetate did dissolve most of these materials after 16 hours of exposure.

12
Test method ASTM D635 was used to test the flame resistance and to screen out the more

flammable systems . Hcwever, it is not established how well this test relates to flammability

of materials in practice.

Generally, all seamless flooring systems were affected adversely during the resistance

to moisture and elevated temperature test. This test was judged as too severe since the test was performed at 158°F (70°C) and floor temperatures in actual use would be belcw 80°F (27°C) . This test would have to be modified for it to be used to simulate realistic exposure conditions.

After reviewing the data in table 1 for desired performance characteristics, four

systems were selected for use in the radiant panel tests. The selection was based upon

arbitrary performance criteria of abrasion resistance less than 0.08 gm weight loss, flow

less than 0.0005, impact resistance greater than 40 inch-pounds (4.5 Nm) , good stain

resistance, flame spread <2 inches per minute, and resistance to moisture and elevated

temperature. The systems were lib (acrylic base, urethane topcoat) , 17 (epoxy base, urethane

topcoat) , 19 (epoxy base, modified urethane topcoat) , and 20 (epoxy base and topcoat)

.

E.2 Radiant Panel Tests

The radiant panels all produced a very uniform surface temperature as measured both by

the digital pyrometer and infrared television camera with the maximum temperature variations

being 8°F (4°C) . An illustration of the infrared television camera measurements is given

in figure 2. The heating elements H-2 and H-4 required less than 40 volts to raise the

surface temperature 10 °F (6°C) above ambient temperature (see table 2 for system measurements)

.

It should be noted that heating elements H-5 and H-6 were designed to be operated at 110

volts and heating elements H-7 and H-8 were designed to be operated at 230 volts. Also,

heating elements H-5 and H-6 were each conductive heating cables placed in a routed channel

(3/16 in (5 mtn deep)) of the plywood panel, and the different geometry of the system and

the aluminum foil covering undoubtedly had some affect on the surface temperatures. Heating

2 systems H-5 and H-6 required 1.6 and 2.1 watts/ft degree C rise, respectively, vhich was

higher than that of any other system. However, the differences in the effectiveness of the

heat transfer of these systems is not completely attributable to the different design factors

mentioned.

E. 3 Radiant Panel-Seamless Flooring System

Application of the four seamless flooring systems to the nine heating systems allowed

for a subjective appraisal of the appearance and cornpatibility of the combined systems. In

all cases, there was excellent compatibility or adhesion between the seamless flooring system

and heating element. The appearance of the system containing heating element H-l was

irregular due to disruption of the fragile fabric during coating application. This was

also reflected in the uneven heat distribution and "hot spots" as seen when heating the

combined system. The appearances of the systems containing heating elements H-2, H-3, and

H-4 were very uniform. Application of the coating increased the electrical resistance of

13
Table

1.

Results

of

Performance

Tests

of

Seamless

Flooring

Systems

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late

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Inchpoundforce

=

0.113

Nm.
Cold 5°C Range Hot

Heating Element H-4

Cold 5°C Range Hot

Heating Element H-6

Figure 2. Infrared television measurements on selected heating panels showing temperature

distribution. The temperature scale is shown at the bottom of each.

15
the system and lowered the surface temperatures for a given applied voltage. The appearance

of the systems containing heating elements H-5 and H-6 were not completely uniform as the

routed channels for the heating elements were visible. This effect could probably be overcome by the use of heavier gage foil or with thin steel plate. The appearance of the

system containing heating element H-7 was also not uniform, and was due to problems in

uniformly adhering the heating element to the plywood substrate. It should be noted that

this heating system is designed for ceiling application. Heating system H-8 was uniform

because of its unitized construction. The appearance of the system containing heating

element H-9 was very uniform since the coating systems were applied to a rigid fiberglasspolyester sheet. It would be expected that appropriate modifications to heating elements

H-l, H-5, H-6, and H-7 would result in a smooth substrate capable of being coated to a uniform appearance.

The power requirements to raise the panel surface temperatures from about 72°F (22°C)

to approximately 80°F (27°C) ranged from about 2 to 6 watts/ft^ (about 2.2 to about 170 watts/m^)

.

However, the upper limit observed was for heating element H-l where local hot spots developed

because the uniformity of the nonwoven conductive fabric was disrupted during the coating

process. These values are listed in table 2.

The coated panels of heating elements H-2 and H-4 were heated for one month continuously

at an applied voltage of 40 volts to determine the stabilities of the systems to prolonged

heating. The surface characteristics of the seamless flooring coating systems were examined

for changes in 60° gloss, color change, and impact resistance. The results are tabulated

in table 3. There is a decrease in impact resistance and noticeable color change in the

epoxy (No. 20) and the urethane (No. lib) systems which could indicate a heat-induced

chemical instability 'while systems Nos. 17 and 19 appeared to be unaffected by the prolonged

heating. There was no pattern discerned in the gloss changes for the different coatings;

however, the changes in gloss were not considered significant.

E.4 Larger Panel Tests

In addition to the heating tests on the coated panels of heating elements H-2 and H-4,

larger panels (3/4 in x 48 in x 96 in (0.02 m x 1.2 m x 2.4 m) ) were prepared of the same heating elanents (see table 4 for system measurements and figure 3 for infrared television

measurements of the systems) . System H-2 had a high resistance between electrodes which is

not clearly understood. A possible explanation may be chemical interaction between the seamless

flooring system and the conductive paint. The larger variation in panel temperature in system

H-2 may be explained by problems in the uniformity of the coating application. Since it was

not possible to raise the panel temperature of system H-2 to approximately 80°F (27°C) without

using higher voltages, seamless flooring was applied only to system H-4. The radiant panelseamless flooring system was tested for comfort by having the authors walk on the panel in their

stocking feet and varying the voltage applied to the panel (see figure 4) . Generally, it

16
Table

2.

Results

of

Heating

Tests

of

Radiant

Panels

and

Radiant

Panel-Seamless

Flooring

Systems

a)

(A (3 V

$

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17
Table 3. Surface Characteristics of Radiant

Panel-Seamless Flooring Systems (Nos. 2 and 4)

after Heat Stability Test (1 month, 40V)

Impact Resistance

Heating Coating Change in Change in inch-pounds*

System System 60° Gloss Color, AE Before After

H-2 lib +4.0 6.1 80 18

17 -5.4 .6 80 80

19 +3.2 .7 80 80

20 -9.7 1.5 40 6

H-4 lib -2.6 4.7 80 20

17 +3.8 .6 80 80

19 +3.3 .4 80 80

20 +5.2 2.6 40 4

* Inch-pound-force = 0.113 Nm.

18
Table

4.

Results

of

Heating

Tests

of

Radiant

Panels

(0.02

m

x

l.i

and

Radiant

Panel-Seamless

Flooring

System

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19
Cold 1°C Range 60 Volts Hot Cold 10°C Range 40 Volts Hot

Figure 3. Infrared television measurements on large panels showing temperature

distribution. The temperature scale is shown at the bottom of each.

20
Figure 4. Large Radiant Panel-Seamless Flooring System

21
was comfortable when the surface temperature was less than 90°F (32°C) . The variability in

resistance and surface temperature in these moderate scale-up tests illustrates the necessity

for uniform film application and good electrical connections.

E.5 Cost Effectiveness of Radiant Panel-Seamless Flooring System

Since the heating elements in the radiant panel-seamless flooring system are of the

resistive heating type, and assuming an efficiency of 1.0, the cost of electricity delivered

to the conditioned space area is $.8 8/therm or approximately twice that of gas ($. 40/therm) or oil ($. 47/therm) [12]. These costs are typical in the Washington, D.C. area at the present

time. Savings in electrical consumption are possible by heating only occupied living areas

and by utilizing the quick response heating characteristics of the system. A potential use of

the system would be in a retrofitting process where it would supplement an inadequate existing

heating system. The low thermal lag time for heating might possibly result in lcwer energy

consumption by a reduction in physiological needs for heating by an occupant. Clinical studies,

involving occupants in residential housing, should be made to validate this premise. Also,

comparison should be made between room-controlled electrical heating units, which generally

are at the rocm perimeter, and the radiant panel-seamless flooring system to determine any

differences in energy consumption and physiological needs.

The installation and maintenance costs of the radiant panel-seamless flooring system

which uses conductive paints as the heating element appear to be attractive, especially in

a retrofitting process. Installation costs of the heating elements would require connections

to the house electric power and each area to be heated would probably require a ground

fault circuit interrupter for safety purposes and these costs of installation would be similar

for all systems. Installation costs of the conductive paints should be comparable to that

2 of interior paints which have an estimated installation cost of $.10-.17/ft [13]. The

installation cost of the conductive paints would be approximately half the cost of the

polyester-laminated heating element [14] and much less than the cost of heating cable

installation [13] . Installation costs for the seamless flooring systems are comparable to

other flooring systems, e.g. vinyl tiles, wood, and less than carpeting [13] . These

seamless coatings are considered durable and relatively easy to repair.

The conductive paints were compatible with the seamless flooring systems. They could

be considered encapulated into the seamless flooring systems. Thus, the durability and

maintenance of a conductive paint would be similar to that of the seamless, flooring rather

than as an interior paint. The longevity of the seamless flooring conductive paint heating

element system may be estimated at approximately 10 years, but the effects of long term

heating on the radiant panel-seamless flooring system needs evaluation before a judgment on

life cycle costing can be made. Repair of heating elements just beneath the seamless

flooring should be less costly than the repair of radiant heating elements embedded in

22
concrete. The power requirements for conductive paints used as heating elements are relatively low; they were determined to be 3.1 to 5.3 watts/m 'degree C rise. However, the

cost effectiveness is dependent on the possible reduction in ambient temperatures and this

is dependent on the results of longer term physiological testing such as the effects of

floor temperatures on comfort.

F. SUMMARY

The following items summarize the general conclusions of this feasibility study:

The radiant panel-seamless flooring system studied appear to be feasible

for use as quick response heating systems; however, larger scale, longer

time tests would be needed before implementing their use.

° The resistance of twenty seamless flooring systems to abrasion, flow, impact,

flame, stain, moisture and elevated temperature were evaluated using

laboratory tests. These results can be used to develop performance criteria on which to base the selection of seamless flooring systems.

° Performance tests on the seamless flooring systems indicated differences in

performance related to generic type, e.g. systems with urethane topcoats

generally rated higher in the initial performance tests.

: Pcwer requirements and the magnitude and uniformity of surface temperatures

of nine electrical heating elements, functioning as radiant heating panels, were experimentally determined and evaluated. Overall, the conductive

paints appeared to have the most premise as a heating element in a radiant

panel-seamless flooring system. While the other heating elements were not

designed specifically for floors nor for use at low voltages, it appeared

that they could be adapted to function effectively in a radiant panelseamless flooring system.

° A number of heating elements had sufficiently low electrical resistances so that it is estimated that they could be used or modified to obtain voltage

drops less than 50 volts with electrodes placed 10 feet apart; this should

allow for supplemental heating in most rooms. However, NEC only approves

electrical radiant heaters buried six inches in a concrete slab for floor

radiant heating installations. The use of safety devices such as ground

fault circuit interrupters and low voltages might provide a basis for

acceptance of this type heating system by NEC. (See Appendix A for the

identification of future areas for work.)

23
2

° Power consumption of the systems ranged from about 2 to about 16 watts/ft

2 (about 22 to about 170 watts/m ) to heat the test panels approximately 10°F

(5°C) above ambient temperature

.

° The effectiveness of producing radiant energy by the heating elements appears

to be dependent on the geometry of the system, i.e., heating elements on top

of the plywood panel and directly underneath the seamless flooring were more

effective than heating elonents embedded in the plywood panels.

G. ACKNCWIEDGVENTS

This investigation was supported by the Department of Housing and Urban Development (HUD)

.

The authors wish to thank George Erickson, HUD, for his helpful advice, encouragement , and

assistance in obtaining materials. We wish to also thank Robert Beausoliel, NBS, and

William Meese, NBS, for their guidance in the preparation and installation of the radiant

panels for testing.

24
H. REFERENCES

1. Scales, G. M. and Schaefer, L, F., Jr., "Seamless Floors," Society of Plastics Engineers,

Technical Papers, Vol. XV, pp. 342-345 (1969)

.

2. "Seamless Flooring Update," Flooring, Vol. 79, No. 7, pp. 30-38 (1973).

3. "Seamless Flooring Comes of Age," Flooring, Vol. 77, No. 7, pp. 48-53 (1971).

4. Frisch, K. C. and Reegan, S, L. , Ed., "Advances in Urethane Science and Technology,"

Vol. 1, pp. 199-209, Technomic Publishing Co., Inc., Stamford, Conn. (1971).

5. Association of Seamless Applicators, "1973-74 Specifications Handbook for Seamless

Flooring," Vol 1, pp. 1-4 (1973).

6. "1973 Director and Buying Guide Issue," Flooring, Vol. 78, No. 11, pp. 120-123 (1972).

7. Temperature Performance of In-Space Electrical Systems, Joint Sections Committee of

the Residential Controls and Electric Comfort Heating Equipment Section (NEMA)

.

8. National Electrical Code, 1975, Article 424.44, Installation of Panels or Cable in

Concrete or Poured Masonry.

9. Electrical Appliance and Utilization Equipment List, June 1974, Underwriters' laboratory,

pp. 186-187.

10. Salter, Walter L., Floors and Floor Maintenance, Applied Science Publishers Ltd,,

London, 1974.

11. Notes on Science of Building, NSB No. 95 June 1967 (Ccmmonwealth Experimental Building

Section, Department of Works, Australia)

.

12. D. Burch, Private communication.

13. Godfrey, R. S,, Ed., "Building Construction Cost Data 1975," 33rd Annual Edition,

Robert Snow Means Company Inc., Duxbury, Mass. (1974).

14. C. Amolts, Private communication.

25
APPENDIX A - Identification of Areas for Future Work

Radiant heating in seamless flooring appears to be a feasible concept, but research

and development will be required before the system can be adapted for general usage. These

include:

0 The National Electric Code (NEC) would have to be modified to permit use of

radiant panel-seamless flooring system. Extensive safety testing would be

necessary prior to usage in family-occupied public housing units.

° The effectiveness of radiant heating is directly related to the physiological

effect on an occupant. For example, with radiant heating, little or no air

motion occurs, the heat is concentrated on the feet, and comfort is achieved at

lower ambient temperatures . Thus, extensive clinical studies would be

desirable to evaluate the effectiveness of this type of heating.

° To demonstrate the merits of the radiant panel-seamless flooring system, the

following information would need to be integrated into a cost effectiveness

study: power consumption, safety costs, installation and maintenance costs,

and the results of clinical testing of occupant physiological responses.

Field testing of the system should be initiated as soon as possible. Where

code limitations would not affect the field tests, flooring areas in selected

buildings should provide a controlled environment for the initial demonstration

tests.

26
NBS-1 14A (REV. 7-73) ' - DEPT. OF comm. 1. PUBLICATION OR REPORT NO. 2. Gov’t Accession

BIBLIOGRAPHIC DATA No. sheet NBSIR 77-1263

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Radiant Heating in Seamless Flooring - A Feasibility

Study

5. Publication Date July 1977

6. Performing Organization Code

7. au riioR(S) Q. Campbell, M. A. Post, M. Godette, W. E. Roberts 8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Office of Policy Development and Research

Division of Energy, Building Technology and Standards

Department of Housing and Urban Development

Washington, DC 20410

13. Type of Report & Period Covered

Final report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The purpose of this study was to determine the feasibility of using radiant

heating in seamless flooring as a supplemental heating source in housing units.

The resistance of twenty seamless flooring systems to abrasion, flow, inpact,

flame, stain, moisture and elevated temperature were evaluated using laboratory

tests. Power requirements and the magnitude and uniformity of surface temperatures

of nine electrical heating elements, functioning as radiant heating panels, were

experimentally determined and evaluated. The radiant heating panels were coated

with selected seamless flooring systems and the performance characteristics of the

radiant panel-seamless flooring system were evaluated. The report contains a summary of test results demonstrating the feasibility of the radiant panel-seamless

flooring system and the identification of areas for future research.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Electrical heating elements; materials performance: radiant

panel-seamless flooring system; seamless flooring; temperature characteristics.

18. AVAILABILITY Unlimited

Q For Official Distribution. Do Not Release to NTIS

Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. Cl 3

Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

29

22. Price

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