Underfloor heating

From Wikipedia, the free encyclopedia

Underfloor heating and cooling is a form of central heating and cooling which achieves indoor climate control for thermal comfort using conduction, radiation and convection. The terms radiant heating and radiant cooling are commonly used to describe this approach because radiation is responsible for a significant portion of the resulting thermal comfort but this usage is technically correct only when radiation composes more than 50% of the heat exchanged between the floor and the rest of the space.[1]

History

Underfloor heating has a long history back into the Neoglacial and Neolithic periods. Archeological digs in Asia and the Aleutian islands of Alaska reveal how the inhabitants drafted smoke from fires through stone covered trenches which were excavated in the floors of their subterranean dwellings. The hot smoke heated the floor stones which then radiated into the living spaces. These early forms have evolved into modern systems using fluid filled pipes or electrical cables and mats. Below is a chronological overview of under floor heating from around the world.

Time period, c. BC[2] Description[2]
5,000 Evidence of "baked floors" are found foreshadowing early forms of kang and dikang "heated floor" later ondol meaning "warm stone" in Korea and Manchu respectively.[3]
3,000 Korean fire hearth, was used both as kitchen range and heating stove.
1,000Ondol type system used in the Aleutian Islands, Alaska[4] and in Unggi, Hamgyeongbuk-do (present-day North Korea).
1,000 More than two hearths were used in one dwelling; one hearth located at the center was used for heating, the others at the perimeter was used for cooking throughout the year. This perimeter hearth is the initial form of the budumak (meaning kitchen range), which composes combustion section of the traditional ondol in Korea.
500 Greeks and later Romans scale up the use of conditioned surfaces (floors and walls) with the hypocausts.
200 Central hearth developed into gudeul (meaning heat releasing section of ondol) and perimeter hearth for cooking became more developed and budumak was almost established in Korea.
50 China, Korea and Roman Empire use kang, dikang/ondol and hypocaust respectively.
Time period, c. AD[5] Description[5]
500 Asia continues to use conditioned surfaces but the application is lost in Europe where it is replaced by the open fire or rudimentary forms of the modern fireplace. Anecdotal literary reference to radiant cooling system in the Middle East using snow packed wall cavities.
700More sophisticated and developed gudeul was found in some palaces and living quarters of upper-class people in Korea. Countries in the Mediterranean Basin (Iran, Algeria, Turkey et al.) use various forms of hypocaust type heating in public baths and homes (ref.: tabakhana, atishkhana, sandali) but also use heat from cooking (see:tandoor, also tanur) to heat the floors.[6][7][8]
1000 Ondol continues to evolve in Asia. The most advanced true ondol system was established. The fire furnace was moved outside and the room was entirely floored with ondol in Korea. Europe uses various forms of the fireplace with the evolution of drafting combustion products with chimneys.
1400 Hypocaust type systems used to heat Turkish Baths of the Ottoman Empire.
1500 Attention to comfort and architecture in Europe evolves; China and Korea continue to apply floor heating with wide scale adoption.
1600 In France, heated flues in floors and walls are used in greenhouses.
1700 Benjamin Franklin studies the French and Asian cultures and makes note of their respective heating system leading to the development of the Franklin stove. Steam based radiant pipes are used in France. Hypocaust type system used to heat public bath (Hammam) in the citadel town of Erbil located in modern day Iraq.[9]
1800 Beginnings of the European evolution of the modern water heater/boiler and water based piping systems including studies in thermal conductivities and specific heat of materials and emissivity/reflectivity of surfaces (Watt/Leslie/Rumford).[10] Reference to the use of small bore pipes used in the John Soane house and museum.[11]
1864 Ondol type system used at Civil War hospital sites in America.[12] Reichstag building in Germany uses the thermal mass of the building for cooling and heating.
1899 The earliest beginnings of polyethylene-based pipes occur when German scientist, Hans von Pechmann, discovered a waxy residue at the bottom of a test tube, colleagues Eugen Bamberger and Friedrich Tschirner called it polymethylene but it was discarded as having no commercial use at the time.[13]
1904 Liverpool Cathedral in England is heated with system based on the hypocaust principles.
1905 Frank Lloyd Wright makes first trip to Japan, later incorporates various early forms of radiant heating in his projects.
1907 England, Prof. Barker granted Patent No. 28477 for panel warming using small pipes. Patents later sold to the Crittal Company who appointed representatives across Europe. A.M. Byers of America promotes radiant heating using small bore water pipes. Asia continues to use traditional ondol and kang—wood is used as the fuel, combustion gases sent under floor.
1930 Oscar Faber in England uses water pipes used to radiant heat and cool several large buildings.[14]
1933 Explosion at England’s Imperial Chemical Industries (ICI) laboratory during a high pressure experiment with ethylene gas results in a wax like substance—later to become polyethylene and the re-beginnings of PEX pipe.[15]
1937 Frank Lloyd Wright designs the radiant heated Herbert Jacobs house, the first Usonian home.
1939 First small scale polyethylene plant built in America.
1945 American developer William Levitt builds large scale developments for returning GI’s. Water based (copper pipe) radiant heating used throughout thousands of homes. Poor building envelopes on all continents require excessive surface temperatures leading in some cases to health problems. Thermal comfort and health science research (using hot plates, thermal manikins and comfort laboratories) in Europe and America later establishes lower surface temperature limits and development of comfort standards.
1950 Korean War wipes out wood supplies for ondol, population forced to use coal. Developer Joseph Eichler in California begins the construction of thousands of radiant heated homes.
1951 Dr. J. Bjorksten of Bjorksten Research Laboratories in Madison, WI, announces first results of what is believed to be the first instance of testing three types of plastic tubing for radiant floor heating in America. Polyethylene, vinyl chloride copolymer, and vinylidene chloride were tested over three winters.[16]
1953The first Canadian polyethylene plant is built near Edmonton, Ab.[17]
1960NRC researcher from Canada installs underfloor heating in his home and later remarks, "Decades later it would be identified as a passive solar house. It incorporated innovative features such as the radiant heating system supplied with hot water from an automatically stoked anthracite furnace."[18]
1965 Thomas Engel patents method for stabilizing polyethylene by cross linking molecules using peroxide (PEx-A) and in 1967 sells license options to a number of pipe producers.[19]
1970 Evolution of Korean architecture leads to multistory housings, flue gases from coal based ondol results in many deaths leading to the removal of the home based flue gas system to a central water based heating plants. Oxygen permeation becomes corrosion issue in Europe leading to the development of barriered pipe and oxygen permeation standards.
1980 The first standards for floor heating are developed in Europe. Water-based ondol system is applied to almost all of residential buildings in Korea.
1985 Floor heating becomes a traditional heating systems in residential buildings in Middle Europe and Nordic countries and increasing applications in non-residential buildings.
1995 The application of floor cooling and thermal active building systems (TABS) in residential and commercial buildings are widely introduced into the market.[20]
2000 The use of embedded radiant cooling systems in middle of Europe becomes a standard system with many parts of the world applying radiant based HVAC systems as means of using low temperatures for heating and high temperatures for cooling.
2010 Radiant conditioned Pearl River Tower in Guangzhou, China, topped out at 71-stories.

Description

Modern underfloor heating systems use either electrical resistance elements ("electric systems") or fluid flowing in pipes ("hydronic systems") to heat the floor. Either type can be installed as the primary, whole-building heating system or as localized floor heating for thermal comfort. Electrical resistance can only be used for heating; when space cooling is also required, hydronic systems must be used. Other applications for which either electric or hydronic systems are suited include snow/ice melting for walks, driveways and landing pads, turf conditioning of football and soccer fields and frost prevention in freezers and skating rinks.

Electric heating elements or hydronic piping can be cast in a concrete floor slab ("poured floor system" or "wet system"). They can also be placed under the floor covering ("dry system") or attached directly to a wood sub floor ("sub floor system" or "dry system").

Some commercial buildings are designed to take advantage of thermal mass which is heated or cooled during off peak hours when utility rates are lower. With the heating/cooling system turned off during the day, the concrete mass and room temperature drift up or down within the desired comfort range. Such systems are known as thermally activated building systems or TABS.[21][22]

Carbon heating film

Carbon heat most advanced and convenient in-floor heating systems. Other than general heating systems, radiant in-floor heating systems, and hydronic in-floor heating systems carbon heating film has many advantages. Some of them are ease of installation, simplicity of operation, equal heating, air purification, and great savings on heating bills.

Carbon heating film comes in rolls and can be easily installed under any floor surface. The film is only 0.338 mm thick and and made of carbon heating elements, cooper stripes for electrical connection, and P.E.T. plastic film that protects the carbon heating elements from both sides. The Heating film should be rolled out on top of the floor underlayment and connected to the thermostat using simple parallel connection. Moisture barrier film and floor should be installed right on top of the film. Carbon heating film comes for installation with 110-120V electrical supply for United States and 220-240V electrical supply for Canada and most European countries.

Hydronic systems

Hydronic systems use water or a mix of water and anti-freeze such as propylene glycol[23] as the heat transfer fluid in a "closed loop" that is recirculated between the floor and the boiler.

Various types of pipes are available specifically for hydronic underfloor heating and cooling systems and are generally made from polyethylene including PEX, PEX-Al-PEX and PERT. Older materials such as Polybutylene (PB) and copper or steel pipe are still used in some locales or for specialized applications.

Hydronic systems require skilled designers and tradespeople familiar with boilers, circulators, controls, fluid pressures and temperature. The use of modern factory assembled sub-stations, used primarily in district heating and cooling, can greatly simplify design requirements and reduce the installation and commissioning time of hydronic systems.

Hydronic systems can use a single source or combination of energy sources to help manage energy costs. Hydronic system energy source options are:

Underfloor heating pipes, before they are covered by the screed
Underfloor heating pipes, before they are covered by a concrete garage slab
Radiant tubing layout, Project: BCIT Aerospace Hangar, Vancouver, British Columbia, Canada
Manifold assembly
Modern factory assembled hydronic control appliances for underfloor heating and cooling, shown with covers on.
Modern factory assembled hydronic control appliances for underfloor heating and cooling, shown with covers off.

Electric systems

Electric floor heating installation, cement being applied
Electric systems are used only for heating and employ non-corrosive, flexible heating elements including cables, pre-formed cable mats, bronze mesh, and carbon films. Due to their low profile they can be installed in a thermal mass or directly under floor finishes. Electric systems can also take advantage of time-of-use electricity metering and are frequently used as carpet heaters, portable under area rug heaters, under laminate floor heaters, under tile heating, under wood floor heating, and floor warming systems, including under shower floor and seat heating. Large electric systems also require skilled designers and tradespeople but this is less so for small floor warming systems. Electric systems use fewer components and are simpler to install and commission than hydronic systems. Some electric systems use line voltage technology while others use low voltage technology. Power consumption of an electric system is not based on voltage but rather wattage output produced by the heating element.

Features

Thermal comfort quality

As defined by ANSI/ASHRAE Standard 55 – Thermal Environmental Conditions for Human Occupancy, thermal comfort is, "that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation." Relating specifically to underfloor heating, thermal comfort is influenced by floor surface temperature and associated elements such as radiant asymmetry, mean radiant temperature and operative temperature. Research by Nevins, Rohles, Gagge, P. Ole Fanger et al. show that humans at rest with clothing typical of light office and home wear, exchange over 50% of their sensible heat via radiation.

Underfloor heating influences the radiant exchange by thermally conditioning the interior surfaces with low temperature long wave radiation. The heating of the surfaces suppresses body heat loss resulting in a perception of heating comfort. This general sensation of comfort is further enhanced through conduction (feet on floor) and through convection by the surface's influence on air density. Underfloor cooling works by absorbing both short wave and long wave radiation resulting in cool interior surfaces. These cool surfaces encourage the loss of body heat resulting in a perception of cooling comfort. Localized discomfort due to cold and warm floors wearing normal foot wear and stocking feet is addressed in the ISO 7730 and ASHRAE 55 standards and ASHRAE Fundamentals Handbooks and can be corrected or regulated with floor heating and cooling systems.

Indoor air quality

Underfloor heating can have a positive effect on the quality of indoor air by facilitating the choice of otherwise perceived cold flooring materials such as tile, slate, terrazzo and concrete. These masonry surfaces typically have very low VOC emissions (volatile organic compounds) in comparison to other flooring options. In conjunction with moisture control, floor heating also establishes temperature conditions that are less favorable in supporting mold, bacteria, viruses and dust mites.[24][25] By removing the sensible heating load from the total HVAC (Heating, Ventilating, and Air Conditioning) load, ventilation, filtration and dehumidification of incoming air can be accomplished with dedicated outdoor air systems having less volumetric turnover to mitigate distribution of airborne contaminates. There is recognition from the medical community relating to the benefits of floor heating especially as it relates to allergens.[26][27]

Sustainability—energy

Under floor radiant systems are evaluated for sustainability through the principles of efficiency, entropy, exergy[28] and efficacy. When combined with high performance buildings, under floor systems operate with low temperatures in heating and high temperatures in cooling[29] in the ranges found typically in geothermal[30] and solar thermal systems. When coupled with these non combustible, renewable energy sources the sustainability benefits include reduction or elimination of combustion and green house gases produced by boilers and power generation for heat pumps[31] and chillers, as well as reduced demands for non renewables and greater inventories for future generations. This has been supported through simulation evaluations[32][33][34][35] and through research funded by the U.S. Department of Energy,[36][37] Canada Mortgage and Housing Corporation,[38] Fraunhofer Institute[39] as well as ASHRAE.[40]

Safety and Health

Low temperature underfloor heating is embedded in the floor or placed under the floor covering. As such it occupies no wall space and creates no burn hazards, nor is it a hazard for physical injuries due to accidental contact leading to tripping and falling. This has been referenced as a positive feature in healthcare facilities including those serving elderly clients and those with dementia.[41][42][43] Anecdotally, under similar environmental conditions, heated floors will speed evaporation of wetted floors (showering, cleaning, and spills). Additionally, underfloor heating with fluid filled pipes is useful in heating and cooling explosion proof environments where combustion and electrical equipment can be located remotely from the explosive environment.

There is a likelihood that underfloor heating may add to offgassing and sick building syndrome in an environment, particularly when carpet is used as a flooring.

Longevity, maintenance and repair

Equipment maintenance and repair is the same as for other water or electrical based HVAC systems except when pipes, cables or mats are embedded in the floor. Early trials (for example homes built by Levitt and Eichler, c. 1940-70’s) experienced failures in embedded copper and steel piping systems as well as failures assigned by the courts to Shell, Goodyear and others for polybutylene and EPDM materials.[44][45] There also have been a few publicized claims of failed electric heated gypsum panels from the mid 90’s.[46]

Failures associated with most installations are attributable to job site neglect, installation errors and product mishandling such as exposure to ultraviolet radiation. Pre-pour pressure tests required by concrete installation standards[47] and good practice guidelines[48] for the design, construction, operation and repair of radiant heating and cooling systems mitigate problems resulting from improper installation and operation.

Fluid based systems using Cross-linked polyethylene (PE-x) a product developed in the 1930s and its various derivatives such as PE-rt, have demonstrated reliable long term performance in harsh cold-climate applications such as bridge decks, aircraft hangar aprons and landing pads. Since the materials are produced from polyethylene and its bonds are cross-linked, it is highly resistant to corrosion or the temperature and pressure stresses associated with typical fluid based HVAC systems.[49]

Typical installation details

General considerations for placing radiant heating and cooling pipes in flooring assemblies where other HVAC and plumbing components may be present. Click Image for Larger View
Typical under floor heating and cooling assemblies. Local practices, codes, standards, best practices and fire regulations will determine actual materials and methods.Click Image for Larger View

Design and installation considerations

The engineering of underfloor cooling and heating systems is governed by industry standards and guidelines.[50][51][notes 2]

Technical design

The amount of heat exchanged from or to an underfloor system is based on the combined radiant and convective heat transfer coefficients.

  • Radiant heat transfer is constant based on the Stefan–Boltzmann constant.
  • Convective heat transfer changes over time depending on
    • the air's density and thus its buoyancy. Air buoyancy changes according to surface temperatures and
    • forced air movement due to fans and the motion of people and objects in the space.

Convective heat transfer with underfloor systems is much greater when the system is operating in a heating rather than cooling mode.[52] Typically with underfloor heating the convective component is almost 50% of the total heat transfer and in underfloor cooling the convective component is less than 10%.[53]

Heat and moisture considerations

When heated and cooled pipes or heating cables share the same spaces as other building components, parasitic heat transfer can occur between refrigeration appliances, cold storage areas, domestic cold water lines, air conditioning and ventilation ducts. To control this, the pipes, cables and other building components must all be well insulated.

With underfloor cooling, condensation may collect on the surface of the floor. To prevent this, air humidity is kept low, below 50%, and floor temperatures are maintained above the dew point, 19 °C (66F).[54]

Building systems and materials

  • Heat losses at the exterior floor framing
    • The heated or cooled sub-floor increases the temperature difference between the outdoors and the conditioned floor.
    • The cavities created by the framing timbers such as headers, trimmers and cantilevered sections must then be insulated with rigid, batt or spray type insulations of suitable value based on climate and building techniques.
  • Masonry and other hard flooring considerations
    • Concrete floors must accommodate shrinkage and expansion due to curing and changes in temperature.
    • Curing times and temperatures for poured floors (concrete, lightweight toppings)must follow industry standards.
    • Control and expansion joints and crack suppression techniques are required for all masonry type floors including;
  • Wood flooring
    • The dimensional stability of wood is based primary on moisture content,[58] however, other factors can mitigate the changes to wood as it is heated or cooled, including;

Control system (see Hydronic heating systems)

Underfloor heating and cooling systems can have several control points including the management of:

  • Fluid temperatures in the heating and cooling plant (e.g. boilers, chillers, heat pumps).
    • Influences the efficiency
  • Fluid temperatures in distribution network between the plant and the radiant manifolds.
    • Influences the capital and operating costs
  • Fluid temperatures in the PE-x piping systems, which is based on;[1]
    • Heating and cooling demands
    • Tube spacing
    • Upward and downward losses
    • Flooring characteristics
  • Operative temperature
  • Surface temperatures for;[59]
    • Comfort
    • Health and safety
    • Material integrity
    • Dew point (for floor cooling).

Sample - mechanical schematic

Example of a radiant based HVAC schematic. Click for larger image.

Illustrated is a simplified mechanical schematic of an underfloor heating and cooling system for thermal comfort quality[59] with a separate air handling system for indoor air quality.[60][61] In high performance residential homes of moderate size (e.g. under 3000 ft2 (278 m2) total conditioned floor area), this system using manufactured hydronic control appliances would take up about the same space as a three or four piece bathroom.

Modeling piping patterns with finite element analysis

Thermal diffusions and surface temperature quality (efficacy) of various piping layouts
Typical FEA output screen shots of wire mesh, thermal isotherms and color-coded mapping

Modeling radiant piping (also tube or loop) patterns with finite element analysis (FEA) predicts the thermal diffusions and surface temperature quality or efficacy of various loop layouts. The performance of the model (left image above) and image to the right are useful to gain an understanding in relationships between flooring resistances, conductivities of surrounding mass, tube spacings, depths and fluid temperatures. As with all FEA simulations, they depict a snap shot in time for a specific assembly and may not be representative of all floor assemblies nor for system that have been operative for considerable time in a steady state condition. The practical application of FEA for the engineer is being able to assess each design for fluid temperature, back losses and surface temperature quality. Through several iterations it is possible to optimize the design for the lowest fluid temperature in heating and the highest fluid temperature in cooling which enables combustion and compression equipment to achieve its maximum rated efficiency performance.

Using thermography to observe underfloor systems

Thermographic images of a room heated with low temperature radiant heating shortly after starting up the system.

Thermography is a useful tool to see the actual thermal efficacy of an underfloor system from its start up (as shown) to its operating conditions. In a startup it is easy to identify the tube location but less so as the system moves into a steady state condition. It is important to interpret thermographic images correctly. As is the case with finite element analysis (FEA), what is seen, reflects the conditions at the time of the image and may not represent the steady conditions. For example, the surfaces viewed in the images shown, may appear ‘hot’, but in reality are actually below the nominal temperature of the skin and core temperatures of the human body and the ability to ‘see’ the pipes does not equate to ‘feel’ the pipes. Thermography can also point out flaws in the building enclosures (left image, corner intersection detail), thermal bridging (right image, studs) and the heat losses associated with exterior doors (center image).

Economics

There is a wide range of pricing for underfloor systems based on regional differences, application and project complexity. It is widely adopted in the Nordic, Asian and European communities. Consequently the market is more mature and systems relatively more affordable than North America where market share for fluid based systems remains between 3% to 7% of HVAC systems (ref. Statistics Canada and United States Census Bureau).

In energy efficiency buildings such as Passive House, R-2000 or Net Zero Energy, simple thermostatic radiator valves can be installed along with a single compact circulator and small condensing heater controlled without or with basic hot water reset[62] control. Economical electric resistant based systems also are useful in small zones such as bathrooms and kitchens, but also for entire buildings where heating loads are very low. Larger structures will need more sophisticated systems to deal with cooling and heating needs, and often requiring building management control systems to regulate the energy use and control the overall indoor environment.

Low temperature radiant heating and high temperature radiant cooling systems lend themselves well to district energy systems (community based systems) due to the temperature differentials between the plant and the buildings which allow small diameter insulated distribution networks and low pumping power requirements. The low return temperatures in heating and high return temperatures in cooling enable the district energy plant to achieve maximum efficiency. The principles behind district energy with underfloor systems can also be applied to stand alone multi story buildings with the same benefits.[63] Additionally, underfloor radiant systems are ideally suited to renewable energy sources including geothermal and solar thermal systems or any system where waste heat is recoverable.

In the global drive for sustainability, long term economics supports the need to eliminate where possible, compression for cooling and combustion for heating. It will then be necessary to use low quality heat sources for which radiant underfloor heating and cooling is well suited.

System efficiency

System efficiency and energy use analysis takes into account building enclosure performance, efficiency of the heating and cooling plant, system controls and the conductivities, surface characteristics, tube/element spacing and depth of the radiant panel, operating fluid temperatures and wire to water efficiency of the circulators.[64] The efficiency in electric systems is analyzed by similar processes and includes the efficiency of electricity generation.

Though the efficiency of radiant systems is under constant debate with no shortage of anecdotal claims and scientific papers presenting both sides, the low return fluid temperatures in heating and high return fluid temperatures in cooling enable condensing boilers,[65] chillers[66] and heat pumps[67] to operate at or near their maximum engineered performance.[68][69] The greater efficiency of 'wire to water' versus 'wire to air' flow due to water's significantly greater heat capacity favors fluid based systems over air based systems.[70] Both field application and simulation research have demonstrated significant electrical energy savings with radiant cooling and dedicated outdoor air systems based in part on the previous noted principles.[71][72]

In Passive Houses, R-2000 homes or Net Zero Energy buildings the low temperatures of radiant heating and cooling systems present significant opportunities to exploit exergy.[73]

Efficiency considerations for flooring surface materials

System efficiency is also affected by the floor covering serving as the radiational boundary layer between the floor mass and occupants and other contents of the conditioned space. For example, carpeting has a greater resistance or lower conductance than tile. Thus carpeted floors need to operate at higher internal temperatures than tile which can create lower efficiencies for boilers and heat pumps. However, when the floor covering is known at the time the system is installed then the internal floor temperature required for a given covering can be achieved through proper tube spacing without sacrificing plant efficiency (though the higher internal floor temperatures may result in increased heat loss from the non-room surfaces of the floor).[74]

The emissivity, reflectivity and absorptivity of a floor surface are critical determinants of its heat exchange with the occupants and room. Unpolished flooring surface materials and treatments have very high emissivity’s (0.85 to 0.95) and therefore make good heat radiators.[75]

With underfloor heating and cooling ("reversible floors") flooring surfaces with high absorbance and emissivity and low reflectivity are most desirable.

Global examples of large modern buildings using radiant heating and cooling

See also

Wikimedia Commons has media related to Underfloor heating.

References

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  2. ↑ 2.0 2.1 Bean, R., Olesen, B., Kim, K.W., History of Radiant Heating and Cooling Systems, ASHRAE Journal, Part 1, January, 2010
  3. ↑ Guo, Q., (2005), Chinese Architecture and Planning: Ideas, Methods, Techniques. Sttutgart: Edition Axel Menges, Part 1, Chpt 2, pg 20-27
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  5. ↑ 5.0 5.1 Bean, R., Olesen, B., Kim, K.W., History of Radiant Heating and Cooling Systems, ASHRAE Journal, Part 2, January, 2010
  6. ↑ Papers on Traditional Public Baths-Hammam-in the Mediterranean, Archnet-IJAR, International Journal of Architectural Research, Vol. 3, Issue 1:157-170, March, 2009
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  10. ↑ Gallo, E., Jean Simon Bonnemain (1743-1830) and the Origins of Hot Water Central Heating, 2nd International Congress on Construction History, Queens' College, Cambridge, UK, edited by the Construction History Society, 2006, <http://www.emmanuellegallo.net/pdf/1043-1060.pdf Bonnemain>
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  33. ↑ Chapman, K.S., DeGreef, J.M., Watson, R.D., Thermal comfort analysis using BCAP for retrofitting a radiantly heated residence (RP-907), ASHRAE Transactions, vol. 103(1):959-965, 1997
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  40. ↑ Baskin, E., Evaluation of hydronic forced-air and radiant slab heating and cooling systems, ASHRAE Transactions, vol. 111(1):525-534, 2005
  41. ↑ Hoof, J.V., Kort, S.M., Supportive living environments: A first concept of a dwelling designed for older adults with dementia, Dementia, Vol. 8, No. 2, 293-316 (2009) doi:10.1177/1471301209103276
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  43. ↑ Springer, W. E., Nevins, R.G., Feyerherm, A.M., Michaels, K.B., Effect of floor surface temperature on comfort: Part III, the elderly, ASHRAE Transactions 72: 292-300, 1966
  44. ↑ Settlement Announced in Class Action with Shell, http://www.classaction.ca/pdf/Shell_PBP_PR_Release.pdf
  45. ↑ Galanti v. The Goodyear Tire & Rubber Company and Kelman v. The Goodyear Tire & Rubber Company et al. http://www.entraniisettlement.com
  46. ↑ Radiant ceiling panels, Ministry of Municipal Affairs, Electric Safety Branch, Province of British Columbia, 1994, http://eiabc.org/pdfQuestionSheets/RCHP%20Info%20Package.pdf
  47. ↑ ACI 318-05 Building Code Requirements for Structural Concrete and Commentary, http://www.concrete.org/PUBS/newpubs/318-05.htm
  48. ↑ E.g. Radiant Panel Association, Canadian Institute of Plumbing and Heating, Thermal Environmental Comfort Association of British Columbia, and ISO Standards.
  49. ↑ Plastic Pipe Institute, The Facts On Cross-Linked Polyethylene (Pex) Pipe Systems, http://www.plasticpipe.org/pdf/pex_facts.pdf
  50. ↑ ANSI/ASHRAE 55- Thermal Environmental Conditions for Human Occupancy
  51. ↑ 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
  52. ↑ Bean, R., Kilkis, B., 2010, Short Course on the Fundamentals of Panel Heating and Cooling, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., <http://www.ashrae.org/education/page/552>
  53. ↑ Olesen, B., (2004) Radiant heating and cooling by embedded water-based systems, Technical University of Denmark, http://www.ashrae.org.sg/Olesen-radiant%20heating%20and%20cooling.pdf
  54. ↑ Mumma, S., 2001, Designing Dedicated Outdoor Air Systems, ASHRAE Journal, 29-31
  55. ↑ Table 3 Soil Thermal Conductivities, 2008 ASHRAE Handbook—HVAC Systems and Equipment
  56. ↑ Natural Resources Canada's (NRCan's) validation of new building designs policies and procedures and interpretation of the Model National Energy Code for Commercial Buildings (MNECB), 2009
  57. ↑ Beausoleil-Morrison, I., Paige Kemery, B., Analysis of basement insulation alternatives, Carleton University, April 2009
  58. ↑ Wood Handbook, Wood as an Engineering Material, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, 2010
  59. ↑ 59.0 59.1 ANSI/ASHRAE Standard 55 - Thermal Environmental Conditions for Human Occupancy
  60. ↑ ASHRAE 62.1 Ventilation for Acceptable Indoor Air Quality
  61. ↑ ASHRAE 62.2 Ventilation and Acceptable Indoor Air Quality in Low Rise Residential Buildings
  62. ↑ Butcher, T., Hydronic baseboard thermal distribution system with outdoor reset control to enable the use of a condensing boiler, Brookhaven National Laboratory, (for) Office of Buildings Technology U.S. Department of Energy, October, 2004
  63. ↑ Olesen, B., Simmonds, P., Doran, T., Bean, R., Vertically Integrated Systems in Standalone Multi Story Buildings, ASHRAE Journal Vol. 47, 6, June 2005, http://doas-radiant.psu.edu/vert_intg_doas_radiant.pdf
  64. ↑ Rishel, J.B., Wire-to-Water Efficiency of Pumping Systems, ASHRAE Journal, April, 2001 http://www.ashrae.org/docLib/20090715_cummings.pdf
  65. ↑ Fig. 5 Effect of Inlet Water Temperature on Efficiency of Condensing Boilers, Chapter 27, Boilers, 2000 ASHRAE Systems and Equipment Handbook
  66. ↑ Thornton, B.A., Wang, W., Lane, M.D., Rosenberg, M.I., Liu, B., (September 2009), Technical Support Document: 50% Energy Savings Design Technology Packages for Medium Office Buildings, Pacific Northwest National Laboratory for the U.S. Department of Energy, DE-AC05-76RL01830
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  70. ↑ Heat, Work and Energy
  71. ↑ Leigh, S.B., Song, D.S., Hwang , S.H., Lee, S.Y., A Study for Evaluating Performance of Radiant Floor Cooling Integrated with Controlled Ventilation, ASHRAE Transactions: Research, 2005
  72. ↑ Leach, M., Lobato, C., Hirsch, A., Pless, S., Torcellini, P., Technical Support Document: Strategies for 50% Energy Savings in Large Office Buildings, National Renewable Energy Laboratory, Technical Report, NREL/TP-550-49213 , September 2010, <http://www.nrel.gov/docs/fy10osti/49213.pdf>
  73. ↑ International Energy Agency, Annex 37 Low Exergy Systems for Heating and Cooling in Buildings
  74. ↑ Fig. 9 Design Graph for Heating and Cooling with Floor and Ceiling Panels, Panel Heating and Cooling, 2000 ASHRAE Systems and Equipment Handbook
  75. ↑ Pedersen, C.O., Fisher, D.E., Lindstrom, P.C. (March, 1997), Impact of Surface Characteristics on Radiant Panel Output, ASHRAE 876 TRP
  76. ↑ Simmonds, P., Gaw, W., Holst, S., Reuss, S., Using radiant cooled floors to condition large spaces and maintain comfort conditions, ASHRAE Transactions, vol. 106(1):695-701, 2000

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