Underfloor heating
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.
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.
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.
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.
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.
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.
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 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.
This has been supported through simulation evaluations[37][38][39][40] and through research funded by the U.S. Department of Energy,[41][42] Canada Mortgage and Housing Corporation,[43] Fraunhofer Institute ISE[44] as well as ASHRAE.
[49][50] The International Agency for Research on Cancer (IARC) has classified static and low-frequency magnetic fields as possibly carcinogenic (Group 2B).
[51] 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.
Fluid based systems using cross-linked polyethylene (PEX) 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.
[68][69] 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.
Economical electric resistance based systems also are useful in small zones such as bathrooms and kitchens, but also for entire buildings where heating loads are very low.
In the global drive for sustainability, long term economics supports the need to eliminate where possible, compression for cooling and combustion for heating.
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,[73] chillers[74] and heat pumps[75] to operate at or near their maximum engineered performance.
[78] 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.
[79][80] 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.
Thus carpeted floors need to operate at higher internal temperatures than tile which can create lower efficiencies for boilers and heat pumps.
