Building Services Engineering 5th Edition Handbook

92 Heating
Floor finish
Screed with pipes or cables
Floor slab
Thermal insulation
Hardcore
Damp-proof course
Binding
4.9 Embedded panel heating.
Floorboards
100 mm mineral
fibre insulation
Electrically insulated
conducting mat
4.10 Radiant ceiling heating.
Plasterboard
Radiant panels
Radiant panel systems employ either a high- or a low-temperature surface to transmit heat
by radiation directly to the occupants, and to other unheated surfaces, producing an elevated
mean radiant temperature. Comfort conditions can be maintained with lower air temperatures
than with convective systems. This should result in economical running costs.
Convection heat output from the hot radiant source is minimized by placing thermal insulation
over the reflector. High-temperature radiation is generated using gas combustion close to ceramic
reflectors, which emit some heat in the visible part of the infrared region and consequently are
seen to be contributing to a feeling of warmth. Domestic gas fires and industrial heaters are in
this category. Covered pedestrian areas of shopping precincts can be warmed from recessed units
in canopies.
The effect of using high-temperature panels is to produce a series of localized ‘sun spots’ over
a small floor area. Careful siting is necessary to avoid overheating of people or objects.
Low-temperature systems utilize hot water, air or flue gas to heat a metal sheet or pipe, which
emits long-wave infrared radiation outside the visible band. They can be installed in factory or
office environments and produce a uniform overall warmth, assisted by re-radiation and convection
from surfaces heated by the radiant source. Unlike convective systems, they are not adversely
affected by room height. Complete systems can be suspended from the ceiling, leaving floors
uncluttered.
An evacuated tube system is shown in Fig. 4.11. Flue products from the gas burners are drawn
along steel pipes by a vacuum pump and discharged to the atmosphere.