Talk:Central heating design
This is a skeleton giving a structure to an article to be written as Tuits permit.
--John Stumbles 18:54, 4 January 2007 (GMT)
Under pipe layout you missed one: radiator on the hot water circuit :). Not as rare as it should be. NT 22:30, 13 January 2007 (GMT)
How is ufh more efficient? Elevated slab temp would surely mean more heat loss than rads? NT 07:36, 15 January 2007 (GMT)
If the floor is not well insulated from the walls you get heat loss through the walls and, for ground floors, into the soil outside. I don't have a link for it but recall reading of a post-WWII housing development in the USA which had UFH in the floor slabs which weren't insulated from the walls. Gardeners living in these houses thought they had green fingers (or green thumbs as they say over there) because the warming of the surrounding soil allowed everything to grow early! Of course fuel was cheap then and there so I guess they weren't too bothered about their fuel bills. (The UFH was also in copper pipe so these installations all corroded through after a few decades and most of the remaining housing stock now has conventional heating systems.)
However assuming one has floor slabs properly insulated from the walls and otherwise correctly installed UFH I understand the amount of heat needed to make a room comfortably warm is substantially less than with radiator-based systems where much of the heat goes into warming the air which accumulates at the ceiling and gets lost through ventilation. It would be good to give some references when I (or anyone else) fills out that part of the article but I was still just roughing it out.
--John Stumbles 11:52, 15 January 2007 (GMT)
It'll be interesting to read about that once its done. NT 19:20, 15 January 2007 (GMT)
I was going to add a brief comment about warmed interior stud walls as a radiator alternative, but was unsure where to put it. Walls are listed under 'other radiant' but I was thinking convection not radiating walls, just like large low temp radiators, which are of course convectors rather than radiators. NT 01:37, 5 February 2007 (GMT)
I've not heard of these. Sounds as if they would work by radiation (like UFH) rather than convection but that it would be difficult to get the sort of heat output you'd get from warmed solid walls or floors. Do you have any more info e.g. where they've been used, sort of construction techniques, heat ouptuts etc? --John Stumbles 09:37, 5 February 2007 (GMT)
OK I've started a thread on uk.d-i-y called Look. no rads. NT 11:07, 5 February 2007 (GMT)
Convection or radiation?
Low temperature surfaces like radiators, UFH, warmed walls etc do not gt hot enough to produce significant radiant heat, so these are all convection/conduction heaters. NT 20:05, 6 February 2007 (GMT)
I thought any warm body radiated heat? How much it emits by radiation depends on the temperature difference between it and its surroundings (since they are also radiating) but it should be a linear relationship.
As someone pointed out in your thread on warm walls "radiators" have vastly greater output when they have multiple panels and fins behind/between the panels, which can only affect convection. You can see shimmer in the air rising above a "radiator" and see dust stains on the walls above them and other evidence of convection. You don't get any of this with UFH yet you can feel the warmth coming off it even if the air is cold, so I guess that is radiation. I would expect warm walls to have a greater convection effect than warm floors because they'd encourage warmed air to 'slide' upwards and get a convection circulation going (thus nicely warming the ceiling!). However I suspect you have to place a warm body in free air to really encourage convection - which is what rads with fins attempt to do.
--John Stumbles 00:47, 7 February 2007 (GMT)
I dont believe there is a linear relationship between temperature and radiation.
For a filament bulb, efficacy/EFFICACY = (temperature/TEMPERATURE)^4.52
Which means that as temp halves, light output drops by around 2^4.52 = a factor of 23.
This is why low temp water based heating produces almost no radiant heat. NT 02:22, 7 February 2007 (GMT)