Subject: In floor radiant heat - any good?

From: [email-masked] (David Leblang)
Date: Thu, 1 Jun 1995 20:49:05 GMT

I am building a house and am considering putting in a radiant
heat system -- the type that runs hot water (90-100 degrees) through
plastic tubes in the floor.

I've been told that this is great for hardware floors and tile floors
but not so good in carpeted areas. 

The HAVC rep says that the system couldn't maintain 70 degrees when
it is 0 outside in a carpeted room 18 x 18 x 18 (open for two floors).

Anyone with comments/suggestions?

thanks,
    David
-- 
David Leblang  <[email-masked]>
Atria Software <URL http:www.atria.com>
24 Prime Park Way, Natick MA 01760
(508) 650-5121 [direct], -5100 [main], 647-1760 [fax]

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From: [email-masked] (Paul Bernhardt)
Date: 2 Jun 1995 23:12:21 GMT

David Leblang ([email-masked]) wrote:

: I am building a house and am considering putting in a radiant
: heat system -- the type that runs hot water (90-100 degrees) through
: plastic tubes in the floor.

: I've been told that this is great for hardware floors and tile floors
: but not so good in carpeted areas. 

: The HAVC rep says that the system couldn't maintain 70 degrees when
: it is 0 outside in a carpeted room 18 x 18 x 18 (open for two floors).

: Anyone with comments/suggestions?

The HVAC rep was giving you an overly simplistic response. I have 
designed several floor radiant systems. They do give wonderful heat, 
especially in locations where the outside temperatures stay uniformly 
cold. Moderate climates where heat is needed in the morning but not in 
the afternoon are _not_ good candidates for in floor systems. The reason 
is that in floor radiant systems are slow to respond to a change from 
needing heat to not (and vice versa). This is because the piping in the 
floor must essentially heat the mass of the floor so that heat can be 
provided to the room. Obviously there is a long time lag between the 
system responding to a call for heat from a thermostat and the system 
actually putting heat into the room. 

About carpet. Yes it does reduce the system's capacity in some ways. 
Carpet acts as an insulating layer over the heated floor. The solution is 
to heat the floor to a higher temperature and to put a layer of 
insulation below the slab (or decking if a raised floor) such that there 
is a lot more insulation below than above the piping. Unfortunately, this 
higher temperature can degrade the carpet, and the glue holding it down. 
Therefore, when selecting the carpet etc, the high temperature should be 
taken into account. By the way, there are a couple of methods of 
increasing the temperature of the heating system to account for 
carpeting. One is to simply increase the water temperature. The other is 
to narrow the spacing of the water tubes (there is a limit to how much 
this can help though.)  

I think that radiant floor systems using hot water are a great solution. 
My fraternity house in college in Atlanta had such a system for the 
downstairs. It was wonderful. Walk around in bare feet in the dead of 
winter and feel wonderfully warm. Good luck!