[Greenbuilding] [BULK] Radiant Floor under wood

[answers at healthyheating.com]

JB, 

My advice is to Ctrl-Alt-Del the direction you may be heading in.

One prime objective with radiant is to use the lowest possible fluid
temperature with sufficient density of tubing which results in the
highest quality surface temperature profile at design conditions. 

Dry sand has a thermal conductivity similar to some woods or leather,
which is why leather gloves are useful for picking up hot items and why
wood spoons left in hot foods are easier to use with bare hands. It also
means compared to better choices, the fluid in the pipes surrounded by
sand will need to run at a higher temperature and the floor mass will
have longer thermal lags, i.e. take longer to raise the surface
temperature of the floor and take longer to disperse the stored heat
within the sand.  

We often use this site to explain such concepts:
http://www.seed.slb.com/en/scictr/lab/energy/notes.htm

Please consider one of several excellent radiant accessory systems such
as aluminum heat transfer plates, which improve the fin efficiency by
expanding the contact surface area of the pipes with a highly conductive
material allowing for lower fluid temperatures and better surface
temperature profiles.  Standard of acceptance would be Radiant
Engineering's C- Fin or Uponor's Joist Trac.  Other products like
Warmboard, QuickTrac, Raupanel or Maxxon's Thermafloor are also superior
choices to using sand between sleepers. (If your areas are small, you
may be able to purchase the Thermafloor by the bag and mix it yourself
on site.) We have thermography photos from an ASHRAE research project
illustrating several of these applications.

If you choose to use the sand you will find such assemblies are absent
in industry standard radiant design nomographs and software used by
professionals.  

Reflective foil works only when it can reflect: i.e. there must be an
air gap otherwise, it just becomes a conductive film.  In addition, the
long-term emissivity of foil in any kind of cavity (particularly
horizontal and one designed to reflect upward) is suspect due to
unpredictable dust/dirt accumulations. Dust of sufficient thickness has
emissivity similar to dirt. ASHRAE Research papers discuss this.  We
also have photos in our archives illustrating same. 

A few thoughts: In my experience, overheating is common with improperly
designed radiant systems installed in energy efficient homes and
people's expectations of having warmfloors are frequently not met.  For
the most part, it's because the radiant system was treated as an
experiment instead of using engineering principles. 

This article
(http://www.healthyheating.com/downloads/Radiant%20Design.pdf) was first
published in the RPA Report and it will give you some idea of what to
consider for properly designing a radiant system.  Simple heatloss
worksheets if you can find someone willing to share them, will still
require the user to make judgment calls particularly on air
infiltration.  Even with a heat loss one still has 11 additional
calculations to perform for a radiant design.

There are many certified radiant designers - for U.S. citizens a list
can be obtained from the Radiant Panel Association. In Canada, contact
the Heating, Refrigeration, Air Conditioning Institute of Canada or the
Canadian Institute of Plumbing and Heating. Several certified members
offer design services for their products at no charge. Its important to
deal with someone who is certified as opposed to holding a certificate.
A certified person has written industry exams as opposed to attending a
product seminar.  

Lastly: Often hardwood problems are blamed on radiant floors even though
100% of all hardwood floor complaints in homes heated with furnaces did
not have floor heating.  Therefore, I would also suggest you research
the type and cut of hardwood and what it takes to acclimate the floors
to inoculate against future finger pointing (not that the flooring man
with heating advice would do such a thing)- chalk it up to paranoia on
my part.  

See these articles:
https://www.nofma.org/Portals/0/Publications/Moore%2003_03.pdf

http://www.hardwood.org/display_article.asp?ID=304

Sorry for the ramble...

RB

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of
josephbecker at riseup.net
Sent: Monday, August 21, 2006 3:58 PM
To: greenbuilding at listserv.repp.org
Subject: [BULK] [Greenbuilding] Radiant Floor under wood
Importance: Low

On the subject of radiant heat...in the ecological house.

I am looking for some science and guidance on what to do with the spaces
between sleepers and tubing on top of a sub floor and beneath the finish
floor of vertical grain red oak.

Our plan is to put 3" sleepers every 12" leaving 9" spaces. Our flooring
man suggested filling the voids with sand instead of leaving air in
order to prevent a hollow sound. The owner does not mind a hollow sound

Would sand help spread the heat or inhibit the spread and trap the heat?

It seems like small convection loops in air would move the heat better.

What about foil used in this application. Has anyone used the foil on
top of sand?


On another note...
Any suggestions for simple heat loss worksheets. We are planning to use
the minimum of tubing and only heat the floor in spaces that are walked
on.

Thank you.

Best Energy,
Joseph Becker



_______________________________________________
Greenbuilding email list
List info:
http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.or
g
List email: Greenbuilding at listserv.repp.org Managed by BuildingGreen,
Inc. http://www.buildinggreen.com
      publisher of Environmental Building News and GreenSpec(r) Hosted
and archived by REPP / CREST http://www.crest.org

_______________________________________________
Greenbuilding email list
List info:
http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.or
g
List email: Greenbuilding at listserv.repp.org
Managed by BuildingGreen, Inc. http://www.buildinggreen.com
      publisher of Environmental Building News and GreenSpec(r)
Hosted and archived by REPP / CREST http://www.crest.org