radiant floor heat

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Visit Dow Chemical for more information on insulation and moisture control.

Table of Contents

For more information on insulating heated slabs visit the CMHC links on the radiant systems pages.

www.healthyheating.com statement on bubble foil insulation can be read in it's entirety in:

Radiant Mythology
22 Radiant Heating Myths

Also read:
Bad Science, By
John Siegenthaler, P.E.

Uninsulated vs Insulated
Ref.: Dr. Straube

Ref.: Foundation heat loss from heated concrete slab-on-grade floors by Pirawas Chuangchid, Ph.D., Moncef Krarti, Ph.D., P.E, Joint Center for Energy Management (JCEM), CEAE Department, University of Colorado at Boulder, Boulder, CO 80309-0428, (CB 428) USA

Learn more about insulation and radiant cooling and heating here. Note: Allow up to 60 seconds to load.



Building Systems, Part II

With all the magical claims consumers get sucked into, there has been one product that has stood the test of time, holds all other newcomers to a high benchmark, delivers as promised and it's extruded polystyrene insulation. Its high compressive strength makes it ideal for heated driveways and slabs and its moisture resistance closed-cell structure delivers stable long-term R-value in building assemblies.

To avoid the snake oil foil trap please feel free to use this excerpt from  our written specifications on under slab insulation.

Thermal Specification: All under slab insulation shall have been evaluated to CAN/ULC-S701-03 by the National Research Council's Institute for Research in Construction (IRC) through the Canadian Construction Materials Centre (CCMC) and must bear the manufacturer's name or trademark and CCMC evaluation listing number.  Standard of Acceptance: Type 2, 3 or 4 as per CAN/ULC-S701-03, Material Properties.  R value to meet current edition of the Model National Energy Code, National Building Code and authority having jurisdiction.

Where appropriate, insulation R Value shall be adjusted upwards for slabs bearing on grades with higher thermal conductivities and at walk out perimeters.

Click Image for Larger View

Structural Specification: (insert your business name) does not purport to have structural expertise in specifying what Type (2, 3, or 4) is suitable for the application, therefore the onus is on the general contractors to specify the Type based on a professional (Civil/Structural) engineers written evaluation of application in consideration of live and dead loads, soil properties and compaction, water table location and methods of construction.

Key Concepts in Insulating Heated Surfaces

Below Grade Walls/Floors

Graphic Copyright Dow Chemical

The thermal objective of any radiant based HVAC system is to direct the energy into the space to the benefit of the occupant.  Downward loss, or heat transferred to the earth is energy not contributing to the purpose. Heat loss to grade is a function of the temperature of the heated slab, soil type and moisture content. The higher the moisture content and soil conductivity the greater the downward heat loss and thus the greater the amount of dollars to heat dirt, rock and sand instead of you  - the occupant.

Insulated Heated Concrete Slab

Graphic Copyright NRDC

A properly assembled concrete slab will outlast most other assemblies in a home. To achieve this longevity and reliability it must have high compressive strength and moisture resistance.

Insulated Drives/Walks/Patios
Graphic Copyright NRDC

Its expensive to operate a snow melt system compared to the cost of hand shoveling but it may be less than the cost of injuries, hazards and security risk associated with accumulated snow and ice. The only way to ensure every dollar spent to melt snow goes into the slab instead of the earth is to insulate with high strength extruded polystyrene insulation designed for vehicle traffic.

We recommend you download these documents below from Dow's website by clicking on the illustration.


Radiant Floors for Cozy Living
Excerpt, “There is a growing demand in both the United States and Canada for the installation of radiant heating. There are several ways to heat a floor, including circulating water through cross-linked polyethylene tubing…"







Radiant Insulation
Excerpt, "Radiant floor heating has been used in aesthetic and energy-efficient building designs since the Romans channeled hot air under the floors of their villas centuries ago. Today, advances in materials and technology are increasing the appeal of radiant floors, offering the promise of cost-efficient comfort for commercial and residential applications."








Insulation, Sealant and Adhesives
Excerpt,"...science-based building
envelope solutions...improve the
comfort and energy efficiency of
your structures..."

The Right Way.

Applications Illustration. Click the image to see a larger version.


A note on moisture and soil conductivity:

The three biggest enemies in downward heat loss is subsoil temperature, soil type and moisture content.

For example moist clay will transfer 7.4 times as much heat as dry sand.

Imagine your heated slab operating at a 90 deg F core temperature over a 55 deg F clay having over 20% moisture content  - draining over 44 Btu/hr/sf out of the slab into the aquifer - that's 44 Btu/hr/sf that should be going onto the building!

How much is 44 Btu/hr/sf? Well that's more than three times the amount of heat it takes to keep a R2000 home warm.

To view a comparison for soil types and moisture content - click here.

To combat downward heat loss one must insulate below the slab.

In Canada and in other parts of the world, insulating under slab is required by the building codes.

Building Systems - Part I, Product Claims

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