FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram Plus Icon Close Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Main Menu
Subscribe

In every issue you'll find...

  • Expert insights on techniques and principles
  • Unbiased tool reviews
  • Step-by-step details to master the job
  • Field-tested advice and know-how
Subscribe Now!
Subscribe
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
  • Join
  • Log In
Main Menu Subscribe
Tools & Materials

Radiant-Ready Subfloor

Three reasons to choose in-floor hydronic heat for houses that could be heated with forced air.

Sponsored by Warmboard

Article Image

It’s hard to beat the warm, even comfort of in-floor hydronic heat. Conventional in-floor systems use a layer of concrete or gypcrete on top of the subfloor to embed the tubing. This huge amount of mass takes a long time to heat up before it can warm the room (sometimes days). And then once the floor is heated, it stays warm and is difficult to cool off again. This lack of nuanced control creates problems in the shoulder seasons when you need a little heat overnight, but no heat during the day. The same problems are even more pronounced in a super-efficient house. Given the potential complications, one might ask why choose hydronic floors for houses that could be heated with forced air.

Comfort rules

There are a several good reasons to use radiant. For starters home owners love hydronic systems because they’re nearly silent and don’t stir up dust and pet hair. In addition, the moving air common to forced-air systems creates a breeze that can make people feel cold even when the system is blowing warm air. Forced-air heating systems also need ducts, which are big in comparison to hydronic piping. Because of their size and because most people don’t want to look at them, ducts must be hidden in chases or run in unconditioned spaces. Neither option is optimal. Chases present design and aesthetic problems and running ductwork in unconditioned spaces comes with a significant energy penalty.

Radiant subflooring

Warmboard-S_profile
Warmboard S is a 1 1/8-in. thick rated subfloor that accepts 1/2-in. diameter radiant tubing. It installs at the framing stage with conventional fastening methods.
Warmboard-R_profile
Warmboard R is a 13/16-in. panel designed for retrofit applications. Unlike competitive products, Warmboard’s aluminum skin isn’t interrupted by the groove, which translates into more-efficient heat transfer.

One of the most-promising ways I’ve seen to create a quick-responding hydronic system suitable for modern construction is Warmboard. These pre-routed panels, which receive 1/2-in. PEX radiant tubing, have an aluminum skin that’s molded into the tubing grooves. The aluminum skin provides efficient radiation and allows the use of energy-saving lower water temperatures (80 to 110 deg.) rather than high mass systems and radiators, which commonly use 140 deg. or hotter water. Early versions of Warmboard had a bare aluminum surface that was so reflective, it was tough to look at when the sun was shining. Fortunately, the aluminum is now painted, so it’s easier to look at in bright light. Warmboard S is 1 1/8-in. thick and is meant for new construction. Warmboard R is 13/16 in. thick and is designed for retrofit applications.

In both cases the manufacturer designs the heating loops and panel layout and ships all the panels necessary to complete the installation. You supply the tubing from a list of approved products identified on the company’s website. The company can work with a heating contractor or design the entire system, including heat-load calculations. Once the design is finalized, you’ll receive drawings that map out the various panels and show the manifold locations and heating loops for every zone.

Along with the panels, Warmboard includes three router templates with an order: an obstruction template for routing the tubing around closet flanges and obstacles. They also include straight and 180° curved templates for connecting the grooves on cut panels and completing odd-shaped layouts. Warmboard claims both versions of the subfloor can be placed under virtually any finished flooring, including carpet, hardwood and ceramic. Since the tubing is visible within the panel, it’s easy enough to avoid damaging it during the finished flooring installation. It’s also a good idea to keep the system pressurized with compressed air during flooring installation so you’re alerted to any damage while it’s still easily repaired. Warmboard panels are about $7 per square foot which is potentially about ½ the price of a completed radiant system. Check out warmboard.com for installation videos and additional technical details.

Warmboard R is a 13/16-in. thick retrofit radiant tubing subfloor
Warmboard R is a 13/16-in. thick retrofit radiant tubing subfloor. It accepts the same 1/2-in. PEX tubing as the new-construction product.

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Sign Up

Get home building tips, offers, and expert advice in your inbox

×
X
X

New Feature

Fine Homebuilding Forums

Ask questions, offer advice, and share your work

View Comments

  1. Lost in Lyme | Sep 26, 2016 01:19pm | #1

    I had Warmboard (now "S") installed in 2006 in massive retrofit (the house was originally built using flakeboard as subfloor -think formaldehyde). Breathed better and reduced energy use (then heated with oil) by 20+%. Have since installed GSHP with further savings. Even though Warmboard is low mass, it does take time to heat the house up (even run chilled water in summer). Suggest setting the temperature at a constant 66-68 degrees the entire heating season. Constant comfort and you wouldn't need auxilliary heat but on the coldest days of the year. Will build next (retirement) house with warmboard for heating/cooling and seek passive house compliance. Oh yeah, put all zones manifolds & pumps in a central mechanical room.

  2. eaklaus | Sep 26, 2016 08:02pm | #2

    I have a gypcrete radiant system with outdoor reset sensing a change in temp . My room temp varies at most , 1 degree. The thermal mass of the gypcrete helps hold heat on a sunny winter day. In the summer, this thermal mass delays the A/C use. I wouln't have it any other way.

  3. PavementGuy | Nov 04, 2016 06:23pm | #3

    The prices quoted in the article for this system are very low and not realistic. I'm installing radiant floors in my home right now and did not go with Warmbaord because I was quoted $8/SF for the Warmboard-R panels alone not including any tubing, manifolds, etc. I live in CO. Not sure where the author found Warmboard for $3.50 a SF but that is way off from the quote I received just 2 months ago (Sep 2016). I agree with the reasoning to install radiant floors which is why I have chosen to go forward with a different system.

  4. User avater
    dylanglenn755 | Mar 01, 2017 02:19am | #4

    new technology very good

  5. clairepazot | Mar 14, 2017 04:19am | #5

    make clean work here....!!!1

  6. user-7768654 | Oct 05, 2020 04:00pm | #6

    Just wondering...
    Looking at the picture associated with the article, is there enough room on top of the subflooring for a concrete topping, of 4"?
    And, wouldn't it be better, and more efficient, to just have the Pex piping enclosed completely by the concrete floor, instead of buried by nearly 75% in a wooden substrate (well, aluminum wrapped)?

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Up Next

Featured Story

FHB's 40th Anniversary Tips Video Contest

Record yourself demonstrating a favorite tip from the Fine Homebuilding archive to win a cordless compact router kit.

Featured Video

How to Install Exterior Window Trim

In this episode of Shop Class, learn how to measure, cut, and build window casing made of cellular PVC, solid wood, poly-ash boards, or any common molding material. Plus, get tips for a clean and solid installation.

Related Stories

  • Old-World Craftsmanship

  • How To Get Pet Stains Out of Oak

  • Interior Finishes for a Cabin in the Woods

  • Radiant Heating and Cooling

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Highlights

  • Fine Homebuilding All Access
  • Fine Homebuilding Podcast
  • Tool Tech

    Plus, get an extra 20% off with code GIFT20

  • "I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

    Get home building tips, offers, and expert advice in your inbox

    Sign Up See all newsletters

Video

View All
  • Shower niche

    Interior Finishes for a Cabin in the Woods

  • Framing Floors and Stairs with Larry Haun

  • Podcast 184: Insulating an All-Brick House, Working with Engineered Siding, and Carpentry as a Second Career

  • contractors working on subfloor installation

    Squeak-Free Subfloor Installation

View All

Floors and Coverings

View All
  • Dead-Flat Bathroom Floor

  • Floating Hardwood Floor with Unmatched Advantages

  • Patching a Hardwood Floor

    2 Methods for Patching a Hardwood Floor

  • Nearly Invisible Floor Finish

View All

BOOKS, DVDs, & MERCH

Shop the Store
  • Musings of an Energy Nerd

    Buy Now
  • 2020 Fine Homebuilding Archive

    Buy Now
  • Fine Homebuilding Magazine Slipcase

    Buy Now
  • Code Check Building 4th Edition

    Buy Now
  • Shop the Store

Fine Homebuilding Magazine

  • Issue 297 - Feb/Mar 2021

    • Foundations for Success
    • Staircase Renovation
    • Ditch the Hose
  • Issue 296 - Dec 2020/Jan 2021

    • Insulating Glass Keeps Getting Better
    • Simple Way to Make Old Walls Straight and Plumb
    • Making Sense of Minisplits
  • Issue 295 - Kitchens & Baths

    • Condo Kitchen Reimagined
    • Row-House Remodel
    • Rise of the IAQ Monitor
  • Issue 294 - Oct/Nov 2020

    • Schoolhouse Reimagined
    • Tool Test: Folding Sawhorses
    • A Better Way to Build Tall Walls
  • Issue 293 - Aug/Sept 2020

    • A Practical Guide to Fall Protection
    • Installing Frameless Cabinets
    • Make Any Tablesaw Safer

Fine Homebuilding

Follow

Newsletter

Get home building tips, offers, and expert advice in your inbox

Sign Up See all newsletters

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Manage Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Privacy Policy
  • Careers
  • Copyright
  • Terms of Use
  • Accessibility
  • CA Privacy Rights

© 2021 The Taunton Press, Inc. All rights reserved.

    Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Reader Projects
  • Magazine
  • Members
  • FHB House
  • Podcasts

  • FHB Podcast
  • ProTalk
  • Account

  • Log In
  • Join

    Podcasts

  • FHB Podcast
  • ProTalk
  • Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

    Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

    All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

    Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

    More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • Customer Support

    Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Sign Up See all newsletters

Follow

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 52%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in