FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Discussion Forum

Discussion Forum

Radiant Heat in reverse ?

Woody78 | Posted in Energy, Heating & Insulation on September 15, 2009 03:04am

I post a question here for those vastly more knowledgeable than myself about thermal gain, loss and transfer.

A pal has a barn with a small 1 room living studio at the end. Barn faces south, has a metal roof and the interior is not yet complete. We ran pex in the slab before the pour and insulated w/ 2″ styro below.

Question? Can he expect to reasonably increase the performance of his radiant slab system by running copper piping or thin fin style diffusers beneath the s. facing metal roof and insulating below to try to capture that heat and transfer it in to his gas fired hot water tank fueled radiant system.

I am sceptical but he feels that he is missing a good opportunity to capture a good free heat source. Cold climate area around Albany NY.

Any one care to chime in ??

 

Thanks

Jim

Reply
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Replies

  1. MikeHennessy | Sep 15, 2009 04:02pm | #1

    I suppose it could be done, but you'd need controls to cut the loop out overnight, on sunless days or when the temp of the rest of the system is higher than the temp in the roof loop - otherwise, you'll just wind up heating the roof, not vice versa.

    If he wants heat from the roof, probably better to use a conventional collector.

    Mike Hennessy
    Pittsburgh, PA
    Everything fits, until you put glue on it.

    1. User avater
      Woody78 | Sep 15, 2009 04:07pm | #2

      I assume you mean one mounted on the outside collecting solar ?

      Lets say that although this structure was dutifully inspected and is legit, at one time it looked like a 4 stall carriage barn it now resmbles a 3 stall barn with a cute little apartment on the end that does not wish to draw the attention of anyone. Needless to say I had suggested that but he wants it to be inconspicuos.

      Thanks Mike.

      1. MikeHennessy | Sep 15, 2009 04:14pm | #3

        Yep. Store-bought.

        Don't forget that you will probably want/need to ventilate under the roof to deal with condensation, so that'll further erode the minimal heat gain you might get from this setup.Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.

        1. Clewless1 | Sep 17, 2009 03:24pm | #9

          You describe a solar collector ... which if not in a box w/ a cover (glass), will not do very well for your purpose. Mounted inside behind the window, maybe. But you would also have to coat it w/ a low-e black coating (like they do on solar collectors).

          While your concept idea holds water (nyuk), it really won't work very well in your application w/out some significant modifications/improvements to your idea. If you feel the need to push the idea, you need to work on details.

          1. MikeHennessy | Sep 17, 2009 09:36pm | #10

            Me -- I didn't describe anything. I think you meant to send that to the OP.Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.

  2. frenchy | Sep 15, 2009 04:48pm | #4

    woody. 

       freezing? In cold weather the risk of freezing offsets possible thermal gains.. Now you can minimise freezing problems with antifreeze but that adds further complicationsIncluding the fact that antifreeze reduces heat transferance. 

      You'd have a very narrow window on bright sunny days in the winter when the thermal gains would offset the thermal losses.   No advantage during cloudy or at night..

      I suspect the net would be a loss not a gain.. Calculations are available..

  3. User avater
    Woody78 | Sep 15, 2009 05:05pm | #5

    Description of the set up as imagined by he in question.

     

    Thanks, I am planing to put a circuit of copper pipes between the Green metal roof and the purlins on which that roof rests( there are 8 "bays" made by the 2X4's, if you will, about 2' apart). The insulation below the 2X's will trap a relatively hot cavity of air and radiate to the tubes, fins from a radiator arraignment will augment the pipes, then collect in a manifold to go to the PEC tube embedded floor when it is hot enough and the furnace( your old hot water heater) is not on. The roof faces South by south-east and in the winter gets about 4 hours of direct sun, more in the fall and spring(trees and sun angle). The space is about 18 ' wide and ridged 20" tube can be run into the purlins easily. The manifold can be constructed in the heated space or the garage and insulated as needed. I had thought of using PEC tubing but I don't think the heat transfer rate is great enough in a tube to air configuration.

    He states it more clearly than I originally did.

    1. NRTRob | Sep 15, 2009 05:10pm | #6

      these guys do that:http://www.dawnsolar.com/this is not an endorsement, I am skeptical myself, but if anyone knows what it does, they have more direct experience with it than most I imagine.-------------------------------------
      -=Northeast Radiant Technology=-
      Radiant Design, Consultation, Parts Supply
      http://www.NRTradiant.com

      1. User avater
        Woody78 | Sep 15, 2009 05:16pm | #7

        Rob

         

        Thanks for the link.

  4. renosteinke | Sep 16, 2009 12:33am | #8

    There's a better way.

    Make a duct or two, using the metal roof as one side of the duct. have openings to the room on both the 'uphill' and 'downhill' ends of the duct. Add dampers, and a thermostst-controlled fan at the exhaust end. Insulate around these ducts so they are outside the building's conditioned space.

    The hot roof will heat the air within the ducts; when the ducts are hot enough, the fan kicks on and delivers hot air to the room. You can add a second thermostat to the room to keep this from happening if the room is already warm enough.

    How well this works depends, in part, on how much higher one end of the duct is from the other. When you have this mounted in the wall, you often don't need a fan; it's amazing just how much heat you can capture this way.

  5. Clewless1 | Sep 18, 2009 03:18pm | #11

    I mis posted/directed this, I guess .... so in case you didn't read it ...

    You describe a solar collector ... which if not in a box w/ a cover (glass), will not do very well for your purpose. Mounted inside behind the window, maybe. But you would also have to coat it w/ a low-e black coating (like they do on solar collectors).

    While your concept idea holds water (nyuk), it really won't work very well in your application w/out some significant modifications/improvements to your idea. If you feel the need to push the idea, you need to work on details.

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

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

Up Next

Video Shorts

Featured Story

Making the Move to Multifamily

A high-performance single-family home builder shares tips from his early experience with two apartment buildings.

Featured Video

SawStop's Portable Tablesaw is Bigger and Better Than Before

The 10-in. Jobsite Saw PRO has a wider table, a new dust-control port, and a more versatile fence, along with the same reliable safety mechanism included in all SawStop tablesaws.

Related Stories

  • Podcast Episode 692: Introduction to Trade Work, Embodied Carbon, and Envelope Improvements
  • FHB Podcast Segment: Embodied Greenhouse Gas Emissions and the Building Codes
  • Old Boots Learn New Tricks
  • Install Denim Insulation Like a Pro

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

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2025
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

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

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

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

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

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

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

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 70%

Subscribe

Enjoy unlimited access to Fine Homebuilding. Join Now

Already a member? Log in

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

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data