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

Opinions sought on Cooling Idea

renosteinke | Posted in General Discussion on June 3, 2011 06:25am

While on the road today, I had a thought so obvious there has to be a flaw. Please tell me what I overlooked.

Summer is here. Air conditioners are humming. As we all know, a hot attic leads to a hot house. So, how do you cool the attic?

Well, the coolest air is in the crawlspace. Crawl spaces also are usually vented so as to prevent moisture problems.

What if we used a duct to ‘pipe’ that cool, moist air into the attic – where it would cool the attic on its’ way out the roof vents? We could even give it a push by using a humidity-controlled fan.

Remember … the moist air would be getting warmer, so there would be no opportunity for condensation.

What have I overlooked? Why isn’t this done?

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

Replies

  1. joeh | Jun 03, 2011 07:15pm | #1

    Ignoring any humidity issues ect,

    How long you think it's gonna take before the crawlspace is filled with hot air?

    Joe H

  2. User avater
    BossHog | Jun 04, 2011 06:34am | #2

    "a hot attic leads to a hot

    "a hot attic leads to a hot house"

    Not if the ceiling is insulated properly.

    1. Scott | Jun 04, 2011 12:10pm | #3

      What Boss said.

      Also, you can get convection-powered roof fans that will keep ambient air circulating through the attic space.

      1. DanH | Jun 04, 2011 03:39pm | #4

        What, pray tell, is a "convection powered" roof fan?

        1. sgbotsford | Jun 05, 2011 02:17pm | #5

          Roof turbine, I think.

          I think he's refering to those wind powered roof turbines.

          If the attic space is properly designed, it shouldn't be a source of heat for the house:

          1.  Here, it's code for an attic to be vented at the eaves, and most have a series of roof vents too.  On a breezy day, air enters the windward eaves, and exits thorugh roof vents and leeward eaves.  On a calm day it enters both sets of eave vents, and exits the roof vents.  My attic is seldom more than 10 degrees warmer than outside ambient.

          2.  If you live in a cooling environment, the only reasonable colour for your roof is WHITE.  Indeed, try for a roof using titanium dioxide as the pigment, as it's both a good reflecter of visible light, and a good emmitter of infrared.

          3.  Cooling the ceiling at the expense of heating the floor is a dubious win.

          Instead, put some fans on a timer or better on differential thermostats.  The attic fan is mounted in a gable, and pulls air out of the attic whenever the interior temp is above the exterior.  Similarly for the crawlspace.

          We cool our house passively.  At night we open the patio doors and the upstairs windows.  By morning the entire house is cool.  The house is massive enough that it never gets more than about 5-10 degrees above outside temps, and to do that requires a series of muggy days with no night time cooling.

          We live in a climate with 10,000 degree days of heating.  And from April to October the furnace never runs.  (Although on a rainy day evening we will often build a fire in the living room stove.

          Blow another 8" of insulation into your attic.  I've got 16" currently.  It takes two people an afternoon.

  3. junkhound | Jun 05, 2011 02:33pm | #6

    For folks with basements before AC and after gravity coal furnaces were replace by gas, that was standard operating proceedure in the summer.

    Open the basement door, take the panel off  that there newfangled gas furnace that has a blower, just turn on the fan - presto, cool basement air into the house.  Common practice in the 1950 IIRC.

  4. renosteinke | Jun 05, 2011 07:25pm | #7

    Fill the crawl with hot air? Well, you might have a point; such would make the system have very limited effectiveness. My model assumes that the earth below will be a source of infinite cooling capacity, reducing the tempreature of the outside air as it passes through the crawl space. If this heat transfer is ineffective, then the idea fails.

    As for comments by others ...

    As humid as our outside air is, I suspect that the ground under the house is even more moist. The whole reasoning behind venting crawl spaces at all is based upon this assumption. I am proposing to 'vent' this air out through the roof, by way of the attic - rather than out the leeward crawl space vents.

    Against the 'natural' direction of air flow? I think not. Sun-heated air will want to exit the attic- and the cooler crawl space air will be drawn into the attic to fill the void. Where, it will be heated, and the cycle repeat.

    A fan? Probably a good idea in any event. One can easily have the fan (below) controlled by a humidistat, or a temperature-controlled fan at the attic side. The second, in particular, would help address the question of what to do when winter comes.

    I won't deny that there are code requirements for attic venting. The problems arise from the simple fact that so many code-compliant roofs don't get any but minimal ventilation- and there seems to be no downside to increasing that ventilation. I'm not even getting into the issue of blocked vents, etc.

    Heat won't pass through a 'properly insulated' ceiling. Balderdash. I've experienced several instances where the addition of shade greatly reduced the temperature within even 'super-insulated' roof decks. Rather than heat the insulation, I'd rather heat the air within the attic  - then get rid of that air (replacing it with moist crawl space air.) I see the moisture content as a 'plus,' simply because water can carry far more heat than air alone.

    Folks used to let the basement air flow through the house for cooling? I did not know that. Maybe this idea has some merit ... only I'm not passing through the house, I'm proposing going straight to the attic.

    FWIW, in a desert clime I did have great success venting the hotter air near the ceiling into the attic - and thence out through the attic turbine. Heck, even the addition of the turbine to the existing static vent made a HUGE difference.

    I'm no longer in the desert. Quite the opposite; here summer air is so hot and humid the locals refer to it as 'breathing Jello." The water table is high enough to preclude basements.

    My calculations say I need 42,000 btu/hr of cooling for this house.  As I see it, anything I can do to reduce that load is a plus. Since my remodel involves opening the walls, adding a duct presents little additional effort or expense- something that can't be said for a new roof, new insulation, new windows, or an air conditioner. Thus, my skepicism that something that simple  could be effective.

    Unless someone comes up with a better explanition of 'what's wrong,' I'm quite tempted to give it a try.

    1. DanH | Jun 05, 2011 08:29pm | #8

      Against the 'natural' direction of air flow? I think not. Sun-heated air will want to exit the attic- and the cooler crawl space air will be drawn into the attic to fill the void. Where, it will be heated, and the cycle repeat.

      Think about it.  You have two columns of air:  One is the air (that you hope is) rising through the duct from the crawl, the other is the outside air.  The outside air is warmer, hence lighter.  The crawl air is colder and heavier.  It's not going to rise up that pipe voluntarily.

    2. DanH | Jun 05, 2011 08:35pm | #9

      My model assumes that the earth below will be a source of infinite cooling capacity, reducing the tempreature of the outside air as it passes through the crawl space.

      Yes, the earth has an essentially infinite cooling capacity.  It's just that the effective heat transfer rate is quite low.  A bit like a water heater -- you've got a "tank" of cold air down there, but once that's used up you need to "recover" via heat transfer with the earth.  That's not going to happen very rapidly, because the air will stratify in the crawl and because soil is a pretty good insulator.

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

FHB Podcast Segment: Embodied Greenhouse Gas Emissions and the Building Codes

Could a building code update make your go-to materials obsolete?

Featured Video

Builder’s Advocate: An Interview With Viewrail

Learn more about affordable, modern floating stairs, from design to manufacturing to installation.

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