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

Attic Fan

RJM | Posted in Energy, Heating & Insulation on November 5, 2003 11:25am

Was wondering whether installing a thermostatically-controlled attic fan would pay for itself in Minnesota. Our second story is hard to cool down even with central-air in the summer time.

With an attic fan would I have trouble with the blown-in insulation in my attic being blown around?

Appreciate any comments.

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

Replies

  1. csnow | Nov 06, 2003 12:00am | #1

    Cannot say enough good things about my Tamarack Tech whole house fan.

    Cools the attic and the house.

    Quiet, seals tight, easy install, low energy consumption...

    You would need to build a 'dam' to hold back the insulation, but it does not blow hard enough to cause troubles.

    Just something to consider as a alternative to a typical roof or gable fan...

    http://www.tamtech.com/hv1000.htm

  2. Scooter1 | Nov 06, 2003 02:16am | #2

    I have three, each wired for a different temperature and a manual overide that can turn it off or on manually. I love mine, but carefull wiring will make it a nice product.

    Regards,

    Boris

    "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934

  3. fortdh | Nov 06, 2003 08:23am | #3

    Bob, do you have duct work in the attic?

    What type of ventilation up there, ie., soffit vents, gable vents, ridge vent or roof vents?

    What is your attic insulation and depth?

    Do you have an idea of summer attic air temps?

    Is the upstairs staying hot long after the sun goes down? Roof black?

    Do you know the A/C tonnage serving the upstairs and the sq footage?

    It will be easier to advise with this info.

    Paul

    Energy Consultant and author of Practical Energy Cost Reduction for the Home
    1. RJM | Nov 07, 2003 03:15am | #5

      Paul, this is in  response to your reply to my letter asking about the feasibility of putting a thermostatically-controlled fan in my Minnesota attic:

      I have a 16 year old 2500 sq. ft. two story house with natural gas forced-air heating system with a 1 1/2 ton central A/C unit. The upstairs is probably 600-750 sq. ft. There is no duct work in the attic. There is roughly 12" of blown cellulose insulation in the attic which has soffit vents as well as roof vents. The roof has one year old black shingles and I have no idea how hot it gets in the attic in the summer, but the upstairs stays warm long after the sun goes down.

      Thanks in advance for your help.

      Bob

      1. User avater
        BillHartmann | Nov 07, 2003 04:55am | #6

        I suspect that you will do a lot better looking at where vents, speically the return air, are located and the balancing of the vents.

      2. fortdh | Nov 07, 2003 06:53am | #7

        Bob, Let me ask a few more questions.

        Are you saying you have only 1 1/2 tons of A/C for the whole house (2500 sq ft), or for only the upstairs (600-750 sq ft)?

        Where is the air handler located that serves the upstairs?

        Do you have metal ductwork in the walls, or is the hollow wall the actual duct?

        Where are the upstairs supply vents located...floor, low on wall, high on wall?

        How does the air velocity feel coming from the upstairs vents compared to the downstairs vents?

        Do you have dampers on the ducts coming off the main trunk lines for each room or zone?

        How many return air grilles do you have and where are they?

        Do you have a gable roof or hip roof?

        Where were you thinking of mounting the attic fan?

        Is the downstairs "cool" in the winter, ie., difficult to heat compared to the upstairs?

        Sorry for all the questions, but the more I know about your situation, the better advice I can offer. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home

        1. RJM | Nov 07, 2003 08:11pm | #8

          Paul, The A/C is actually 3 tons, my mistake. The metal ductwork is in the walls, with supply vents located on the floor by the outside walls. There are return vents in all three bedrooms and in the hall, all located high on an interior wall. The air velocity feels good upstairs except for one bedroom that has poor air flow. It's always the coldest room in the house. The upstairs as a rule is more difficult to heat in the winter compared with the main level. I had a squirrel cage duct booster on the ductwork for that room where it came off the furnace in the basement but it was noisy and didn't help much. I remember seeing dampers on the ductwork, they were all open, but now the basement ceiling is finished and they are for the most part inaccesible.

          I was thinking of mounting the fan in the gable end of my gable roof, or as a roof mount.

          Thanks.

          1. fortdh | Nov 08, 2003 12:26am | #11

            Bob, thanks for the extra info. Here is what I gather and suggest.

            You have 833 sq ft per ton of A/C capacity. That is a stretch for most houses on hot days, unless very tight and well insulated. By tight, I mean both the house envelope and the forced air system.

            You are pushing the air from a basement to the 2nd story. Cold air is heavier than hot, and you have a long up hill distance. It would be helpful to be able to partially close some of the dampers feeding the downstairs during the summer so that more cold air was pushed to the upstairs. Understand you can't get to them.

            You have about R-42 in the attic, not bad, another R-8 wouldn't hurt, but let's do some other things first.

            So what can be done...

            Let's reduce the heat load, increase the air flow , and check the A/C performance.

            The heat load. I would put in the gable fan, but don't go overboard on cfm. Size it to the sq ft of the attic, and be sure you have adequate outdoor supply air to the attic. The box or paper work that comes with the fan will give you the info. Check that the fan has a high temp cut off in case of fire. You can use either a timer or a thermostat to turn on the fan. Most people use a thermostst; I use a timer to get an early jump on moving the air out before too much heat buildup.

            I would put in a radiant barrier on the underside of the roof rafters, from just above the insulation to about 1' below the ridge. You can order a roll from Solar Shield at 1-800-645-3645. An air staple gun makes the job pretty easy. You will be channeling the hottest air from attic floor to the ridge between the rad barrier and the roof decking.

            If you have collar ties forming a triangle of space at the top of the attic, you can go across the bottom with the foil/paper barrier, and using some foil backed foam board, channel the air to the gable fan.

            The idea,is to pull fresh air into the attic,up behind the rad barrier to the ridge area, and then out the gable vent via the fan. You may find that your attic with out this system is 140 deg +++, and with the system is about outdoor temp. That is just the temp improvement. You will also be avoiding the radiant heat gain which even penetrates insulation. (this is why the upstairs stays hot so long after the sun is down)

            Now let's look at the air flow. Take a strip of tissue paper and tape it to one of the supply grilles upstairs. Turn the blower to "fan on". Fix the strip so that it flutters or is supported by the air stream. This is your visual indicator to see if you can make air flow improvements.

            Remove all the supply grilles and using aluminum tape, seal any gaps between the sheetrock or floor and the duct work. You want a smooth air tight liner to prevent any air from blowing into the wall or under the floor. Don't overlap the tape beyond the border that the grille will hide.

            At the air handler, you want to tape all the seams and connections. Feel for any air leaks, especially where the plenums connect to the air handler case. Now do the same procedure to the return side. Those returns in the bedrooms will probably have some gaps between the wall and the duct.

            If you have return air filter grilles, you can remove the filter from the air handler and tape the panel door closed. Note, you must have filters in all returns before you can eliminate the one at the air handler.( Before taping the seams of the blower compartment, you can turn off the unit, including the breaker,open the case and inspect the blower vanes. After many years, they often build up a layer of crud that reduces their ability to scoop air. It is not difficult to pull a blower out and clean the vanes. If you do this, clean all the vanes to maintain balance.)Check for oil taps while in there.

            Tape the seams on the air handler that are on the return end. You won't be able to feel air blowing out because that is the "suction or negative pressure" side of the blower.

            With the system tight and well fitted to the house interior, you have done about all you can for air flow. The tissue strip should show greater action if you made any sealing improvements.

            Check the air temp across the cooling coil in A/C mode. I use a couple of $10 digital thermometers with a 10' wired sensor from Walmart or Target. Put a small hole in the return plenum and in the supply plenum and stick the sensors into the air stream about 10". With the unit cooling, you should find about a 15 deg or greater difference, unless it is very humid in the house. You may find as high as 20-22 deg. This is a rough test to see if the refrigerant, compressor etc are correct.

            I trust you have checked the tightness of windows, doors, access to the attic etc. Are you supplying out door air to the clothes dryer, gas water heater and gas furnace, and keeping that air from joining house air? Isolate those appliances so that they are not sucking conditioned air out of the house, or causing backdraft from the flues.

            There are a number of other things to do, but these should make an improvement and save some energy cost both cooling and heating.

            Please let us know how this turns out. You are not the only one to have a hot upstairs. Good luck PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home

          2. RJM | Nov 08, 2003 01:05am | #14

            Really appreciate your help, Paul. I'll probably get cracking on the fan end of things in the early Spring before it starts to get too warm.

            I'm heading to the bookstore tonight to look for your book.

          3. User avater
            rjw | Nov 08, 2003 07:30am | #15

            Paul, very interesting info in that post.

            You have 833 sq ft per ton of A/C capacity. That is a stretch for most houses on hot days, unless very tight and well insulated. By tight, I mean both the house envelope and the forced air system.

            If I recall, he's fairly northernly -FWIW,  in my area 3 ton is what I expect to see on that size and age of house.

            _______________________

            Albert Einstein said it best:

            “Problems,” he said, “cannot be solved at the same level of consciousness that created them.”

            Your mileage may vary ....

          4. fortdh | Nov 08, 2003 09:00am | #16

            Bob, he is north, and I hope he can get by on 3t. I have a bunch of clients in NJ with houses in the 2800 sq ft at 4t and 3500 at 5t. Single systems for whole house, air handler in the basement, and hot upstairs. Houses only 6-7 years old with thermo windows, a lot of attic insulation, and billed by the builder as "energy efficient" construction. They are having the same problem, hot upstairs, and freezing basements. After better sealing,and pulling down the attic temps under the black roofs, we can usually get enough cold air to the upstairs by seasonal changes to the dampers. PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home

  4. User avater
    rjw | Nov 06, 2003 07:52pm | #4

    Bob. a theoretical concern is that a power vent might leave areas of the roof sheathing in "still air" which can lead to condensation problems (even in summer!  - get super saturated humid air up there, sun foes down, roof cools down -voila! condensation.)

    I can'tr say that I've seen any attics which actually (and obviously) have had that problem.

    A whole house fan is generally used at a different time of day and for a differentr purpose.

    _______________________

    Albert Einstein said it best:

    “Problems,” he said, “cannot be solved at the same level of consciousness that created them.”

    Your mileage may vary ....

  5. BillMcG | Nov 07, 2003 09:38pm | #9

    There are two types of 'attic fans', at least I've heard people call both types 'attic fans'.

    One goes on the gable end, and exhausts hot air from the attic, on a thermostat. The other kind pulls air through the house and into the attic, to cool the house with outside air.

    I have both types, and the first one I highly recommend. Even with a ridge vent and clear soffit vents, my attic was getting > 140 in the summer. The ceiling underneath was noticably hot. The gable end vent went in pretty easily and keeps the attic cool, which keeps the house much cooler.

    The other type, which is installed in the hallway ceiling, blows air up and out, theoretically cooling the house by pulling in cool nighttime air. My attic roof is probably only 4-5' high at the peak and I think there's probably too much back pressure, because the fan is loud and pulls a vacuum, but doesn't do all that much cooling. It's also expensive to run. I also had to build a custom insulation cap for keeping the cold air out of the living space in the winter.

    Remember to put a high-temperature cut-off switch in-line with either type of fan - you don't want it to turn on and feed a fire!

    1. csnow | Nov 07, 2003 11:08pm | #10

      Many of the problems you mention with your whole house fan can be eleviated by getting a Tamarack fan instead.

      Part of the energy savings comes from running the AC a lot less.

      1. BillMcG | Nov 08, 2003 12:38am | #12

        Wow, they look nice.

        for others:

        http://www.tamtech.com/hv1000.htm

        It might be worth saving up for one of these, even though it's about 6x the cost of the one I got.

        1. csnow | Nov 08, 2003 12:53am | #13

          They have to sell direct for full retail.  Some of their distributors do sell them for less than MSRP.

          Not saying they are cheap, just less expensive...

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

Podcast Episode 690: Sharpening, Wires Behind Baseboard, and Fixing Shingle Panels

Listeners write in about fireplaces and ask questions about sharpening hand tools, easier wiring upgrades, and fixing cedar siding.

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 690: Sharpening, Wires Behind Baseboard, and Fixing Shingle Panels
  • FHB Podcast Segment: Hand Tool Sharpening Tips
  • Old House Air-Sealing Basics
  • A Drip-Free, Through-Window Heat Pump

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
  • Old House Journal – August 2025
    • Designing the Perfect Garden Gate
    • Old House Air-Sealing Basics
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work

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