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

Choosing new furnace

Dunc1 | Posted in Energy, Heating & Insulation on February 10, 2009 06:56am

Getting around to replacing my old, low efficiency (<60%) forced air/natural gas furnace though I will wait for better weather. This is
the original equipment and is now 20+ years old. Still works but I figure that I am on the short end of the leash.

Most offered around here (Ottawa, Ontario, Canada) are 95% efficient.

A few questions: in-store mock-ups use plastic pipe as the exhaust. Is this for real? Seems I remember a big screw-up with this arrangement several years ago. Is there a consumer choice of materials? What are they? Pros/cons?

Will also install a new central ac unit. Systems offer SEER ratings from 13-20. I appreciate that “you get what you pay for”; however, is there a way to evaluate how much do I really need based upon the amount of air conditioning required (degree days?), energy costs and payback time? How much more efficient is – for example – a 16 rated machine vs a 13 rated system? Would I see a difference in electricity consumption month-to-month or would it be a little bit that adds up over time?

Any other pointers appreciated.

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

Replies

  1. seeyou | Feb 10, 2009 07:09pm | #1

    I installed a 17 seer hybrid heat pump/nat gas system last summer, replacing a 50+ y/o gas furnace and 20  y/o A/C unit.

    Cooling costs have dropped by close to 50% with greater comfort and the heat pump works down to around 12F. I realize you're in a much colder climate, but I'm pretty darn impressed with this system. My heating bills have been about 50% less as well, but we're experiencing a much colder winter.

    And yes, the PVC exhaust is for real. Little or no heat going into the flue, but lots of moisture.

    http://www.quittintime.com/      View Image        

  2. DanH | Feb 10, 2009 07:30pm | #2

    Yes, all high efficiency gas furnaces use the plastic flue. They must use plastic since the moist, acid flue gas would corrode normal metal flues and destroy masonry ones.

    Note that the high efficiency furnace will also need a condensate drain. This can be just a hose into the basement floor drain, or run outside (in warmer climates where this is permitted), or it may require installation of a condensate pump (not too expensive) to pump the condensate up and over to the washing machine standpipe or wherever.

    My understanding is that SEER is, roughly, inversely proportional to energy consumption. Ie, a 10 SEER AC will use about twice as much electricity as a 20 SEER AC to produce the same amount of cooling. It is, of course, calculated as an "average" over some mythical cooling season, so you can't exactly take SEER to the bank, but the numbers really do mean something.

    One important thing is to make sure the installer uses the right components. A 16 SEER condenser unit may only do 13 SEER if the wrong A coil is installed -- be very leery of someone who wants to reuse the existing A coil or use an off-brand one.

    The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith
  3. GPAH | Feb 10, 2009 07:31pm | #3

    There was a recall on Plexvent - a type of plastic venting system for moderately-high eff furnaces & boilers. There has been some controversy regarding PVC as a venting material, although the test of time seems to be showing it works well. Polypropelyne is preferred by a few manufacturers while others require stainless steel to carry the exhaust. The higher the efficiency, the lower the exhaust temperature & the more likely plastic is suited. Condensate - a by-product of the combustion process - is mildly acidic and you'll produce aprox 1-gallon per each 100K BTUs burned for gas & 1/2-gal for oil in high eff boilers & furnaces. Condensate grants a boost in eff when collected and its latent heat is extracted for heating. It's easily neutralized & should be treated before being discharged to the plumbing system. With the cost of fossil fuels on the march upward (again), your best investment is in a 90+ model instead of an 80+ chimney-vented appliance. Typical ROI (return on Investment) is well above 10%. You can project the ROI if you know two things: the difference in cost between the 80+ and 90+ eff models; and the projected fuel savings. Divide the cost diff into the fuel savings. EX: $2,200.00 more for the 90+ model with $300.00 projected fuel-cost saving = .14 or 14% ROI.

     

    A hybrid heating system (furnace coupled with heat pump) adds about $600.00 & allows you to switch between electricity & fossil fuels if one is less than the other for heating. Right now electricity via a high-HSPF heat pump beats fossil fuels, but that's going to flip following deregulation of electric utilities. 80% increase is being projected for my area.

    SEER ratings: for each rise of 1-point, you will see an average reduction of 10% in operating costs from the previous point level. So, a 26-SEER unit will operate at half the cost of a 13-SEER unit. Mini-split inverter (variable speed drive) units are available with 26-SEER and 13-HSPF. Mini-splits give you the ability to spot-cool/heat just the area(s) you're occupying instead of the whole house = additional saving$.

    However, for central systems, there are a ton (pun intended) of options from inverter high-SEER units to two-stage to single speed. ROI can be calculated the same way as outlined above.

    It's your money and your investment to make. A/C units last an average of 16-years, so R-410a is the best option for refrigerant in spite of R-22 units still being available. 2010 marks the end of manufacturing R-22 units & 2015 the end of making R-22. R-22 equipment purchased today at discounted prices may well bite you in the rear when, or if, service is required.  

     

  4. Jay20 | Feb 11, 2009 07:31am | #4

    I also installed a Hybrid system this past year and have the same results as another contributor here. You are further North than me so your circumstances may be different. Just wanted to add the following. The heat pump on my system is staged. Runs slowly when only needing a little cooling. This feature saves a lot of money. It will run longer at a lower output which keeps the temperature inside of the house more constant and because of that a higher thermostat setting is more comfortable. The gas furnace on my system is 95% efficient but is either on or off. I noticed there are a few furnace manufacturers that are now offering variable output units. Low output when only needing a little heat. This seems like a feature  that can keep the home comfortable with using a lot less energy.

    1. seeyou | Feb 11, 2009 02:40pm | #5

      a few furnace manufacturers that are now offering variable output units. Low output when only needing a little heat. This seems like a feature  that can keep the home comfortable with using a lot less energy.

      That's true with my system. We seldom realize it's on. None of the hard cycling as with the old system.

       http://www.quittintime.com/      View Image        

    2. User avater
      BillHartmann | Feb 11, 2009 05:08pm | #8

      Well you already have 3 stages of heating. There is no need to have more in the furnace..
      William the Geezer, the sequel to Billy the Kid - Shoe

      1. sledgehammer | Feb 11, 2009 05:43pm | #9

        Low output when the heatpump goes into defrost mode is nice.

      2. Jay20 | Feb 12, 2009 03:59am | #12

        Bill:  Since the first week in December till this week the outside temperature has keep the heat pump off. What I was referring to was the gas portion of the system. I normally keep the fan on low in the winter. I am heating 3 floors and that seems to even out the heat. When the heat pump is off and the system calls for heat it shuts down then the gas burners kick on and when it decides that the heat exchanger is warm enough the fan kicks back on. I have seen newer systems wear the gas unit kicks on with a lower amount of heat and runs for a longer time. This keeps the inside temperature constant. If the newer unit scenes the amount of heat it is providing is not keeping up it will step up the number of burners it is firing. My gas portion of the system is either on or off.

        1. seeyou | Feb 12, 2009 04:32am | #13

          If the newer unit scenes the amount of heat it is providing is not keeping up it will step up the number of burners it is firing.

          That's how mine works - low fan speed with a few burners running longer times. If it gets colder, burners are added and fan speed increases. http://www.quittintime.com/      View Image        

          1. Jay20 | Feb 12, 2009 05:26am | #14

            You might be right. Just doesn't seem that way. I have a service guy scheduled for May to do yearly service. I will ask him if your thought is correct. Jay

          2. Jay20 | Feb 12, 2009 06:01am | #17

            I went down stairs and read the installation manual. The furnace has the capability for low,medium, and high heat depending on the need if certain trip switches are set correctly. . If those switches are set differently it will only come on at one heat level. I will have the service guy check these settings. Thanks for the info.

            Edited 2/11/2009 10:03 pm ET by Jay20

  5. danski0224 | Feb 11, 2009 02:45pm | #6

    Biggest thing is the installation, not the name on the box or the company salesmen.

    PVC pipe is OK for vent material. Have it installed with 2 pipes- one for intake, one for exhaust.

    Most people that live where it snows will never see a payback from a high SEER straight AC unit... that 16 SEER unit is quite a bit more money than the 13 SEER unit. The SEER ratings also encompass the rest of the HVAC system (ie: ductwork) and a fudge factor. If you want to measure the true efficiency you need to look at the EER ratings which is simply a number arrived at from the btu's you get from the kW you put in.

    Nothing wrong with a heat pump, but you have got to watch the specs. Performance of most air to air units goes down as it gets colder outside. Some single stage units provide more heat than multi stage units. For most, register temp is lower than fossil fuel.

    So far, the only exception to the above is the Acadia from Hallowell.

    Multi stage or modulating furnaces do not maintain their efficiency rating at less than full output. Heat stages/modulation is there to improve homeowner comfort, not to save money on utility bills. You still need #### number of btu's to heat or cool. Multi stage equipment is pointless if you do not use the correct thermostat.

    Your energy savings will come from installing a properly sized piece of equipment... that means a load calculation.

    Improvements in the thermal envelope of the home will return more in energy savings than a high dollar HVAC system.

    The best bang for the buck in equipment and energy savings would be a variable speed blower. That savings will be maximized if your ductwork is done correctly. A VS blower connected to bad ducting could cost more than a PSC motor because the VS electronic feedback system will try to develop/maintain the cfm the computer tells it to deliver despite duct/filter restrictions.

    Do not reuse any component of your existing AC system- especially the lineset if going to R410A. That R410A system must be installed properly or it will die an early death (it will make it thru the 1 year warranty, but the problems will happen). Micron gauge and nitrogen purge while brazing are important.

    1. sledgehammer | Feb 11, 2009 03:42pm | #7

      I was also shopping for a replacement system, looking for a spring or fall install, but the deals out there right now were too hard to turn down. New system was installed last week.

  6. dude | Feb 11, 2009 09:55pm | #10

    i got advice on here from Junkhound a couple of years ago and he was right

    when you talk gas   are you talking propane or natural and what cost per mil btu,s

    gas furnaces are 95 % efficient

    oil is 85% efficient , however there are more BTU,S in a gallon of oil than A gallon of propane

    gas furnaces are cheaper to install , one of the reasons installers push them

    they always talk about the furnace efficiency gas vs oil none i found will ever discuss BTU,s  i found

    after working it all out i found oil was  cheaper than gas

    PS , i live just south of Ottawa near Winchester so weather is the same only we dont get any hot air from the Hill !

  7. Chucky | Feb 12, 2009 01:32am | #11

    Did you get your energy audit done yet ?  The audit will cost you around $350 but you get 150$ back from the Ontario government and the audit will give you a $1000 rebate for the furnace upgrade.  You can also get other rebates for other upgrades such as new windows, doors, low-flush toilets, etc.

    I'll post more on furnace later,  my daughter as a fever and is calling me...

     

  8. barmil | Feb 12, 2009 05:41am | #15

    Some of the answers digressed into heat pumps, which shouldn't be an option in Canada or here in Wisconsin. I changed out both the heater and the A/C at the same time last year, even though both were fairly efficient. They were just noisy, and I got rid of the Lennox Pulse heater, which sounded like a German buzz bomb in the vents when running, and a York compressor that was just too loud outside for comfortable grilling and relaxing. Now all I hear is a faint air movement inside and nothing outside. The contractor was a bit baffled that they both still worked welll and I wanted them out of here, but I'm 61 and I just didn't want the noise and wished to change it while I could still afford it. I guess the answer is to do what you want for the long run and can afford. As to what size to get, leave it to them -- I think they do a good job of judging by my expeience. Be sure to mention any additions like finished basement you might be planning for the future. Oh, I have the variable speed fan and two stage heater -- worth it for comfort and energy cost.


    Edited 2/11/2009 9:44 pm ET by BARMIL



    Edited 2/11/2009 9:46 pm ET by BARMIL

    1. DanH | Feb 12, 2009 05:43am | #16

      I'm amazed that there were any Pulses still out there. Thing must have been about 30 years old, and it was one of the first-generation condensing furnaces.
      The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith

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

A Classic Paint Sprayer Gets a Thoughtful Refresh

The Titan Impact X 440 offers great coverage with minimal overspray.

Featured Video

A Modern California Home Wrapped in Rockwool Insulation for Energy Efficiency and Fire Resistance

The designer and builder of the 2018 Fine Homebuilding House detail why they chose mineral-wool batts and high-density boards for all of their insulation needs.

Related Stories

  • Podcast Episode 693: Old-House Hazards, Building Larsen Trusses, AI in Construction
  • FHB Podcast Segment: Finding Hazardous Materials in a Fixer-Upper
  • A Classic Paint Sprayer Gets a Thoughtful Refresh
  • Podcast Episode 692: Introduction to Trade Work, Embodied Carbon, and Envelope Improvements

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