New H.E. furnace & old windows vs. New windows & old furnace

Trying to see if anyone has ever experienced what the marginal savings would be between the two options.

Both are sizable investments into a home, but which yield's the "best bang for the buck"?

My thoughts are better windows & insulation first, so that the furnace doesn't work as much in the winter; and won't need A/C in the summer.

This is for a home built in the early 90's with a mid-efficiency furnace and double pane glass already. Exterior envelope has additional Styrofoam insulation underneath the vinyl siding already, would be adding additional blow-in fibreglass in the attic space

Thinking of switching to triple pane low-e glass; or a H.E. furnace & A/C.


My previous house was awesome with triple pane low-e windows, H.E. furnace and R60 insulation in the attic. Nice & warm in the winter and cool in the summer w/o A/C. Gas bill barely broke $50/month when it was -30C outside, with a constant 20C inside temp in the winter.

I've been doing a whole ton of research on furnaces lately since I need to replace my POS. There isn't much savings going from a relatively modern (ie last 20 years) furnace to a fancy high efficiency 2 stage furnace in terms of gas usage. Where you'll get savings is on your power bill by switching to the old school AC motor to a new DC motor in the blower. So you can get that either with a furnace upgrade, or just upgrade the blower. There are retrofit kits available now for AC to DC motor replacements. Oddly pricey in Calgary, about $1000 going rate installed. People seem to be buying parts for about $500 out east and installing it themselves as there are big rebates for switching to an ECM DC motor.

I believe (my contractor told me) you can also get low-e thats double paned. Because if you have sliding windows as my house does you cannot use triple pane due to their weight.

Changing out your windows will do sweet fuck all (your windows are about R-2, the best windows will give you R-6). Get the attic insulation up to R-70 at least, R-90 if you can. Spray foam your rim joists in the basement. Change out the dryer exhaust. Air seal your kitchen fan exhaust. Remove all your window trim and spray foam the gap.

are the prices of replacing windows and replacing furnace comparable? I thought windows would be significantly more

Replacing windows is incredibly expensive.

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Originally Posted by suntan

Replacing windows is incredibly expensive.

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+1.

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Originally Posted by rage2

I've been doing a whole ton of research on furnaces lately since I need to replace my POS. There isn't much savings going from a relatively modern (ie last 20 years) furnace to a fancy high efficiency 2 stage furnace in terms of gas usage. Where you'll get savings is on your power bill by switching to the old school AC motor to a new DC motor in the blower. So you can get that either with a furnace upgrade, or just upgrade the blower. There are retrofit kits available now for AC to DC motor replacements. Oddly pricey in Calgary, about $1000 going rate installed. People seem to be buying parts for about $500 out east and installing it themselves as there are big rebates for switching to an ECM DC motor.

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I recently retrofitted a Mars Azure into my furnace in April. It's hard to tell if there's any energy savings so far since the furnace doesn't run much in spring. The motor also has an option to do a constant low speed run which helped even out the temps in the house a bit especially when the temps outside caused the furnace/AC to never kick in. Available from Amazon but a little pricey right now, I've seen the price hover around $250:
https://www.amazon.ca/Mars-10860-Azu...rds=mars+azure

Pretty simple and straight forward to install. Here's a guide:
https://thelazycouple.com/give-your-...nd-9b7bfb4f8ea

Windows average around $1000 per unit. At least thats what we averaged with low-E double plane vinyls. We replaced our 40 year old double sliding aluminium and wood framed units.

I agree that in newer homes, other efficiencies should be found first. Furnaces arent generally upgraded unless they are completely shot.

Thanks for the info guys.

Yup the windows are definitely pricey to do the entire house in triple pane low-e; I had Pella triple pane low-e in my previous house and they were awesome (keeping out noise and helping to keep heat in/out).

Just trying to see whether or not upgrading the furnace w/o doing the windows first defeats the purpose, as the heat-loss in the winter would negate the savings.

rage2 - interesting info, will have to look into that conversion. I didn't think there would be much benefit on the burner technology going with the H.E. furnace.

suntan - yup the air sealing will definitely be done too. All the exhausts have had a one-way flapper either replaced or installed (bathroom fans, dryer, hood vent etc.)

goldfish168 - I'll have to check that out too.

Replacing a working furnace or your existing windows - you won't see the payback for decades. Find and address inefficiencies elsewhere as others have suggested.

Don’t replace your mid efficient furnace. Those things are usually great and you should run into fewer problems keeping it over getting a new high efficient model. You certainly can still get ac. It doesn’t matter if you have a mid or high. But I would recommend getting a cased evap coil and spacing it 4-7 inches off the top of your furnace, just to ensure enough room for the eventual new furnace and to keep the heat from the furnace from melting the condensate tray.

Edit- I fully agree with suntan.

Forty year old home. Had double sliding aluminium windows. We replaced all our windows, a patio and front door. Very noticeable difference. Both warmer and much quieter. Also noticed that as they are now much better sealed up then the old windows, we no longer feel that cool draft coming from the windows. We went with triple pane units that now open outward. Basically, our first phase of a internal rebuild that we plan on doing over the next four years. New furnace and hot water heater are one of the last things we'll do as they are in great shape.

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Originally Posted by JDMMAN

Thanks for the info guys.

Yup the windows are definitely pricey to do the entire house in triple pane low-e; I had Pella triple pane low-e in my previous house and they were awesome (keeping out noise and helping to keep heat in/out).

Just trying to see whether or not upgrading the furnace w/o doing the windows first defeats the purpose, as the heat-loss in the winter would negate the savings.

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Sounds like your house is already fairly efficient, why spend a lot of money chasing diminishing returns? You probably won't ever make back the initial investment. If you're doing it for conscience / to be a hippie, go talk to Gestalt about solar.