Choosing Windows for Best ROI
I live in Iowa. Our home was built in 2010 and has cheap builder grade vinyl windows–at least double pane though. We are looking to replace them. We are very energy efficient conscious but also budget conscious. Two things that conflict when window shopping. My question is this, compared to high quality vinyl double pane with argon and low-e, which would be the best value.
1) Moving up to high quality fiberglass double pane with argon and low-e.
2) Moving up to high quality vinyl triple pane with argon and low-e.
I don’t think we could stomach the cost of fiberglass triple pane.
To make things more complicated, we also have a patio door (north side) we want to replace too. Thoughts or suggestion on that?
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This isn't a simple question. To begin to answer it you'd need to know the cost of installing the new windows, the annual energy cost with the existing windows and the annual energy cost of the new windows. Then you'd have to make some assumptions about future energy costs and the cost of money. Windows don't last forever, so you'd have to make some assumptions about the life of the new windows and the remaining life of the existing windows. In a way the decision isn't so much about keeping or replacing the existing windows as replacing them now or at the end of their natural life.
To get you started, here's how you can estimate the annual energy cost of a window. Every window sold in the US since about 2000 is required to be rated by the NFRC. They rate windows on three factors that are of interest to energy efficiency: U-factor, solar heat gain, and air infiltration. Note that infiltration is voluntary and may not be rated. Your windows should be labeled somewhere (usually discreetly) with the manufacturer name and other identifying information, from that you should be able to find out the NFRC ratings.
U-factor and air infiltration affect heat loss in the winter and heat gain in the summer. Solar heat gain is trickier because in the winter it's a good thing and in the summer it's a bad thing. It's also highly dependent upon how the window is oriented and mounted. The general rule is if you spend more on heating than cooling you want higher solar heat gain, and vice versa.
The formula for estimating the annual energy usage of a window through heat loss is to take the U-factor, multiply by the area of the window in square feet, multiply by the heating degree-days for your area, and multiply by 24. That gives energy usage in BTU. Multiply that by your cost per BTU to get dollars per year.
The conventional wisdom is that it's usually not cost-effective to replace windows until the end of their natural life. However, life isn't just about dollars and cents. Nice windows make for a nicer house.
Why do you want to replace the windows you have now?
The current windows don’t seal well and feel drafty in winter. We will be living here for 15+ more years so we are trying to slowly replace things to make the house nicer and more comfortable.
Are you sure it's drafts through the windows or are you experiencing convection effects from the cold glass? If you tend to feel it in the winter months, it's more likely to be a convection effect. That suggests to me that moving up to triple panes might be the best way to address comfort issues.
https://glowindows.com/why-do-i-feel-a-cold-breeze/
Unless your old windows are literally falling off the house or have aluminum frames you are very unlikely to be alive to see the day when replacement window have saved enough fuel to repay their high cost! It is a lie to say replacement window have an ROI because they cost so much and save so little and they add almost nothing to the price of a home at sale.
If you want to justify new windows on the basis that the home will be more comfortable and smoothly operating windows give you joy instead of frustration if you can afford that luxury then I say go for it but don’t fool yourself in to thinking you are saving money in any way.
Walta
New windows can't really be justified just using energy savings. You'll have to value the other aspects highly.
As others have noted, ROI is the wrong framework for thinking about new windows. What they do is make your house better -- more comfortable and more pleasant to be in.
The thing is, those are highly subjective measures, only you can decide whether it's worth it to you. We can help you with some of the factors that make windows good windows. But the other thing to consider is that the window business is highly regionalized, so pricing and availability varies depending upon what part of the country you're in and it's hard to make recommendations about specific brands.
Remember to consider the frames too, they have a nontrivial effect on performance.
Dave is sound transmission a factor at all here?
Just a few comments on the windows based with a lean towards budget. Double pane sliders are very difficult to seal, and as you've found, leak pretty badly with air pressure at play (windy day). Replacing those sliders with decent casement, double or triple pane would make a big difference. You can replicate the look of a slider with a fixed top light, and outward opening awning lower, so you can open them in the rain.
A decent triple pane reduces sound transmission a surprising amount and can improve thermal performance considerably. I've taken quite a few thermal images over the years which really highlight issues with frame design, but you're largest issue right now is air leakage. A casement/awning setup from a reputable manufacturer will address that.
If you're replacing windows, I'd also consider how many actually need to be operating based on your use, and code. Fixed windows are a lot easier to deal with when air leakage is a concern.
I would see if you can get an energy audit done with a blower door test. Really try to pinpoint where the air leakage is. Did they stuff fiberglass between the frame and opening instead of spray foam? Maybe your windows just need the weather stripping replaced?
As others have said, its really hard to justify new windows if they are still operable. Another thing to consider is if you are going to re-side your house in the next 10 years or so (assuming you have siding). This is a great opportunity to do both projects at once and make sure the windows are flashed properly and integrated in the wrb.