New Windows In Basement: Worth It?

Windows would insulate better but it will probably be chilly in the basement by nature - that is why it is cooler in the summer despite +100 temps. To be honest I see you live in CO? It might be good to have a bit of airflow in the basement due to the natural surroundings.
Please don't run screaming from the room when I say uranium is a rock, it is present in CO and it decays into radon. It is normal in CO to have high radon in basements, and what keeps if from settling in your basement is airflow.
I would recommend a good fuel efficient electric space heater. They can be very nice.

 

Do you use the windows for light? I know that sounds silly but during the winter I found our basement windows weren't providing any more light than the lights in the room. So I actually covered them with foam during the winter.

Other than that, I normally recommend just insulated glass. However, in Colorado you might consider some argon gas in between the glass panels. The low-e probably isn't necessary as it's a basement and doesn't get much light, and if it did in the summer I doubt it would heat up too badly.

 

Windows can be fairly expensive, and it's difficult to make back your outlay in energy savings alone. Given that they're in the basement, I'd hunch you're less concerned about their looks than you would be if they were in the living room. Home made storm windows, inside and out, will probably give you just as much thermal efficiency at a fraction of the cost.

 

Even with insulated glass the R-value is ~R-2. (Single glass ~R-1)

Adding a $2 3M indoor window insulator kit, heat shrunk with a hair drier will cost next to nothing, will cut down direct heat loss by 30-50%, plus will cut down on cold air infiltration adding to the reduction in heat loss, all at a cost way less than replacing the windows. The 3M kits are perfectly clear, you can't see them inside or out, and in the summer, you can take them down and reuse them year after year if you wish.

Low E glass is fine for cutting down on thermal solar gain, but does noting for cutting down on heat loss. Exotic gases reduce heat loss somewhat, but what really cuts the heat loss is the dead air space between two panes of glass.

Icarus

 

A caution should be added about blocking the windows with rigid foam. Sure, it'd be great for stopping the heat loss, but if worse comes to worst, you may need the window as an escape route. I'd recommend against the foam for that reason alone, and suggest you keep a suitably sized rock handy on the windowsill, just in case.

 

Currently, I have three full-sized windows down there that feel cheap, and have aluminum frames but not any problems with condensation or drafts that I can tell.


Is it noticably cooler in front of the windows?


However, it's noticeably colder than upstairs, and feels very chilly in the winter.

That's because the upstairs is insulated, and the basement is not.


I'm considering putting in low E4 glass with better composite frames,

What if you left the existing sashes in place, and went with an E4 storm window? More bang per buck, no? Do you have a picture of a typical window in its opening? I redid my basement windows this summer and now have DIY triple glazed.

 

I work in my basement and have roughly the same issue, but with old casement windows. I decided to go with interior storms using the 3M film (but with a twist), and add a heater. Here are my observations.

First, don't confuse temperature with insulation. With 20-20 hindsight, my basement is almost certainly the best-insulated room in the house. It just happens to be a) the sump where all the cold air flows and b) doesn't have enough heat. So, it is cold, but it is not poorly insulated.

I should have realized it, but in fact I only figured it out by accident. In the process of adding a permanent heater, I had to run an electric space heater, on low, to get some adhesive to cure. The tiny little space heater, on low, kept the basement comfortable. This is a pretty big basement -- about 40x30 or so -- but almost entirely underground, with just five small casement windows. (I should also say that the basement is mostly finished, and that was done right -- with insulation-filled stud walls over the cinderblock.)

The upshot is that it takes less energy per square foot to keep my basement warm than it does to keep the above-ground portion of the house warm. This might also be true for your house.

Second, I have had the 3M film on the windows and it works great. But lately I've started making interior storms using a PVC pipe frame, covering both sides of the frame with the 3M film, fitting that inside the casement window opening, using foam (caulk saver) to fill the gap between PVC pipe and window frame. Now I get two properly-spaced air gaps. When I've done all the windows, I might put a second one in each opening.

Finally, for heat, I went with a Toyotomi direct-vent kerosene heater. I just happened to have it on hand -- I'd used it to heat a shed where I used to live. There's a high up-front cost for that, but Toyotomi claims 87% efficiency. Anyway, it's a dandy piece of equipment and I already owned it. In no way would it be cost-effective relative to a portable electric space heater.

I was reluctant to use an electric space heater on a permanent basis. It's probably not dangerous, but resistance heat is inefficient, and I've seen one case (my sister-in-law) where long-term use of a resistance heater screwed up the house wiring where the heater was plugged in. Certainly should not be a problem if you don't run it on a high-current setting.

My advice: Test to see whether or not small improvements will make the basement comfortable. If so, leave well enough alone. With hindsight, 3M film plus a small electric space heater would have done me fine. I suffered through two winters because I had assumed I'd have to dump a lot of energy into the basement to heat it up. And I was dead wrong.

 

Just watch out for CO levels if you're heating your basement with fuel...

If your house is properly wired, you shouldn't have any issues running a 1000-1500w electric heater.

A heat pump would be 2-4 times more efficient depending on the model and outside temps, but the install is a lot more difficult. You could probably get a window fit heat-pump. Basically the same as a window fit AC unit, except the heat pump can either heat or cool, but a lot more efficient than straight electric resistance heating.

Edit: Could use a portable heat-pump like this, too: http://www.amazon.com/Soleus-Air-LX-140-Evaporative-Dehumidifier/dp/B000HHJ13I

 

Drees,

I think his kerosene heater is :"Toyotomi direct-vent kerosene heater"

Vented.

My favorite small heater is a Rinnai vented gas space heater. Great product, super efficient, easy to install, little parasitic energy cost, great for zone heating. (and no maintenance except for the air filter!)
Browse Direct-Vent Wall Furnaces - Rinnai

Over 80% afue. Available in natural gas or propane. Personally I hate kerosene and oil. Both oil and kerosene are smelly fuels both in the liquid and the exhaust, and burners need annual cleaning. On a per BTU/$$ basis, natural gas almost always wins if you have it. Propane/oil/kerosene can all be in the same ball park depending on location. Right now I am paying ~$2/gal for propane, with ~79,000 BTU/Gallon. Kerosene has more BTU/gal I believe, but I know I pay more than $4 for it. By the time you calculate the BTUs into the room the propane wins hands down for me.

 

Nice, no worries about CO unless it develops a leak - still not a bad idea to have a CO alarm for each level of the house.

Just installed a 95% AFUE gas furnace in my home. Works great. Even though the new furnace is 60% of the capacity of the one it replaced, it's still a bit oversized for my climate.

Still working on solar for my home, then I will use our heat pump more for heating.

Edit: Back on topic - there are snap-in frames for windows as well - same concept as the 3M window film but easier to install/uninstall. Long term may be less expensive and less hassle.

 

Yes, mine's vented to the outside. No way I'd run an unvented kerosene heater -- that's not very different from breathing diesel exhaust all day.

If I'd had natural gas at the time, I'd have gone with the Rinnai as well. No question.

No doubt that kerosene is nasty stuff but I've had good luck so far with the Toyotomi. Between using it lightly (I'm on my 4th winter and I've run maybe 80 gallons of K1 through it), and being totally paranoid about fuel quality (I'm seldom burning kerosene that's more than a few weeks old), it's been really clean. No kerosene smell in the house (the tank is outside), and only the occasional whiff of exhaust outside. If I had to use it as a whole-house heater and ended up burning last year's fuel, I'd probably be singing a different tune. But as a small-area space heater, with constantly fresh fuel, it's been fine.

What finally got me to try it was peak capacity. Which also might be a useful guide to the OP. A 1500 watt electric space heater is about 5000 BTUH. I have the smallest Toyotomi and on high it does 15000 BTUH. So you might want to step up from an electric space heater if you need more than about 5000 BTUH to keep you comfortable or to bring your space up to a comfortable temperature in a reasonable period of time.

I have to admit I never even considered a heat pump. Just plain prejudice -- I vaguely recall that when it's really cold, they default to being resistance heaters or some such. But that could just be ignorance on my part.

Finally, I should mention window treatments. Properly installed insulating drapes give you about another R or so, but they have to be done right -- have to hang right down to the floor, to stop the thermal siphon of air falling down the cold glass of the windows. If you have a lot of glass area, going from R2 to R3 can make a pretty big difference. I have a set in my den across the glass doors and I notice it if they are left open. But you lose the light when you do that.

 

It depends on the heat pump and the outside temps.

Since a heat pump is just moving heat from outside to inside, the warmer it is outside, the more heat is available to move inside.

The colder it gets, the less heat output it has. Efficiency also drops at lower temps, but they generally are always more efficient than electric resistance heating.

At some temperature point, generally somewhere around freezing, it won't push enough keep to keep the room warm, and that's when you need backup heat (typically resistance heating, though for full-size systems you can back it up with gas now - I have one of these setups).

 

Our Montana home was built in the 1890's and the basement windows are still original ... it's one of the last things we need to cure. We don't need to go down into our basement much, and the ceiling is insulated, so our 1st floor stays warm, above the basement. Last trip up there, we insulated the central heater ducting in the basement. Incredable ... the prior owner went for over 40 years, pee'ing away probably 1/4 the heat output. Low hanging fruit. Get the new windows!

You can even hang a hunk of styrene/foam in front of the windows. Heck, we've already done that and it's GREAT as a temp fix. Try it out! We've done that as a temp fix for our original 1890's basement door too.

.

 

Consider the idea of a geo-thermal heat pump that either uses ground water or the earth as a medium. Especially in colder climates it is a much more efficienct. In hotter climes, consider using the heat pump (in ac mode) to heat domestic hot water.

Icarus

 

I've heard that bubble wrap works great, too, and still lets in a decent amount of light. Double up for extra layers.

 

To address the OPs question directly:

I think you literally need to experiment to see whether or not changing the windows would make the basement more comfortable. There are just too many variables.

It was not clear from your post what your current windows are. Sounds like they are tight and don't leak a lot of air. If they are single pane, assume they are R1, if they are double pane or singles with storms, assume R2, and figure that your new windows might come in at R3.

Or look at some reputable source for typical R-values for window assemblies, e.g.:

ColoradoENERGY.org - R-Value Table

Above ground, standard construction, you can just do the arithmetic to figure roughly what fraction of your total heat loss is through your windows. Say, with R30 roof, R12 walls, R1 glass, the fraction of your heat loss through the glass = glass area/(glass area + 1/12th wall area + 1/30th roof area). Doing that for real, you'd need to factor in floors and doors, but that's the gist of it.

But for a basement room I can't even hazard a guess. That's one of the reasons why I think you need to find out experimentally.

So, let me assume you're planning to up your windows by R1 (or R2). While there is no hard data for this, the consensus seems to be that one layer of big-bubble bubble wrap is about an R1. That seems about right to me.

My suggestion is to temporarily tape a layer or two of big-bubble bubble wrap over the windows, and use the results from that as your proxy for what better insulated windows would do for you.

So if were up to me, I'd use bubble wrap and a portable electric space heater, and over the course of a weekend or maybe longer, I would form my best guess for how much new windows would help. Try four scenarios, giving each a few hours to reach equilibrium. If you are a data-driven person like me, use a thermometer to record interior and exterior temperature.

Four scenarios, bubble wrap (y/n) crossed with more heat (y/n).

Room as is (nn)
Couple layers bubble wrap taped over windows (yn)
No bubble wrap, but set a small electric space heater on low (or medium or high) (ny)
Both bubble wrap and space heater (yy).

If bubble wrap alone makes it comfortable, then you have an answer. Windows that provide that much insulation will solve your problem. Your main uncertainty if exactly how much insulation value the bubble wrap had.

By contrast, if bubble wrap plus space heater doesn't solve the problem, then your problem is bigger than your windows.

In between, it's a judgment call. If bubble wrap alone doesn't solve it but (say) a space heater on low does, then the issue is too little heat being put into the room. That's what I've got -- a well-insulated room with one lousy heat vent.

And so on.

So that's my recommendation. I think you should assess the R-value of your current windows, assess the R improvement you are likely to get with your new windows, mock that up with bubble wrap, and test for impact.


FWIW, I actually did an experiment like this to determine that my cellular shades added no more than R 1.5 to my windows, nowhere near the R4 that the manufacturer claimed. Using multiple thermometers and all that. So I think it pays to test things yourself, as best you can. You don't want to buy new windows and still be cold.

 

I have found cellular shades to be very helpful. If I had it do do over I'd buy them again.

They were just not as helpful as the manufacturer claims, for my particular situation. They were well worth the investment. They are a snap to install. And in my case (a modern home), they look much nicer than, say, window quilts or thermal drapes.

The issue is that the manufacturers will quote about an R4 or so for double-cell shades. Which, if you achieved it, would be really great. And you might, in the right circumstances. But I suspect that is under optimal conditions, and I suspect that ignores air leaks around the shade.

My case is not typical, and my case is not the best situation for using cellular shades. I have a roughly 5' x 10' bow window with single-pane glass. I bought two shades to cover the entire front of the window bay.

The problem is that this left a large air space behind the shades. So I get a lot of convection behind the shade, and a lot of thermal siphon, which negates the insulating value to some degree. I want still air, but I don't have it.

On a still day, cold air streams out the space between the two shades. Basically, the window space creates its own breeze -- that's how strong the thermal siphon is. I've since placed a piece of foam between the two shades while I think of some better solution.

Anyway, today, it's 30 outside, and the air behind the bottom of the shade is 42. Well worth it to keep that 42 degree air in the window bay instead of flowing into the room.

(For comparison, I have a set of thermal drapes in another room, roughly similar situation, and, adjusting for differences in room temperature, the air behind the bottom of the thermal drapes is 50. Situations aren't identical, but they tell me what I suspect anyway: cellulars work better than thermal drapes, or at least, better than the drapes I have.)

That said, when I measure the temperature profile all the way up the bay (gets warmer toward the top) and average, assuming the original single-pane glass is R1, I estimate R1.5 for the whole shade assembly. So, better than thermal drapes, but in this instance, not a miracle cure. And definitely not R4.

On the other hand, I realized my setup was not good when I bought the shades. I'd be willing to bet they'd do better placed close to a flat pane of glass -- much harder to get convection going in a thin air space.

Based on my experience, my recommendations would be to do everything reasonable to minimize convection and thermal siphon. So:

1) If possible, fit just one shade in the window. If the window is too broad for that (mine was), then get the "two shades on one header" option to minimize the gap between them.
2) With 20-20 hindsight, I'd have gone for the shades with side tracks. I didn't like the look when I bought mine, and the manufacturers show very little R improvement for them. But my experience is that air flow around the shade matters.
3) Barring that (e.g., if you don't like the look of side tracks), I'd overstate my window width by 1/4" and, if necessary, leave the end caps off the metal parts of the shade, to minimize gaps at the sides. (I measured exactly and the shades were cut 3/8 smaller than the exact measurement. That's a reasonable thing to do but I think I'd try to game the system a bit the next time, see if I could get a slightly tighter fit.)
4) You have to have enough flat windowsill to allow the bottom of the shade to sit flat on the window sill. That's what stops the thermal siphon. This will work for pretty much any window as long as it is not set too close to flush with the interior wall.

I ordered mine here: decent price, good service, nice-looking product. Discount Faux & Wood Window Blinds, Window Shades, Mini Vertical Blinds

Basically, not regrets. I'd just do things differently if I were to redo. Plus, I just like the elegance of the concept -- they use very little material and they do their job well and stylishly.

Finally, you can get these so that they'll open either a the top or bottom or both. That's so you can open up the tops to let in some view yet maintain a pocket of cold air next to most of the window. Might be useful for a basement room.

(Final aside: How did I estimate the effective R-value of the shade? In theory, in equilibrium, the heat flowing into the space behind the shade must match the heat flowing out of it. So, again in theory, the ratio of temperature differences between outside air, air behind shade, and room air tells me the ratio of the R-values of the window and shade. I think. If 2/3rds of the total temperature drop occurs across the shade, and one-third across the window, then the ratio of the R-values is 2 to 1. If the window is R1, then the shade in that example would be R2. I fully realize that when you have air moving around, R is not really the right concept, but I still think this gives a pretty decent measure of the overall effectiveness of the shade.)

 

Yeah, but it's really hard to walk around in.