Good trivia question

Paul Mitchell

Figured I would run this by you guys. I recently replaced my windows downstairs in my home. I heat with oil. How would I calculate the savings in oil gallons.? I figured I would do a heat calc based on old windows...Then one on new. Somehow use the differance with the average degree days and I should get close.
Any Ideas or answers to assist? Boy we sure do think of some odd things in our down time...at least I do.

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Mark Hunt

Ahhh windows!


I have a software program that allows me to calculate energy savings for home improvements like windows.

I have yet to see a pay back period of less than 70 years for windows.

People spend HUGE amounts of money on windows and they are told that the new ones are "Energy Efficient". Well, they are still glass and they are still sources of heat loss.

You may actually see your fuel bill rise with new windows, if they were not installed and sealed correctly. Stuffing fiberglass around the edges is NOT sealing. Fiberglass does NOT stop air infiltration.

A blower door test will let you know how well the new windows are sealed.

Mark H

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Dave H_2

Interesting enough

about windows.

We construct a wall with 6" insulation (R-19), then we cut a hole in it and place a piece of glass or two (double-pane) which has a higher R-Value than that of a single pane.

So new windows with an R-Value of 2.2

That is still almost 10 times less than the insulating factor of the wall!!!

Dave H.

eleft_4

trivia question

Paul,
It's a little late but a clock that is energized when the burner is actually firing would have given you the info you are looking for when calculating the difference by degree days.

al

Dave DeFord

> I have a software program that allows me to

> calculate energy savings for home improvements

> like windows.

>

> I have yet to see a pay back

> period of less than 70 years for

> windows.

>

> People spend HUGE amounts of money on

> windows and they are told that the new ones are

> "Energy Efficient". Well, they are still glass

> and they are still sources of heat loss.

>

> You

> may actually see your fuel bill rise with new

> windows, if they were not installed and sealed

> correctly. Stuffing fiberglass around the edges

> is NOT sealing. Fiberglass does NOT stop air

> infiltration.

>

> A blower door test will let you

> know how well the new windows are sealed.

>

> Mark

> H

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 238&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Dave DeFord

Thanks for the ammo...

I've been telling friends for a long time that replacing windows doesn't save any appreciable amount of energy - even if they are installed correctly. I've been told a number of times that I couldn't possibly know what I was talking about because all of the window companies say otherwise. Now I can at least quote some figures to back up my statement.

Paul Mitchell

Good idea

Firedragon said maybe a little meter on the oil line. But your idea would also work. I could just multiply the gph by the run hours and there you go.
Thanks

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Paul Mitchell

I agree but

My old windows were single pane. Therefore I have to believe the new ones...installed correctly are better than what I had. I don't assume that I am going to get this huge savings but was just curious...5 gallons a year less...50?

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Roger Litman

Multiplying for gallons

The nozzle tolerance(as much as 5%) and the accuracy of the oil pump pressure will probably be more than the savings. The use of an elapsed time meter(non-resetable) does work very well for many other situations and I have used one from Grainger quite successfully. I mount it in a deep 4"electric box and cut a hole in a blank plate(with a knockout) and cut a large hole with a Greenlee 2.25" punch(the steel in the blank is too tough for the average hole saw).

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Lurker_2

re

by the same token, windows can cause half the heatloss. You've done the math. Double the r value and you have saved a ton of money.


Changing old thermopane for new is probably pointless

Unknown

I changed all mine before winter started

Well , almost all - the year before I changed the front windows , all single pane , one was about 6 by 8 , all were extremely drafty . You know the type - you can see the window shades moving on a windy day .

I would have to respectfully disagree on the 70 year payback when you go from old single pane drafty windows - to new double or triple pane , properly insulated ones . I can feel a huge difference , and I know the house will heat faster and keep the heat alot longer than before . It's hard to make a fair comparision with all the variables - like hot water usage , and if other winters were as cold as this past one . But I have kept all the fuel bills for the last few years .

Total cost on all the windows , insulation and trim for the 1st floor was around $2000 . That would be around 30 bucks a year in fuel savings over 70 years to justify replacement , if my math is right . Going by pure intuition , I am guessing we saved much more than that , but we insulated the front wall too , so it gets more fuzzy .

Most important factor for me - no cold drafts anywhere , anymore .

Dave DeFord

Not an expert..

But I think you hit the nail on the head with the drafty part. I think that the old windows weren't sealing properly and needed attention to caulking, sealing etc. As I said I'm no expert but an engineer at a window company and Mr. Hunt above have both confirmed to me that a double pane window does not pay for itself when it is replacing a well-caulked and fitted single pane window with a storm window. Not to say that new windows don't have benefits (I'm looking at replacing one right now) but I don't think that energy efficiency is ususally a big benefit. However, replacing an ugly 1950 aluminum-framed single pane window without a storm with a nice wood framed window of modern construction is a very good deal from an asthetics point of view and I get better energy efficiency to boot.

jerry scharf

I have a hard time believing that

Mark,

Windows will save enery costs. How much it will save is almost impossible to say because so much is in the details. I know of no calculator that is worth anything in predicting this with any accuracy for a given house. Installation care in both the old and new windows is a huge factor. Blower door tests can find out overall leakage, but that won't pinpoint the window specific losses.

Old wood windows perfectly installed and gasketed are R1. The ones that are the old aluminum are even lower. A typical higher quality vinyl or fiberglass double pane lowe^2 window is about R3. You can go nuts (R9 or higher), but R3 windows are not that expensive.

Infiltration is harder to quantify in terms of energy usage, because it depends on wind speed and building location as well as static losses. New windows certainly seal better, and correct foaming in of the rough in frame buys alot. It can be done wrong, but the same went for the original windows.

That said, as with any energy savings prediction, it's way too easy to cook the books and look great. If I set up a situation where the dominant heat loss is the windows, then you get high numbers. Chnage it so that the dominant heat loss is the ceiling, windows don't look good and insulation looks fabulous.

Finally, people tend not to put the same quality window in the replacement as was in the original relative to the construction norms of the day. It's the esthetic decisions that determine how fast the payback is. Even with the doubling of gas prices, if someone chooses Marvin/K&K/etc. top of the line windows it won't pay back. If I buy a moderate prices vinyl or fiberglass window, the numbers look very different.

I wish everyone involved would pick up the mantra "no voids, no voids" as these kill overall insulation value.

jerry

Mark Eatherton

See here...

Last year I replaced several windows in my house and they were
the expensive double-pane energy-efficient kind.

This week I got a call from the contractor complaining that his work has been completed for a whole year and I had yet to pay for them.


We must have went the rounds for 10 minutes. Just because I'm getting old doesn't mean that I am automatically stupid.


So, I proceeded to tell him just what his fast talking sales guy had told me last year...


"that in one year the windows would pay for themselves."


There was silence on the other end of the line so I just hung up and I haven't heard back.

Guess I must have won that silly argument.

eleft_4

I love IT

Fred Robinson

Heatloss

Using your example of the window in the well insulated wall, I compare it to the a/c ductwork in the unheated attic. Sometimes with multiple layers of insulation on the ceiling, we cut a hole and place long runs of duct with maybe two inches of insulation. Is the duct a poorly insulated extension of the ceiling surface?
However, I believe I have read some advice that said it was not benifical to insulate the duct to the same degree as the ceilings.

Fred Robinson

Fuel savings

This thread reminded me of a home owner who after doing all the energy upgrades saved over 100%. Then experienced the oil tank overflowing from all the energy savings.