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Inside storm windows

Post in 'The Green Room' started by MishMouse, Aug 30, 2013.

  1. MishMouse

    MishMouse Minister of Fire

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    http://www.larsondoors.com/storm_windows/products/insider_windows/

    I wish I would have seen this earlier.

    The interior storms I created using 2x sheets of Plexiglas and building a frame out of 1"x2" definitely cut down on heat loss but since they are solid and not flexible they have a disadvantage over the ones listed above for windows that aren't a perfect rectangle/square. Actually the one in my bathroom become permanent when the house shifted.

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  2. WES999

    WES999 Minister of Fire

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    That's a nice idea. What do they cost?
    I made my own inside storms, using heat shrink window plastic film.
    I think they were less than $10 ea., and work quite well.

    PDR_0002.JPG
    Last edited by a moderator: Sep 22, 2013
  3. woodgeek

    woodgeek Minister of Fire

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    What do these cost....I just had new double track low-e aluminum exterior storms put on at $240/window, installed, including demo on the old units. Should get me to R-3 with my single pane primary windows.
  4. save$

    save$ Minister of Fire

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    You might want to PM Somkeythebear. He made inside storm windows last year. They are removable and reusable.
  5. MishMouse

    MishMouse Minister of Fire

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    The ones I made were close to $100 a piece due to the 2x pieces of Plexiglas that I used. They work quite well, and are removable but since they are solid and straight they do not fit as well as I would like them. The window frames are not exactly straight which causes them to not fit as tightly as I would like them to fit. The bathroom one I actually used 3 different measurements to design the window, it fit tightly with zero air loss, problem is it fit to tightly and now is a more permanent window.

    I still have 2 more to build so I may check their prices and my remaining windows.
  6. StuckInTheMuck

    StuckInTheMuck Member

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    Can you post a pic of your plexiglas indoor storm window design? I was thinking about making my own also, but wanted to see what someone else had tried. Thanks.
  7. woodgeek

    woodgeek Minister of Fire

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    Ok, maybe I have a bad attitude, but the more I learn, the more I am down on DIY strom window projects. On a energy/$$ saved for the effort basis. Very few people in cold climates still have single pane, and if you already have 2 panes (e.g. an exterior storm), then you are going from R-2 to R-3 by adding a layer to the interior. Pushing the numbers, this works out to be about 100 kBTU/window/yr, maybe $3/window/year if you used oil, half that or less for everyone else. If you use film glazing, I guess you can get $$ ROI, but anything 'real' (I tired of looking through blurry film) will have cruddy payback on material, even DIY.

    As for airsealing the window, replacing/repairing the weatherstripping is a lot easier/faster than building and painting an interior storm.

    Of course, I just spent a lot of money to go from R-2 to R-3 exterior storms (low-e), and I will not see any payback. The old units were basically falling out.
  8. StuckInTheMuck

    StuckInTheMuck Member

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    While the SIMPLE math may work against the interior storm window, there are a ton of other variables that I think should be taken into account with my proposed project. I plan to start with the second floor windows. My wood stove installation is on the first floor (first winter using it) so if I install interior storms on the second floor, it will help to retain SOME heat. If it makes the difference between having to run the boiler or not run it, I'm probably saving more than $3 per window per year. Sure, the boiler may be 80% efficient, but the boiler isn't on the second floor where the heat is needed. So there is heat loss to the basement and first floor on the way up and to the first floor and basement on the way back down. Whether or not I have to run the boiler will depend on (as we all know) outside temp/wind and desired indoor temp. As long as the heat loss equals the convective heat gain upstairs, the boiler can stay off (we turn the switch off in my house). If the heat loss exceeds the convective heat rise, we'll have to switch the boiler on. Of course this year will require experimentation, first without the interior storms, and then I may add a few to specific rooms to see what the effect is. Bottom line, if I'm doing it myself, I'm not losing a ton of money. I'm figuring about $50 per window. Less than a round of golf. If it doesn't work out, I'll repurpose the plexiglas for a greenhouse. The effort will be half the fun. FYI, my house, built in the 90's has original double pane windows and no storm windows.. Only screens.

    The house I lived in last year only had single pane drafty windows (in Rhode Island) with storm windows (original from 1972). We put the plastic film on the windows and literally watched the plastic film bow out into the room when a strong wind blew. I think the $50 or so spent on the window film saved us hundreds in Heating Oil costs.
    Last edited: Sep 10, 2013
  9. Seasoned Oak

    Seasoned Oak Minister of Fire

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    Any idea of the cost on these?
  10. GaryGary

    GaryGary Feeling the Heat

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    Hi,
    Enough with that bad attitude :)

    Here is a calculator you can do a pretty accurate estimate on:
    http://www.builditsolar.com/References/Calculators/InsulUpgrd/InsulUpgrade.htm

    For my climate (8000 HDD), and propane at $2 per gallon, a 3 by 5 ft window comes in at $15 per year -- not to bad.

    Lots of other window insulation solutions:
    - Bubble wrap costs nothing and saves about the same as a pane of plexiglass as long as you don't need a view out the window.
    - Twinwiall (or triple wall) polycarbonate gets an R value of +2 or +3 ish -- again you lose a clear view out the window
    - Insulating shades can give you up to +R4 or so if you use the ones with the inside reflective layers -- we use these on almost all our windows -- cost is not that bad when you consider you would have some kind of shade anyway. Some now have tracks on the side to prevent air circulation behind the shade.
    - Pretty easy to make a double wall interior storm

    The interior plexiglass storms I use on a few windows have no frame -- they are just a sheet of plexiglass cut to fit in the window opening and held i place to the Vinyl window frame with either a couple small screws or Velcro (but the Velcro does not seem to hold up well over time). You can hardly tell these storms are in place at all as there is no frame and the plexiglass is very clear.
    http://www.builditsolar.com/Projects/Conservation/acrylicstormwindow.htm

    Gary
  11. MishMouse

    MishMouse Minister of Fire

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    I do not know what they sell them for.
    But, since I have 2 more windows to go, I may give them a call for the price.
  12. MishMouse

    MishMouse Minister of Fire

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    How I made mine I measured the window from all 4 corners, top was typically 1/4 - 1/2" different than the bottom.
    I cut, 1"x2" and made a frame and glued a piece of Plexiglas matching the measurements of the frame to the side that was going closest to the window, I than I cut another piece of Plexiglas about 1" bigger all the way around and attached that to the side that goes on the inside. Since this created multiple vapor barriers it was a major improvement.
  13. woodgeek

    woodgeek Minister of Fire

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    Ok. I think typical double hung windows are 10 sq ft, and I assumed 5000 HDD more appropriate for the East Coast, and that we went from R-2.5 to R-3.5, (single pane + storm) to (single pane + storm + interior film), I also did $3 oil and 80% burner, and got $3.60/year with your calculator. Lets assume a 6000 HDD, lower initial R-2 from old storms, and $3.50 oil, and we are up to $7/year.

    I still think windows get WAY too much attention, just because they are in your face. There is a lot more low hanging fruit (e.g. airsealing or insulation) that can save hundreds of dollars or thousands of dollars a year.
  14. woodgeek

    woodgeek Minister of Fire

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    If you are partially heating with wood, your savings go down relative to oil heat. You seem to be arguing that they will go up somehow? If the windows are farther from the boiler, that will also cut your savings, not increase them.

    I think the shrink film on single pane windows in the NE climate with oil heat has roughly a 100% ROI/yr based on R-value.

    And the bowing in thing is a measure of wind driven pressure, not airflow. A small opening can be enough to pressurize/bow the film, but doesn't necessarily add up to a leaky window. As for the hundreds of dollars in savings, do you have data? To get that much additional loss from infiltration, I would need to leave a bunch of windows open 1/4". Were they THAT leaky? If they were, you could install cheap self adhesive weatherstripping on each window in less than 5 minutes, cheaper and easier than the frame/film.
    Last edited: Sep 10, 2013
  15. begreen

    begreen Mooderator Staff Member

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    Nicely done Wes. How did you join the corners? biscuits, dowels?
  16. brian89gp

    brian89gp Feeling the Heat

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    I was surprised when I started playing around with a HVAC calculator to see what mattered the most and what didn't matter much. I was very much on the windows bandwagon until I started messing with the attic insulation and air infiltration values....

    I suspect windows get so much attention in the market because they are in your face as you said it. They are something that most people cannot and will not replace DIY, there is perceived value that may exceed actual value with the new energy saving features, everyone has felt a cool draft off the windows in the winter, and it is far more sexy (with a higher markup) to get new windows then to spend money on sealing and insulating. Makes for the perfect storm of marketing.
  17. WES999

    WES999 Minister of Fire

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    Just wood screws. Drilled and countersunk clearance holes for the screws.
    You can see how to make them here:

    I was getting condensation and mold on the window frame before I installed them, now
    I don't get any.
  18. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    One of the advantages of interior storms is that if you make them double sided and foam sealed the R value doubles for a normal double pane window and triples for a single pane window and the "small" air infiltration problems that windows present irrespective of the frame to building sealing goes bye bye.

    One needs to do a full heat loss calculation to determine what to tackle first but windows and doors are large wasters of heat and become even worse as the other problems are corrected.

    Bear's rule of playing with heat losses: Use a shotgun approach, get all of them.
  19. woodgeek

    woodgeek Minister of Fire

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    In practice I got all the thermal bypasses that pay back in less than 3 years DIY, hired out all the rest that paid more than 10% annual ROI to some pros, paid with 10 yr 0% financing from the DOE, and left the rest alone. Indoor storms would have < < 10% ROI if I use any clear glazing other than shrink film, so I am sticking to glass.

    So far I have shaved >50% off the heating demand in an already well-insulated 1960 split level. :cool:
    Last edited: Sep 22, 2013
    Seasoned Oak likes this.
  20. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    Well if I ran the figures correctly I had a savings of 31 bags of pellets for an equivalent set of degree days I made 16 interior storms if you grant me $4.18/bag that is $129 my cost in materials was under $100.00 for those panels.

    A funny thing happens when the one item one has plenty of is time and that one of the lumber yards sells what they call hobby wood (mill end runs) frequently for $50.00 per 1,000 board feet. They even delivered. I ordered two units when I built my second chicken coop in 2010 so I had tons of extra just sitting around. The expensive panels were the two I made for the patio door leading to my second floor house length deck. I had to buy some longer length lumber and large shrink wrap sheets.

    Oh I got my shrink wrap from the bargain bin at the local surplus/salvage store Marden's and used bulk purchased sheet rock screws from the same place to fasten together the frames. The most expensive single item was the foam tape.

    Where there is a will there is a way.
    PapaDave, save$ and woodgeek like this.
  21. Seasoned Oak

    Seasoned Oak Minister of Fire

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    Impressive! At some point you get to the place where a central heating system is not even needed. That is with a little solar gain thrown in.
  22. begreen

    begreen Mooderator Staff Member

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    Frugality is what built this nation Smokey. It used to be a national virtue.
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  23. Redbarn

    Redbarn Burning Hunk

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    I agree with SmokeyTheBear. Use a shotgun approach, get 'em all !
    We have a 1815 Federal house where we have reduced the considerable heat losses by using the shotgun approach.
    Took 3 years to do it but calculating our energy used per heating degree day, we are using 40% less energy now.
    We are now chasing diminishing returns but keep looking anyway.
    Worth saving 40% every winter whether cold or average.
  24. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    That is how I get my supply of material for making wine, forage and plant. Fruit is cheap if you buy it by the tree or it grows wild all around you.

    I'm not frugal, I'm plain out cheap.
  25. GaryGary

    GaryGary Feeling the Heat

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    This is a pretty easy to use and free home heat loss calculator that breaks out heat loss from ceilings, walls, floors, windows and infiltration.
    It will give you dollar amounts your heat bill that goes out each path.
    http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

    But one difficulty with this approach is that its very hard to do a good estimate of infiltration losses without at least doing a blower door test. Since infiltration is nearly always a big player on anything but very carefully built new homes, its probably best to just figure on doing a lot of sealing -- especially the ceiling that separates the living space and attic.

    Gary
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