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Community and Q&A

Pella Impervia Casement Windows

cmcgrath09 | Posted in Energy Efficiency and Durability on

Hello all. I am a owner builder, building in Northern NH zone 6. I have been reading countless questions and articles on here but here is my first of many questions.

I am looking to build a Net zero home this summer, I am looking at Pella Impervia triple glazed, foam filled frames, casement and a few awning fiberglass windows. They have a U factor of 0.23, SHGC 0.40, VLT 0.49,  Low E glass argon filled.  I choose Pella due to price, and less lead time than Andersons. I also wanted a all fiberglass window. Some were I read how to calculate U factor to R value, I thought, but I cannot seem to find that. So what would the r value be?

Any one have experience with this window? I will be posting a other question in a day or two running my wall assembly by you all.

Thank you I have really enjoyed reading everyone’s thoughts on this page. It is well worth the prime membership,

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  1. Expert Member
  2. ktoro | | #2

    Hi Chirs,

    We have installed 10 impervia casements with the easy slide mechanism. We chose the impervia due to it being fiberglass and the new slide to open mechanism, which is really nice way to operate the window. Our are with the integrated fin which is one piece into the frame material. They are easy to install and required no adjustments after removed all the shipping spacers. FYI, we embedded our fin in zip liquid flash, except for the bottom.

    Let me know if you have any specific questions regarding them.

    1. cmcgrath09 | | #9

      Thank you. I planed to also install them in a similar fashion as you mentioned. Did you also get triple pane?

  3. PBP1 | | #3

    I have older model Impervia (2017?) doubles with foam filled frames, though with the advanced comfort, low-E option some came in with U values less the 0.25. I see that some of the Impervia tripples have U values as low as 0.16. The windows can be dual color and have relatively small frames widths.

    The casement opening/closing mechanism has been updated. I have the crank handles on the casement windows and one window had with a bit of a problem latching, but that got adjusted (not perfect but acceptable). I also had to make my own adjustments on slider locks/foot locks, which was relatively easy. I have not had/noticed any major performance issues.

    My windows are set flush to the exterior vertical wood siding, which provides a relatively deep inset in the 2x6 walls. In sub-zero, frost can form near the base for the sliders and a couple of casements that are about one foot off the floor. The frost is worse with the screens in place (interior side screens), which I have learned to remove in the winter to minimize frost.

    As the house was new construction, I thought I may experience some issues as things settle, expand/contract, etc. But didn't really see much.

    As to pricing, I waited until Lowes had a sale, I think there was an additional contractor discount too. If I had known what the ultimate budget was going to be (as I was the source of increases), I may have upgraded on windows. They range from I think as low as U 0.21 for fixed to U 0.3 for sliders (some got mis-ordered by Lowes with merely "comfort" and not "advanced comfort"); but, overall energy performance has been OK (as predicted).

    1. anonymoususer | | #6

      Remove the screens to reduce frost?! I have never heard this but will keep it in mind! I wonder what the explanation might be…?

      1. oberon476 | | #8

        The screens block warmer room air from the glass surface so that the glass temp goes below the dew point and moisture forms on the cold surface.
        Removing the (interior) screens helps keep the glass warmer and hopefully above the dew point.

  4. oberon476 | | #4

    A U factor of .23 on a triple pane window is not very good, in fact there are dual panes that do better than that. A triple should have a U factor at .18 or better.
    U factor is the reciprocal of R-value, 1/U=R and 1/R=U.
    Andersen doesn't make a fiberglass window, but they do use a composite material called Fibrex that sounds like it should be fiberglass but isn't.

  5. bigred | | #5

    When I resided my house with zip r-sheathing, I installed some Pella wood picture windows, and a mix of Pella Impervia casements and sliders. All dual pane (I'm in zone 2A, so hot humid). My dual panes were 0.27 to 0.28 (casements were slightly higher R/lower U). I did the work myself with hired carpenters to assist. Used zip liquid flash, stretch tape, and regular flashing tape. I've been very happy with the windows. Good fit, on a hot Texas day you can put your hand on the glass and it feels cool. Have had some condensation (on the outside of the windows) during periods of very warm, very humid temps and running the AC on the inside. We also installed STC rated glass in our Master bedroom as we live in a typical Surburban neighborhood with close neighbors with a heat pump that sounds like a 747 taking off when it runs. This slightly increased the U value but has a STC rating of 31 dbs so make a huge difference in sound transmission (particularly with Zip R-sheathing and Rockwool insulation.)

  6. AC200 | | #7

    "I am looking at Pella Impervia triple glazed, foam filled frames, casement and a few awning fiberglass windows. They have a U factor of 0.23, SHGC 0.40, VLT 0.49, Low E glass argon filled. "

    What's the coating they are using? My guess is Cardinal LoE 180 from the specs. You can get close to those specs with double glazed and 272+i89 or 366+i89. A triple glazed with two coats of 272 or 366 should be around 0.15 U factor.

  7. cmcgrath09 | | #10

    Thank you, I am going to meet with the window guy and see if I can upgrade something to increase the u factor. Or maybe look at other windows. I just want to order soon as most lead times are 3-6 months, sales man are telling me.

  8. jadziedzic | | #11

    I spoke with someone at Inline Fiberglass last week and they mentioned they were estimating 10-12 weeks for windows orders. Might be worth taking a look at Inline's all-fiberglass windows; I read somewhere (can't recall where) that Inline provides the "pultruded" frame material to other window manufacturers.

    (Fellow NH resident)

  9. AC200 | | #12

    I actually visited the Inline and Fibertec factories and showrooms last week. Inline makes pultrusions for Cascadia and Duxton amongst others and of course their own windows. Fibertec is supplied by Omniglass. I have all the NFRC performance data for double and triple glazed with various coatings for Inline and Fibertec if you need any comparisons.

    I looked at the Pella Impervia units early on in my search. They quoted me a significant premium for a code compliant window when compared to a better performing Inline or Fibertec. I also found Pella more difficult to get detailed specifications on coatings and glazing. I felt like they just wanted to buy their "standard offering". I will end up with a mix of double and triple glazed and different coatings depending on the room, orientation and window area relative to wall area. Should finalize my decision in a couple weeks.

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