Upgrading existing windows R Value

last year

last modified: last year

Looking to increase the R value of existing fixed pane windows with something similar to indows - but using VIG (Vaccum insulated glass) and wanted to solicit feedback. The house has a east facing wall consisting of ~212 sq ft of fixed pane windows (of a total window space of 517 sq. ft.). The house is located building zone 4 . The existing windows are circa 2000 Pella ProLine Low-e double pane with an argon backfill. I'd be going from an R-value of approx. 3 to 13 (existing window to existing window + VIG).

The intent is to size the VIG for some small expansion, set the VIG on the interior during a warm, low humidity day, seal the glass to the wooden sash (the sash has 1/2" flat faced wooden surface that extends around the perimeter of the window), use a thin strip of weather sealing with dual sided adhesive, and leave some desiccant inside the gap between the two windows. The gap between the windows will be approx. 1/2".

Primary considerations are:

Optical clarity (both with the double glass and from a cleaning perspective)
Moisture penetration and condensation (both optically and as a potential for mold)

- Seal Failure- Diffusion through the wood- Serviceabiltiy

Also may try this with operating windows, but will only insert the the glass during winter. (replacing with screens in other season) - so the optical clarity will be similar (but still better for the non-screened windows).

Currently investigating sourcing from Haanglas - Fully tempered vacuum insulating glass -China HaanGlas. The U-Value is listed at 0.5W/M2.K)

Thoughts/Concerns/Considerations?

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Comments (10)

millworkman
last year
@oberon
PRO
toddinmn
last year
Biggest concerns would be cost, reliability of the source, shipping, warrantyTy,ROI ,condition of existing windows.
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Dr. Lstiburek's rule of thumb is a minimum R20 in basement walls north of the Mason-Dixon Line. (Of course, he doesn't always follow his own rules.) I've used R13 dense fg batts and 1" of XPS in basements plus spf in the rim joist area. That yields a nominal R18. However, in your colder climate (very cold on climate maps) I would be concerned that the 1" board (R5) would not be enough to keep the wall free from condensation on the above grade portion. What's more important than the nominal R value is the tightness of the wall to air penetration. That's why the tape, t&g, caulking and polyurethane spray is so important. BTW, since I live in my own homes, I can say the basement comfort in homes with the XPS/fg combo is noticeably greater than the previous standard fg. Plus there's less need for supplementary heating.
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One would think that sealing penetrations is standard. I just built an energy star house which required foaming around windows and door and making sure all fiberglass on walls was covered on 4 sides. That meant extra blocking especially on knee walls in attic and behind bathtubs. I added a few other things but I'm not sure that one of the options was to seal the penetrations from ceiling into attic. I just did it myself - was easy without insulation there yet. No infrared camera needed as there was light whereever the holes were. In some cases, a lot of light. And that was just from windows, in a completed house, you could turn on lights at night and really see any leaks. I also foamed around any penetration even if I didn't see light. Basically light fixtures (1 per room + closets), smoke detectors, HVAC vents, and bath fans. I had put some speakers in so I built boxes around them that were also foamed. While on the subject, I built a box around the attic stairs and put a second lift off door with insulation and weather sealing. Costs I think most people around here would want to do their own just because then you know the job is done right. But I'd ask you insulation people. They might suggest just foaming for an inch everywhere - costs about $1 a sqft. Not a bad option and it doesn't require any thought or attention to detail. The foam has r-value of course and so you can cut back on the blown-in part (how much depends on foam but r-7 would be typical closed cell).
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No bb, that is not what I have. I guess I'm still learning. I just remember that when they sold me the hot water heater and boiler, they said it was a "direct vent" type. that's why I reiterated that. I thought a DV was just an appliance which was vented forcefully (horizontally outside of the wall or otherwise) instead of with a chimney type instrument. Thank you for the clarification. My two forced air heating units are in the attic and it's unfinished with a gable vent near them. A lot of (cold) air gets in through the vent when they turn on. Maybe that would do the trick. It does seem that it should somehow get air INTO the living space though. I definately understand what you mean about the negative pressure. I'll have to look closely at my units to see if they are indeed direct vent and if they're even installed properly. The hot water heater has a 3 inch PVC pipe going straight out the side of the house, that's it. The boiler (not hooked up yet) is the same way, near the HWH in the basement in a closet with louvered doors. The two units in the attic have that ven like I described. I need some kind of house audit... but the pros I hired to do the original work should have mentioned all this. I'm just learning this now after reading here for a while. thanks again for all the replies. I'm learning a bit from this. One more thing, I can't stop talking here... lol If I have both vents, in and out, at the same location, would'nt the "out" air just come back "in" with that setup? It would seem like a circle exchange of some kind and you'd suck the "old/bad" air back in.
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Jeff Fodi
Original Author
last year
Thx... good feedback.

- Existing windows are a concern (there was a class action lawsuit for failure of the exterior sealant between the aluminum cladding and glass pane - that has been recaulked, but - worst case, I should be able to salvage the VIG and frame it in by itself)

- cost is $25 / sq ft.

- agreed on shipping - will definitely need some type of insurance.

- Warranty is 10 years, proof of failure would be easy but I'd expect I'd own shipping and installation for any replacement.

- ROI - Given I'm heating with wood mostly - ROI is probably not there (the low-e coating should help mitigate morning heat up from the summer sun - so some savings on AC when we run it).
PRO
Windows on Washington Ltd
last year
Pella ProLines? How good a shape are they in?
PRO
East Bay 10
last year
Agree with WOW's question, Proline is Pella's low-end wood product and you are probably off replacing it with domestic windows and the glass package you are looking for.

I also thought Vacuum was an old technology but Oberon knows better. Not a fan of importing glass products, especially from our comrades in China.
oberon476
last year
last modified: last year
Immediate thought, and agrees with WoW, those are 23 year old ProLine windows. That they made it 23 years is a surprise in itself.

Second thought, agree with Todd 100% on his questions/concerns.

Third thought (actually my initial thought when I read your original post..) .$25 sqft for VIG??? $125 I would say was a great price and $225 I would call reasonable, but $25, including shipping from China? There is no way in hell that I would touch that at any level.

Two biggest concerns about VIG's, first is how the edge is sealed since it has to seal a vacuum for years in a potentially very hostile environment in a window system and second would be the pillars separating the glass.

VIG space between lites is crazy narrow, about .3mm (3/10's), with the glass panes being held apart using tiny pillars placed every square inch throughout the entire glass area. The pillars are clear but not invisible, you can see them when looking through the glass. I find it distracting, others maybe are fine with it.

I truly hate to discourage someone who is trying to be cutting edge and pushing the envelope, but IMO in your situation you would be much better off installing new high performance conventional triple pane windows rather than trying to mesh what you have with what you want in a questionable hybrid of an IG unit. For what it's worth there are very good reasons why IG manufacturers don't use wood spacers when building IG units....there were some that tried 40 years ago, and they are no longer around.
PRO
Windows on Washington Ltd
last year
last modified: last year
Missed that part. Vacuum sealed for $25 per sq/ft...?

Didn't think that was even possible.

https://media.tenor.com/6u54NQDezycAAAAM/inutil-plastic-bag.gif
Jeff Fodi
Original Author
last year
Haha i like the video

i have seen a sample - 5-6 very small ball bearings comprised comprise each pillar there is a wide border around The frame and there is a dessicant in the window to ensure any moisture is trapped

i like the idea of pricing standard replacements but doubt i can find something at a similar price point and anything close to the R value

not sure if the cost includes shipping - in fact i expect it doesn’t - I’ll confirm
PRO
toddinmn
last year
This would be an interesting project to follow. The idea of saving it and reframing to fit presents another set of problems and cost. If your serious I would carefully evaluate the condition of the windows. I would also do a mock up on 1 of the windows with a piece of glass the same thickness. This would let see what problems you will run into deglazing the existing, creating a filler to make up the glass thickness and being able to put them back together in a professional manner. The labor is the other factor as well. I have replaced many Pella’s that look good on the out side and the bottom rail is powder behind the cladding. I have also seen some Pella’s in amazing condition for being 20+ years old. A thorough inspection concentrating on the wood behind the aluminum , especially the bottom rail would be well advised before ordering glass. If this is done in the name of saving energy there are other things worth looking at as well. Sometimes when you do one thing and dont look at the project as a whole the results can be less than desired.
Jeff Fodi
Original Author
last year
Good points... might even be worth taking one of them apart to see what is going on behind the scenes. I do have some windows on the north side that are probably close to the power state you describe. I've also already replaced a few. The wall of fixed pane windows faces mostly east and is protected by a nice sized overhang. It doesn't see as much weather and late day sun as the north side - so are generally in better shape.

My thought is to keep the existing windows in place and apply the VIG panes on the inside - sealing them to the wooden sash. This approach (assuming the existing windows remain in decent shape) would be fairly simple compared to a full on replacement (or rebuild).

Upgrading existing windows R Value

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millworkman

toddinmn

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Upgrading existing windows R Value

Comments (10)

millworkman

toddinmn

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Jeff FodiOriginal Author

Windows on Washington Ltd

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