Greetings and a question about some "smart" windows

[EEEngineer]

Greetings! I've been a longtime lurker, valuing the wealth of information and professional wisdom here for HVAC and building performance. I'm an engineer specializing in commercial and industrial energy efficiency, now getting more familiar with residential energy efficiency. Outside of work I wrench on a former military truck (a 1995 AM General M35A3) and do some 3D printing.

What finally got me to register and post is a question I had about "smart" windows. These windows are electronically photosensitive and automatically "dim" themselves depending on the building owner's preferences, which can be set from a computer or a phone app. Does anyone here have any practical experience with installing and maintaining these windows, or know of anyone who has? I was asked to consider Inovues windows in particular (can't post links yet, sorry!).

Throughout my career, I've had tons of questions from commercial building owners about Energy Star window replacements for saving energy. It has been my experience that windows are a poor retrofit option because they typically cost a lot for the energy savings they provide compared to building envelope crack sealing or new insulation. So I'm skeptical that these windows will be any different.

Any thoughts?

[VTP99]

I didn't know that was such a thing until you posted it.
What's the R value difference as compared to a 3 pane with argon fill ?

[VTP99]

Looks expensive have to wonder what the ROI is in real numbers.

[Artrose]

Greetings! I've been a longtime lurker, valuing the wealth of information and professional wisdom here for HVAC and building performance. I'm an engineer specializing in commercial and industrial energy efficiency, now getting more familiar with residential energy efficiency. Outside of work I wrench on a former military truck (a 1995 AM General M35A3) and do some 3D printing.

What finally got me to register and post is a question I had about "smart" windows. These windows are electronically photosensitive and automatically "dim" themselves depending on the building owner's preferences, which can be set from a computer or a phone app. Does anyone here have any practical experience with installing and maintaining these windows, or know of anyone who has? I was asked to consider Inovues windows in particular (can't post links yet, sorry!).

Throughout my career, I've had tons of questions from commercial building owners about Energy Star window replacements for saving energy. It has been my experience that windows are a poor retrofit option because they typically cost a lot for the energy savings they provide compared to building envelope crack sealing or new insulation. So I'm skeptical that these windows will be any different.

Any thoughts?

I don't have your answer, but I do have a couple questions, and amongst them, why have you only been lurking?


What has been your experience with smart windows in a commercial application?

What's the pay off? Do you recommend, if so, where? Are they an easy sell?

We already know that lighting, and plumbing, the low hanging fruit in commercial, has long ago been picked.

So, from the beginning of a project, we generally start off diagnosing other things looking for savings opportunities. Infiltration, mechanicals, etc.., on and on..... and on......

But windows have always had a lousy payback, and unless you find a structure filled with old jalousie windows, forget about it.

Has commercial progressed now to the point that windows have a reasonable payback?

I know wind and solar have made progress, but understand that the return on investment for those is still pretty lousy.

Please bring us up to speed.

[BNME8EZ]

I have seen the office windows that you can flip a switch and they go from clear to can't see through usually reflective. If you could keep direct sun out then tint them when it is not direct sun there may be some benefit but I can't imagine enough payback to pay for them in the life of the window as I have just replaced a couple double pain windows that were 25 years old that lost the seal and got moisture inside. I would doubt that tech has that kind of lifespan yet. but I could be all wrong too. Seems like the old fashion shade would provide a better bang for the buck even if it does not have the "cool" factor

[Artrose]

I don't have your answer, but I do have a couple questions, and amongst them, why have you only been lurking?


What has been your experience with smart windows in a commercial application?

What's the pay off? Do you recommend, if so, where? Are they an easy sell?

We already know that lighting, and plumbing, the low hanging fruit in commercial, has long ago been picked.

So, from the beginning of a project, we generally start off diagnosing other things looking for savings opportunities. Infiltration, mechanicals, etc.., on and on..... and on......

But windows have always had a lousy payback, and unless you find a structure filled with old jalousie windows, forget about it.

Has commercial progressed now to the point that windows have a reasonable payback?

I know wind and solar have made progress, but understand that the return on investment for those is still pretty lousy.

Please bring us up to speed.

Retrofitted adaptive glazing films? Basically, windows you can tint on demand. I know virtually nothing about them, but to my knowledge, this technology has been around for a while.

I went to their Facebook page because you peaked my interest, and basically all I found was a lot of sales hype, complete with no design, or actual numbers being offered up.

Maybe I understand why you're asking questions here?

I get the impression they're attempting to profit from riding the wave of the green revolution.

Anyhow, I could be mistaken, but, for now.... No thank you.

[EEEngineer]

[Q

I don't have your answer, but I do have a couple questions, and amongst them, why have you only been lurking?


What has been your experience with smart windows in a commercial application?

What's the pay off? Do you recommend, if so, where? Are they an easy sell?

We already know that lighting, and plumbing, the low hanging fruit in commercial, has long ago been picked.

So, from the beginning of a project, we generally start off diagnosing other things looking for savings opportunities. Infiltration, mechanicals, etc.., on and on..... and on......

But windows have always had a lousy payback, and unless you find a structure filled with old jalousie windows, forget about it.

Has commercial progressed now to the point that windows have a reasonable payback?

I know wind and solar have made progress, but understand that the return on investment for those is still pretty lousy.

Please bring us up to speed.

Hi there! I'll answer your questions the best I can:

1) I've only been lurking because I'm not an HVAC professional. After all, the website is called "HVAC Talk" I've used the knowledge contained on this board to help me do some sanity checks when evaluating the energy usage and efficiency of commercial HVAC projects. When I found this Building Performance message board, I decided to register and ask my question!

2) I have no experience with commercial smart windows. I was hoping someone here might have it My experience is limited to evaluating the feasibility of Energy Star windows from a energy efficiency retrofit standpoint.

3) I'm not sure yet, but hope to find out soon!

4) I don't think window retrofits have a reasonable payback at this time compared to crack sealing or new insulation, crack sealing being the most cost-effective energy saver in my experience. I agree that new Energy Star windows only make sense to install if they're replacing trashed or broken windows.

I have little experience with renewables besides knowing what they are and how they work. I'm just happy that solar panel efficiency has gone up a few points since I started down the energy engineering career path in 2011. I'm a huge fan of nuclear power and would love to test a little cogen unit in my back yard if the DOE ever asked for volunteers

That said, I am focused on energy efficient retrofits and new construction for commercial (and now residential) buildings and facilities.

[EEEngineer]

Retrofitted adaptive glazing films? Basically, windows you can tint on demand. I know virtually nothing about them, but to my knowledge, this technology has been around for a while.

I went to their Facebook page because you peaked my interest, and basically all I found was a lot of sales hype, complete with no design, or actual numbers being offered up.

Maybe I understand why you're asking questions here?

I get the impression they're attempting to profit from riding the wave of the green revolution.

Anyhow, I could be mistaken, but, for now.... No thank you.

That's my feeling too. Part of what I do is determine whether emerging technologies are all talk and no shock so that people spend money on stuff that can actually help them save energy instead of buying energy snake oil. I was hoping to get some advice on the matter from other folks here

Copied and pasted from the INOVUES website:

The baseline version of INOVUES Glazing Shield, GS100LF, can result in up to 40% reduction in building energy consumption and peak heating and cooling loads (simulations, ~20% on average, varies based on the building design/location and window-to-wall ratio/WWR). A case study on Lever House in New York City (single-glazed curtain-wall with 50% WWR) was performed and several intervention scenarios were analyzed using partial- and full-building energy simulations performed using Comfen by LBNL and OpenStudio by NREL. The results showed an annual reduction of 24-42% in natural gas and ~12% in electricity (heating-dominated), leading to a total reduction of ~15-22% in Site Energy Use Intensity (EUI).

​The payback from energy savings alone was estimated to be up to 10 times faster than window replacement and the return on investment (ROI) was up to 400% over the estimated 20-25 year service life of the Glazing Shield. The studies also showed about 15% improvement in thermal comfort in the perimeter areas and about 10% reduction in glare discomfort.

Pairing the Glazing Shield system with smart/dynamic glass is estimated to further improve the energy efficiency by 15-20% while offering even greater thermal comfort and higher quality of the indoor environment. With vacuum insulated glass, for example, applied only to 50% of the curtain-wall area (i.e., the vision panels only), the results showed a reduction of 66% in natural gas consumption.

The baseline version of INOVUES Glazing Shield, GS100LF, can improve the overall performance of most window and curtain-wall systems as follows:

​Total U-Factor (thermal transmittance) by ~2x.
Condensation Resistance (CR) by ~4x.
Sound Transmission Class (STC) by ~10 points.
Outside-Inside Transmission Class (OITC) by ~4 points.

This was validated through thermal simulations per NFRC 100 and successful testing per industry standards (AAMA 1503 and ASTM E90) at a leading independent testing facility.

​Pairing the Glazing Shield with advanced glass/glazing options would yield greater results. For example, the Glazing Shield GS100VIG with R10 vacuum insulated glass can improve the center of glass R-Value of a single-pane window from R1 to R14 and increase the total system U-Factor by up 10x.

All they have is sim data, which is only as good as the company running the sim, whether it's real life or on a computer. I really want to scrutinize case studies. If I could, I'd love to look at before/after installation energy usage and do a degree day analysis to see if there were any differences attributed to such a window retrofit.

I agree that there is a lot of hype, in pictures too even! Their actual website has a couple dead links, notably for "Resources" and "Projects". Even their data sheet link is dead I'm not sure if it's still a bit of a work in progress or if they're just sloppy. I'm not impressed.

[Artrose]

That's my feeling too. Part of what I do is determine whether emerging technologies are all talk and no shock so that people spend money on stuff that can actually help them save energy instead of buying energy snake oil. I was hoping to get some advice on the matter from other folks here

Copied and pasted from the INOVUES website:



All they have is sim data, which is only as good as the company running the sim, whether it's real life or on a computer. I really want to scrutinize case studies. If I could, I'd love to look at before/after installation energy usage and do a degree day analysis to see if there were any differences attributed to such a window retrofit.

I agree that there is a lot of hype, in pictures too even! Their actual website has a couple dead links, notably for "Resources" and "Projects". Even their data sheet link is dead I'm not sure if it's still a bit of a work in progress or if they're just sloppy. I'm not impressed.

I know as an engineer, you're looking for some verifiable data gleaned from their data loggers, as well as their supporting data, rather than a bunch of words touting unverified percentage numbers. That could simply be a sales or marketing disconnect on their part.

Who knows, but from what I've seen, it doesn't sound like they're directing their efforts towards the engineering community. It sounds more like they're targeting building owners and facility managers. Much easier targets than you.

If I had a project where I thought their product might have value, I'd explain to them basically my who, what, and why, then I'd ask for some real technical data. If they refuse, or come back with more of the same, your choice is simple.

[EEEngineer]

I know as an engineer, you're looking for some verifiable data gleaned from their data loggers, as well as their supporting data, rather than a bunch of words touting unverified percentage numbers. That could simply be a sales or marketing disconnect on their part.

Who knows, but from what I've seen, it doesn't sound like they're directing their efforts towards the engineering community. It sounds more like they're targeting building owners and facility managers. Much easier targets than you.

I've experienced that first hand. I've worked with facility managers who put money towards stuff like this only to get burned in the end after they read the measurement and verification results.

I read a little more about this technology. The proper name for it is electrochromic glass. It works like a big LCD, except on a window. They have an effective useful life of 10-20 years and cost anywhere from $50-$100 per square foot. The technology can also be combined with a layer of solar cells in the window to use the sunlight to generate electricity, though I haven't looked into how efficient that process is compared to dedicated solar PV cells.

What's a typical non-Energy Star window cost, materials and installation? $25/sq.ft? The Illinois Technical Resource Manual (TRM) says that Energy Star windows cost about $8 more per square foot than regular windows in materials alone. So electrochromic windows are about 3x the cost of Energy Star windows.

If anyone has better cost figures, please share. I got my $25/sq.ft. figure from my father-in-law who has done a few window replacements in hundred-year-old homes, so it's probably going to be a little off compared to commercial building glass.

I just found some more information about this INOVUES glass from one of my colleagues. It has a U value of 0.38 and a Solar Heat Gain Coefficient (SHGC) of 0.35. These numbers came from a snip that looks like it came out of one of their product data sheets, which I can't look at on their website. With a U value of 0.38 and a SHGC of 0.35, these windows can only be Energy Star-certified for Southern Climate zones, but NOT the South-Central, North-Central, and Northern climate zones. This means that these windows as they are now can't be Energy Star-certified in most of the United States, which may also affect their eligibility for energy efficiency rebates.

Energy Star certification is important for what I do, so now I have an answer for my question. A definite "no"!

I think windows still have a ways to go in energy efficiency, and they'll probably get more attention as efficiency measures as the low-hanging fruit becomes the industry standard.

[EEEngineer]

Apparently I can't edit my last post. Maybe it's because I'm new here? Anyway I think I made a mistake about the INOVUES glass Energy Star eligibility. Per the "ENERGY STAR® Program Requirements for Residential Windows, Doors, and Skylights Partner Commitments" from 2015 or 2016 (hard for me to tell), these windows actually would not meet Energy Star requirements for windows:

Table 3: Energy Efficiency Requirements for Skylights
Climate Zone U-Factor_1 SHGC_2
Northern ≤ 0.27 Any
North-Central ≤ 0.30 ≤ 0.40
South-Central ≤ 0.30 ≤ 0.25
Southern ≤ 0.40 ≤ 0.25

1 Btu/h ft2∙˚F
2 Solar Heat Gain Coefficient

The INOVUES glass with its U value of 0.38 and SHGC of 0.35 does not meet any of these criteria. I encourage others to double-check this if so inclined as I want to make sure the right information is out there.

[hvacker]

Another window consideration not associated with the glass is leakage.
I'm in the process of replacement because of this problem with windows where the SW sun warped them.
They suck air 24/7 if any negative pressure exists or when the wind blows it enters the structure.
Then there's the blow sand. Sand so small it blows in.
If smart windows aren't priced out of range willing to pay, they will probably be our future.

Good windows might not have a big payback but there's something about quality that makes it often worth it.

[EEEngineer]

Another window consideration not associated with the glass is leakage.
I'm in the process of replacement because of this problem with windows where the SW sun warped them.
They suck air 24/7 if any negative pressure exists or when the wind blows it enters the structure.
Then there's the blow sand. Sand so small it blows in.
If smart windows aren't priced out of range willing to pay, they will probably be our future.

Good windows might not have a big payback but there's something about quality that makes it often worth it.

This is very true. Before I moved into my current home, the previous owner did some renovations where the new windows were poorly done. They weren't sealed properly and the frames don't seem to be installed straight, causing them to warp a little bit. Having my home re-insulated last year helped with the windows some, but I could still make some improvements.