Looking for low U factor with high SHGC windows?
Give the window company a call directly. I was ready to give up and order the standard low SHGC windows offered by everyone when I decided to call up Gerkin (midwest company) and ask them about their coatings. I talked to a nice lady who told me they get their coatings from Cardinal and that the 366 coating is the one they use. When I asked if I could get the 180 coating on some windows she told me that if it’s a current Cardinal coating that they can get it. This made my day as nowhere in their printed literature or online do they give any coating options (other than clear or LowE).
Hopefully other window manufacturers will be as accommodating.
Alan
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
i'm sure many window mans will be, but you'll PAY for it
unless say you're building a mcmansion, in which case you are already paying
Alan, the 179 glass is the best standard low-E I have found for higher SHGC, but the U value is probably not that low. Do you have figures and costs?
We typically use Jeld-wen windows with Cardinal glass - the Low-e 366 has a U Value of .32 and SHGC of .22 (varies slightly on the type of window and grills). When we do passive solar homes we will use this glass on all sides except the south where we use the Low-e 179 - U Value of .28 and SHGC of .70. The cost to upgrade the glass is minimal. Only problem is it is not an option in some of the lower end widow lines like vinyl. This is also true for Anderson and many other manufacturers that I recently priced.
Those figures for 179 don't exactly correspond with mine, which depending on window operation, are U value of .32 and SHGC of .52. We always need to make sure we are looking at whole window values and not just glass figures as well.
I don't have window specs for the 180 coating directly from Gerkin but according to Cardinal the U-factor/SHGC ratings for the glass in a 3/4" double pane with Argon fill are:
366 - .24/.27
180 - .26/.69
I imagine that's probably the glass only rating and that it will change when put in a frame but the U-factor is pretty close so I won't be giving up much there.
Gerkin specs for the 366 coating with Argon fill in a casement are: .29/.19
I'll only be using the 180 coating on my living room windows, the rest of the house will be 366. I have prices on the 366 coated windows but nothing on the 180 windows yet. I'll have my building center check next week and hopefully get them ordered.
Link to Cardinal coating performances - http://www.cardinalcorp.com/technology/reference/loe-performance-stats/
Alan
Matthew - good point on whole window value. My window salesman gave me the values and I had assumed he gave me whole window value but he didn't even know what loe-e 179 was until I told him about it so who knows. Cannot find the document he gave me but the cardinal website show a .26 and a .69 but may be for glass only - the old chart had different value for vinyl vs wood vs clad, SDL, etc.
http://www.cardinalcorp.com/products/coated-glass/loe-180-glass/
Apparently the 179 has been changed to 180 glass.
I think the 179 has also been known as 172, 178, 180 depending on manufacturers, at least that is what I have been told.
Cardinal has four different coating types - no silver, surface 4 (I81), single layer silver (LoE 178, 179, 180 (three different coatings), dual silver (LoE²-240, 270, 272 (formerly 172 before nomenclature change), and triple silver (LoE³-366).
LoE 178 and 179 are being phased out in favor of 180, but both 178 and 179 are still currently available in some areas as 180 is being phased in.
LoE-180 has a slightly better U value than 179 (as mentioned previously, U - .26 versus .28 glass only), but it does drop from SHGC of .70 (179) to .69 (180).
Also keep in mind that the single silver coatings are designed for IG surface 3 application while multi-silver coatings (LoE² and LoE³) are intended for surface 2 application. I mention this so that if you are ordering the HSHG coating REMIND THE WINDOW COMPANY unless they are very familir with using both HSHG and LSHG....otherwise you may find that your HSHG coating is on surface 2 where you won't get all the benefits you want in a HSHG product.. It is not uncommon for that to happen.
Oberon
I noted a few references low-e 'hard coat' in Marvin's book (U 0.31 and SHGC of 0.50 for the window). Those numbers are similar to Matthew Amman's above (manufacturer?), and since Marvin is also spec'ing LoE2 and LoE3, the generic 'hard coat' may be Cardinal 179 or 180. Anyone have any experience with Marvin and getting HSHG windows from them?
An update:
Finally got a price and the windows are ordered. Doesn't look like the 180 coating cost me any more than the standard 366.
14 windows total. Mostly normal sized double hung with 2 casements for bedroom egress and 2 large picture windows (56x60). Total was about $4000. I was happy with the price and I've got the coatings I want. Sure glad I decided to call the company directly before ordering.
Alan
My low-E179 windows and doors came in this weel as well. My window stickers said SHGC of .6 which is what the literature said. The door labels however had a SHGC of .38 which I was not expecting. I guess it is the same glass but they are rating the entire door unit and I guess the wide stiles and rails on a door lower the overall rating more than a window. I am wondering what my verifier is going to say about this and if it will effect my HERS.
Marvin's glass comes from Cardinal and Cardinal only produces softcoats, no hardcoats, but if Marvin needed glass with a hardcoat for a specific application, then Cardinal would supply it to them....but with the LoE180 and I81 I can't think of a reason for requiring a hardcoat, except possibly for a single pane option, for example.
Danny, you are correct that SHGC is the full window or door including sash and frame parts. A door with a small window is going to have a low SHGC - as you noted - because the not-glass parts would be included as part of the formula.