Lotsa glass, need good glazing!
I am helping a guy resolve the design for a house he’ll build, and it is full of windows and skylights.
Here is a view of the elevation that sees the heart of the 180 degree view the site has. You can get a feel for how punched through with window holes the exerior is.
Will triple-glazing do us any good here? What well-represented and rock solid window companies make superior products, when it comes to windows with a low U-value?
Replies
I think Hurd still makes windows ... they used to have Heat Mirror glass (low-E coating on a suspended mylar film ... thermal not visual one way mirror).
In my opinion Heat Mirror still is an excellent product ... particularly w/ large areas of glass as you retain significant comfort and better efficiency than generic low-E glass.
Unfortunately availability may not be easy ... and the result is expense.
You can get U-values down to 0.10 if you want and generally u-val is in the 0.25 range with a wide range of any glass finish you want (e.g. tinting, mirror). I've used tinted and mirror for a strong west exposure with VERY good results.
If available and you can afford it ... you must be able to if you are putting that much glass in to begin with. You only have one chance with windows ... do it right, choose carefully!!
And don't forget overhangs to protect south glass from summer sun.
I think Kensington Windows still uses heat mirror. I personally don't feel comfortable with a window based on a piece of mylar between the panes.There are other ways of getting good U-ratings. Triple-glazed, low-e, krypton. Schuco windows have good U-ratings. Canada has some interesting FG window manufacturers.
I've seen Heat Mirror glass last 20+ years w/out issues. You can't even see the film, either ... even up close. The only way to tell the film is there is to look for the pressure hole in one corner of the glass. Failures can happen w/ any glass and maybe there is somewhat of a higher chance w/ Heat Mirror, but I've seen very good performance. I knew a big developer who used thousands of sqft of it in large commercial office projects. With modern edge seal technology, I think that reduces risk even more.
As mentioned above window manufacturers in Canada are way ahead of those here in the US. Also as mentioned above Fiberglass Frames filled with foam are the most efficient. They come in various colors and if you can't find the color you want they are easily painted. One final thought is some Canadian manufactures will wood vernier the inside so you can stain and trim out on the inside with stained wood casing.
Other than that one set of rafters, is there any plane in that structure not punched with an opening more than 2' square?
I'm still trying to decide what ResCheck would give back for the probable wall & roof assemblies . . .
With this being close to 50% doors & windows, it may not matter if you go from an R-3 to an R-4 window for the number and exposure of the openings. That is, without having to get the walls to R-40 somehow (ceiling/roof higher than that, too, like as not).
Hope this is not to be sited either under 3000'msl elevation or south of, oh, 42ºN ... ?
Ring of 30-40' tall post oaks on the sunward perimeter might be a better investment than upgraded windows.
Does not (presently) look like it's going to have a lot of contiguous attic space, so the mechanicals are clearly from below, which wil complicated any cooling that structure will require. Shading the glass will be tough without that shading either blocking the view or becoming distracting to the elevations (as improbable as first glance makes that, even so).
GeneDavis
I did the calculation of return on triple glazing since my views are similar.. I have a lake in front and lake behind so two walls are really open. I could never find a payback point especially when I factored in the inevitable broken window or two.. (I went out 100+years)
Over that big of an area it's really problematical to provide enough heat to offset the losses. I used in floor radiant heat because of it's comfort but I supplemented the area with forced hot air under the windows in extreme temps.. 95% of the time the supplemental furnace isn't needed but I saved enough by not having to so massively increase tubing under the windows to more than offset the increased costs involved. MY total energy bill is thus much reduced..
This was with superinsulated walls. (SIP's)
Eagle windows or marvins, both have good representation, with superior service.
That being said I read somewhere about glazing with an R11, with that much glazing and given your climate I would find, if possible.
I also remember reading that R-11 glass will be coming out in a couple of years. The technology has existed for a few years in the labs. Someone has now figured out how to do it commercially and is building a factory to manufacture it. As I remember it was one of the major glass companies.
I've seen glazing values as low and lower than R-11 ... 20 years ago ... this ain't lab stuff. It is real. Put in real buildings. The Canadians know about it better than most. I've seen double and triple Heat Mirror. I remember a 3" + thick glazing unit w/ double Heat Mirror and if I recall ... values in the 0.08 range.
Triple glass is heavy ... Heat Mirror is far superior energy wise and much lighter. I don't know why it isn't more widely available. The quick easy E-coated glass has flooded the market with the notion that it is the best way to go ... certainly inexpensive.
Maybe you can tell I'm a die hard Heat Mirror fan?
http://architect.loewen.com/architect_site.nsf/glazing_heatsmart
just a guess, but i'll bet the window and door bill for triple pane windows on that house will go $150K to $200K.
i've had one experience with a Hurd job.
no more.
carpenter in transition
Buy the cheapest windows you can get. With that many holes through perfectly good walls they'll need the money for heating costs.
Cute house - is every top plate broken with fenestration?
Oh - and you have to get one of these http://www.3dconnexion.com/3dmouse/spacepilot.php -
a 3-D left handed, object-control joystick - comes set up to work in Sketchup (and in AutoCAD Inventor, my use). Lots of extra buttons for instant view planes and macros. You can spin the part around on-screen in the middle of commands for a better view or whatever.
Got mine Tuesday; already can't imagine 3-D without it. Scary-God-like in Google Earth.
Forrest
Edited 6/21/2008 8:32 am ET by McDesign