Hi all–hope I can tap into the depth of knowledge here.
We (HO) are designing a high efficiency home, i.e., we plan on building with a steel frame with an integrated EPS insulation to make an airtight envelope.
My concern is that we want to put in a lot of windows to take advantage of the wooded views. What will a lot of windows, specifically the low-e (double/triple pane or what-have-you) types, do to my high efficiency envelope? How much more will I have to pay for windows that will not defeat my insulation scheme? The winters in the midwest is our driving factor.
Thanks.
Replies
tuf.. the eternal compromise..
windows will be one of your biggest losses..BUT
windows are your eyes on the world.. your egress for natural light..
your access to ventilation by nature..
and.. esthetically .. they are probably the MOST prominent architectural feature of your house ( well ok.. scale and roof lines , and doors , and texture... oh , never mind )
anyways..we've been building super insulated houses since 1974.. we've gone the whole gamut.. half-buried homes.. no northern windows... double walls.. blah, blah,blah..
sometime in the early '80's i decided thta hey... our winter is really only 5 months (November,December, January, February, March )... we can hunker down for 5 months.. but we really want to enjoy our house for the other 7 months..so.. our philosophy is now:
design for the summer... insulate for the winter..
choose a good window.. choose it for function, ease of maintenance, R-value, warranty ( actual vs. pie-in-the-sky ), appearance...
make your windows a once in the lifetime of the house decision..
we choose Andersen... so , we use what is architecturally correct from Andersen
others will choose Marvin.. or Pella .. or some such.. that's fine
read the literature, and decide how yu want to spec your windows in terms of energy conservation... but don't skimp on the windows to save heat
watch your doors too.... avoid sliding doors.. anyplace you want a sliding door, you can get a better function with a patio door..
on your primary doors, include storm doors.
think about mud rooms as air locks for the family entrance
Actually if you get custom euro style sliders they are excellent. They have lift slide hardware and triple gasketed. Course they will run you in the neighberhood of $1000 a lineal foot.
When you are looking for energy effiecint windows look for the windows U factor, and make sure that it is for the entire window and now "center of glass" reading. Also find out what size window the U factor was based on.
I've heard propaganda that Schuco makes high-efficiency windows that blow out the competition, including the Big 3 (Schuco being bigger than all three combined). Triple-glazed, krypton, TPS spacer. Boxy in appearance though, and all vinyl.
Although I love Marvin for the aesthetics, I was real disappointed when I looked at their energy ratings. Just average, argon is an option not the default, etc. I assume Andersen and Pella are similar.
taylor.. i've never heard of Shuco.. so i went looking..
here's a web site that talks about windows.... and Shuco ain't doing so well
http://www.vinyl-replacement-windows.com/replacement-window-discussion/read.php?f=1&i=853&t=399
we had a similar window being distributed here.. nice window.. but so what.. no service when the local contractor went outMike Smith Rhode Island : Design / Build / Repair / Restore
I have to agree with Mikes big picture view.And, I just did a sunroom with 9 big cottage Marvins, and a set of Marvin french doors.....all in a room that is basically 13 x 15. And it's the most comfortable room in the house. Granted the radiant I put in the floor is a large factor, but I just don't get the cold chill I get in my own house from the windows.It seemed to me, when I looked at the ratings, that all the windows were actually pretty close to each other in the big picture...there are so many other ways to be much more effective. So I made my decision as Mike did. Marvins, Andersons, and Kolbe and Kolbe have good pricepoint/value ratios.Jake Gulick
[email protected]
CarriageHouse Design
Black Rock, CT
Mike,I'm not an advocate for Schuco, I am curious to hear contrary opinions (as long as they're not competitor shills...). The issue you link to has been discussed a few times, people who bought direct from Schuco when they did retail have been left high and dry. Now they only sell through dealers, this is a problem for me since installing a replacement window is not rocket science, I'd sooner DIY.In any case the Europeans are way ahead in window technology, my understanding is they invented replacement windows. Schuco is the largest window manufacturer in the world, they're trying to get a foothold here in the US (and blowing it by the sounds of things). But they do have a very efficient window based on everything I've heard, and you pay accordingly. You will not find them with the other junk at Home Cheapo.I learned about Schuco from that windows forum, I'm still trying to decide if FenEx is really Killer Monsoon :-) (that's an in joke for all your Remar Sutton fans).
do they make primary windows .. or just replacement windows ?
the similar window i saw was Great Lakes.. nice window...but i hate going outside of my normal distribution system for materials... first thing you know, you're shut outMike Smith Rhode Island : Design / Build / Repair / Restore
I believe they're just vinyl replacement windows.http://www.schuco-usa.comDon't think of them as Ford Escorts, that's what you get at Home Cheapo. Think of them as the Mercedes or BMW of vinyl windows.Marvin windows come in with U-ratings in low .30s. Schucos come in with U-ratings in low .20s. Schucos are not cheap though.As I said, I'm not an advocate and I'm interested to hear negative reports. But I'd say they are worth investigating rather than just blanket dismissal, if you're willing to consider vinyl. My impression is that most vinyl windows in the market are junk.
taylor....
if you want low U-values.. look at Hurd...i've use a lot of Hurd.. but their main distributor around here switched to Kolbe&Kolbe
lots of good vinyl windows.. problem is.. in custom work most people want a wood window / clad exterior
look at the U-values of Andersen... Shuco doesn't impress me as being something my market would buy..
and they have no distribution in the Northeast... at least not thru normal channelsMike Smith Rhode Island : Design / Build / Repair / Restore
I have come to the point in choosing windows, that the distributor/rep is 40% of the decision. How well they know the product to help you choose, and hiow well they do follow-up on complaints...
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Each year the Arch deptartment as KU builds a project house.Last year or the year before it was to use some special exotic windows that if I remember correctly had an R value of 11 or 13.The article about this was in the newspaper so it did give much details, but I think that they where also super, super expensive, but that they have been donated.But something happend with them (either damaged in shipping or the wrong sizes) and they had to go with a local supplier.CAG was promising to give the inside story on that group after he graducated.But I think that they bought him off <G>. Haven't heard anything more from him.
"Schuco is the largest window manufacturer in the world"I know exactly nothing about schuco windowsBut the kind of argument I quote above just sort of always leaves me cold. In order to be the largest and market to the most, you have to produce to hit the median or below. That never means a high quality product so far as I know.
For instance. The Ford Escort was for years the largest selling vehicle in the world. I never heard anyone claim that as evidence that it was amoung the best...Just a thought to throw out
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Crown and the other 14 names that company used were thee same way...
they never seem to get a repeat consumer...
other than developers...
proud member of the FOR/FOS club...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
The Ford Escort was for years the largest selling vehicle in the world. I never heard anyone claim that as evidence that it was amoung the best...
Piffin,
I liked that analogy. Will have to remember it for someday use....Just like the POS Taurus that beat out the Honda Accord in '92.
Jon
If you want high efficiency a steel frame is a really bad idea. Using steel studs instead of wood studs causes the heat loss through the walls to fully double. Even though the surface area of the steel is small, it is so much more conductive that the heat loss through them is as much as the entire remaining surface area of the insulated wall. If you like steel studs for some reason, confine their use to interior partitions.
I am aware of the conductivity of steel. The system I am evaluating solves that by embedding the steel into the EPS foam--no steel makes contact with the exterior.Have a look-see and tell me what you think: http://www.elfiwallsystem.com/products.htm
It looks like a good concept. It is not clear how exterior sheathing and siding are to be attached. And the web site conspicuously omits stating the R-value. It has some promise, though.
That reminds me of a system that I saw at the home show when I was getting ready to build my house in 79.It was foam pannels with slots molded in it for 2x4". But they where stagered on each side of 6" foam and used a 6" plate. Looked like a good system thermowise. Don't have any idea of what they cost, but apparently where popular enough to have lasted.
The prime difficulty with steel is that it will increase construction costs rather dramatically.; SIP's on the other hand will allow normal surface treatment, ie the ease of applying sheetrock or siding for example.
Frency:Always appreciate hearing from someone with prior experience.I've also looked at SIPs and ICF. For a variety of reasons, mainly dearth of experienced builders, I've settled on steel framing. By only building the external walls with this system, I hope to marry its high efficiency advantage with standard carpentry work on the inside.
Steel studs are only "bad" is you use them badly--the devil being in the details, as with just about everything else in life.
Sure, they are not the best thing to just slap some sheathing * siding up on the outside--but that's jsut as bad a thermal detail in wood, though (transmission value is different, but wood has greater mass).
The big "however" is that, IIRC, the OP wants a steel support frame with SIP infills. Which is rather a different kettle of fish. Then, it's down to the isolation of materials--just like a timber frame.
Now, a "structural stud" frame versus wood frame might be worth debating. Both have some advantages, and some disadvatanges.Occupational hazard of my occupation not being around (sorry Bubba)
Installation is at least as important as the window itself.
Windows are beautiful but even the best ones are a major source of heat loss, so it's a trade-off. Such a trade-off that it makes a person wonder why they bother superinsulating the rest of the wall space: in some cases, 70% of a wall's loss can be via the windows. Dropping the remaining wall's heatloss in half can be major money for minimal benefit.
Stay away from sliders, spend more than you figure you can afford, and then count on providing some secondary insulation on these during the coldest nights- heavy curtains are surprisingly helpful. Doubt you're seeing much out your windows at night, but they're spewing heat outdoors just the same.
Duly noted. You summed up the reason for my question in the first place. I am starting to find that windows loose more energy than I thought.
If you are shopping windows,and thereis no posted R-Value the U factor is basically the opposite The lower the U Value the less energy (heat) is transmitted through the glass, the other obvious consideration is the pressure test rating I'm not sure what that is called (if anything else) or what score to look for there...SCRIBE ONCE CUT ONCE!
all the u and e numbers are useless when the seal blows out after 10 or less years and you have to replace it all. The GREAT energy calculations never include replacing the glass every 10 or so years
wain... i've had Andersen come in and replace 20 year old sliders for some of my customers... for nothing ( just our labor )
i've also had Andersen Narrow lines on our home built in '85 .. about 16 windows.. no seal failures .. no fogging... and i really don't expect any failure for another 20 yearsMike Smith Rhode Island : Design / Build / Repair / Restore
That is one feature of a window supplier I wish they could put in the NFRC rating chart.
I looked into using steel also, picked up the Residential Steel Framing Handbook, did some reading and started asking around. Seems the Mashentucket-Peqout Indian Tribe (Foxwoods Casino in CT) had started building steel houses for tribal members a few years ago. Supposedly they had major problems with "conduction between sheathing screws thru the steel studs to the drywall screws, caused black spots on the walls and in some cases rust. they tried galvanized screws and then finally gave up. I was told in that they should have used exterio Dri-vit, a foam & stucco type finish as this would have "isolated" the screws. After hearing all the problems with Dri-vit and water leaks I went back to good old wood!!!
I've thought of using steel studs for a basement wall....with foam panels against the wall providing a thermal break, it seems that one could avoid these problems.... There's got to be something better than the garbage they're selling for dimensional lumber these days....
Steel studs on a foamed basement wall work well. See the partially completed wall below. I used 1 5/8" 20 ga studs.
Billy
Looks good, Billy. Although I'm surprised you didn't use EPS (white board) if that is an interior useage. Usually cheaper than the XPS Foamular.
But both work. I know a few basements that could use your treatment. :)
jt8
Our lives improve only when we take chances -- and the first and most difficult risk we can take is to be honest with ourselves. -- Walter Anderson
You're right - EPS is cheaper and it allows a little better vapor transmission than XPS. At the time I couldn't get my hands on the T&G EPS foam panels, although it's not a big deal when you seal the gaps.
Billy
Thanks, I will probably go that route. I still have some concern about conductive heat loss through the things that penetrate the foam insulation (windows, pipes), but I can't imagine going through a pile of 2x4s looking for enough straight ones to cover the basement perimeter.... Are there techniques for thermal breaks between steel studs and the penetrations? Say RO made of wood in a steel RO....
I did you use 20 ga studs?I did the same thing last year and use 25 ga 1 5/8"You have "solid blocking" with it resting against the foam so there aren't concerns about it being ridgit.
Yes, I used 20 ga studs. They were a little harder to find but worth it. The studs are not exactly flush against the foam, but are spaced about 1/2" away because the wall (and foam) are not exactly flat & plumb. After the photo was taken, I shot a spot of spray foam every 1 or 2 feet between the steel studs and the foam wall. This made the studs more rigid and it helps hold the foam panels against the block wall if they become unglued in the future.
Billy
BigMan:
I am considering DryVit, or something similar. And yes, I know the controversy about them too. Keeps me up at night thinking about the risks I am taking with the money we are spending. I just have to think there's gotta be a better way to build than stick framing.
Framing carpenters, mercy please...
I used to design HVAC sysems in the midwest and have answered this question many times, including tin the design f my own home.
The average to good windows that are reasonably affordable (double pane, sealed and filled with inert gas) have unit U values in the range of 0.2 to 0.5. Compare that to a 2x6 stud wall with blown in cellulose with an average U value of 0.06, or so. The heat loss of your home is directly related to the U value of the insulated and heated envelope. If your home has 2500 sf of walls at 0.06 and 500 sf of windows at 0.3 and a design temp of -10 to 70 then the transmission loss of the walls/windows would be 24000 btu/hr, equal parts wall and glass. Now if you had 2000 sf wall, and 1000 sf glass, the loss would be 33600 btu/hr. Other losses would occur, through the ceilings, floor, perimiter and due to air changes, but you can see that by doulbling the window area in the example, you increased roughly 1/2 of the heat loss by 40%.
Overall for heating, in my opinion (and in the final analysis for my home) more windows is worth it. Buy the best you can afford and enjoy the view. And make sue the HVAC contractor has enough accurate information to get the heating right.
Air conditioning is a whole other ball of wax. Shading and siting make a big difference. As do window treatments and obviously climate.
Thanks Timbo for a most enlightening reply. I've never had anything but old single pane windows. So this is all new--something I'd want to get right the first time around.I'm a layman, what is the $$$ difference in heating cost between the 2 examples? And with fairly decent windows, will I experience draft (assuming just the windows)?I am currently in an apartment, and I swear if I could put thermal goggles on, I'd see rivers of cold air running down the windows and slide doors.
The assumed glass area in the example is the equivalent of fifty (50) 5'x4' windows. Will that cover your plans? (Which, BTW, will cost you about $70k installed, in a Pella Architect or equivalent window line)
The actual cost depends on local prices, but as a example I can use my fuel and prices for an estimate. I use LP as a fuel source and I believe my last tank cost about $1.30/gallon. I also have a 94% efficient furnace, as you are proposing to use in your home. I know from my handy dandy conversion table, that 1 gallon of LP is good for about 91,910 btu of heat. The tough part of estimating costs is to determine how much (equivalent) time you will be at design conditions. Lets say that your furnace runs 20% of the time for three months or about 450 hours. 450 hr x 9600 btu/hr (the difference in the previous example) = 4,320,000 btu. This is equal 47 gallons, or about $61/season. With longer (and colder) heating enviroments, higher prices of fuel, etc., actual costs will vary, but even if it tripled to almost $200/year, would make or break you? Doubtful. However, a large expanse of south facing glass, without shade will add significantly to you air conditioning bill in some locales, but I don't know if you ever actually get sunshine in WA, do you?
"And with fairly decent windows, will I experience draft (assuming just the windows)?"
There are two potential "drafts" that can be experienced with windows. One is due to air leaking past the seals when the wind blows.
Another is due to convection caused by diffences in temperature at the window inside surface and elswher in the room. A big radiator under a big window creates a nice well planned updraft that counters the effect of a large cold surface, ie. the window. Warm air rises and mixes with cold air at the surface of the glass and circulates around the room before being "felt". Designers of old knew that the windows were the biggest heat loss and that's where they put the radiators. The same windows with no heat source underneath it will produce the opposite, a downdraft of cooler air that will be noticeable.
Well insulated windows will limit both types of drafts. A well thought out and properly designed heating system will mitigate the remaining effects. Keep this in mind as you go forward on this project. An acceptable HVAC contractor will want to know about any large amounts of widows. The unacceptable HVAC contractors will ask no questions about such. Beware of those.
Timbo:Yeah, I was meaning the convection type draft. Thanks for the HVAC heads up.
There's a 3rd cause of drafts which can, in my experience, be bigger than either of the others: Leakage around the outside of the frame, between the window frame and the rough framing. Care taken in carefully sealing this gap can greatly reduce air leakage and drafts.
I made the assumption that a competent installer was involved in the process. I ignored general poor workmanship, as the quality of the windows concerning drafts was the question. Were you refering to personal experience on your installations?
I was referring to most of the installations I've seen. Not by anyone here, of course.
I was just ribbing ya a little. But the point you bring up is a good one. The best windows available, poorly installed, will not be satifactory. A good HVAC system will help.
Canadian company:
http://www.loewen.com/
Are supposed to have windows which are energy-efficiently superior to Anderson/Pella/Marvin. I haven't used them, but you could probably start a new thread asking about them.
But there is a lot to be said for local service. If you only have one place locally that can take care of your windows... that is kinda putting all the eggs in one basket.
jt8
Our lives improve only when we take chances -- and the first and most difficult risk we can take is to be honest with ourselves. -- Walter Anderson
Here is the distilled science of what I learned when I went through the process of designing the "ultimate" window for our Structural Insulated Panel house. http://forums.taunton.com/tp-breaktime/messages?msg=35243.1 I spent about three months on research and design before I had my windows built to a custom spec. - hope it helps.
What is not in that thread is what I learned by experience in the following months. Others have mentioned it already but let me reiterate. Use the local representative with the most stellar reputation and pick a window from their lineup that will most closely meet your needs, or work with them to design one that will.
Much as I love my Traco windows I will never, ever, ever, ever use the out of town supplier I had to order them through to get them again. Give local, intelligent service as high a mark as U value when making your decision, and remember that pioneers often ended their research with arrows in their back.
Innovation is sometimes a very good thing, just be smart about it.
'had my windows built to a custom spec'
Could you post those specs. And what did they cost you per sq ft?
My specs, window drawings, and I believe my costs, are posted in the thread I linked. I think I paid a little over 10K for 25 windows if memory serves. They were on the low end of the high end window prices I got and two or three times the price of the lower end Atriums.
If you need the cad file just e-mail me through my profile. I'll be happy to forward it on to you. I didn't go back and read the linked thread. If the info you need isn't in there just let me know and I'll try to dig it up and post it here.
Thanks for the link to your info. Good stuff.
I was kinda surprised that people think real thick glass units are more energy efficiant. I have heard that if the space between two layers of glazzing is more than a 1/2" that mini convection currents can form inside reducing the thermal efficiancy.
Convections happen for several reasons including too wide of a gap. 1/2" is very conservative and seals and coatings play every bit as critical a role.
Ideally you would have multiple narrower chambers of air inside the glass unit (triple or quad glazed) making up the overall wider glazing thickness. The Heat Mirror film serves as the divider in my windows preventing convection from starting. I could have gone wider without convection concern, but not cost effectively.
I've been where you are and believe me I searched high and low for the truth.;
In the end there is such a little real world differance between any window manufactorer's energy cost.; (assuming similar configuration ie Low e, Argon, double pane, etc.;) that the end result becomes meaningless. Carefull plment of windows will have a far greater impact on heating costs than which brand you select. Then window treatments affect your heating bill dramatically.; Heavy curtains or drapes pulled closed at night will prove to dramatically reduce heating bills.;
As for the steel building idea, look instead at SIP's.; energy efficent.; 200% stronger than raditional stick building
I've been in the energy and building industry for 25 years.
I've always been fond of Heat Mirror tm glass and tend to recommend it to anyone with a concern for energy and windows. Heat Mirror is not a mirror finish, but an invisible thermal mirror. It is the 'original' low-E glass ... but it is different in that the low-E coating is on a suspended film of mylar suspended between the two panes of sealed glass. This is not a new product, but has been and is used on many residential and commercial applications (I knew a major developer use exclusively Heat Mirror on a large new office building w/ large glass area).
If you can afford it, use Heat Mirror. Cost may vary depending on where you get it ... so shop around. Many window suppliers may not even understand what Heat Mirror is. So you may have to look around a little. If you want to go super efficient, you can get double (or even triple) Heat Mirror (two layers of mylar). You should be able to order just about any standard window frame and use the Heat Mirror glass option. Pella may not allow it due to limitations in glass thickness (Heat Mirror may require a minimum thickness of the sealed glass of 3/4").
Try http://www.southwall.com to get some info. on what Heat Mirror is about. There are not a lot of manufacturers of Heat Mirror (only one in the entire Northwest is in Seattle, I believe). They may tell you where the manufacturers are, too.
Heat Mirror glass is superior to low-E due to the added air spaces ... you get triple glass w/out the weight and increased efficiency, too.
If you have large expanses of windows, Heat Mirror has a huge advantage in that it will substantially reduce the 'cold wall' affect commonly associated w/ large window areas in cold weather. I used it for an unheated sunspace and even when it was well below freezing outside, you really didn't feel that cold draft coming off the windows like you do w/ most glazings.
You can get Heat Mirror in all the normal finishes that you might want ... e.g. tinted or mirrored/reflective ... or just clear. Generally, you can't tell Heat Mirror from any other glass at a glance. It is clear and invisible ... w/ the exception of a tiny hole you can see in the film in the lower corner of the pane.
I am not paid by Heat Mirror or any glass company. It is just a great product. I've seen Heat Mirror products approach the R-value of standard 2x4 walls!
Also ... consider rethinking your window design a little to reduce window area. You may not need panoramic views to be effective in enjoying your view of the woods. Use windows to frame views like you would paintings. Hinting at what is outside and framing particular views that are most interesting. Do this first; decide on glass last.
Install the best glass/windows you can possibly afford ... you only get one chance usually.
If you are stuck and still want more help/info ... drop me a note.
That was a good post wally but it should be noted that Heat Mirror does have a slight mirror effect and a definite color tone. Traco can't put heat mirror in their arched top windows and I can see the difference between my HM-88 heat mirror units mulled together with the arched top units that don't have the film. It's not dramatic but it's noticeable if you are looking for it, especially the reflectivity. I see the cloud reflections floating across the Heat Mirror windows a lot clearer than the ones without it. I like the look a lot but some others might not care for it.
There are also several different options with heat mirror for different climates and conditions. There is a slight green hue to the HM-88 I specified but you can get it in blue, gray and bronze as well. The green has the highest level of light transmittance in the color range I prefer.
If you want to get really carried away you can specify different heat mirror films for different windows in the house depending on which direction they face, light transmittance levels desired, Solar Heat Gain Coefficient and reflectance properties. The outer pane of glass should also have a low-e coating suitable for your environment. It makes a significant difference.
The other key is the need for wider glazing. Some of the manufacturers using Heat Mirror are not getting that great of numbers in their test samples. I believe it's because they are adding the heat mirror in the middle without increasing the depth of their standard double glazing. The width of those air gaps is very important in the thermal efficiency of a triple glazed set-up whether you are using glass or heat mirror for the center glazing.
A final caveat - Heat Mirror is an expensive option. I think it cost me an extra $75 or so per window and I was getting a very steep discount. You have to weigh the amount of time you are going to be in the house against the long payback time for using the more expensive glazing.
Heat Mirror most certainly increases the comfort level in a house, especially if you have window seats and will be sitting right there by the window. I can put my hand on the glass on a 90 degree plus day and it's just slightly warm to the touch. On the other end, the temperature dropped steeply here last month and I had the heater on in the house. As the temperature started rising outside in the morning, I was shocked to see several of my ultra efficient windows suddenly covered with condensation. I was even more shocked when I realized the condensation was on the outside of the glass, not the inside - that was a nice switch from the non-insulated single pane windows I was used to in my last house.
The comfort level sitting in front of those windows and taking in the view is greatly enhanced by the Heat Mirror so it was worth the extra cost to me because that's something we do a lot in our house, but if someone is specifying H.M. for the energy payback alone it will be several years before the film pays for itself in energy savings.
If it's a retirement home, or a place where you plan to spend a lot of time right up next to the glass, I would say go for it, but most people still find the relatively quick energy payback on good quality, double glazed, low-e coated windows a better bang for their shorter term investment buck.
If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again
A better solution may be another Southwall product called V-Kool. It has a much less noticable effect on color tone and blocks 70% of the IR coming into the home. I may yet consider using it for our home (since 40kBTU of 60kBTU of heat gain are transmitted via the windows) if the attic AH cannot handle the load in the dead of summer. Having said that, I would treat window films very carefully. Not because they don't work - they certainly do - but because they may work against you. In our climate, the heating DD overshadow the cooling DD by a factor of 7-1. Thus, there is a lot to be gained from insolation in the wintertime. In fact, despite open windows during the day, 40-60 degree exterior temps and a internal setpoint of 60 degrees on the heating system, the house is consistently between 65-70 degrees on the inside. That is, the heating system barely comes on, despite the cold conditions on the outside. The source of all this heat: the solar gain via the windows, of course.So, I'd do some careful figuring with the help of spreadsheets, heat gain/heat loss programs, etc. before applying a window film. You may miss the heat more than you realize... in an ideal world, we'd have V-kool coated storm windows for the summertime and clear ones for the wintertime. One approach I am contemplating is a thin piece of Lexan with a V-Kool cover to insert between the storm and the antique double-hungs, thereby creating a clear, removable UV- and IR-blocking system.Naturally, the folk who live in areas where the heat gain to heat loss ratio is the reverse of our situation will have nothing but to gain from using quality window films like V-Kool, Heat MIrror, Hüper-Optik, etc. However, IMHO, given the cost of these products, the biggest bang for the buck is to design a house sensibly from the start, i.e. orient the house appropriately, install proper overhangs to limit insolation in those areas that need it, etc.
Edited 4/27/2005 2:36 pm ET by Constantin
Absolutely! We are completely opposite your climate. I put my efficient energy design efforts into keeping the air conditioner load down. V-Kool must be the new film the Southwall rep told me was on the way. If it is, it was still under development when I ordered my windows.
Edit: Scratch that - I took a look at the site and V-Kool is not the product I was told is under development. I think V-Kool is a film that is applied to the inner layer of glass. If that's the case, make sure that it doesn't void your sealed glass unit warranty on a double glazed window before you apply it. Inside applied films often void these warranties because the heat reflected is compounded back inside the glass assembly causing pre-mature seal failure. The applied films are also susceptible to scratching. Perhaps they can apply it to the inside of the outer layer of glazing. That would indeed help quite a bit in a hot climate while negating many of the potential negatives.
If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again
Edited 4/27/2005 3:54 pm ET by Golden Wrecked Angle
Thanks for the added thoughts/notes.
The high cost is unfortunate. The cost back in the late 80s was much better (relatively speaking). I had 2 ft x 7 1/2 ft units in my sunspace and had to replace them a couple of times due to breakage ... the first time was a little over a hundred dollars for the glass ... the 2nd time it exceeded $300!!
My window dealer I am working w/ now has also stated that the cost is probably prohibitively high for new windows I'm about to order. It's such a good product that is going to waste due to this high cost!!
The tinting as you say ... generally minor and not noticeable ... but if you have them side by side ... you can see the telltale difference. Even standard low-E glass has a different shean or tint when placed next to other glazings ... e.g. standard clear insulated.
And, yes, Heat Mirror is available in a wide variety of coatings to accomodate your specific climate/needs. HM-88 is generally for cold climates and as you decrease the numbers (e.g. HM-33), they are geared more for the cooling climates/needs.