More Building Matters
Remember “passive solar design,” whereby houses were built with giant south-facing windows and thermal mass was key? That mass was supposed to store solar energy, but often more energy was lost at night through the glass than was gained during the day.
Frank Lloyd Wright designed the Solar Hemicycle House based on passive solar principles, and come winter, the residents got dressed in the bathroom, which was the only room with a radiator.
Passive solar design was popular in the 1970s, until studies like the one Rob Dumont and Harold Orr conducted in 1978 comparing a passive solar house to the Saskatchewan Conservation House, which concluded that the passive solar house, “although possessing a larger south-facing window area, required a considerably greater amount of auxiliary heating.” Other studies confirmed this.
According to GBA’s Martin Holladay, every extra square foot of glazing beyond what is needed “to meet the functional and aesthetic needs of the building,” is money down the drain. “In a way, this advice is liberating,” he says. “It compels the designer, secure in the knowledge that no technical or functional issues are at play, to think about aesthetic issues—and that’s almost always a good thing.”
Wrong priorities
The problem today is that designers are thinking too much about aesthetic issues and making windows too big. This increases costs, reduces energy efficiency, and cranks up the embodied carbon–or as I prefer to call it, upfront carbon emissions—because of all the glass, aluminum, and vinyl used to make windows.
Professors Jo Richardson and David Coley make the case here, saying: “If an architect starts by drawing a large window, then the energy loss from it might well be so great that any amount of insulation elsewhere can’t offset it. Architects don’t often welcome this intrusion of physics into the world of art.”
The bottom line is windows are hard to get right when it comes to size. Designers work their sizes and proportions to get the look they want, designing primarily from the outside rather than the inside. Engineer and Passive House consultant Nick Grant says that windows can cause “overheating in summer, heat loss in winter, reduced privacy, less space for storage and furniture, and more glass to clean.” He suggests that “size and position are dictated by views and daylight.”
Some recent studies support Grant’s idea that we must be careful about oversizing windows. Among them is the work of Dr. Hannes Gauch, who led a “simultaneous sensitivity study” that built a model with input variables for a building’s shape, size, layout, structure, ventilation, windows, insulation, air, and use. Results indicated windows have a significant impact.
“Decisions concerning windows are most influential for heating and cooling loads,” Gauch states, “especially the window-to-wall ratio. While higher window-to-wall ratios decrease all three efficiency metrics, windows with lower U-values (triple and quadruple glazing) entail higher costs. This suggests a non-negligible trade-off between energy efficiency and construction costs.”
Recent work by Kelly Alvarez Doran of the Ha/f Studio at the Daniels School of Architecture compared the upfront carbon emissions of double vs. triple-glazed windows. The latter has 50% more glass, 100% more spacers, and roughly 30% more frame. (Note: This assumes electric heating and cooling and north-facing glazing.)
Doran’s results are shocking: It takes years—in some places, decades—for a crossover date, when the reduction in operating emissions from triple-glazed windows matches the increase in upfront carbon emissions.
Of course, there are other reasons to choose triple-glazed windows, including comfort. They also have a significant impact on mean radiant temperature and climate resilience, given their ability to reduce heat loss when the power goes out. But, most importantly, even in an all-electric heat-pumpified world, we must minimize operating energy consumption to minimize the peak loads that our electrical grid has to be designed to handle.
Writing in Passive House Accelerator, Skylar Swinford and Zachary Semke say, “A misperception has taken hold: [If] you’re not careful, Passive House practice will do more climate harm than good; that the extra insulation and triple-pane windows on a Passive House can backfire, adding more upfront carbon emissions than the operational carbon emissions than they reduce.” No doubt Doran’s research would reinforce this misperception.
Other considerations
There are low-carbon options for insulation, but that’s not the case for windows. So, if you are worried about the upfront carbon “burp” of triple-glazed windows, the right approach is to tweak the window size, not the number of panes.
Of course, windows do more than provide light and air. As this Swedish study states: “Windows represent an enjoyment of the home and fulfill much more than physical needs. They must allow sufficient personal control over fresh and cool air, sound, sunlight, streetlighting, and privacy.” In addition, views of the sky are necessary to synchronize our internal circadian rhythms; views of trees encourage biophilia.
Some say that windows are superfluous and no longer necessary, as evidenced by Berkshire Hathaway’s Charlie Munger proposing a giant dormitory without windows, and real estate developers selling apartments with windowless bedrooms. But even Grant admits their importance, saying: “Despite my banging on about efficiency and sufficiency, I’m partial to the odd window placed for a Zen view or mid-winter sunbeam that does nothing for heating or daylight but lifts the spirits.”
The lesson here is that windows should be as small as possible while still letting in light and views.
Bottom line
Windows are complex, multifunctional, carbon-intensive, expensive, difficult to get right, and too often they are designed primarily for aesthetics. I concur with the findings of professors Richardson and Coley: We must change how we look at the aesthetics of buildings and “drive a revolution in what architects currently consider acceptable for how houses should look and feel. That’s a tall order, but de-carbonizing each component of society will take nothing short of a revolution.”
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Lloyd Alter is a former architect and developer. His journalism career includes 15 years as a contributor to Treehugger.com. Today he teaches sustainable design at Toronto Metropolitan University. His work can be found at Carbon Upfront.
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94 Comments
The building in your lead image shows one way to address a problem you hint at in your final paragraph: exterior aesthetics. Although small windows are better than large windows for many reasons, it's difficult to design an attractive house with small windows. It's possible but it requires a lot of talent and some luck. An easy way to make most buildings look better is to throw more glass onto them. I'd like to see a style popularized that uses low-carbon building materials and careful use of glazing, but that doesn't look like a bunker. Or that does look like a bunker but people like it.
Michael,
That's one of the downsides of modernism having banished exterior ornamentation.
Definitely. The current style of using a variety of exterior materials on boxy buildings, multi-families in particular, helps a little but it usually looks as fake as it is. What I like about the building at the top of Lloyd's article are the flared openings around the windows, finished in a contrasting color to the rest of the siding--it's an honest and practical replacement for larger windows, without looking like large openings that were closed in for smaller windows, as we often see in the northeast on factory buildings repurposed as housing.
That's why I picked that photo, I liked how they put a picture frame around it. As you say, it takes talent.
I like the look. But I suspect it comes with a significant cost penalty, especially labor and staging.
Stephen, here's a project in Maine with a similar concept but that doesn't look too onerous to build: https://woodhullmaine.com/work/residential/pieri-pines. A little more complicated than "regular" details but well within range for any higher-end firm.
There is a long history of fake windows to manage exterior aesthetics. I don't know that history, but I've heard others talk about it.
https://thatsliguria.com/en/why-are-the-facades-of-ligurian-houses-richly-decorated/
RMI always emphasizes energy services.... glazing generally provides them, but that doesn't mean there aren't substitutes. E.G. operable glazing is neither necessary nor sufficient for ventilation. LEDs are giving glazing a run for its money on providing efficient lighting. Egress doesn't require glazing either.
Non-rhetorical question: Can we make housing significantly more affordable (and more durable with eliminating openings in walls) by dramatically reducing or even eliminating glazing altogether? We can supply 'connection' to the outdoors through faux windows (google it) that can be a simulacrum of direct connection. OLEDs are pretty good these days and don't cost nearly as much per square foot (installed) as the typical windows I see in my work. Ventilation can be provided through efficient balanced ventilation. Egress can be provided through well insulated, cheaper opaque openings (or fine-- maybe design the glazing to just meet egress requirements and no more).
This probably strikes us as a BAD idea. But why? Is our intuition correct?
I believe
Replacing windows with screens is a bad idea, for what I would think are obvious reasons. The window will always show you what's outside. The screen relies on power, and is subject to failure. How many people want their power outage to effectively change their house into a dungeon?
There's also the issue of limited field of view, and range of focus. With a window, as you walk closer to it, your view increases, and you can focus on objects on the other side of it at any distance (within the limitations of your eyes). A camera has a fixed field of view, and limited focus range. As you walk right up to a window, you expect to be able to see what's beside the window. As you look out the window at an angle, you see things in that direction. With a screen, you just see the same image, except at a bad angle. There's no way around the fact that you'll constantly be aware that you're looking at a (sometimes moving) picture, not the real outdoors.
Another huge problem is resolution. A big screen requires you to be a considerable distance away from it in order to not see individual pixels. So forget sitting in a chair a couple of feet away from this faux-window and looking at it. I guess you could try to develop a screen with orders of magnitude more pixels, but then your "doesn't cost nearly as much" turns into "costs more than the rest of the house combined".
I also disagree with the statement that windows are not sufficient for ventilation. Not practical to use all the time, sure, but opening just a couple of windows in my house drops the house pretty much to ambient outdoor CO2 values. With the house closed up and the ERV running, it can't get it anywhere close to that.
"This probably strikes us as a BAD idea. But why? Is our intuition correct?"
Connections to the circadian rhythms are fundamental to human health and the physiological stimulus for this is the daily cycle of day and night. Actual daylight is physically essential. Cutting people off from this natural cycle is absolutely a bad idea, and medical research has proven it.
So, yes, our intuition is correct.
Is it possible to substitute an artificial replacement with artificial light? I don't know. We don't know until the medical research has been done.
Should we even seriously consider the option?
I strongly doubt that cutting people off even more from the natural environment is going to bring us closer to solving the huge environmental problems we've created because of our ignorance of the natural environment.
No, we can't get rid of glazing. Also, the cost of housing has very little to do with materials, labor, embodied energy, operational costs, utilities, or anything of that sort.
Tom, can you explain what you mean? The last time I checked, the main costs going into building homes involves a lot of material and labor. Embodied carbon and operational costs are rarely considered at all. Do you mean that land costs can be high, or something else?
Michael, the cost for a home buyer, not a developer. The main factor in that cost is the location. The same identical house that cost a developer $50k to build might sell for $150k in a rural area but multiple millions in an urban area.
But cost of labor is probably also a lot higher in the expensive market. There are correlations.
Nobody is building a house for $50,000. Or anything close.
Our primary views are through a large group of south facing windows. We look at the bird feeders in the foreground and a distant field below. In evenings, we often remark about the colorful sunsets. No windows is an awful idea. We're disconnected from the natural world enough already.
This was taken through a window.
Stephen,
I agree, but why does that connection need to come via glazing. Why can't it be via high-definition screens and video cameras.
(BTW-- I know that's a disgusting idea-- but why?)
That's not a bird feeder, it's a fox feeder!
I think it's a disgusting idea because looking out the window is better than looking at a screen. I can walk around the room and change the view much more easily than I could manipulate an array of video cameras. And of course getting video equipment as good as my 75 year of eyes would cost a fortune.
As for ventilation, windows also let in sounds that I like. A few nights ago, I opened a window briefly to hear the peepers, which are a nice reminder that Spring is really coming. My HRV doesn't do that.
I think the interesting study would be to evaluate the assertion that video equipment of sufficient quality would cost a fortune. Windows also cost a fortune. What is the relative cost parity?
I don't buy the change of view argument. Changing the channel on a video screen is a really easy thing to do these days.
I'm being argumentative in good-faith here-- I'm trying to get at the underlying science.
I think there's something to the argument about inferior spectroscopic properties of video screens and full-spectrum (albeit heavily filtered via low-shgc coatings) of a glazing element to the outside.
Yes, it's easy to change the view on the screen. But when you move your head with respect to a window to scan the view outside, you are building up a sense of what's where around you that does more to help you feel oriented and connected. It's more than just data gathering.
I don't think the video equipment you'd need even exists. Windows cost in the tens of thousands of dollars. Developing and producing the equipment to adequately replicate the image quality and features of windows, that's difficult to guess the price. I think it would very conservatively be in the millions of dollars, and perhaps a lot more.
How did the discussion wander down this path? Windows simply aren't a problem big enough for us to consider eliminating them.
I sometimes wonder whether it would be nice to be able to swap-in sound-transparent air-tight moderately insulating panels in windows for being able to hear outdoor sounds when you want to. They could be fitted where the screens go in a conventional operable window. A start would be simply a plastic sheet on a screen frame.
Windows connect us to nature; without them we would be living in prisons more or less. Good luck, convincing homeowners to shrink them, as the trends now are larger than life.
A great thought, but why go after windows when there's things such as ThinGlass which is now 6x less carbon intensive than 1/8" glass. Glass can be recycled, where most insulation installed in homes when remodeled is trash and destined for the landfill. I've seen this over and over again. As well, window performance is increasing more and more, we will get to the point where windows insulate like walls.
Instead of aluminum frames, Fiberglass can we used. We can make these windows as green as we want to go..
Can you put a price/cost on natural sunlight or views? Society likes things that are beautiful, people take care of beautiful things, perhaps the real carbon footprint is what happens to homes with large windows vs homes with small windows. I can bet the more beautifully-designed home doesn't get demolished the future.
Too many factors at play here.
First it's smaller windows, then it's no windows.
And that's no way to live comfortably.
Also speaking of air leakage, Alpen's Tyrol line for example, has virtually 0 air leakage. (Not actually zero, but darn close to it) The number is so incredibly insignificant that window air leakage just isn't even a factor anymore with quality windows with multiple-chamber seals, etc.
My house had a corner bedroom with a big window on one side and no window on the other side. When we did some renovations, I added a small window to the previously blank side. I'm very glad I did. I probably only look through that window a few minutes a day, but being able to see out in that direction first thing in the morning makes me feel connected to the world out there. My only regret is that we didn't also shrink the big window on the other wall. There's no need for it to be that big and we often go for a week without open the curtains more than halfway.
I'll toss my hat into the ring and take a third view,
We ought to require better windows, not reduce the number or count. This is an area that could drastically benefit from a concerted research approach. The world has had windows with a sub 0.2 U values for a *long* time, just not in the US. This is one place regulation could do us all a favor. A window with a U value of 0.5 is just a hole in the wall - we might as well use a single pane.
A house with small, or fewer windows just isn't fun to live in.
Agreed, as much as I dislike freedom of choice, regulation to improve performance codes would greatly kick things in the butt. Officials have been pressured for FAR too long not to change.
One of the requests I had on our last commercial retrofit project (starting with a windowless warehouse shell) was to have the architect do solar modelling on the proposed windows to maximise light penetration into the building. On Dec 21 for example, we had natural light penetrating nearly halfway into a 4500 square foot footprint by tweaking location and height of the strategic window installations. We also modified the 2nd floor trusses in the R&D area to install a clerestory (only 3 small wind0ws) and Solatubes (interior upstairs hallway) to maximize light while keeping window number and size strategically low.
We used Wattstopper ceiling mounted sensors throughout that building which were programmed to hold interior lights off at programmed lux levels...another way to offset carbon inputs on the windows themselves.
I don't see too many conversations here on these techniques, but I will say the software modelling extending remarkably well into the working structure.
I am a big fan of using acrylic inner magnetic panels (cold climate) which based on FLIR thermal images at very cold temps (-25 c) can easily elevate the performance of a double pane window to as well or better than a triple. No idea on embodied carbon on these panels, but I did notice that Stephen Aiguier, founder of Green Hammer ( The Retrofit Podcast Episode 7) used them as a substitute for triple glazed windows on a historical project that required double hung sliders. I used them on the commercial project mentioned above, and use them on my home.
Just more food for thought to compliment an excellent article :-)
I have acrylic window inserts in my home and they are great, they cut heat loss and noise dramatically while keeping the original 1916 windows.
I had no idea such a thing existed! I've seen the window film approach, but it never occurred to me to use a magnetic mount / acrylic panel.
Mine are a compression fit from Indows https://indowwindows.com they even account for the fact that my windows are parallelograms, not rectangles.
Kyle, as Lloyd has suggested, adding an acrylic panel and an air layer is quite magical. I'd say sound transmission is cut in half (double hung slider) and air passage is cut to the point that the panels on a few north side windows bulge and flex as winds get to the 50-70 km/h level.
They are more or less invisible with the magnetic frames in white. I've attached a few of the FLIR images I took a few years back...
I can see how these would be good for preserving old windows for aesthetic or historical reasons. They're pretty pricey, however. I used their quick calculator, and the price is not a whole lot less than the triple pane windows were on my house.
Hi Lloyd, this is an interesting option. I'm going to look into cobbling together something like this myself. I'm an American, now living in an old house in rural France. My 120 year old house has its original windows. The frames are made of locally grown chestnut and in impeccable condition, since that's such a durable wood. (They knew what they were doing back in 1903.) But of course they are single glazed. I think I could get acrylic panels that I could attach either with magnets or velcro to the inside frame faces. I'll look into that. Thanks again for the idea.
By the way, once a year the local PVC window contractor rings my doorbell and I politely tell him to go fly a kite. He has, unfortunately, made serious inroads into the community.
Here's another fun one: Alpen's WinSert, which is the window insert on steroids... Insulated frames, 2x panes, 2x gaskets, etc. Thermal performance is wonderful, but I love the 97% air infiltration reduction the best personally.
https://thinkalpen.com/products/winsert-window-inserts/
Unfortunately, Alpen only makes them for commercial projects at the moment. GSA study attached, Department of Energy.
“[Deleted]”
It was a local business. Acrylic is cut to fit, and they slide trim over the edges which has magnetic tape on one side. White painted J trim (steel) is installed on the inside reveal which provides the magnetic attachment point.
They just pop off in the spring (for operating windows), but we leave most of them in place year round.
Going back over 10 years, they were not cheap, but we’ve had zero issues.
You want thermal efficiency? Ignore all this baloney about aesthetics (it's all personal
opinion anyway) put them in in the size that pleases you, then cover them with insulated
shutters (inside or out, in a style that suits, custom made or something off the shelf such
as insulated doors used as a shutter). You will usually find that an insulated shutter over
inexpensive glass has a considerably higher R value than even the most expensive high tech
glass you can buy and is usually considerably cheaper - even when custom built. The downside?
They look different than what people are used to - and they have to be closed at night in cold
climates or perhaps in the day in really hot - and interior, they interfere with furniture placement.
I realize that I'm just wasting my breath (or print here) - the general public cares not a wit about energy efficiency or any other engineering ideas - the only thing that really counts is location, location, and location at the price they can afford. This might sound bitter, but it isn't, I designed,
built and lived in several (for a large number of years) all with interior shutters (climate zone 6)
and was able to make them attractive enough to sell quickly when the time came. But it
wasn't the energy efficiency that sold them (although it didn't hurt) - it was their appearance
and the neighborhood!
gstan,
The "baloney about aesthetics" is why people flock to Venice and Bruges each summer and don't arrange to visit new energy efficient apartment complexes in Seattle.
"But it wasn't the energy efficiency that sold them (although it didn't hurt) - it was their appearance and the neighborhood!"
Which I think is as it should be. Houses are primarily cultural artifacts. That's always been the case in every society. They aren't boxes optimized to keep us alive, they are there to support the whole wide variety of our human existence. The same is true of almost every other thing we make. Clothes, cars, furniture, dishes, food, and on and on. Why should houses be any different?
MALCOLM - My wife likes to maintain that it was her beautiful plants that
sold those homes - she jokes, but there is an element of truth in her humor!
It's not just aesthetics. Shutters are labour intensive. I don't mean during the construction process, but living with them. Most people would eventually grow weary and just never use them. You could try to automate them, but there'd still be lots of times you had to manually override the settings. And there's a functional difference. Sometimes you want to see out the window, even at night. So instead of just glancing out the window, you have to decide how much you want to look out and decide if you want to go through the trouble of opening and closing the shutter.
Most people find it convenient (and often necessary) to open and close their
drapes, blinds or whatever - do you really think there is an appreciable
difference in effort between those and shutters?
There have been a few articles like this recently. Let's just be done with it and only design houses with code minimum room sizes, with code minimum window openings, and then hyper-insulate everything. (Ex. bedroom, 7'x10', one window, 2'x3', narrow wall to the outside)
Forget creating homes that actually do more than satisfy base physical requirements and actually bring pleasure to people's daily lives.
We don't need reminders not to be wasteful. Those of us reading this website already know that, otherwise we wouldn't be here. As professional designers and builders my hope is that we can actually improve people's quality of life and not just minimize by cutting back more and more.
Enough of my rant. Thank you for your patience.
jgsg,
Yup and eat three meals of a tasteless gruel specifically designed to be nutritionally complete. This is the stuff of dystopian science fiction.
" that we can actually improve people's quality of life and not just minimize by cutting back more and more."
The problem is that we've developed cultures that equate more with better. It needn't be some sort of dystopian novel as Malcom suggests either. We can consider the possibility that less can be more.
And I disagree that 'we' don't need these lessons. In fact, in my time perusing GBA's pages and other similar avenues, I have come to see that much of the focus of so called 'green building' is cover for expensive 'high performance' building and comfort. I don't exclude myself from this. Just an observation.
"And I disagree that 'we' don't need these lessons. "
It's been my experience that the people I've interacted with here, people like you, seem quite aware of the issues.
I agree that many of the projects that get featured in "green building" articles tend to be high end and certainly larger than needed by their residents. There are a couple of issues related to this. I'd like to see not just more articles about smaller projects, but more of those smaller houses being built to a high standard.
But I think people who can only afford to build smaller homes are less likely to hire an architect to design them something.
Another thing is that when we push the limits on any technology or change in the paradigm, it tends to be more costly for the pioneers. So the rich clients with the vision will be willing to pay the cost. But the clients on a much tighter budget are going to be inclined to go with the lower cost and lower perceived risk solutions. This is a fairly common dynamic in a lot of fields.
Also, I'm imagining the following conversation.
Mr. Moneybags, "Hello Mr. Architect. I'd like you to design me a 5000 square foot state of the art showcase home, featuring the most advanced features and ideas in green building. I've got loads of cash and I'm ready to pay you a hefty fee."
Mr. Architect responds, "Mr. Moneybags, I can design you a home featuring the latest and best. But based on my personal convictions, I'm only willing to design it if it will be a small home, of around, 2000 square feet, because that is all the space you and your family really need. I'll also require you to donate the rest of your budget to a worthy non-profit and of course, I'll reduce my fee by the appropriate amount."
jgsg,
I live on a road that at its far end runs along the sea front, where the h0uses are much larger and more expensive than elsewhere in our rural community. After spending a fair amount of time discussing pointless additions and renovations with some of the owners of those houses, last year I adopted a blanket policy of simply not considering any work there.
I'm luckily in a position that I can do that, and can't claim that the decisi0n was entirely based on principles related to preserving resources, rather than finding it impossible to muster any enthusiasm for work that has no good purpose. And I agree, I can't see lecturing clients on their prospective projects as useful.
Beyond financial necessity, the arguments for taking on that sort of work appear to be twofold: If you don't do it someone else will, or that such work often affords the opportunity to drive building science forward. I'm not making any moral judgements on either. Each designer has to decide what motivates their work and what work they feel is meaningful and worth taking on. In my own case I've decided to forgo projects that might be classified as lacking purpose, or boutique green.
I have told many potential clients that their project is not a good fit for me, after they make it clear that they won't be constrained on size or other environmentally impactful items. And for a long time I worked at a discount compared to my competitors, though I never required the savings to go to a particular cause. I have never lacked for work and find a ready market of people who want help doing a little better than average, and a few who want to do far better than average. I also do larger, expensive homes with big windows, but the homes are smaller and better-performing than they would be if they had gone with a conventional architect or designer.
You're right that the regulars here don't necessarily need to learn these lessons. But after being involved with GBA since before it went live, every day I find new things and reminders on here that help keep me inspired; different ways of looking at things I thought I understood, and new ways of explaining concepts to clients and builders.
Up until WW2 it was common knowledge and practice that principal rooms such as bedrooms should be placed at building corners so that they could receive light from 2 sides and have effective natural ventilation. Houses commonly even had dining and sleeping porches. Read design books from the turn of the 1900s and you'll see this over and over.
Many of us live in climates where we can leave the windows open for at least a few months of the year.
Maybe the real solution is a 2-generation long project to reduce population and move the remaining population to more temperate climate zones that require less costly building interventions to moderate the weather.
Hawaii anyone?
Having windows on at least two walls is definitely important in any room used often during the day--not just for ventilation but for light and views as well. I like putting windows near the corners of the room when possible; it goes a long way toward breaking down the indoor/outdoor visual barrier.
Living in a house with windows entirely replaced by screens sounds about as appealing as eating astronaut food or MRE rations for the rest of your life.
Even if the precise mix of macro and micro nutrients works out to be the exact same as you might get from a meal made with fresh ingredients that you cooked yourself, there's no way the MRE is going to match the human experience and be able to deliver any sort of delight in the process.
And I would argue that no LED/OLED/QLED/HyperUltraUberSuperDuperFantastaLED screen will be able to deliver sustained delight either. Our bodies will know the difference. And more than likely, the research will prove 50+ years from the time this is attempted, that it was incredibly damaging to human physical and mental health.
Hi Lloyd. Here's is a fantastic video from Christine Williamson of Acelab for Architects called "Why Glazing Matters So Much More Than Insulation" that I hope you'll like.
https://www.youtube.com/watch?v=zJRsmiaqh6A&t=36s
That video is fabulous, I wouldn't have needed to write the post if everyone watched it!
Thanks for all the good advice. I love my windows.
Yes to reducing window square footage, but as a general rule I would prioritize reducing the number of windows before reducing their size.
While building a no-frill well insulated building, it occurred to me that each additional window opening involves more than a day of labor. When including trim material, that's at least $700 per opening in my area, not including the price of the window itself. That's because each opening require so much labor at every phase; framing, window install, flashing, air sealing, insulation, additional siding and drywall work, casing/trimming and painting. Even on a low budget, each fully installed window cost over $1000 . The total cost difference between, say, a 12 sqft window and a 18 sqft window is minimal, but the same 36 sqft of glazing will be much cheaper to accomplish with two windows than three.
Similarly, the relative upfront and operating carbon footprint of smaller windows is higher given that the frame is where most of the material go and that the center of the pane is typically the best insulated part.
Hypothetically, I'd start with a glass house made of 100% windows. From there, I'd reduce them as needed for:
* Privacy and unwanted views;
* Thermal performance of the home;
* Budget constraints; and
* Solar glare / solar heat gain.
As window design advances, I think we'll see more glass in homes, not less.
Adam,
That's a really odd approach. It assumes that an ideal house would include as much glazing as possible.
I'm also not sure that outside the rarefied world of the GBA community that the energy penalty incurred by excess glazing has any noticeable effect on residential design. Architects have generally been using other values to decide what sized windows to use, and I doubt better windows would have much affect on that.
Malcom,
This is "hypothetical" and implies that if there were no energy or cost penalties, people would want more glazing - especially if a home or building were situated within nature, had privacy and views.
Once you start adding in energy costs, financial costs and other factors, we get much more practical results.
..for context, we're in the final stages of a home design and window sizing is the proving to be most difficult.
I like your idea. Do you have a favorite house from a classic movie? Mine is perhaps the home of Dr. Morbius in Forbidden Planet. Essentially it was a dome in a garden, with the garden carrying right into the dome so that the house "interior" was a continuation of the garden. There was even a small stream passing through and a natural rock outcropping serving as one wall of the house.
It's a hugely romantic notion of an environment that fosters well being. Dramatically, it contrasted with Dr. Morbius' own subliminal destructive urges.
https://www.flickr.com/photos/morbius19/12075820543
Is there an ideal window-to-wall ratio that we should be going for on new construction projects?
On relatively conventional designs, I've found (and probably heard elsewhere) that facades look best with at least 15% of the wall area as glazing. Most traditional North American homes that are broadly considered attractive have about 15-25% glazing on the front facade. The sides and backs of those homes often have a lower percentage of glazing (and often look worse than the front). Homes with modern design often have a higher percentage of glazing, sometimes approaching 100% of the facade.
That's for aesthetics. For energy efficiency, in a cold climate, having no windows (but excellent insulation and air-sealing) is ideal. The IRC requires habitable rooms to have glazing at least equal to 8% of the floor area of that room, though artificial lighting can supplant the glazing requirement.
Short answer: not really.
If you're not familiar with Christopher Alexander's book, "A Pattern Language" you might be interested in it. He has a pattern called "Light on Two Sides of Every Room".
https://www.patternlanguage.com/apl/aplsample/apl159/apl159.htm
Up until WW2 it was common practice to give all the main living spaces, including bedrooms, light on 2 sides, typically adjacent sides. This distributes natural light more evenly around the space. Also, taller windows, rather than the horizontal openings of the Modernists, allow light to penetrate deeper into spaces.
jgsg,
"Also, taller windows, rather than the horizontal openings of the Modernists, allow light
to penetrate deeper into spaces."
Yes, this is what I call high glass, a window above the typical height. Makes a room come alive.
JGSG, good reminder--that's one of my favorite books and I'm overdue for a re-read. The patterns included have withstood the test of time remarkably well, especially compared to other architectural guidebooks of that era.
Question for the forum:
When you have deep insulated walls (~ 20") what types of windows work best? The tall (and narrow) windows as described above block views/light from side angles. Wide horizontal windows allow panoramic views, but you lose the height effect, especially in rooms with taller ceilings.
Has anyone here dealt with this? What have been your solutions/findings?
Thanks
It depends on your goals. One of my favorite buildings, absolutely stunning in person, has very thick walls: https://www.archdaily.com/84988/ad-classics-ronchamp-le-corbusier/5037e71028ba0d599b000388-stringio-txt?next_project=no
Or more local to me, this Maine company uses thick straw-panel walls with evocative designs: https://www.instagram.com/croft_co2/
I loved this idea that I saw in a Passivhaus outside of Vienna, where they made the walls even thicker with bookcases and turned them into window seats.
Traditionally, deep walls would have had splayed interiors, widening inside, and would have had lighter surfaces, to reflect light and reduce glare. Michael Maines' photo of the Ronchamp chapel shows how one of the great Modernists understood that.
Punched openings in thin walls tend to increase the light level contrast between window and adjacent wall, which causes glare. So deeper openings are actually an advantage.
I personally like large windows to create a bench seat, or with a deep enough trim to add potted plants and hanging basket plants. Turns them into a seat + a bookcase of sorts.
Our house has 20" walls. We have some wide windows (92in) and some narrow ones (32in), all of which are 55in tall with the exception of three windows in the bathrooms and above the kitchen counter which are 45in tall. All of them work at bringing in plenty of light. The narrow ones aren't as good for views, but as long as you're reasonably close to the window it's fine. You probably want to place the window at least in the middle of the wall, or even a bit towards the outside for this purpose.
Thanks everyone for your comments and suggestions. I don't seem to be able to reply to them directly, but I do appreciate the feedback this forum provides.
We do plan to add deep seating benches on a few of the windows.
Thanks also to the architects here who posted their fails (if only in their eyes). It solidifies to me that windows are a balancing act. Ideally we could site design and build them as we frame the house, but in today's world, that's not practical when we need to model room-by-room energy needs, preorder windows and materials 2-3 months out and obtain permitting approvals before a shovel hits the dirt.
I was lucky to have been able to study from Alexander for a while.
I'm all about the emotional aspect of windows. But in my own work there is a fine line between not enough and too much. I am often critical of other's work wherein they push way past that line. Or critical of myself when I push past or don't go far enough. (the lift and slide on this project should have been 8" -12" taller.)
Robert,
Those windows look OK to me, or would look fine to me if you hadn't called it out. Is it more noticeable in person? How far from the ceiling do you typically place these large view windows?
Thanks,
Adam
I like the difference in height. It's such a post-WW2 thing to keep window and door heads all at the same height.
Michael,
I think a lot of that came from eight foot high walls becoming iniquitous. Once you install the necessary headers directly under the top-plates, the windows almost always need to be tight up to it to be functionally high enough.
Here is what can happen when the client and builder decide to move and add windows based entirely on how they work from the interior - and yes it's a design of mine, and no I wasn't too happy.
That makes sense, Malcolm. It's just become such a standard even with the current trend of higher ceilings that people think it's important. I know that Robert thinks outside the box so this doesn't really apply to his project.
Here's a common question I hear a lot: When calculating the "proper" percentage of glazing for a house people often say that the south side of the house has no more than 10%, the east and west side no more than 4% and the north side no more than 2%.
Is that a percentage of the entire vertical wall area for one side of the house, the vertical wall area for one side of an individual room, the floor area of the entire house or the floor area of an individual room in the house?
I believe that's a per room calculation. It's rule of thumb however and doesn't take into account many factors.
I'm not sure what people may be intending when they give those figures. But the IRC 2021 code spells it out in terms of floor area. Section R303.1 gives an aggregate area for habitable rooms of 8% of floor area minimum, and 4% of floor area minimum must be operable for natural ventilation.
I assume the "aggregate" means you can take the area of ALL the habitable rooms, get your ratio and distribute how you wish between them. But I'd check with a building official on that point if you're planning any odd distributions. The safe bet would be to satisfy the ratio requirement for each room individually.
It's certainly a good idea to reduce west and north exposures. But I'm a big advocate for generous windows on the east side, to bring in morning light, especially in bedrooms and kitchens, the spaces people occupy in the morning hours. East facing bedrooms are ideal in terms of health, keeping people connected to a natural circadian rhythm.
I'm building a passive home outside of North Bay, ON. and opted for windows built using glass from Litezone. Window account for 16% of the total walls. Approx. 50% of the windows are fixed R19 windows, 40% casement windows R14 and 10% smaller triple-pane R9. I've done the solar heat loss/gain calculations and balancing the gain/loss for different times of the year was tricky. Don't want to lose much heat in the winter and don't want to gain too much in the summer. The slab-on-grade and material under the slab is being used as a heat sink to regulate the home across seasons. Being off-grid we also had to balance power usage wrt heating/cooling. A wood stove heats water in a buffer tank that gets circulated to rads when needed or used to supplement DWH. In the summer when I have excess power a heat-pump water heater extracts heat from the home for DHW. A backup propane water heater kicks on when needed. Hopefully my calculations are close and everything works together once the home is built.
Back in the 80s when "Passive House Design" meant something entirely different from what it does today, we designed successful houses with enough south glazing to provide a large fraction of a well insulated dwelling's heating requirement. But achieving that success required careful engineering to provide adequate thermal mass to avoid overheating, overhang design and deciduous tree locations to shade south glass in summer, minimizing glass on other exposures, and use of shutters [remember William Shurcliff] to raise the R-value of glazing at night. Sun spaces, that could serve as entryway "air-locks," were effective tools to separate large glass areas from the occupied space. Closing shutters did require some participation of the owners, which led to the mantra was "Passive houses need active people." Sadly, most of these effective design strategies seem to have disappeared from the lexicon of today's "solar" designers. Glazing need not be an expensive enemy, when the building design compensates the weaknesses embodied in the material.
user ...614,
It's funny you bring up William Shurcliff in a discussion about successful passive solar houses. On reflection he abandoned it as a strategy, and instead championed improvements in the building envelope as a better approach.
I don't think passive solar has simply been forgotten. If fell out of favour due to the shortcomings and complexity inherent in trying to use solar gain in conjunction with thermal storage
Sometime I'll write about my friend's house, a cutting-edge passive/active solar design from the early 1980s, complete with attached greenhouse and 200 barrels of water for thermal storage. Oh, and triple-glazed windows using thin film technology. They bought it last year and have spent a fortune trying to get the greenhouse glass to stop leaking, draining the barrels of water which are now rusting, dealing with broken films on many of the windows and trying to stay comfortable with far too much glazing that renders the house either too hot or too cold most of the time. I remember when it was built and was always curious about how it performed. Now that I know, I'm even more of a fan of insulating, air-sealing and not over-glazing.
I've been considering building a home. Critical to me is a boat load of natural light and the feeling of being connected to the outdoors not isolated from it. When I've come up with designs they end up being about 30 to 40% glazed (5% on the north). Is that the most efficient? Definitely not. But the purpose of the house is to serve me first. My number one complaint about new spec homes is too little glazing and too little natural light.
There are of course ways to reduce the impact. Building a square house reduces the wall and glazing to volume ratios. Overhangs can reduce heating in summer. And triple pane with appropriate coatings makes sense in the cold climates I enjoy living in. Most of the windows can be fixed to reduced leakage, and vinyl to reduce thermal bridging.
Mark,
A room with a view !! I added a 16' x 28' (448 sf) room in 1998 to our 1958 vintage and very well built rambler on our farm in the SE Red River Valley in MN. There is 182 square feet of glass in this room with 6 sf on the north, 50 sf on the south and 126 sf on the east wall. To the east we see the last shoreline of Glacial Lake Agassiz. This is the first full winter and spring I have spent here since the room was built. Watching the sun move north over the course of the winter and the arrival of spring has been inspirational. Would not change a thing with this room. This house needs another layer of insulation before some new siding so I have plans to upgrade the efficiency. Might consider a shutter system for the large east facing windows to increase comfort.
Doug
Look at glass from Litezone. Their top performing glass is R21 and 7.5" thick for a fixed window.
Litezone looks amazing! Thanks, this is worth a closer look. People have mentioned them on GBA before.
Lloyd,
A pretty comprehensive discussion of their technology: https://www.greenbuildingadvisor.com/question/litezone-windows-up-to-r22
It looks like my last comment on that thread was a few hours before the company rep came in and responded to a lot of the key questions, so I appreciate being pointed back to it. It was really interesting to read his responses. I am impressed. He gave real answers and it sounds like they have a unique technology that should work well and give good durability.
Charlie,
I had missed it too. It was refreshing that he took so much time to give real responses, not sales pitches.
Nice! I hadn't heard of that. It would fit easily in the depth of a double stud wall.
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