Orientation / South Facing Windows

Passive solar houses typically have windows on the southern side of the building.

Based on the movements of the sun, passive solar buildings typically have windows (glazing) on the southern facing side* of the building in order to absorb the sun’s heat energy to warm a building during the winter.  In order to stay cool in the summer, passive solar houses rely on a system of shading (or an overhang) to keep the building cool.

Simply by building in this way, a house can reduce its heating and cooling costs by 85%.

See how the house pictured on the right achieves Net-Zero Energy.

*In the northern hemisphere, in order to face the sun and obtain maximum solar gain, the windows would face the south. In the southern hemisphere, however, it is opposite, with the windows facing the north in order to maximize solar gain.

Seasonal Window Considerations

The diagram shows how the low winter sun can enter the building, while the high summer sun can not.


The diagram to the left shows how the sun is lower in the winter, while it is much higher in the summer.  (See the building at Zion National Park.)  During the day, the low winter sun can shine through windows are to allow heat energy to be absorbed into the building’s thermal mass.

While windows allow heat into a building to be absorbed, their thin and transparent nature also allows heat to escape a building.

In order to keep this from happening in cold climates, it is recommended that the glass panes are doubled (double glazing) or even tripled. An insulated window covering or thick shade can also be used to help insulate the windows and help keep the heat in the building after the sun goes down.


In the summer, as temperatures rise, a passive solar building uses its thermal mass to help keep the building cool. In order for this to happen, the summer sun is kept from reaching the thermal mass of the building.

The summer sun’s path aides in this process by traveling high in the summer sky, thus a proper overhang or other type of system is needed to shade or cover the widow, in the summer so that the sun’s heat energy is blocked or avoided when it is desired to have the building cooler than the outside temperature.

A properly designed overhang keeps the heat and energy from being absorbed into the house in the summer. (In the picture at the very top of this post, you may also notice that the overhang is keeping the high summer sun from entering the house.)

Building Orientation

Because the sun rises in the east and sets in the west, the side of the building that is utilized for solar gain needs to be facing the south to take maximum advantage of the sun’s potential energy.  If the building’s axis is located on the east-west direction with its longest dimension facing the south, more of the building is situated to absorb the sun’s heat energy.

If the building in the middle were longer, stretching toward the two houses located on either side of it, more of its mass would be ideally situated to absorb and radiate heat in the winter

Passive solar buildings are typically rectangular with the long side of the building facing south.  The distance from the source of incoming heat (south) to where it is absorbed (typically a northern wall) should be minimized. The resulting shape is a rectangle.  This is one of the lessons learned in the construction of this Off Grid Passive Solar Earthship-Style Home.

South Facing Windows and Orientation

It is ideal to have the windows (solar glazing) within 5 degrees of true south. However, windows that are within 15 degrees of true south are said to function almost as well.

As the degree difference from true south expands, the overall potential solar efficiency of the structure decreases. Put another way, the greater the degree variation from true south, will decrease the amount of the the building’s solar gain. As a result, larger amounts of supplementary energy may be needed to heat the building in the winter. As the building’s glass (glazing) faces more to the southwest, more energy may be needed for summer cooling.

Passive solar buildings typically have many windows facing the south

Southern facing windows (southern solar glazing) are a vital component for a passive solar design and building. Because the southern side of the building is the side that will potentially receive sunlight throughout the day, most passive solar buildings will feature glass dominating the southern side. Southern facing glass allows the sun’s energy to be absorbed and distributed through the building’s thermal mass.

You may hear people referring to glass as glazing. Glazing is the fancy architectural word typically used for southern facing glass that has the capacity to transfer the sun’s energy.

Another benefit of having windows on the south side, is that it allows natural light to bathe the house throughout the day. This aspect can also lower energy use throughout the house since it minimizes the use of artificial light.

All of these factors can be used to one’s advantage, depending upon the site location and depending on the specific characteristics that you want within the house.

While southern facing windows (glazing) are a necessary component of passive solar design, care must be taken to insulate them in the winter after the sun goes down, as well as shade them in the summer.

world equator diagram showing the northern and southern hemispheres

The northern hemisphere is highlighted in yellow. The southern hemisphere is white.

Note that because the Earth is a sphere, depending on where you are located, the sun will interact slightly differently than in other places.  For example, the angle of the summer and winter sun will be different.

If, however, you are located in the Southern Hemisphere, in order to build a passive or active solar home, the building will need to be oriented to the north.

Here’s a little more information about solar building in the southern hemisphere.

Vertical and Angled Glass (Glazing)

Most glass that is used in building is vertical.  Angled glass, however, is frequently used in passive solar design because it increases the amount of solar energy that can be absorbed. Caution! This can cause overheating in the summertime.

*This information pertaining to facing windows to the south works for those in the northern hemisphere. Down under, in order to use solar gain, they need to face the windows to the north.

72 Responses

  1. David says:

    Hi. Please explain further: “ Orientation
    It is ideal to have the windows (solar glazing) within 5 degrees of true south. However, windows that are within 15 degrees of true south are said to function almost as well.”
    Is the 5 degrees more to the east or west. Thanks.

    • Keya Lea says:

      If the thermal mass and overhang are close to ideal, then the variance of the degrees to the east or west has been found to not be as significant, as solar gain is achieved throughout most of the day. I think the efficacy is similar for the angle to the east or west.

  2. Feng Shui says:

    Any advice, say, in a hot tropical country, a rectangle house with long side facing east-west, which means the challenge would be the afternoon sun & heat. How to design in such a way to overcome too much sun light & heat problem?


    • Keya Lea says:

      In the case of a building in a hot, tropical country, you’d want to keep the sun away from the thermal mass in order to keep it cool. If most of the solar gain is in the south, you’d want to keep the house and thermal mass (brick, adobe) shaded from the sun. For a house like this consider putting windows where there will not be direct sun, or build an appropriate solar overhang to help keep the house cooler.

  3. vipin says:

    Interesting article, simple to understand.

  4. Carina says:

    Hi Keya,

    I’ve chosen a passive solar house design with clerestory windows facing south to be built southern Ontario, Canada. Could you tell me the best roof angles and overhang needed to achieve optimal passive solar?

    Warm Regards!


    • Keya Lea says:

      That all depends on the lat/long of where you live, combined with local weather conditions, as angles and roof overhangs are impacted by snow and rain, cloudy days and other factors that aren’t often considered. For example, if it rains a lot, where you are, the angle of the roof will impact overall drainage. Drainage (water) could impact the overall building’s temperature and ability to maintain a constant temperature.

      Optimal passive solar is more impacted by the amount of solar gain (windows) and the thermal mass that can absorb the heat from the solar gain. The best to find out information about angles and overhang would be to talk to local passive solar builders and other home owners in your area.

  5. Rosalind Williams says:

    Why would someone want a north facing home in terms of energy efficiency living in the northern hemisphere?

    • Keya Lea says:

      If someone lives in a desert, or other extremely hot area where solar gain from the south is not desired, it could be possible to build a more efficient house that stays cool by building windows to face the north, in the northern hemisphere.

  6. Dave Puig says:

    Hello There
    I am a builder in Wisconsin and I am trying to situate a house to fit the landscape best but also to maximize solar gain. I know that south facing wall and windows is best. However, I am considering this idea. A house that is oriented so that a corner is facing due south and therefore it has a lot more wall surface that is facing south, just not due south. So there would be glass that is getting southeast sun and southwest sun and all of them would be getting due south sun at an angle. I know this is not as efficient but I am wondering if that might be cancelled out due to the fact that you would have a lot more surface area of wall and windows facing some version of south? Does this make sense?
    Thanks so much for you thoughts.

    • Keya Lea says:

      Yes, that makes sense. In regard to maximizing the solar gain and the solar heat that could be used in the house to moderate the temperature, it would depend on the thermal mass that can absorb the solar heat that is allowed in the house by the windows. The sun that enters the house and strikes various surfaces (floor and walls) will impact how much solar heat/gain the house has through the winter. The surfaces that absorb, then later remit heat, are those that have thermal mass, like brick, stone, adobe, tile, and other dense materials. Depending on the material of the wall, if it has thermal mass, more solar gain can potentially be achieved, regardless of the angle of the southern facing windows.

      Depending on where you’re located in Wisconsin, the overhang of the roof will also impact how much winter solar gain can be achieved, I think, more so than the angle of the windows. Hope that makes sense, and hope your build is going well. 🙂

  7. Tigger says:

    Hi, Keya: Thanks for providing this article. I wonder how to correct/improve the air quality in a passive solar building and how to cool the house without an A/C.

    Our home is constantly at high temperature (winter: 77F @ noon and Summer 85F @ noon) because of the direct sunlight coming through our south facing windows/glasses (floor to ceiling). When the sun sets and outside temp drops significantly, the inside still remains pretty warm and temp did not drop by a lot. It’s as if the house is so well insulated that there is no vent and the hot air is standing still.

    Only when we open many doors/windows to let the air flow for a long while, we will then cool the house a bit. Then, we’d feel like we live in an open space and not in a house. It’s not practical.

    Any advice on what we can do to cool the newly built house and evenly distribute the heat throughout the house? Who can we work with to make it a comfortable living in the house all year long?

    Thanks in advance

    • Keya Lea says:

      Many passive solar houses build airflow into the house, sometimes this type of building is referred to as an “envelope house”. A passive solar build that incorporated this is this transition from a former farmhouse into a passive solar one. It’s broken into two parts, so here’s the second part.

      A lot of passive solar builds also incorporate clerestory windows that open and close near the top of the house. Because warm air rises, the clerestory windows allow the heat to easily escape out of the house, and can be closed when the house reaches a temperature that the occupants determine.

  8. Meli says:

    Does sunlight hitting roof and side of apartment still raise temp inside if there’s no window?

    • Keya Lea says:

      Yes, absolutely. If there isn’t insulation, heat will be transferred from the outside to the inside, regardless of what it’s hitting. Typically windows are seen as the opposite of insulation, which is why heat is transferred through windows more easily. Heat can also be the roof or walls if they are not well insulated.

  9. Yen says:

    I’m from Vietnam. Vietnam is on the Northern hemisphere but the location is very near the the equator. So, does the south facing windows is specifically different with other sides?

    Thank you!

    • Keya Lea says:

      Hi Yen!
      It depends on what you’re wanting to do. Typically homes in more temperate weather locations that have 4 seasons have a need to warm in the winter and cool in the summer. People who live / build in warmer, more tropical climates will have a different solar pattern through the seasons, while it still will be predictable, so placing windows in certain locations will have a heating or cooling effect.

  10. Marcin says:

    I am looking for specific data about the angle of face glazing. It depends of sun position in winter time = latitude (geographical location). For my latitude (north hemisphere 50 ° 50`40“ N and 19 °14`17“ E) that maybe 50-70 ° angle of face glazing. What is the exact value? If I remember well in winter sun should hit the glass at 90 ° to give the best effects of heating. If anyone knows some web with that information or calculator based on latitudes data, please let me know.

  11. James Stufano says:

    Is there a passive solar design where the north, non-sun side has mountain views to take advantage of which are located on the exact opposite sunny south side? I guess we could do smaller windows on the north and maybe put a porch or upper deck.

  12. Aaron says:

    Keya, thanks for this article. I’m wondering: to what extent is *direct* sunlight responsible for over-heating south oriented homes in the summer, vs. simply the fact that there is hot air outside?

    We live in Texas. So cold-ish in the winter, very hot in the summer. Our home has a beautiful garden on the southern side of the house. The living room has no windows, but if it did it would look out onto that garden. We’d like to put in a patio/sliding door on that wall so we can look out onto the garden.

    Right now there is already an overhang on that side of the wall that jets out quite far, so that wall doesn’t really even get much direct light even in the winter. Also we have several big trees that shade the area.

    So I’m wondering: if we open the wall and put in a patio/sliding door, as long as the glass doesn’t get any *direct* sunlight in the summer, will it not heat up the room?

    Even triple-glazed glass is worse than a wall for keeping the cool air inside, right? And even if the overhang/trees prevent *direct* sunlight from entering the glass, the fact that there is simply 95 degree air on the other side of the door would be enough to make the room more difficult to cool, right?

    From reading this article and your responses to some questions here, I get the impression that as long as the overhang prevents *direct* sunlight from entering a room via windows, it won’t heat it up. So even if it is 95-100 degrees outside, as long as no light enters directly through windows, that hot air won’t make the room hotter?


    • Keya Lea says:

      In regard to what is worse, a wall or triple-paned (or glazed?) glass, it all depends on the insulating properties of the materials used. Typically glass has less insulating properties than a wall, but there are many different ways to build a wall.

      Passive solar building works with the integration of different materials, so typically, the house has southern facing windows and an overhang is also built with thermal mass that slows heats up and slowly releases stored heat. In the summer, the concrete/adobe/stone floor stays cool if direct sunlight does not hit it. If the inside of the house does not have thermal mass, then the transfer of heat through the air is more of a factor. In a passive solar house, the integration of the elements (including air flow – as hot air rises) heats and cools homes.

      Many of the homes here are built in Colorado, where the summers get to be 90 – 100 degrees, and many of these homes have only double paned windows, but with the integration of other materials and passive solar design, they stay cool in the summer.

  13. Yvonne says:

    Hi Keya, thanks for your blog. I have a question. We live in a concrete house in the south of Spain. In july and august it can become above the 30 degrees. But I would love to have a big south facing window (3,60 m wide, 1,80 high) because the view is very beautiful. And in winter the sun can warm up the house. Do you think it will become to hot in summer?? I always thought that in summer the sun was high enough not to touch the windows. Hope to hear from you. Greeting Yvonne

  14. Swati says:

    I am an architecture student and I am using trombe wall with the theme of thermal comfort in my thesis project. The site is located in Pragati Maidan, Delhi, India. But i am confused that weather it is applicable in Delhi or not. please clear my doubt, it will be really helpful. Thank you.

    • Keya Lea says:

      Weather is an environmental factor that impacts a building. If a passive solar home is built and designed to gather the sun’s heat in the winter, but if the weather in the area is such that there are more cloudy days than sunny days, then perhaps the windows should be smaller so that captured solar warmth doesn’t escape out the windows as easily.

      I’m not sure how to answer your question, as weather is an incredibly important factor that should be taken into account, but local weather varies depending on where you live.

      Yes, weather is an important factor anywhere when designing a home with a Trombe wall, even in Delhi. All designers should be grappling with this questions, especially architectural students using thermal comfort in a thesis. Do some research. Visit the Taj Mahal and note how the mass of the marble stone helps to keep the building cool in the hot summer. Best of luck!

  15. Muhammed Gambo says:

    Mine is a question not a comment, if you people can help me. It goes like this: what is the thermal performance comparison of a recessed facade window shading of the same depth with horizontal overhang facing the same orientation?

    • Keya Lea says:

      Sounds like an exam question. It depends on many factors, although the answer that’s given will need to be supported with other assumptions, like where the building is located with its lat/long, time of day, time of season, type of materials, etc. Good luck!

  16. George Tsamis says:

    I m coming back to the two passive solar villas which we intend to build on Lefkada, Greece as I face a very similar problem to that of Donna (12/11/2012). The plot is flat with no special view in a green area just outside the city center. The city is very hot since often the temperature reaches 100-110 degrees Fahrenheit during summers and respectively very high humidity levels. Winters are relatively mild with high levels of rainfall. In our desire to build passive solar met two architects with different approach anyone.
    The first argues that we should apply the classical conception of passive solar strategic and the long side of the buildings should be at east west orientation while a bunch of windows oriented to the south. The second considering the microclimate of the area and the fact that the phenomenon of climate change will constantly raises the temperature of the planet considers it should be exactly the opposite: to have a bunch of windows on the north having this way the best cooling system. Each of the side is having serious arguments….I feel confused….. Could you please tell me who of the two architects is closer to the truth …. I feel like it will never start ……Since this dream comes true you are more than welcome to visit us. Thank you so much in advance for your help…

    • Keya Lea says:

      Both designs could work if the other facets of passive solar are integrated, although if the summer is going to be sunny and hot, I would think that no summer sun is desired, so either there should be an overhang that blocks the summer sun, if the windows are facing the south, to allow for some solar heating in the winter (but it sounds like it’s rainy a lot).

      If the windows are predominantly facing the north, then the building will get no direct sun. If it’s correctly integrated, this way could also work, to keep the building cooler throughout the seasons – but ultimately, it’s hard to side with either without knowing how other elements of the build (thermal mass, any active solar – if desired, overhangs, air flow) would be integrated.

  17. Allen Bird says:

    Hello I am building a house on top of a mountain have great views facing west i am building a a frame style with all glass on west side, should I angle the house true south I do have a few windows facing south. Also worried about the western heat at the end of the day any sugestions it will be a off grid home.

    • Keya Lea says:

      Every build will be a little different. To build a home that is efficient, you’ll need to consult a reputable local professional to take into account the conditions within the soil, climate, specific longitude and latitude other aspects specific to your area.

  18. Rich says:

    I’m loving the idea of a passive solar design. Looking at building a smaller (1,250-1,500 sq ft) single story home in Northern Nevada. I have no issues with placing the house w/ long axis facing south with ~ 10% glazing, but our view is really mostly to the west.

    I’d really like to place windows on the west side of the house as well – at least partially. If I were to utilize highly insulated windows on this west side, could the system still work effectively/efficiently?

    • Keya Lea says:

      It could work, but can also have downsides depending on the climate. Here are a couple of examples that have windows on the west side of the home: Modernist Concrete House and Log Net-Zero Home.

      Overall happiness also depends on the quality and type of windows. For example, the concrete home is in a warmer climate and the owner wishes he hadn’t placed so many windows on the west, while the other home is in a colder climate, and the owner really likes the late afternoon sun.

      Best of luck, let us know how it goes!

  19. Betsy says:

    We are ready for replacement windows and have several large windows facing southwest. We love the warm winter sun during the day. In the summer, trees block the sun most of the time, but we need to lower shades about 2 hours a day in NC. Do we need to use Low E windows, or will this block our wonderful winter sun? I know it would help with the 2 hours of summer sun, but would hate to lose our winter warmth.

    • Keya Lea says:

      I think it depends on the window and manufacturer. You’ll need to look at the actual values that the manufacturer gives, then compare them with reviews. For example, some manufacturers of windows use a film or tint on the inner layer of the window (some on both sides of the double pane window) while other manufacturers insert a gas between the panes.

      Apologies for not giving a more definitive answer, but it tends to depend upon manufacturer. I’ve looked at some homes that have used low-E windows in passive solar homes to great success, like this home with Trombe walls, while other home owners/builders wished they had used different windows (modern concrete home) and could tell a big difference with windows that had different tints or films within them – which are sometimes labeled as low-e.

      Let is know how it goes and glad to hear that you love the warm winter sun!

  20. Paul Frenzen says:

    We just bought a house in Colorado that was well-designed back in 1985 to provide some passive solar heating during the winter through south-facing sliding glass patio doors, with roof overhangs and deciduous trees that provide summer shade. It’s time to replace the doors, but I cannot find a local installation firm that will provide doors with an SHGC greater than about 0.45, even after explaining the situation and confirming on the NFRC website that the particular door manufacturers offered by each firm include doors with SHGC’s as high as 0.55 (which is probably too low for our house, but apparently the best option available.)

    What’s going on? Can you provide any guidance about how to find the doors that we need with a reasonably low U factor (hopefully < 0.30) but a suitably high SHGC? Do the glass door manufacturers perhaps limit sales of products with high SHGC's to certain regions excluding Colorado, and the installers prefer not to let us know about this problem?

    Thanks for any suggestions that you might have!

  21. Scott says:

    I’m building a home in Mishawaka Indiana. My question is how much of a control overhang do I need and what angle should it be at?

    I’m going to use the windows in the top of the roof like in your design above.

    How high should the windows be?

    Should I use an interior Brick wall for a thermal Mass?

    I also have a waterfront view to the North I thought I would use Triple pane glass for Northern windows combined with insulated curtains.

    The southern view is obstructed by a garage so the best place for southern windows is along the roofline

    • Keya Lea says:

      Hi Scott,

      I’m going to refer you to another website that has a list of tools that can help you calculate optimum specs for your specific site.


      I have used the SolarPathfinder in the past. It’s a good tool because it can be site specific and can help to identify trees and other issues that may be forgotten in passive solar site planning. http://www.solarpathfinder.com/index

      I’m not familiar with your specific location. You should talk to architects in your area and ask them about heating and cooling degree days. Here’s more information about that: http://www.degreedays.net/

      The answers to your questions depend on other factors as thermal mass, windows, overhangs, trees and other shading devices/methods all work together to make an efficient home.

      Best of luck to you! It sounds like an exciting project.
      Keya Lea

  22. Brian Whalen says:

    A second question for radiant floor heat and insulating the entire concrete slab on grade. While the heat loss into the ground is reduced, it would seem to isolate the area from the cooling aspects of a slab on grade in the summer time, an often times forgotten component similar to shading the south facing windows.

    • Keya Lea says:

      (This seems like a question on a quiz or test.) It actually depends on your location and the type of materials used in the build, for example, the thickness of the mass along with the type, density and amount of insulation used. The overall amount of glazing or southern exposure in the windows is also a factor. I’m also not sure what you mean by hemicircle. Best of luck to you though.

  23. Brian Whalen says:

    Question regarding passive solar wall design (south facing in northern hemisphere). A straight east to west facing due south, the Frank Lloyd Wright curved solar hemicircle (?), corner pointing due south with two walls at 45 degrees to that and lastly a variation of the curved solar hemicircle, a straight wall east to west facing true south with 2 wings offset to 30 degrees on each side. The question being which design will provide the most access to sun exposure over the course of a day thereby allowing for the most solar gain. The straight walls allow for sun exposure at various angles as the sun moves across the sky. The others allow for concentrated exposures for some areas with little exposure for the other areas as the sun moves across the sky. Without the concentrated exposure it seems the other areas could be a source for heat loss during winter months.

  24. Amy says:

    This is a wonderful resource! Thank you!

    We are hoping to build a passive house in northeast Ohio, but have strict local standards regarding the style of the house as there are mostly traditional elegant appearing houses from a century ago in the neighborhood. We have the opportunity for South facing windows. What determines the window placement on the Southern face? Is there any reason the house can’t have a typical Georgian style appearance (evenly spaced tall windows, long eaves from the roof line). We have more flexibility with the East/West and North sides as they do not face the street. Also, is there any reason you can’t have a full basement (with proper insulation), or screen porch on the North side, as long as the porch is separate from the envelope of the house? For thermal mass, does the placement of an area carpet in a room over concrete or stone negate the effect? Do you have any links or sources for more traditional appearing home exteriors that are passive houses?

    • Keya Lea says:

      The amount of windows needed largely depends upon the amount of thermal mass in the house, along with a few other factors like overhangs and insulation.

      The sun’s angle depends upon your specific location on the earth. This can be gleaned from resources like the Passive Solar Energy Handbook by Edward Mazria.

      The suncalc.net is also a cool online resource that gives you a visualization of your specific place in the world to see how the sun’s angle can vary from June 21st (summer solstice) to Dec 21st. It’s best to either be really good with math or contact someone in your area that is familiar with the sun’s angles and how to property build a home to maximize solar efficencies.

      You can have sort of home design that you want. Most passive solar homes have a modernist look, but anything can be done.

      You can most definitely have a full basement. Many houses are bermed, but they doesn’t have to be. An important consideration is that the basement is adequately insulated.

      You can put a porch wherever you want. Passive solar building is pretty flexible and easy. That said, I only write about the ones that work, but I’ve heard of building horror stories too.

      If you’re located near Ohio State University, they competed in the Solar Decathlon with the enCORE home and should have good resources.

      In regard to thermal mass, yes, if you place a rug over it, because it’s covered, it would not be able to absorb as much heat, so won’t work as efficiently as it could. There’s plenty of examples on this site of attractive homes with exposed thermal mass.

      Best of luck and let us know how it goes. 🙂

  25. Nick says:


    Thanks for the blog! I found this while taking the ARE’s examinations was researching best orientations for artist studios. In the Northern Hemisphere, it is traditional for artist studios to face north; this is because the indirect light allows for continuous soft lighting rather than the direct glare and washed out light associated with direct south facing windows.

    Of course, with modern glazing, light-shelves, and intelligently designed overhangs, this becomes less of an issue, but north facing studios are a long tradition among most artists.


  26. kent gallaway says:

    I am thinking of building a solar home using either aac block or vertical icf concrete core . Which would be more efficient.

    • Keya Lea says:

      It would depend on how they are used in the configuration of your home. Remember that passive solar homes store the sun’s heat in the winter, while slowly allowing it to dissipate in the cooler evening, and they are designed and built to stay cool in the summer. There are a few basic things that passive solar homes need based on the predictable motions of the sun: south facing windows (northern hemisphere), overhang(s), mass, and insulation. They can also use natural air flow through the house to help heat or cool.

      I say it would depend on how they are used because the two materials are different and should be used in different places. An icf (insulated concrete form) has the insulation on the outside and thermal mass on the inside. It would not make sense to use the icf in a place where it is desired to store solar heat since the insulation on the outside would keep the mass in the middle from getting as warm as it could. I’ve seen ICFs used on the northern bermed side of a home with Trombe walls used on the south side.

      Once again, the efficiency of materials depends on how they are positioned and being used in the home.

  27. xinming says:

    hi, Keya:
    we are building a house in los gatos, ca, and house faces south, however, the good views are on west and some views on north, and property goes down hill on north side. I know that we are supposed to put a lot of windows on south, which is fine for us, but we will also need a lot windows on both west and north since that is where are the views. Do you have any suggestions on window placement? thanks

    • Keya Lea says:

      It’s pretty basic. Just remember that windows are a gap in insulation that can be used to gain and loose heat. In order to keep the house cool in the summer, make sure that there is an overhang over the southern facing windows. Since the sun sets in the west, if you don’t want heat gain late in the day, plan accordingly.

      The north side of the house will not receive any sun, so it should be the place where you place the most expensive windows. In a colder area like Colorado, that’s typically where people will invest in triple paned, gusseted windows. I don’t know the microclimate of Los Gatos, but you should talk to people who have built houses and/or know the areas climate traits. Good luck!

  28. prerna says:

    I am doing architecture [1st year] i want to know orientation of windows and how to make my house climatologically efficient for delhi india… which is north facing..

    • Keya Lea says:

      Depending on where you are in India, you may want to do more cooling. How a building is situated and built depends upon what is desired.

      I’m also not sure if you’re asking about retrofitting a building with windows on the north side, or if you are wanting to build, then place the windows on the north side to keep the building from gathering any solar heat. Passive solar building is an integration of a few simple concepts, but they are easy once you know them.

      The sun has a different relationship with locations depending on where you’re located in the world, but once you figure it out, it will be the same pattern throughout each year.

  29. Maria Janssen says:

    We are getting ready to build and we have the choice of building facing North for maximum sun or turning the house north east to face the sea view. What is best? Thanks

    • Keya Lea says:

      Hi Maria,

      From your email address, it looks like you’re in New Zealand. Because you’re ‘down-under’ the equator, if you face the house and its windows to the north, you’ll be facing the sun. As to the angle that you want to face your house, it’s up to you. Passive solar buildings are efficient and comfortable when you combine elements like overhangs and thermal mass in addition to the direction the windows face.

      If facing the north-east, I would assume that you’d get the late afternoon sun before it sets in the east. (That’s strange for me to fathom – being so used to rising in the east and setting in the west being above the equator, but I think that’s correct.) If you’re in a place where you want to be warmer in the evening, then it makes sense to capture the afternoon-evening sun’s heat.

      Here are a couple of homes that have windows on the south and west sides of the home (similar for you under the equator). They both get really warm in the evening in the summer: Concrete modernist, and log cabin. While these examples have windows that face the south and west, the result would be similar. I can’t say specifically which direction is best, because it depends upon the overall design and the materials that are used. That where you have a lot of creativity and control.

      I hear all good things about New Zealand. I imagine that you have a beautiful view. Let us know what you decide and how it goes. Best of luck!

  30. Karina says:

    Hi Keya.
    We are building our house in Bella Vista, Buenos Aires… So in the south hemisphere and I have to turn around all your answers! 😉

    The front of our lot goes from a to b http://goo.gl/maps/R0PAE

    Our lot is quite small 200 m2 and the street is on the north-west and we are planning to face it south-eastish (towards the back garden, but reading you i think it will be better facing it to the side north eastish… we can’t build the house in diagonal cause the lot is too small .

    Any ideas?
    Karina (from Argentina!)

    • Keya Lea says:

      Hi Karina,

      It’s exciting to be at the start of a project as there are endless possibilities. I took a look at your lot and it reminded me of another project. The home below was also built in a city that is situated in a diagonal grid, so the lots are similarly situated. He also has a narrow lot, but made his passive solar house work. Being located in the southern hemisphere, you would have to switch the orientation around from south to north, but it could work.

      See how this house is situated toward the sun – in his case, closer to true south. The axis of this house is in slight contrast to the surrounding homes.

      Aerial view of retrofitted passive solar home

      You can take a look at his house at the following passive solar Quonset Hut retrofit project.

      In his case, he rented a crane, then moved the whole house as close as he could to true south, while honoring the setback code (of 5 feet) on a lot that is similarly situated.

      You’ll have to check with your local building codes to see if there are setback requirements that need to be met.

      Your project sounds fabulous. Let us know how it goes. Best of luck!

  31. SteveD says:

    Thank you for your response Keya.

    Yes, my wall is similar to the one you linked to in Washington. But very basic. Other than the slant, and south facing, they added no other ‘passive solar’ attributes. As far as moisture barrier, all there is is tar paper beneath the cedar shingles. the inside of the wall is just finished with 6″ tongue and groove boards.
    We considered changing the windows to vertical, but are initially looking to see if there’s an ‘easy way out’.

    We’ll take your advice and try to contact a local (new england) architect.

    Thanks again,

  32. SteveD says:

    We bought a house that has what I would call a passive solar wall. It’s facing the south, tilted back about 15 degrees, and has (9) 4’x6′ casement windows. Sounds good so far.
    As it turns out, this wall is a maintenance nightmare. We realized shortly after buying that about the bottom 4′ of the wall had major rot, including the window frames. I repaired all this, put new cedar shingles on and repainted.
    Well the paint immediately started bubbling off, due to water getting under the shingles and keeping the backside soaked. And the windows dont seem like they were designed for slanted walls. (The outer sill slopes UP at a 10 degree angle, acting like a catch basin for rain) I’m going to replace the cedar shingles with imitation (vinyl siding type) cedar to match the rest of the house.
    My big question is: Do you have any ideas on special windows designed to be in slanted walls?

    Thanks in advance,

    • Keya Lea says:

      Hi SteveD,
      Sorry to hear about your predicament with the house you just bought. When I first read your post, I was a bit confused because I thought that the wall was facing the south, located on the north side of the house. (We always tend to project what we’ve seen before. I thought you were talking about problems with northern walls, but I think that you’re talking about a slanted wall that composes the southern side of the house. To further confuse the issues, people also often call a Trombe wall a passive solar wall.)

      Leaking within slanted windows can be a problem. Builders initially utilized slanted windows because it is better way to capture solar heat. Rain, however, can be an issue. People have done test between vertical and slanted windows and found the difference in solar gain quite small, thus most modern builders use vertical glass in passive solar bilding. The only slanted windows that I see are on this Passive Solar House in Washington, and on Earthships. By design, Earthships still use a wall of slanted glass within the southern wall, but they have also added another inner, vertical wall of windows. (I don’t know why they don’t just make one wall of vertical, double or triple-paned glass.) When I visited and toured the Eartships in Taos, I noticed leaking along the slanted windows.

      Most of the efficient passive solar homes that I’ve seen use high-quality, fixed, sealed windows and install them vertically. (Along with the other needed passive solar attribues of insulation, thermal mass, overhang, etc.) Saying this, however, does nothing to help your situation. Let’s think about what can be done. It sounds like you live in a really moist area. The south? Northwest? (I currently live in the arid, high desert.)

      Is there a liner or some sort of vapor barrier that is between the inside and outside of the house? If so, between which layer is it? A vapor barrier can help, or can hurt, depending on the other materials it is used with. What other materials are used in the house? For example, is the inside of the wall drywall, or adobe? It sounds like the shingles are on the outside of the house, and it sounds like they have not been ‘sealed’ with an oil based protectant for a long time. If it hasn’t been done in a while, they turn into sponge-like devices. If it were me, I’d wait until things dry out as much as possible and place an oil-based protectant on the singles (repel the water), vs. seal it out with paint. But this would be a very short term thing to do, and it may not even be a solution.

      The best advice that I can give is to talk to other experienced (if possible, passive solar) builders in your area to see what materials and tecniques can be used to enable your house to be better protected from the elements. Most likely, issues within your area have been faced before, and they’ve found ways to deal with them. Best of luck!

  33. Sneha says:

    I’m designing a solar passive guesthouse in Leh(India) and have a few doubts.

    The South is diagonal to the site (the site being rectangular).
    Will a compact structure make more sense (some of the rooms won’t face the south and will be unusable in the winter) OR will planning it in separate wings facing the south such that the shadow of one building does not fall on the other be more effective.
    In the latter case, the south facing wings will be connected via adobe passageways cutting through open courts.
    The entire structure will be in adobe and insulated rammed earth.


    • Keya Lea says:

      It’s difficult to answer your question because efficient passive solar building occurs at the confluence of many different aspects.

      For example, are you incorporating any insulation? Do you need insulation? How are you insulting the rammed earth? Are you simply making it really thick, or are you inserting some sort of poly-fill? What is the climate like? Do you have many sunny days? What are the cooling vs. heating degree days? Are you going to build an overhang? If so, what will the overhang be like? Are you orienting toward true south? Exactly how big is compact? Why won’t certain rooms be usable?

      I’m not necessarily asking you to answer these questions on this post, but these are all things that will influence how your guest house should ultimately be built.

      I do think it is a great idea to used adobe and rammed earth though. This site simply serves as ideas as to what other have built.

      Passive solar design is a way to build that uses the prevailing circumstances that are in your environment. The sun is a big one. Depending on where you live in the world, this will be different. Leh, India looks like it is in the Himalaya mountains. Sounds beautiful! Best of luck!

  34. Heather KV says:

    We live in a cold climate (Winnipeg Canada) and are building a cabin on a lake with a North Facing view. The main entrance will be on the south side, but this is not where we want to look out, as the view of the lake to the North is obviously WAY nicer! We would like to build as sustainably as possible, and were thinking about going with passive solar design. I have read that thermal mass does not work well in colder climates and am wondering if Passive Solar house design is even worth considering? If it is (or isn’t for that matter), could you suggest any websites or resources that would assist us in building something relatively energy efficient and environmentally friendly? Oh yes, did I mention that we don’t have a huge budget?……

    • Keya Lea says:

      I just did a search for Winnipeg, Canada to find that it has over 300+ sunny days in Winnipeg, so passive solar building should be fine there. Remember that passive solar building is the integration of key elements. http://greenpassivesolar.com/passive-solar/building-characteristics/ There are many passive solar homes built in Colorado and Canada, some in the coldest parts of the country that are warm in the winter and cool in the summer.



      Thermal mass is part of the equation that makes passive solar work. If you heard that it doesn’t work, you may want to ask a couple of questions: 1. Was the thermal mass placed in an area of the house where it could soak up the sun’s heat? 2. Was the thermal mass adequately insulated? If the answer is no, and no, then they didn’t build a passive solar house.

      Remember that passive solar buildings are called as such because they are designed, situated, and built with materials that allow them to soak up the sun’s heat in the winter, and block it in the summer. In order for them to do so, the windows must be facing the south (in the northerrn hemisphere – you’re in the northern hemisphere). This is based up the sun’s predictable movements.


      Location is really important in passive solar design. If I really wanted both an efficient passive solar house, and a good view, I would have bought a property on the other side of the lake. There may be creative designs that can be worked into the home, but conceptually, windows are the opposite of insulation. The northern side of the house of a passive solar home should be a block of insulation. Many passive solar homes do not have windows on the northern side to help them be more efficient. If the view is to the north, then that side of the house will never get direct sunlight, so if you have a bunch of large windows on the north, it will be a cold house.

      Remember that well built homes will be comfortable and require less energy to heat and cool. Skimping on the build process is not recommended.

      Best of luck!

  35. Carol Benally says:

    Do you have any ideas for an artist’s studio which has windows on the the North side for the the best light? Do you have any plans using a trombe wall, heating the floor ideas? anything would help.

    • Keya Lea says:

      Passive solar building must have windows on the south side of the house to be effective (in the northern hemisphere). This is because passive solar design works with the predictable movement of the sun.

      Passive solar buildings often do not have windows on the north side because windows loose energy. Here’ a post of what is typical for a passive solar home.


      Scroll down the article to see the north side of the house. Note that most of the windows are on the south side of the house, while there are only three very small windows on the north side of the house.

      Typically for an artist studio, windows are on the south side of the building so that the studio is filled with natural light throughout the day. Windows on the north side will give a darker, blue-ish coloring of light.

      Hope that helps.

  36. Pamela says:

    My husband and I have property in western Massachusetts and want to build a passive solar house. Unfortunately, our land slopes towards the north and the southern views are angled towards the road. We plan on building a long southern wall filled with windows (a la an Earthship), but would also like to have the beautiful views to the north. Do you have any suggestions for constructing the north and side walls?

    • Keya Lea says:

      As long as there is good southern exposure along the southern side of the proposed building, along with good design/build, you should be okay. It would also depend upon how much the land is sloped. Ideally, the north side of the house is bermed into the hillside, but it sounds like you have the opposite situation.

      It sounds like you’re planning on having a southern facing wall of windows. That is good for solar gain. It will also be important that there is a shallow distance from the windows to where the solar heat is absorbed into thermal mass. This can be done through heat absorption into the floor and walls (some sort of Trombe wall perhaps?).

      The northern side of the house is usually a block of insulation in passive solar design. Large windows are typically not placed on northern walls because they loose quite a lot of energy. (On the northern wall, since they do not get any solar heat into the space, potentially northern windows just loose energy.) But a great view is worth it right? I would recommend super insulated walls and the most energy efficient windows that you can get.

      Here are few houses to draw lessons from:
      This house is so well-built and insulated (and they have double and triple paned windows, with triple gusseted windows on the ones that open) that the energy loss from the windows on the east and west sides are not an issue. They bought insulated curtains, but aren’t using them since the house was so well-built and insulated. http://greenpassivesolar.com/2012/03/optimally-efficient-off-grid-passive-active-solar-home/

      Here’s another one: They had an interesting situation where they wanted to build onto the northern side of the house and did so with a two story Trombe wall on half of the structure. http://greenpassivesolar.com/2013/02/passive-solar-retrofit-on-adobe/

      This Solar Decathlon home from the University of Tennessee utilized double paned windows around the perimeter of the house, but they are special windows that integrate airflow into the space between the panes, thus they allow views while potentially cutting down on energy loss.

      In short, try to retain as much solar gain as possible by utilizing southern windows exposure, thermal mass and insulation, while using the most insulating materials in the walls, windows, roof, and even under the house.

      Good luck and let us know how it goes!

  37. amy abels says:

    Have a question for you. We are getting ready to build a new house and will be picking our lots soon. We are in Texas, very hot, and i am assuming we would want a northwest facing house to keep our house cool. But we also want a pool in the backyard and would like that pool to be in the shade in the afternoon for swimming. what is your best advice please? thanks so much. amy

    • Keya Lea says:

      Hi Amy,

      It would totally depend upon the design of the house. I’m currently living in the high desert of New Mexico where it can get cold in the winter, but is blazing hot in the summer. Because of this, many homes here have small windows placed high on the building, and some are even clerestory windows. This might be a partial solution for you. If the front of the house faces the south, then the pool could be in the north, where there would be more shade. The larger windows could also face the north, also toward the pool. That’s one possibility.

      It’s important to communicate with the architect and others living in the area to see if there are other environmental factors (wind, slope, etc.) that could contribute to the overall design and orientation of the house.

      Or for other possibilities, take a look at for clerestory windows that would allow in light, but block the summer sun with overhangs, or this home greenpassivesolar.com/2011/09/new-technology-traditional-solar-inhome/ for some ideas.

      Here’s a link to the older adobe style of building in New Mexico.

      Hope that the design and building stage goes well. It’s fabulous that you’re thinking about the home’s orientation in the planning stages. It can make a huge difference in overall comfort and energy use. Let me know how it goes!

  38. Donna says:

    We have bought some property on a lake but the property as it sits facing the water is north. We wanted a chalet style house but now I don’t know if that is practical unless we turn in around, right? We plan on using solar panels. Don’t know if there is a house style that is better suited in this instance that could be facing the lake, any suggestions?

    • Keya Lea says:

      There are passive solar designs that might work, although if the lake was to the south, instead of to the north, it would be easier to design a passive solar house to have the windows face the lake and the view, however, your situation is the opposite. It will be more difficult to build passive solar, but it can be done. Depending on where the lake is at (for example, a mountain lake in the mountains of Colorado at 12,000 feet vs. a lake in the humid south, say, in Louisiana) would make drastically different design choices to be passively efficient. In a cold climate, it would be really bad to have a bunch of windows on the north side, since a large portion of heat is lost out of windows. In a warm climate, it might not be a bad idea to have more windows on the north side of the house.

      I’ve seen some really bad scenarios in the mountains where houses are quickly shaded in the winter because of the location near a hill where the hill blocks the afternoon and evening sun. If you are building a house that relies on solar, it’s really important to buy a site that allows for the sun to hit the house throughout most of the day.

      Your best bet is to hire someone and have that person go out to the site to see what might best work. Sorry to not have any definitive answers, but good luck and let us know what you work out.

      There are other design considerations and site issues to take into account. Passive solar houses can be bermed into the hill, so that the north side of the house backs into the hill.

  39. santiago garcia says:

    Estamos en proceso de construir una casa en una zona verde y humeda
    segun sus comentarios entendemos la casa se debe construir de Sur a Norte con los ventanales que den al Sur.

    We are in process of building a house in a green and humid climate.
    According to your articles, it means the house must be built from south to north with the large windows that give the South.

    • Keya Lea says:

      Sí. Eso es correcto, si usted quiere construir una casa solar pasiva y tener la casa calentada por el sol en el invierno. Si usted está en un área que es caliente todo el tiempo, entonces usted no quiere tener grandes ventanas en el sur, ya que no se desee que la casa se ​​caliente demasiado. Todo depende de su clima y las condiciones locales.

      Edificio de la energía solar pasiva es como el aikido en las artes marciales. Uno tiene que utilizar las fuerzas que rodean en la circunstancia para hacer una casa eficiente. Edificio de la energía solar pasiva es una forma muy eficiente de la construcción en la mayor parte del mundo – pero depende de lo que usted está tratando de lograr.

      Yes. That’s correct, if you want to build a passive solar house and have the house warmed by the sun in the winter. If you are in an area that is hot all the time, then you would not want to have large windows in the south because you wouldn’t want the house to get too hot. It all depends on your specific climate and local conditions.

      Building passive solar is like aikido in martial arts. One needs to use the surrounding forces in the circumstance to make an efficient house. Building passive solar is a really efficient way of building in most parts of the world – but it depends on what you are trying to achieve.

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