How Many Operable Clerestories Does a Permie Even Need?

I was doing some reading around on the forum regarding passive solar design and I came across a fellow mention just opening the windows up 1.5" makes a huge impact regarding cool air flow in the home.

So that got me thinking... I have all these nice clerestories in our design but I guess I don't need them all to be operable, eh?

If you had this home (1,000 sqft living space, open concept so the whole space is open to all 5 of the windows) how many of these clerestories would you make operable?



I live in central Texas (hot-humid) so I'm quite excited about being able to open them to let the hot air escape out and draw the breeze through the home :) At least I read that is what is supposed to happen in theory. The skeptic in me is scared we're building a hot box!

We're also trying to do this as cheap as possible and fixed windows are cheaper.

While I have you're attention here talking about our clerestory windows... We're trying to wrap up loose ends so we can begin building our home ASAP this year (who knows when that will be...) and I came across an issue with our architect making the clerestories slightly asymmetrical because of a temporary wall we have in the room...



Super silly for a temporary wall to be making such a huge permanent change! So I've been playing around with the windows on my cheap-y program and have the above spacing for the windows currently. (the colored pic, not the architect's drawing)

I guess, in doing this, I've just become a bit self conscious about the large spaces between the windows because all other examples I come across have them way closer to each other, thus there are also more windows. (even the architect's drawings of our home has one more window included) But these images I'm looking at are often very extravagant "green" homes mansions so it doesn't seem right for me to be basing my decisions on what they are doing...

So I come to ask you, a fellow Permie, does my clerestory set up look aesthetically pleasing, practical, and economically prudent?

And for fun, here's our floorplan.



The interior bedroom walls are the temporary ones. So... for now all the clerestories are not actually open to the living spaces like I said above! This is 'Phase 1' of our build and as our family grows we'll build Phase 2 which will be a separate building attached by a dogtrot with only bedrooms in it (and maybe a new laundry room). When that occurs we'll remove those walls making the previous bedrooms the official living room. Hence why one of the bedrooms has a random fireplace in it...

Having lived with clerestory windows in Southern New Mexico, I have opinions on this! I love them, BUT in NM I deliberately faced them east and west (with a heavy overhang on the west ones. This let in lots of light, and made the whole house bright and happy, without just cooking me.

I initially built them all to open. I learned fast that that was not a good plan.  Wind at that house was from the west, and the west sloped roof made the wind bounce into any open window, for better, or mostly worse. Opening the west ones on a windy day actually pressure blew out one of the east ones, had to replace the glass.

I ended up, after several years of experimenting, getting my best results for that house with one window facing east opened about 3 inches all summer.

I have moved to Missouri, my house design for here contains clerestory windows, facing south because that's how it works to light up the house, but only two of them will be openable, one sort of at each end, and I expect to actually open only one of them. All the rest are fixed glass.

That's my advice, pick one or two you might open, fixed glass on the rest. And consider your orientation with respect to your weather and actual microclimate. They don't HAVE to face south. The heat gain is incredible, and I saw several places in NM either remove them or put heavy drapes on all their south facing glass walls or clerestories they didn't realize would cook them. Saw one place getting built and said "oooh, bad plan, they moved here from up north!" They lasted three years before they ripped all those lovely floor to ceiling south facing windows out.

:D

Just looked closely at your plan, which side is the clerestory on? I don't see orientation marks...

And spacing: I don't have mine spaced tightly on my plan either. I need the structural stability more than the extra light, wider space makes the roof easier to hold down tightly, against wind storms. If you get wind, consider that.

:D

We had clerestory windows in my childhood home. They faced east. I want to say that only 2 were operable and my father had to climb onto the roof to open them, not the plan but that's how it worked out. I absolutely loved them, kept the house so much cooler. They did act like a giant ear though, whenever there was a concert nearby we could hear everything.

Rebecca,

Regarding the number operable.  Here is family experience to share.  My mother grew up on Galeveston island in the 50's.  Hot and humid with no A/C.  Her father whom was a natural mechanic/engineer had an attic fan in the access cut out in the ceiling.  He knew exactly how many cubic inches those fan blades displaced.  He had windows on either side of the house opened on blocks equaling that displacement.    As a child my mother always remembered how he would know right away if someone changed the window opening, as the air flow in the house would change immediately.    so it is not necessarily the number that are open but total exchange, whether active or passive, of air.  

If it were me, I would install and attic fan somewhere, perhaps even behind one of those open windows, calculate the cubic feet of air I wanted to exchange per minute and find the appropriate fan rated to that cubic feet per minute.  then calculate the number of cubic feet need to allow air in to match the air expelled.  Then you know  how much aperture you will need.  

Don't discount the idea of having that aperture connected to pipe buried in a few feet of ground, geothermic cooling.  Dig down a few feet, even in the summeand one will find the earth much cooler than ambient.  Let that piping cool your exchange air as it comes into the house.  There is a lot of information on in ground geothermic here and on the web.  Earthships use the concept and there are some good examples on youtube.  

Good luck on the project!

Pearl Sutton wrote:That's my advice, pick one or two you might open, fixed glass on the rest. And consider your orientation with respect to your weather and actual microclimate. They don't HAVE to face south. The heat gain is incredible, and I saw several places in NM either remove them or put heavy drapes on all their south facing glass walls or clerestories they didn't realize would cook them. Saw one place getting built and said "oooh, bad plan, they moved here from up north!" They lasted three years before they ripped all those lovely floor to ceiling south facing windows out.

:D

Oof, this is one thing I am worried about. I have pretty limited experience with passive solar, clerestories, and every other thing of the like.

I have been doing a ton of research on the matter but it has proved difficult finding recommendations for hot, humid climates. But, from what I have learned I put the bulk of our glazing on the north side (the 12' glass door and two 6' windows) and the southern side is the one with the long porch. No windows except for the door on the west and smaller windows on the East.

The clerestories; however, are the only southern facing windows that are not covered by a porch. I'd love to have them for the amazing light southern windows bring in. My current bedroom has an uncovered southern window and the light is amazing <3 But it can get toasty. Nothing too bad to where I'm outrageously uncomfortable though.

In theory, what I'm hoping would happen is that the clerestories will provide great light reducing the need for electric lighting, give a place to allow the rising hot air to escape, and perhaps capture wind coming from the south (not the main purpose). The microclimate there has great southerly wind.

I guess it'd be more ideal to have them facing east, but with the topography of the land our home has to be situated East-west longwise so it works best due to topography to have them facing south as well. This also is perfect for providing light to our living areas which we want on the northern side both for coolness and for the view.

For future reference our roof slope is 4/12 and we of course will be extending the roof beyond the clerestories to give adequate covering in the summer. We may even do more roof cover than typical to make sure we get adequate shade through out all of September the first half of September can be just as hot if not more hot than August (high 90-100). This would just be a bummer in that it will give more shade in the Spring, but that's okay :) Our winters aren't that bad.

One other thing that plays a factor in this is that we are doing screen grid ICF, like EZ Block. Thermal mass... but it's insulated thermal mass so it won't be as intense as flat out thermal mass to my understanding.

Again, my experience is still limited and that makes me nervous. Argh.

Jack Edmondson wrote:Don't discount the idea of having that aperture connected to pipe buried in a few feet of ground, geothermic cooling.  Dig down a few feet, even in the summeand one will find the earth much cooler than ambient.  Let that piping cool your exchange air as it comes into the house.  There is a lot of information on in ground geothermic here and on the web.  Earthships use the concept and there are some good examples on youtube.  

Good luck on the project!

Thank you for the information on the fans! Is that something that is fairly simple to add after the fact? I just feel too stressed out with all other things house I can't imagine adding on another foreign-to-me thing I would need to research. We also will have a fairly tight building envelope so the idea of putting holes into it isn't too appealing.

Geothermic pipes sound cool but we're building on a hill with little topsoil so putting pipes into the rock sounds very... unattractive. (crazy idea for a wanna-be permie, but isn't that what permaculture is about? Growing food on rugged land? lol)

Also don't think my husband who is wanting most everything to be like a typical build would be into the pipes.

Rebecca: Yes, you can add a fan (or fans) after the fact. They will pull the air through, so something down low has to be open, it will not be effective to pull hot humid air through with them, as that will add to your hot humid in the house. At night they'd be awesome for forcing the pull of cooler air in. if you rarely get cooler air, it's probably not worth your time to force it with a fan. if you decide it is' it can be added alter, just hook a fan so it blows out the openable window up top.

Bulk of your glazing on the north is wise!

I have south orientation for the same reason, where the house can go easily and willing to add heat in summer for the lovely light :D

You might consider making it possible to pull drapes or vertical blinds across them if you need to.  That will help if you decide it's too much.

Do your temporary interior walls go high enough to be in front of the windows?  If not, then there is zero issue with where you place windows. And again, I like having less a full glazed clerestory than a STUDY one with wall between the windows. esp if you are in storm territory.

As far as nervous, you sound like you are doing it right!! :D
I'd say make sure you have your alternative options possible like fans or drapes, and absolute worst case would be you have to pull your drapes more often that you might like. Put an outlet on a switch that can have a fan on it right near openable window, and, if you can, put drapery rods or at least brackets in place when the tall ladders are there, so you can easily add rods and drapes or blinds.  Those are the only things I'd say you need to account for, just in case, other than that, you are doing it fine  :D

:D

Pearl Sutton wrote:Those are the only things I'd say you need to account for, just in case, other than that, you are doing it fine  :D

Pearl, I appreciate you sharing your wisdom with me!

Glad to see I’m not screwing ourselves over xD

I wasn’t sure what I was going to do with the temporary walls so I essentially gave the architect the plans I had drawn and said “I don’t know what I’m doing here. Fix it!”

And I think I like what he did 😁
My image was to just have the bedroom walls and ceilings be 8feet with dead space above to not complicate things with the windows but he put the wall that is perpendicular to the clerestories going all the way up.

The parallel temporary wall is only 8feet so this makes bedroom 2 have 8 foot ceilings and bedroom 1’s ceiling will go all the way to the top allowing two of the clerestories to shine into the master 😁

And we get a tiny bit of extra space above bed 2’s ceiling for storage/maybe an office if it happens to be tall enough to stand.

With the spacing of 5 windows I shared above that leaves 2 of the windows in the temporary master bedroom/eventual living room, 1 in the dining room, 2 in the kitchen.

Oh and I forgot to say I think I like the idea of having two operable so I can direct the breeze toward whichever side of the house I’d prefer at the moment.

Just not sure if I should do windows 1 and 5 (if I numbered them 1-5 in order)
Or windows 2 and 4... hmm 🤔

Rebecca Blake wrote:Oh and I forgot to say I think I like the idea of having two operable so I can direct the breeze toward whichever side of the house I’d prefer at the moment.

Just not sure if I should do windows 1 and 5 (if I numbered them 1-5 in order)
Or windows 2 and 4... hmm 🤔

Whichever are most likely to be easy to reach to open.  :D

Pearl Sutton wrote:

Rebecca Blake wrote:Oh and I forgot to say I think I like the idea of having two operable so I can direct the breeze toward whichever side of the house I’d prefer at the moment.

Just not sure if I should do windows 1 and 5 (if I numbered them 1-5 in order)
Or windows 2 and 4... hmm 🤔

Whichever are most likely to be easy to reach to open.  :D

So, none of them! lol I'm hoping to get ones that can be opened with one of those pole things for that reason.

Now my ‘window guy’ is telling me to go with 0 operable because of leaks... but then there isn’t much good use for them except aesthetics and light.
And I guess heat in winter but I’m not really worried about that so much.

Anyone have crazy clerestory leak horror stories to share?

I don't understand why your window guy would think that clerestory windows would have any more leakage issues than any other windows. We never had any problems with leakage. We had some leakage problems with skylights but not the clerestory windows.

By the way, we had the pole thing to open and close them but we just couldn't get enough leverage for it to work that's why my father would get on the roof, but we had very high ceilings. Maybe you will have better luck.

Rebecca, these windows are going to keep you awake at night!!

Now my ‘window guy’ is telling me to go with 0 operable because of leaks... but then there isn’t much good use for them except aesthetics and light.

Windows that do not leak are made every day.
Also think about how you will open them, I have used 'rope' pulley systems no electricity or long poles. prestons-cord-operated-fanlight-opener
I will chase an image. Its below.
These windows need shading on the South side.
For cooling I have built towers, similar to those used in the middle east and India. [ I have written about them on this site ]
They are tall and draw the air through the building. Its better if you can draw the air from a courtyard with ponds in it because it picks up moisture which is cooling in a dry climate.
wind_tower_iran/wind_towers.html This information was what started me 50 years ago investigating the use of them in 'western ' homes. Simple explanation of when and where they work The preference being a consistent breeze from the same direction most of the time.
I just remember your climate is humid.
In Australia, Queensland in particular they built high homes with verandas and louve windows.
They encouraged air flow.
The same in Singapore and many islands in South East Asia.
Here are some sites that have ideas
home-building-tips-hot-climates
/passive-design/passive-cooling This is a great resource for general info.
passive-design/design-climate Another chapter of the same book, its great
From above
Orientate the building to take advantage of cooling breezes, and position landscaping and outbuildings to funnel breezes over, under and through the building.
Make sure your design maximises night-time sleeping comfort. Locate sleeping spaces in lower levels.
Use low or no thermal mass in sleeping spaces to prevent radiant heat. Consider sleep-out spaces.
Install ceiling fans in all rooms.
Use passive cooling measures; ventilate roof spaces well with fans or whirlybirds and design for condensation removal
Locate cooking areas and heat-generating appliances (for example, fridges) on external walls and away from sleeping areas.
Provide shaded outdoor living areas.
Locate pools and spas on the northern side of the building where they will be shaded in the hot humid season and warmed during the dry season.
Use light colours on roofs and walls.
Maximise planted areas in landscapes.
Have high raked ceilings
From my own work, consider what I call a Safari roof, its an extra layer of roofing iron installed above the water proof roof, its insulated but open to the atmosphere so air moves through it, cooling the 'normal' roof. It lowers the external face of the roof from 79 deg. C to 38 deg C, which vastly reduces the heat load on the building.

Wind towers for cooling

John C Daley: I love the window opening thing!! That's neat low tech! I bookmarked the page, thank you :D

John C Daley wrote:These windows need shading on the South side.

Are you saying this is a terrible idea or just that I need to account for shading?

We're planning on doing the roof overhang for summer protection and perhaps shade curtains for Sept/Oct since those months can still be kind of hot.

Who knows, maybe we should just close up the roof line and not have them. Or is it still more advantageous to keep them?

No I am not saying its a bad idea, but shading will be necessary.
They are very beneficial for cooling and light

Rebecca Blake wrote:Now my ‘window guy’ is telling me to go with 0 operable because of leaks... but then there isn’t much good use for them except aesthetics and light.
And I guess heat in winter but I’m not really worried about that so much.

Anyone have crazy clerestory leak horror stories to share?

Unless you get rain with strong driving wind from the south, your plan with overhanging roof, should not pose a problem.  The window guy is probably the one with horror stories from people who have not made the effort to plan that you have.