Louvre windows in hot dry summers « Alternative Technology Assn Forums

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Louvre windows in hot dry summers

(30 posts) (7 voices)

Started 5 years ago by Catopsilia
Latest reply from Bushwalker

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Catopsilia
Member

Louvres long used in hot humid climates

Louvre windows are popular in places with hot humid climates, where heat discomfort, due more to high humidity than to high temperature, persists day and night. Louvres, which have a larger area of opening than other windows, freely admit breezes to cool people in the house.
Louvre windows have not been popular where summers are very hot and dry. There, daytime breezes are too hot, and must be kept out. Louvres could be opened at night to let in cool air if they were fitted. They seldom were, because most louvres would not keep the house cool when they were closed. They conducted heat freely (high U-value), and leaked hot air in large amounts.

New louvre windows have effective seals?

Recently, manufacturers have claimed that their louvres "...seal tightly to give the best performance possible...". If that is true, then louvre windows can play a part in the design of low energy houses to be built in places with hot dry summers. They can be opened automatically on summer nights to purge the house of hot air. At all other times they can be kept closed to seal the house against outside air that is too hot or too cold.
For use only for ventilation at night, louvres need not have transparent blades. Wooden ones provide more insulation that any kind of glass.

Something to discuss?

I have not found any discussion of the use of louvre windows for night-time heat purging where summers are very hot and dry. In "Warm House Cool House" (1995), page 42, Nick Hollo mentions a house near Melbourne where "[cool] air is drawn into the house through controllable vents below the bedroom windows". So it has been done, a generation ago.
Does anyone have experience using louvres in this way?

My night purge louvre

I have now had an automated louvre window installed solely to admit cold air on summer nights. The job was not finished before autumn, but the system does operate. I have thermometers set up to find whether there is better cooling.

I have described my louvre set-up, with more photos, on my blog. Later there will be analysis of its performance.
https://climatebysurly.com/2016/07/04/louvre-window-for-summer-nights/

Posted Monday 4 Jul 2016 @ 8:39:34 am from IP #
Bushwalker
Member

Interesting idea there Captosilia.

Do you have an automatic opening window system at the top windows so the system is completely automatic?

The ideal would be a control that monitors inside/outside temps and opens the windows on the basis of temperatures rather than time.

How air sealed are these louvre windows really, I couldn't find air pressure testing on the Breezeway site.

Posted Monday 4 Jul 2016 @ 10:41:05 pm from IP #
wlb
Member

Looks like we've been running on parallel paths Catopsilia. I came to the same conclusion about 20 years ago but could not find suitably sealed louvres. I looked at quite a few newer types about 10 years ago and still couldn't find what I was looking for. Then again a few years ago and found several. I've seen brochures for some similar to the type you have, but not that brand. I've never seen any in the flesh.

My aim was to entirely separate the role of ventilation from the window. Leave the window strictly for light admission and the view, and use louvres for ventilation. No more window sealing problems, cheaper double-glazing, and no flyscreens messing up the view. The louvres would have flyscreens or dust filters on them. The house would also have 1 or 2 very large roof vents.

Thanks for the post and the link to your blog. I'll read it with great interest, follow your progress, and return with some questions.

Posted Tuesday 5 Jul 2016 @ 12:32:01 am from IP #
Greg
Member

I have louvers in place for this purpose. I have ground level windout windows which are on the south side of the house opening onto a space that will house a water feature. On the opposite side of the house I have louvers set high up. The theory being to purge the hot air and draw in cool air. They seal very well.
It works quite well and hope it will improve once I get the water feature built. The high louvers also come in handy when the teenager in the house burns, I mean cooks.

In winter they are a bit of a liability as the single glazing is very cool (single digits). I'll have to address this once I do everything else

Posted Tuesday 5 Jul 2016 @ 2:22:08 am from IP #
wlb
Member

What brand are yours Greg?
I was also wondering about heat loss/gain when closed.

Posted Tuesday 5 Jul 2016 @ 2:39:06 am from IP #
dax
Member

Greg said:
In winter they are a bit of a liability as the single glazing is very cool (single digits). I'll have to address this once I do everything else

If you have the room, you could consider putting a polycarbonate window over the louvers. Done this in a couple of homes that have louvers for summer cooling, but don't want the air flow in winter, it acts like double glassing. Not expensive and can either but taken down when not in use, or hinged and swing away against the wall if there is enough room, or put them on the outside like shutters.

It's better inside, outside they are subject to weather and not as damage proof as glass. There are homes which use this method for double glassing and it works really well.

Posted Tuesday 5 Jul 2016 @ 2:53:09 am from IP #
Greg
Member

Dax, thanks for the idea. They are 2.8m off the floor (base) so leave them on for the season sounds like a good idea!

Can't remember the brand, wlb but they are pretty common. Just a plastic arrangement that holds the glass louvers (aluminium on the sides also plastic coated) and the overlaps click together when closed.

Look similar to these -> http://alunobuilding.sell.everychina.com/p-98941032-aluminium-louvre-window-frames.html

Posted Tuesday 5 Jul 2016 @ 3:14:49 am from IP #
Catopsilia
Member

Bushwalker asked about sealing and air pressure testing of the louvre that I have.
A Breezway representative referred us to this web-page, headlined
"Altair® Louvre Windows are designed to exceed the requirements of AS2047-2014 “Windows and External Glazed Doors in Buildings”.
http://www.breezway.com.au/building-code-compliance/as2047-product-performance-warranty/

In his e-mail he said:
"When he asks about air sealing, this could be a couple of things. If it is relating to weather performance, our louvre rate very highly, up to a C4 in the residential categories. More details on this can be viewed here (the link given above). This page outlines recommended sizing depending on the wind and water pressures of the site.

He could also be referring to general air infiltration. If this is the case, this will ultimately depend on the size of the particular window, but our rating for this ranges between 1.48L per m² per second and 2.6L per m² per second. To put this in perspective, most fixed lite windows with no openable portions will have an average air infiltration rating of around 0.3L per m² per second. All windows will have a level of air infiltration. If they didn’t they would explode."

Posted Tuesday 5 Jul 2016 @ 6:06:34 am from IP #
gazmo88
Member

I believe Rylock can do a pair of windows where one side is double glazed, and the other has a louver insert AND a sliding window which slides to the side of the window across the double glazed unit.

Not seen them myself in the flesh but is seemed like a good idea.

Posted Tuesday 5 Jul 2016 @ 8:07:46 am from IP #
Bushwalker
Member

Catopsilia said:
He could also be referring to general air infiltration. If this is the case, this will ultimately depend on the size of the particular window, but our rating for this ranges between 1.48L per m² per second and 2.6L per m² per second. To put this in perspective, most fixed lite windows with no openable portions will have an average air infiltration rating of around 0.3L per m² per second. All windows will have a level of air infiltration. If they didn’t they would explode."

Yep. That is what I am asking about. Air leakage.

I guess all windows have some level of air infiltration, but if they are euro spec, it is negligible to virtually nil. We have lots of them and none of them have exploded. Why would windows explode if they didn't leak?

When we did a blower door pressure test, a smoke generator was used to test window leakage. If there was a leak of any significance you could see wisps of smoke coming out of the window seals outside. We had one type of window that had seals replaced and no further leakage.

1.48-2.6L/second per square metre = 5328L/hr to 9360L/hr per square metre. If that is correct, then no, these windows are not effectively sealed by any reasonable expectation.

Posted Tuesday 5 Jul 2016 @ 8:37:44 am from IP #
Greg
Member

What are the advantages of louvers over an opening DG window? Could not almost any type of opening window offer the same airflow yet be far better sealed and insulated when closed?

Posted Thursday 7 Jul 2016 @ 2:03:34 am from IP #
gazmo88
Member

Well in our case we were looking at a floor to ceiling window about 2 metres above a pool.
A louver window is deemed to be "safe" in this situation, whereas a window which opened sufficiently to let in an equivalent amount of air represents a fall hazard.
An awning or casement window in that situation would have to have its ability to open restricted.
The internal sliding window only required single glazing to meet our BASIX requirements.
In the end we tackled the problem a different way for a number of unrelated reasons.
Oh, and we are also in an N4/C2 wind area and most of the manufacturers we approached required restrictions on the ability of casement or awning windows to open and their maximum size.

Posted Thursday 7 Jul 2016 @ 6:53:18 am from IP #
Catopsilia
Member

To answer Greg
In my case, what I wanted was simply a large ventilator that could be closed automatically and would seal well. Double glazing, with extra expense, was not required. Transparency was not required. Even translucency was not required.
Preferably, the window should not take up much more space when open than when closed.That is, the action of opening automatically should not cause a hazard or possible damage.
An automated louvre window with wooden blades is a product now on the domestic market that seemed to meet my needs.
I think a 14 mm wooden blade insulates as well as double glazing. In the gap between the blades there are soft rubber seals like windscreen-wiper blades. Whether these seals are sufficient remains to be proved.

Posted Thursday 7 Jul 2016 @ 11:46:10 am from IP #
Bushwalker
Member

Uncontrolled air infiltration overcomes insulation. Double glazing would always out perform louvre windows with timber blades with massive air infiltration per square metre.

Why would windows explode if they didn't leak? That comment make no sense!

Posted Thursday 7 Jul 2016 @ 12:34:06 pm from IP #
Catopsilia
Member

I hesitate to be thought to endorse a brand of window, but my contact in Breezway did refer again to "explode":
"Regarding my response to Bushwalker’s comments, forgive my use of hyperbole in saying ‘explode’. What I was trying to say is that if the window is completely air tight, it will break under pressure.
Under WERS, windows in Australia are reported as 5L per m² per second unless they have had the relevant testing done. So 1.48L per m² per second is not a very high rating, especially for a window with 90% ventilation.
One thing to note here though would be that louvres are designed to be opened most of the time anyway, so these figures are redundant when the window is open."

I am very happy with the interest shown in my blog post. In two years blogging, this is my most viewed post by a large margin: 55 views in the first day!

Posted Thursday 7 Jul 2016 @ 1:19:41 pm from IP #
Bushwalker
Member

Under WERS, if a window is not yet tested, it sounds like the default is to report them as a failed window with 5L per m2 per second. I guess if that works to pressure manufacturers to test, but that number is not based on fact because the window has not been tested!

If louvres are designed to be open most of the time then they will not work to maintain comfort during outside temperatures beyond comfort range. Do you leave your windows open during the heat of a summer's day or the cold of a winter night? Wouldn't it be more comfortable if the louvre was shut during these times and it did not leak?

Captosilia, what is the purpose of the wooden hinged cover for your louvre?

"If a window is completely airtight, it will break under pressure" I guess that is a possibility under pressure beyond normal environmental conditions. Perhaps a hurricane or cyclone could cause those kind of pressures. Sorry, that excuse for air leakage sounds like a load of bunk. A properly engineered window has next to nil leakage and it will only break under wildly extreme wind loading or other physical impacts.

Posted Thursday 7 Jul 2016 @ 2:10:30 pm from IP #
Catopsilia
Member

Bushwalker, you are referring to the cover panel that I have had fitted on the indoor side of the automated louvre.

When closed, (provided that the gaps between the blades seal well) the 14 mm-thick wooden blades of the louvre window provide much the same protection as the fibre-board outer cladding of the wall. The cover panel is to stand in for the plaster-board lining of the wall in the same way.
I am resigned to doing without the cover panel in summer (4 months, November to February), when the louvre is to be opened automatically at night. Through the winter (8 months, March to October) the cover panel will be in place. In winter the temperature difference through the wall may exceed 20 degrees.
https://climatebysurly.com/2010/06/17/indoor-versus-outdoor-minima-1096-days/
Both the closed louvre blades and the cover panel should provide a degree of protection against both heat conduction and air infiltration.

The cover panel has been made with two sets of piano hinges because the refrigerator restricts access. The panel is to be moved only twice a year. Even so, it is inconvenient to move the refrigerator to do it. The hinges allow the panel to be withdrawn and replaced (with swearing) through the 220 mm recess for the kitchen curtain.

Posted Friday 8 Jul 2016 @ 12:23:45 am from IP #
wlb
Member

Catopsilia said:... but my contact in Breezway did refer again to "explode": ...

My guess is that the salesperson at Breezway doesn't understand the testing method or the purpose. My limited understanding of AS 2047 is that after the standard water and air infiltration test and pane deflection test, the window is pressure tested to the point at which the glass fails. It has to withstand the wind pressure from a once in 100 years storm.

It sounds like he thinks that air leakage through a window is necessary to avoid glass failure. Unless there is something seriously wrong with the installation, a fixed non-opening window doesn't leak air at all, under any circumstances.

It sounds like you are happy with the quality of the louvres. What is the timber used? Is it plywood, solid cedar, something else?

Posted Friday 8 Jul 2016 @ 12:47:11 am from IP #
Bushwalker
Member

Catopsilia said:
I am resigned to doing without the cover panel in summer (4 months, November to February), when the louvre is to be opened automatically at night. Through the winter (8 months, March to October) the cover panel will be in place. In winter the temperature difference through the wall may exceed 20 degrees.
https://climatebysurly.com/2010/06/17/indoor-versus-outdoor-minima-1096-days/
Both the closed louvre blades and the cover panel should provide a degree of protection against both heat conduction and air infiltration.

The cover panel has been made with two sets of piano hinges because the refrigerator restricts access. The panel is to be moved only twice a year. Even so, it is inconvenient to move the refrigerator to do it. The hinges allow the panel to be withdrawn and replaced (with swearing) through the 220 mm recess for the kitchen curtain.

The problem with this approach is that this is just a guess. How much air infiltration occurs with the louvre, and how much less with the cover in place? Is the cover even making any difference because it is not sealed? How much leakage is throughout the house with the other windows, doors and joins in the structure?

Professional testing requires a trained technician, a blower door and computer software to calculate the result. Not easy to find even in capital cities in Australia, Manilla would be a struggle, and costs would be significant. On the other hand, it would be possible to hire a blower from a hire place, temporary seal it into a doorway or window and use some incense sticks or even a party smoke generator to discover any major leaks in the structure. That is how the professional testing uses the blower door to identify leaks in the building envelope.

eg: http://www.kennards.com.au/index.php?fuseaction=product.view&productid=73&ctu=&type=Carpet%20Drying&lvl=2

Posted Friday 8 Jul 2016 @ 1:53:12 am from IP #
Catopsilia
Member

I am an early adopter of automated louvre windows for energy efficient houses in dry climates.
After building my house rather frugally in 1998, I decided recently to spend money adopting innovations that may not succeed, such as this automated louvre.
I agree with wlb's thought that the various windows of a house should have distinct functions, whether winter solar gain, daylight, views, or ventilation. In my house, as built, ventilation during summer nights required doors to be opened because few opening windows were in the right places.
In correcting this, I took a gamble that the louvre windows on the market have adequate seals. Bushwalker's doubts about this are justified. I hope to achieve proper sealing in the end, but I certainly don't have it yet!
I like this statement in the wikipedia article on "Early adopter":
"Typically this will be a customer who, in addition to using the vendor's product or technology, will also provide considerable and candid feedback to help the vendor refine its future product releases, as well as the associated means of distribution, service, and support."

That is what I am doing right now.

Posted Monday 11 Jul 2016 @ 1:56:25 pm from IP #
Flying high
Member

If I my ask, what was the cost of the said louvre 'window'?

I'm looking to use this or something similar for two of may gable ends of the house during summer in Melbourne, south to north config.

Posted Monday 26 Sep 2016 @ 12:39:22 pm from IP #
Catopsilia
Member

The installed cost of this small automated louvre window was $7,140. In my case, the advantage (if it works well) will be only in the convenience of avoiding the chore of opening and shutting doors twice a day all summer. There will be no benefit in savings to amortize the cost.

Posted Monday 26 Sep 2016 @ 11:38:36 pm from IP #
Bushwalker
Member

Ouch! That is a lot of cash for an automated window!

An electronic window actuator is only a few hundred dollars. Maybe with a controller and install it might cost a thousand if you didn't do it yourself... $7k would probably automate all the windows.

Posted Tuesday 27 Sep 2016 @ 12:51:41 am from IP #
Catopsilia
Member

Bushwalker, I don't have a record of the cost of the hardware. I think it was about one-fifth of the cost of the labour.

Posted Tuesday 27 Sep 2016 @ 6:20:40 am from IP #
Bushwalker
Member

Sorry to hear, Captopsilia. So about $1400 for the hardware and $5500 to install it. That seems an awful lot for a small window.

I hope it works well for you.

Posted Tuesday 27 Sep 2016 @ 12:08:56 pm from IP #
Flying high
Member

$5500 just install......ouch, agreed hope it works exceptionally well for you.

Posted Wednesday 28 Sep 2016 @ 8:24:33 am from IP #
Catopsilia
Member

I am surprised that others think these prices for building work are high. I thought they were normal. Every building job I have heard of in recent years has been several times the price that one might have expected. Very high prices have been mentioned in several threads.
Accepting a low tender is very likely to result in shoddy work and perhaps a job that may never be finished at all. I trust my builder, who built my house 18 years ago, and has done other work for me since.
In an area of towns and villages, I think the costs of transport may be higher than in cities.

Posted Wednesday 28 Sep 2016 @ 12:12:16 pm from IP #
Catopsilia
Member

My ventilation louvre for night purge ventilation now has glass blades.
The blades of western red cedar that I specified could not be made to seal well enough to exclude daylight. They were replaced on warranty by glass blades.
Gaps between the glass blades were less than 0.40 mm nearly everywhere, as shown on this graph.

I am satisfied that leakage will not be significant.
Details are on my blog, at "Ventilation louvre hassles".
https://climatebysurly.com/2016/12/18/ventilation-louvre-hassles/

Posted Sunday 18 Dec 2016 @ 12:53:04 pm from IP #
wlb
Member

Thanks for the update. Why do they advise against painting the glass? Could not opaque glass be used, or automotive window tinting film applied?
Do the glass blades rely solely on accurate edges to seal, while the cedar blades rely on rubber seals?

Posted Sunday 18 Dec 2016 @ 1:15:19 pm from IP #
Bushwalker
Member

Sounds a lot better with glass blades. Pity they didn't offer tinted glass.

Perhaps you could install shadecloth outside the window to lower the light ingress and view to the back of the fridge?

0.4mm would be a significant leak if the building is under pressure. There are 10 joins between glass/glass and glass/frame, of around 50cm? length each. So about 5m of unsealed joins. Also the edge of the louvres to the side of the frame. How well are they sealed there?

Good to see you have a significant improvement compared to the cedar blades.

Posted Sunday 18 Dec 2016 @ 9:46:46 pm from IP #

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