Clerestory windows to heat double storey house? « Alternative Technology Assn Forums

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Clerestory windows to heat double storey house?

(13 posts) (7 voices)

Started 4 years ago by HowardH
Latest reply from Catopsilia

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HowardH
Member

Hi everyone,

I am designing a dual occupancy development that is facing east-west. Because of the share party wall in the middle, one of the units will not have any north facing windows.

The house will be constructed on a waffle pod concrete slab with timberstud/masterwall polystyrene cladding and double glazing throughout.

I'm thinking of having clerestory windows to the upper living areas so it will help warm up the house in winter but is it really worth having?
will i lose more heat than i gain?

I have upload some drawings if anyone is interested in having a look.
https://www.scribd.com/document/355653422/Ground
https://www.scribd.com/document/355653426/first-pdf
https://www.scribd.com/document/355653424/Elevations

Posted Sunday 6 Aug 2017 @ 11:27:16 am from IP #
Catopsilia
Member

Hi HowardH

It depends on where your building is but, unless it is on the seaside or in the monsoonal north, I am sure you should build in clear-story windows. The elevations that you linked to would hardly need any change!
As you have just joined, you may not have seen my three recent posts that show how much mid-winter benefit I get from my clear-story windows:
http://www.ata.org.au/forums/topic/46857#post-98969
http://www.ata.org.au/forums/topic/46857#post-99150
http://www.ata.org.au/forums/topic/3/page/10#post-99220

My concluding post in this set will show that the clear-story space in that mid-winter period remained 13.5 degrees warmer than the environment throughout each sunny day.
Even on days when the sky was flat overcast, the clear-story space stayed 8 degrees warmer than the environment.

I haven't worked through the heat gains and losses. I am sure someone here could estimate the balance from the temperature profiles, indoor and outdoor, that I have shown in the graphs in my posts.

Posted Sunday 6 Aug 2017 @ 1:30:43 pm from IP #
dave lawrence
Member

unit 1 with north facing clerestorey windows will benefit .Unit 2 with potential South facing clerestorey windows wont benefit (from a heat gain perspective). it is a pity that unit 1 garages are in the north east corner . I would try to reconfigure to get the garages on the inside. .. they neither need nor want winter sun .

Posted Sunday 6 Aug 2017 @ 9:45:23 pm from IP #
Russell Moore
Member

Clerestory windows can also be use to vent the house at night in summer.

Posted Sunday 6 Aug 2017 @ 11:00:46 pm from IP #
HowardH
Member

@Catopsilia
thanks for the reply, I will take a look at them. I have a slight feeling having it is better than nothing but I'm pretty sure this setup will mean that the upper floor will always be a few degrees warmer than downstairs.

Is there a way to circulate the air from the top floor to the bottom without any mechanical ventilation if possible?

@dave lawrence
I have thought about it, i prefer to build off the boundary and just a single crossover but doing so means i will lose alot of usable internal space. (would probably need to get rid of study and reduce the living areas)

@Russell Moore
I would like them to be openable but that means more money to operate and a stronger thermal seal, I live in melbourne so im more concerned about keeping warm than cool.

Posted Tuesday 8 Aug 2017 @ 5:58:34 am from IP #
Catopsilia
Member

Hi HowardH

Rather than try to shift air around, I think it would pay to build most of the south wall of the south house as "reverse brick veneer". I would make the internal leaf double-brick, with its base on the concrete floor slab, and at least four metres high. That wall would receive the sun on its upper part and conduct the heat into the lower room and into the floor slab. It takes more than a day, but it will surely get there.
In the same way, the north house would benefit from having the north face of the central spine wall built in double-brick.

Are you sure that the upper floor will be warmer? The first and second links that I posted show that in my place in mid-winter the upper floor was one degree colder than the lower floor on average, and even colder (pretty damn cold: nine degrees!) at night.

Posted Wednesday 9 Aug 2017 @ 2:25:34 am from IP #
Ruffy
Member

Important points:
*north-facing clerestories will help to warm the rooms that have them during the day, but unless the sunlight is hitting and warming up internal thermal mass that benefit won't transfer to night time. They are relatively small in area so whether they're letting in enough sunlight to change the temperature of the thermal mass much would require calculation.
*south-facing clerestories should only be installed in the northern hemisphere!
*And yes, clerestories will lose heat rapidly at night even if double glazed, so make sure to install excellent honeycomb blinds (I'd go with bracketed Luxaflex Duettes or similar with R-value ~1) behind them inside the reveal spaces, and put them down at night.

Other important points on things you've mentioned:
*insulate the edge of your slab with at least R2 XPS. This should be standard in all cool-cold climates. ~80% of heat is gained/lost from the slab edge. The waffle pod will provide about R0.5 underneath the slab, but that's not nearly as important due to the relative constancy of temperature in ground below about 50cm depth (unless you are installing in-slab hydronic heating, in which case you want R2+ XPS underneath as well).
*make sure to buy DG with proper framing - standard Al framing reduces the effectiveness of the DG by up to 40%! Go with thermally broken Al, timber or uPVC.
*at least R4 in ceiling and R2 in walls, but why not go R5 and R2.5? Cost difference is minimal and will pay itself off quickly.

Good luck!

Posted Wednesday 9 Aug 2017 @ 6:58:46 am from IP #
HowardH
Member

@Ruffy,

Thanks for the information, i will consider them in my design. Regarding unit 2, there will not be any clerestory windows, only unit 1

"And yes, clerestories will lose heat rapidly at night even if double glazed, so make sure to install excellent honeycomb blinds (I'd go with bracketed Luxaflex Duettes or similar with R-value ~1) behind them inside the reveal spaces, and put them down at night."

so does this mean having them in the bedroom will not really do anything, the blinds might help slow down heatloss but in the end is it better to just remove it all together and have more insulation to the roofspace?

Posted Wednesday 9 Aug 2017 @ 10:44:47 am from IP #
Morbo
Member

but at least wou will have plenty heat gain in summer

Posted Wednesday 9 Aug 2017 @ 12:06:45 pm from IP #
Catopsilia
Member

I don't think that I have convinced HowardH that clear-story windows are worth having.
That is a pity.
In wintertime north-facing windows gain very much more heat than they lose. Clear-story windows are especially good because they are less likely to be shaded.
Once the house is built, this winter heat is free. Any other heat will cost more and more as time goes on.

Posted Thursday 10 Aug 2017 @ 1:49:00 am from IP #
ilmessaggio
Member

The question, 'is there a distinct advantage to the potential heat gain' given that you also have light ingress which in itself is rarely a problem
The question of heat loss is a separate exercise and can be effected with a roof ventilator with a wireless remote closure especially as it's a raked ceiling and gain via an overhead sun in summer is unlikely

Posted Thursday 10 Aug 2017 @ 12:07:12 pm from IP #
HowardH
Member

@Catopsilia
I am not going ditch them, just a bit concerned from reading other forums and websites.

anyways i think i'll keep them in for now, cant really know if they will work until i build the house.

thanks all for the discussion

Posted Friday 11 Aug 2017 @ 5:51:25 am from IP #
Catopsilia
Member

I finally got around to posting on my blog the graphical model showing that the clear-story space in my solar-passive house was over 13 degrees warmer than the environment in mid-winter 2016.
I had promised it in the first reply to HowardH's opening post in this thread.

My blog post about it is:
https://climatebysurly.com/2017/10/18/house-june-warmth-profiles-iv/

Posted Wednesday 18 Oct 2017 @ 6:58:40 am from IP #

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