Double story passive solar design why is lower level North facing rooms colder

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Double story passive solar design why is lower level North facing rooms colder

(8 posts) (6 voices)

Started 2 years ago by warek
Latest reply from d.darroch

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warek
Member

Hi there

I am looking at building a double story North facing passive solar design home and we are also looking at North facing living areas in double story homes that are for sale.

A general observation in all the ones we have seen for sale or that friends have, is that the ground floor is always cooler, sometimes up to 10 degrees less than upstairs. This is the case in houses that have large void to upper level and to a lesser extent houses that simply have a staircase to the upper level without any doors.

Example we say yesterday, ground floor living areas North facing, 2.4 m ceiling height, concrete slab with floor tiles, narrow eaves 300-400 mm, 2 windows on North side plus large glass North facing sliding door. 10 m by 8 m open plan room. No shading from upper story as upper story rooms does not cover ground floor North facing living areas. No large open void to upper level, just a small staircase without a door. Significant temp difference as you walk up straircase to upper level.

I would like some feedback about these 2 questions

1 With good design and a well built home with appropriate insulation what temperature difference can be achieved between ground floor North facing passive solar rooms and upper level North facing rooms? Looking for a smaller difference as possible.

2 What are the design approaches that work to minimize temperature variation between ground and upper floors?

Thanks for any suggestions and have a good day

Cheers
Kevin

adn insulation

Posted Wednesday 7 Mar 2018 @ 5:06:00 am from IP #
ilmessaggio
Member

1 'With good design and a well built home with appropriate insulation what temperature difference can be achieved between ground floor North facing passive solar rooms and upper level North facing rooms? Looking for a smaller difference as possible.'

Design has very little to do with it....you're dealing with natural phenomena
You should have paid more attention during physics classes.
Have someone explain the principles behind a hot water storage unit

2 'What are the design approaches that work to minimize temperature variation between ground and upper floors?'
The only fool proof design is 'don't build above ground floor'
However if you find a way....don't tell anyone 'cos we could make a lot of money

good luck, if you want a little more information on natural phenomena try Condor Kinetic

Posted Wednesday 7 Mar 2018 @ 9:45:15 am from IP #
Johnnojack
Member

We have an upstairs room, behind a well sealed door at the upper level. It is always warmer in summer up there. This not because of heat going up there from the ground floor but because the ceiling insulation is compromised by lack of distance between tin and gyprock. In winter it is not warmer upstairs unless the door is left open. When walking up the stairs at any time particularly when it is a bit hot say 26 downstairs, when walking up the stairs as soon as ones head gets above the ceiling level you can feel the rise in temperature. To summarise, hot air rises.

Posted Wednesday 7 Mar 2018 @ 11:27:18 am from IP #
Johnnojack
Member

We have an upstairs room, behind a well sealed door at the upper level. It is always warmer in summer up there. This not because of heat going up there from the ground floor but because the ceiling insulation is compromised by lack of distance between tin and gyprock. In winter it is not warmer upstairs unless the door is left open. When walking up the stairs at any time particularly when it is a bit hot say 26 downstairs, when walking up the stairs as soon as ones head gets above the ceiling level you can feel the rise in temperature. To summarise, hot air rises.
Building a two story home with no door between the levels is a bit dumb IMHO

Posted Wednesday 7 Mar 2018 @ 11:30:23 am from IP #
Benny
Member

Sorry about the reply from ilmessagio warek - most people are more helpful and polite on here than that. Try to ignore it.
All the houses I've audited (including my own) that have a second story have been warmer upstairs - in summer day and night but in winter warmer during the day ad colder at night. I think there are 2 main reasons - 1 is that the upper storeys are often not built as well as lower - often a framed construction compared to brick on the ground floor (at least here in Perth). The upper storeys are usually far less well insulated. Second is that the upper storeys are much more exposed to sunlight - they are often completely above any surrounding vegetation - or house next door etc and so collect more sun heat. The ground floor is effectively insulated by the upper floor where'as the upper floor often has the biggest problem - the roof space where most heat gets in to the building. Upper windows rarely have external shades - just blinds inside and these don't work well to stop heat getting in.
"What are the design approaches that work to minimize temperature variation between ground and upper floors?" I think its just the usual design rules - good insulation all round and external windows shades.

Posted Wednesday 7 Mar 2018 @ 1:32:48 pm from IP #
warek
Member

Thanks to all posters for their insights.

Sounds like one of my thoughts of having a master bedroom downstairs and another one upstairs, so we could sleep upstairs in winter to take advantage of heat rising does not work if it cools down quicker and is colder in the night upstairs.

I did not study Physics,instead it was humanities.

Benny, your suggestions sound pretty logical, thank you

Have a good day

Kevin

Posted Wednesday 7 Mar 2018 @ 11:29:15 pm from IP #
Catopsilia
Member

Hi warek
Have you seen the thread "Staircase position for stack affect and energy efficiency" begun by micky?

In that thread I posted a relevant graph of temperature logs upstairs and downstairs.
They were for the cold of mid-winter, and showed uptairs and downstairs similar at daily maximum (4 pm) on sunny days, but upstairs colder at all other times by up to two degrees.
I have not posted results for the heat of mid-summer, but a quick check shows upstairs and downstairs similar at daily minimum (7 am), but upstairs hotter at all other times by up to three degrees.

Downstairs is able to hold a more constant temperature through the year because of the heat bank effect of the soil and the slab.

Posted Thursday 8 Mar 2018 @ 5:47:21 am from IP #
d.darroch
Member

ilmessaggio said:
1 'With good design and a well built home with appropriate insulation what temperature difference can be achieved between ground floor North facing passive solar rooms and upper level North facing rooms? Looking for a smaller difference as possible.'

Design has very little to do with it....you're dealing with natural phenomena
You should have paid more attention during physics classes.

Of course design plays a part! Yes, hot air will always rise. But good design is much more effective at limiting this temperature increase than poor design.

OP, along with your usual passive design principles, good design would include thinks like;
- avoid voids & open staircases. As these just act like chimneys, pulling warm air upstairs.

- use well sealed doors at the top & bottom of staircases.

- insulate to a high level.

- minimise thermal mass in upper levels, as thermal mass will inhibit night purging in summer. As Catopsilia says, summer minimum temperatures are very similar for both the upper & lower levels, occurring in the early morning. But the upper level is warmer for the rest of the day. So the quicker you can cool of the upper level in the evening the better. Effective nighttime purging required good cross-ventilation, the use of the stack effect, & limiting thermal mass in the upper level (as it will radiate heat well into the night).

Or, embrace a warmer upper level by designing an upsidedown house! Living areas upstairs, bedrooms downstairs.

Posted Thursday 8 Mar 2018 @ 4:58:43 pm from IP #

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