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hanuman
Posts: 13
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 Posted: Fri Dec 15, 2006 6:02 am Post subject: lightweight roofs and floors |
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Hi
I'm modeling light weight buildings.
The building has an uninsulated vinyl covered timber floor with an enclosed sub-floor 500mm above the ground.
I'm finding the explanation in the help file difficult.
Could someone please explain?
Thanks
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hanuman
Posts: 13
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| Posted: Mon Dec 18, 2006 10:42 pm Post subject: |
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replying to my own post
Could someone check this construction please?
I am confused in the naming of the elements. Roofspace floor slab and semi exterior unconditioned are not terms I'm familiar with.
I have a lightweight building which is 500mm above the ground.
I have created a block for the building and divided it into partitions, a block for the roof space and block for the subfloor space. The walls of the the sub-floor are different to the main parts of the office/toilet block and are only around the perimeter of the building.
I marked the roof and subfloor zones as 'semi exterior unconditioned'.
The floor is uninsulated 19mm particle board.
Underfloor zone:
Floor
- construction of the ground floor slab: 'nothing' created material consisting of a 5 mm air gap.
- no floor fitted above slab
- marked the adjacency 'adjacent to ground'
Walls, changed wall construction to 6mm fibre cement sheet
Roof
- Flat Roof 19mm particle board
- no suspended ceiling
Main building block:
External floor - 'nothing'
Ground floor slab – 19mm particle board
External Wall – set to 75mm thick; colorbond + R2.0 + 10mm gyprock plasterboard
Ceiling – no suspended ceiling
What should the top layer be set to Ceiling/Roof
Roof block:
Pitched roof – steel pitched roof – made light color by changing the emissivity to 0.3
Ground floor slab – 'nothing'
External floor – 'nothing'
Floor fitted above slab - ticked
- Suspended height 0.00
- Floor 10mm gyprock ceiling
- Roofspace insulation R2.0 (66mm glasswool)
Thanks
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Andy Tindale
Posts: 1235
Location: Stroud |
| Posted: Wed Dec 20, 2006 5:37 pm Post subject: |
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| Quote: | | am confused in the naming of the elements. Roofspace floor slab and semi exterior unconditioned are not terms I'm familiar with. |
'Roofspace floor slab' is the main structural construction between the occupied space of the building and the roofspace. It is the internal slab shown in Detail 1 on the 'Construction location' program help topic.
'Semi exterior unconditioned' is (as I suspect you may have worked out) for semi exterior spaces such as roofspaces, conservatories/sunspaces, under building crawl spaces etc. Take a look at the program help for more information on this.
| Quote: | I have a lightweight building which is 500mm above the ground.
I have created a block for the building and divided it into partitions, a block for the roof space and block for the subfloor space. The walls of the the sub-floor are different to the main parts of the office/toilet block and are only around the perimeter of the building.
I marked the roof and subfloor zones as 'semi exterior unconditioned'. |
So far so good!
| Quote: | | The floor is uninsulated 19mm particle board. |
So to model this floor you should set the 'Internal floor slab' to this construction in the occupied space and switch off raised floors. Also switch off suspended ceilings at the building level. You have insulation in the roofspace so you should switch on 'Floor fitted above slab' in the roofspace block and set the roofspace insulation.
| Quote: | Underfloor zone:
Floor
- construction of the ground floor slab: 'nothing' created material consisting of a 5 mm air gap.
- no floor fitted above slab
- marked the adjacency 'adjacent to ground'
Walls, changed wall construction to 6mm fibre cement sheet
Roof
- Flat Roof 19mm particle board
- no suspended ceiling
Sounds about right, though it doesn't matter what you set the flat roof to if there are no flat roof surfaces in the underfloor zone.
Main building block:
External floor - 'nothing'
Ground floor slab – 19mm particle board
External Wall – set to 75mm thick; colorbond + R2.0 + 10mm gyprock plasterboard
Ceiling – no suspended ceiling
What should the top layer be set to Ceiling/Roof |
The ceiling construction between the main building block and the roofspace will be defined by the internal floor slab and the roofspace insulation data assuming you have switched off suspended ceilings. I hope this answers it.
| Quote: | Roof block:
Pitched roof – steel pitched roof – made light color by changing the emissivity to 0.3
Ground floor slab – 'nothing'
External floor – 'nothing'
Floor fitted above slab - ticked
- Suspended height 0.00
- Floor 10mm gyprock ceiling
- Roofspace insulation R2.0 (66mm glasswool) |
Remember the construction model data you set for each surface type is the data used when surfaces of this type are encountered. If for example there is no pitched roof in a zone then the pitched roof construction data is not used. So it shouldn't be necessary to use your 'nothing' construction.
You may find the 'Construction location' program help topic useful in understanding the way constructions are used in DesignBuilder. If you have any further questions about this I would recommend uploading your model so that I can see more clearly what you are trying to do.
Regards,
Andy
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hanuman
Posts: 13
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| Posted: Thu Dec 21, 2006 8:00 am Post subject: buildng model OK, now for the hvac |
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Thanks Andy your a gem!
To summarise.
for a lightweight house.
1. create three blocks: main, subfloor & roofspace
2. mark the subfloor & roof space 'semi exterior unconditioned'
3. barriers between blocks
3.1 building level - switch off suspended ceilings at the building level
3.2 underfloor block - set the floor slab to 'nothing' & adjacent to the ground.
3.3 main block - set internal floor slab to 19mm partical board
3.4 roofspace block - set internal floor slab to 10m gyprock ceiling
3.5 roofspace block - switch on floor fitted above slab in the roof space block and set the roofspace insulation.
They use metal framed studs. How do I approximate the thermal bridging?
I'm doing this to meet a total energy use target for the Australian Building Code.
The builder specifies the size of the heating and cooling plant, split systems of known kW size and COP figs.
I've set the HVAC to compact/manual and the natural ventilation to scheduled.
How do I model the HVAC?
| Description: |
| lightweight recreation room at a mine in a hot dry climate |
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3832_oxana_rec.dsb |
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hanuman
Posts: 13
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| Posted: Wed Dec 27, 2006 4:31 am Post subject: |
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One more thing.
These buildings use metal studwork. Is there a way to approximate the thermal bridging?
Thanks
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hanuman
Posts: 13
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| Posted: Wed Jan 03, 2007 4:00 am Post subject: simple + manual hvac -> capacity |
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Hi again
Still working on the hvac modeling.
I have chosen the following
1. simple hvac
2. manual plant sizing.
(the help file says "2-Manual- heating and cooling capacity Model Data must be entered manually" where is this done?)
3. updated the cop figures for the heating and cooling
4. changed the heating fuel type to electricity.
Q. where do I enter the heating and cooling capacity?
Q. is the capacity in the Auxiliary energy?
Q. Any news on the thermal bridging?
Q. where is the best place to find suitable weather files for Australia?
Hopeful thanks.
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Andy Tindale
Posts: 1235
Location: Stroud |
| Posted: Wed Jan 03, 2007 9:39 am Post subject: |
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| Quote: | To summarise.
for a lightweight house.
1. create three blocks: main, subfloor & roofspace
2. mark the subfloor & roof space 'semi exterior unconditioned'
3. barriers between blocks
3.1 building level - switch off suspended ceilings at the building level
3.2 underfloor block - set the floor slab to 'nothing' & adjacent to the ground.
3.3 main block - set internal floor slab to 19mm partical board
3.4 roofspace block - set internal floor slab to 10m gyprock ceiling
3.5 roofspace block - switch on floor fitted above slab in the roof space block and set the roofspace insulation. |
This sounds reasonable.
| Quote: | | They use metal framed studs. How do I approximate the thermal bridging? |
There is no easy way to explicitly represent this sort of thermal bridging in EnergyPlus. You can define thermal bridged elements by drawing subsurfaces in walls at the surface level, though this is probably not appropriate for modelling metal framed studs.
Another option is to use an existing software utility to generate simplified equivalent construction layers for a bridged construction. I can't remember what this utility is called, or whether it is generally available but if you are interested in using this approach I can find out more for you.
| Quote: | | Where do I enter the heating and cooling capacity? |
You can enter the heating and cooling capacity at the zone level under the Heating and Cooling headers on the HVAC tab. There is no way to set boiler/chiller capacity - this is taken as the sum of the individual zone capacities.
| Quote: | | Is the capacity in the Auxiliary energy? |
No, the Auxiliary energy represents energy consumption of fans, pumps, control gear and any other auxiliary equipment used to operate the HVAC system.
| Quote: | | Where is the best place to find suitable weather files for Australia? |
I assume you are asking this question because the Australian weather files supplied with DesignBuilder do not meet your requirements. DOE will be making available a large range of hourly weather data for Australia soon, and it may be worth contacting them now to see if they already have the data you require:
EnergyPlus-Support@gard.com
I hope this helps.
Regards,
Andy
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hanuman
Posts: 13
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| Posted: Wed Jan 03, 2007 12:15 pm Post subject: thermal bridging |
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Thanks for your reply!
I'm keen to estimate the thermal bridging. The reason for modeling the buildings is to get away from having to install the thermal break prescribed by the code.
Q. How much effect does it it have?
Q. Can you point me in the right direction for approximating the effect please?
Best regards
Jim
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Andy Tindale
Posts: 1235
Location: Stroud |
| Posted: Thu Jan 04, 2007 2:55 pm Post subject: |
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Jim,
I don't know much about calculation methods for estimating thermal bridging, but do have a couple of ideas:
1. A web site provided by ORNL provides an online R-value calculation procedure to allow you to estimate the effect on R-value of metal studs with insulated cavities:
www.ornl.gov/sci/roofs+walls/calculators/modzone/modzone2.html
2. DesignBuilder allows you to set up bridging across individual layers in constructions and it calculates R-values which include the effects of this bridging using ISO 6946 calculation method.
EnergyPlus does not allow bridged layers so this bridging data is not used in EnergyPlus simulations but if you need to find the effect of bridging on energy consumption, you could use this to calculate the necessary R-value and set up a new construction having this R-value (by trial and error).
I will contact some of my colleagues to see if they have any other suggestions.
Regards,
Andy
Last edited by Andy Tindale on Thu Jan 04, 2007 6:22 pm; edited 1 time in total |
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Gustafson
Posts: 36
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| Posted: Thu Jan 04, 2007 4:48 pm Post subject: Default wall cavity values |
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Greetings:
You've probably got this data, but the PDF attached is from our local energy code and gives you wall cavity values that include thermal bridging.
Hope this helps.
| Description: |
| Default "R" and "U" values. Watch the units, these are "IP". |
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Download |
| Filename: |
MetalDefault.pdf |
| Filesize: |
222.46 KB |
| Downloaded: |
625 Time(s) |
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