material void

[S3229558]

Hi,

i have a maybe stupid question.

I want to do a opening between two zones, in particular between a internal zone and a greenhouse.

I tried to use the material : void but i noticed that the u-value is the same of a interspace.

The greenhouse have a normal conduct but the internal zone do not show any contribution from the greenhouse.

The material void is realy void or there is an other way to make it?

thanks and sorry for my english 

Chiara

[Pennetier1 · Accepted solution]

Hello S3229558, 

I think you are on the right track.

The correct way to model your case is to create two separate thermal zones - one is your interior space, the other one is your green house.

Insert a VOID object on both the wall of the greenhouse AND the wall of the interior zone so that the VOID objects overlap each other.

Ecotect will know that that area of the wall is a void and will account for thermal transmission between the two zones. 

Note, however, that the heat gains and losses from the greenhouse to the interior space will be under "Inter Zonal" gains, as the greenhouse is modeled as a thermal zone.  You should be able to track inter-zonal gains and losses in the analysis page of Ecotect, under the Inter-zonal gains - Qz drop down calculation menu; i.e., the interior space will see inter zonal heat gains during the day, and heat losses during the night.

Try it and see it makes a difference.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

[S3229558]

Hi,

Thanks very much for the replay, I did this test but I have the some perplexity.

A question, then if a zone has not  external adjacency  the hourly heat gains /losses grapich shows all gains and losses in "internal zone" and not in "conduction", is right?

My zone has not external adjacency but the grapich shows losses for conduction

Thanks

Chiara  

[S3229558]

Hi,

sorry for my insistence but my bachelor's degree is near ;(

I read the post "trombe wall"and i have a question 

My greenhouse works for convention, between greenhouse and internzone there are vents.

Ecotect do not calculates the convention? Material void exchanges for conduction and not for convention?

thanks very much

best regard 

Chiara

[Pennetier1 · Accepted solution]

Hi S3229558, 

That is correct, Ecotect does not assume convection processes in the calculations, only conduction.

If you have a voids between two thermal zones, Ecotect will assume that there is no thermal resistance between the two zones at this particular area, and you should see some heat exchange between the two zones under the "Inter-Zonal gains/losses graph and calculations. Some zones will gain and lose heat from and to the adjacent zone(s), as in the case of your greenhouse.

If your thermal zone is not adjacent to another zone, you should not see any numbers under the "ZONAL" column (except if your zone is on the ground in which case the heat losses through the slab will show under "ZONAL", but that is in reality conduction losses.  

The "INTERN" column shows the heat gains produced by internal gains such as occupants and other appliances as input for the zone settings under "Occupancy and Operation".  These can only be gains.

The "FABRIC" column shows the heat gains and losses through the external walls, windows, floor and roof of your zone, as conduction with the outside air.

I hope this clarifies things a bit.

Cheers,

[S3229558]

Thanks for the reply!

best regards

Chiara 

[S3229558]

Hi Olivier,

I have another question 

I created my model and my thermal zones in Revit. In Revit, my zones are included between the floor and the ceiling (height net of the room 2,7 m).

When I import the xlm model, it seems to me that Ecotect consider the middle line of the wall, but between the ceiling of the first floor and the floor of the second floor there is a void (corresponding to the thickness of the slab). The zones have the correct height (2,7 m), if I control the property of the ceiling and the floor they are fully exposed.

What is the correct way to proceed ? I must move the second floor in adjacency with the first ceiling and extend the walls of the second level till the first ceiling or I must use the middle line of the slab?

Thank you for your help.

Best regards 

Chiara 

[Pennetier1 · Accepted solution]

Hi S3229558, 

That is a good question.

First of all, I think it is possible in Revit to set your thermal zone so that it uses the internal surface of the walls, not the middle, since it would be more accurate.

For the space in between the zones (the slab), you can either assume that it is part of the zone's roof below or part of the floor of the second zone above; i.e., you use the slab thickness in the overall volume of the zone.  That is not the most accurate method but it is simple.

What I typically do is leave the gap in between the two zones and "fill" it with a partition element like a "skirt" ( I use the partition tool set to the height of the slab) so that no solar gain reach the roof of the lower zone.  Then in the Inter Zonal Adjacency calculations, step 2,  I use a value equal to or higher than my slab thickness, so that even though the floor and ceiling are not physically touching, Ecotect assumes they are.

I hope that makes sense.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

[S3229558]

Thanks for the reply.

My zones in Revit are already inclunding between internal surface of the walls, I believe that Ecotect for dafault considers the middle line of the walls; for the slab I try the two options 😉

Thank you for the help

Best regards 

Chiara 

[S3229558]

I Olivier, I have an other problem 

I don't understand how Ecotect calculates conduction losses.

In zone management - type of system, I put "none"; in confort band 18 °C- 26 °C.

Help guide writes for "upper band" : "...In an unconditioned zone, this specifies the top of the desirable temperature band" and I thought that this value only influenced "confort band graph".

For example, with confort band 18-26, at 8.00 am the temperature of my zone is  2 °C and the conduction loss is 1030 Wh.

If i put in confort band 2 °C- 26 °C and type of system "none", at 8.00 am the temperature of my zone is 2 °C  but the conduction loss is 4 Wh.

It seems that Ecotect calculates conduction loss with the difference between external temperature and confort band temperature and not with the difference between external temperature and real zone temperature show in the graph of temperature. 

There is a way to not consider the confort band temperature but the real internal temperature of zone ? 

Thank you very much

Chiara 

[Pennetier1 · Accepted solution]

Hello S3229558, 

Yes, you are correct, Ecotect uses the lower band of the thermostat setting to calculate both the heating loads when the heater is on, or the comfort level when there is no hvac system. Unfortunately I do not know a way to set it so that Ecotect uses the actual internal air temperature for calculating heat losses.  It does give you a "Total Conductance" value for each zone, and you could multiply that number by the difference of degrees between the outside and inside of the zone, but even then you would not quite get the same numbers as what is calculated in the Hourly Heat Gain Losses because Ecotect uses the Admittance method which is a dynamic method - compared to static steady state method - which compares the hourly interior temperature of the zone with the mean daily outside temperature... It is a bit more complex and take into account the other material properties such as lag and Admittance.

I am attaching a draft document that was given to me by Andrew Marsh a while back and explains quite well the assumptions of the Admittance method.

Sorry I cannot be of more help on that one.

Cheers,

[S3229558]

Thank you for the reply 

Chiara