# [TRNSYS-users] Help needed with Type-56 thermal mass thermal time constatnt problems

Mateo de Guadalfajara mateog at unizar.es
Sun Mar 23 04:39:56 PDT 2014

```Dear Joynal Abedin

Thanks for your question because it makes me to think about concepts of
building physics.

In highly insulated buildings, passive house or NZEB most of the thermal
losses are produced by the ventilation system because the envelope is quite
insulated.

The time constant depends on the ratio between thermal losses and thermal
inertia in the room. If most of the thermal losses are produced by the
ventilation system the thermal inertia of the walls will produce a small
effect.

Reduce your ventilation ratio to a value of 0.6 or calculate the minimum
required ratio for your house according to your national standards or
ashrae.

You can make a quite interesting essay for your house analising the effect
over the time constant of different ratios of ventilation.

Good luck with your research.

El 23/03/2014 10:37, "Joynal Abedin" <J.Abedin at lboro.ac.uk> escribió:
>
> Hi,
>
> I'm simulating a domestic building using Type-56 with three thermal
zones. All the building fabrics such as the external walls are massive with
the correctly defined conductivity, heat capacity and density. However,
when  I simulate the building the thermal response of the rooms appear to
have very low thermal time constant i.e. it changes very rapidly and it
seems that the massive walls with specific heat capacity are not having any
heat storage impact. The capacity value in the Air Zone Regime gets
automatically to 1.2 times the volume of the room. If I manually increase
this value the thermal time constant does increase, but should I be
increasing this value? The main problem I think is that the thermally
massive walls are not having any thermal mass effects on the temperature
response of the rooms. What am I doing wrong? Why is the heat capacity of
the air zone set to 1.2 times the zone volume? One building in TRNSYS17
Example projects have this set to 3 times the Volume.
>
> If anybody as any ideas or suggestions please please email me. Your help
will be very much appreciated.
>
>
>
> Thanking you in advance.
>
>
>
> Kind regards,
>
>
>
> Joynal Abedin.
>
> Loughborough University, UK.
>
>
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at cae.wisc.edu
> https://mailman.cae.wisc.edu/listinfo/trnsys-users
>
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