Hours of passive surviveability - energy stored in a building?

Hi all

Following this graph I ask myself and now you all if there is a way to figure out how long a building can last until it reaches a certain temperature.
For example how long it takes until the temperature is down from 20 to 17C?

Is there a way to calculate hours of passive surviveability with Ladybug Tools - EnergyPlus?

Are there ways to get the present amount of energy stored in a building?
Maybe Output variables I can ask for?

1 Like

I’m curious as to how this passive survivability is defined. Any input will be highly appreciated.

There’s no official definition of “passive survivability hours” that I know of but I usually try to assess this by running an energy simulation for the extreme_hot_week or the extreme_cold_week from the LB Import STAT component. I’ll create a thermostat setpoint schedule such that the space is conditioned on Sunday (the first day of the simulation) but not any other days of the week. Then, I’ll look at what happens to the interior operative temperature as the week progresses to get a sense of how long the conditions in the building are tolerable. Of course, “tolerable” has a bit of a subjective meaning and it isn’t nearly as well defined as “comfortable” but, if I want to assess whether the space is occupiable at all, I might use the “heat stress” or “cold stress” categories of the UTCI model.

2 Likes

Hi @chris,
Your assumption using the UTCI for interior spaces is that, for this survivability, it is like outdoors?
The limits are too large (9-26 C). Can be interesting to assess this also with the adaptabilty model.
-A.

Somewhat. I just know that both the PMV and Adaptive models can only assess thermal comfort. They were developed without any data for extreme levels of heat or cold stress and so they really cannot inform questions about survivability or mortality risk under extreme conditions.

On the other hand, the “heat stress” and “cold stress” categories of UTCI are used by meteorologists to give severe weather warnings and they were developed using simulations of human physiology that could properly account for dangerous conditions that affect the core body temperature of human subjects. Granted, the underlying assumptions of UTCI are not an ideal match for indoor survivability since UTCI assumes that human subjects are walking and have a corresponding metabolic rate. But UTCI is still probably the best model we have right now for this case and it’s definitely a much better fit than trying to figure out what PMV corresponds to deadly heat/cold stress.

Well @chris & @AbrahamYezioro, it is for sure a possibility to go for extreme conditions.
But in my experience good clothing and a well isolated feather bed is working well for some time even at -20C.

Survivability is a strong term. The way I thought about it is more like if I for example build a house without heating then I’d like to know what are the worst conditions I have to face.
Or the other way round, how do I have to isolate the building to “survive” the cold period wearing one more layer of clothing while working seated at lets say 17C.

I kind of agree with you @Martin6 , survivability is a strong world when we get into buildings. Thousands of years mankind built shelters (maybe that under this basic principle, survivability was a goal, but still i’m sure it was more and beyond that). Now we speak about comfort. So maybe the question to be asked is how long can you be in a building without any mechanical aids. It can be livable? I know more than one building that after the mechanical systems failed it was almost impossible to stay indoors. Not sure the term to use here is survivability. I can also recall older people dying in France during harsh heat waves a few years ago.
The question maybe well deserves some research …

-A.

Hey all,

Speaking from the experience of designing heating systems in cold climates, the survivability may be interpreted as how long the thermal mass of a building can store the heat when there is an outage of heat supply. The criteria is the building materials not get permanent damage, which can be not getting condensation between the layers of materials.

It can be something like having enough thermal mass to withstand two days of no heat supply, in case there is an accident on a power station.

Cheers
D

Hello @chris I liked your recommendation on setting the schedule off. I am doing something very similar survivability study, and I wonder how you set the schedule to “off”. When I try to do this, and I connect it to the HB_Apply_Room_Schedules component, it does not like it. See simplified file attached.


Survivability Schedule Issue.gh (93.0 KB)

You are setting the heating/cooling to 0 instead of shutting them off.
-A.

@AbrahamYezioro how though?

I can think about 2 options:

  1. Set rooms as unconditioned
  2. Set heat/cooling availability to a 0 schedule.
    Like so:

-A.

Fantastic! thanks! this worked