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increase in heat loss with more insulation thickness.

asked 2024-02-10 21:59:48 -0600

Houri's avatar

updated 2024-02-12 07:27:31 -0600

I am using energyPlus to see what is the impact of insulation thickness on thermal transmission load (heat gain and heat loss) in a thermal mass material. In AZ climate, I get increase in the amount of heat loss with increasing insulation thickness. and when I checked back OpenStudio results, I noticed that this happens in non winter months. I am using the med-office building as the base model of DOE and just changing the wall material. Any clue why this is happening? Also this does not happen in cold climate simulation

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answered 2024-02-11 14:09:14 -0600

Jamie Sullivan's avatar

This could be caused by ventilation or cooling clashes. It's something I've encountered before when trying to implement Airflow Networks. If you have a high ventilation rate (as an airflow network with good cross-ventilation can easily produce, for example) then it can create a problem where increasing the insulation levels makes the model warmer, which causes the ventilation setpoint to be triggered in cooler weather, and the high ventilation rate kicks in and drops the zone temperature below the heating setpoint. At which point, EnergyPlus turns the heating on, and the result is that it claims that increasing insulation levels increases heating loads.

I don't know if your situation is exactly the same as this, but I would suggest looking at your ventilation rates and cooling and see if they're turning on at the same time - or close to - as your heating. If so, you'll need to look at their controls.

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Jamie, how did you resolve the issue in your simulation? Could you advise how I can adjust the ventilation rate?

Houri's avatar Houri  ( 2024-02-17 16:11:26 -0600 )edit

Well, if you're using the AFN then the answer is to use the EMS to create a better control system - see my answer here. This is a complicated solution, and I would suggest thinking about how much you actually need to use the AFN.

Similar, though simpler, EMS scripts can also be applied to simple zone ventilation objects to prevent clashes if desired. Though the easiest option in that case is to just lower your ventilation rate.

Jamie Sullivan's avatar Jamie Sullivan  ( 2024-02-18 16:50:40 -0600 )edit

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Asked: 2024-02-10 21:59:48 -0600

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Last updated: Feb 11