Glazing & Winter Comfort Tool


I understand that the Glazing & Winter Comfort Tool (as found on Hydra) represents the impact of glazing geometry and U-value on occupant thermal comfort during winter months with NO perimeter heat…is there the potential to modify the script to show the same impacts with various added levels/capacities of perimeter air DISTRIBUTION (i.e., slot diffusers, etc.)?

I saw this post (Effect of convector in comfort maps) that focused on convectors and potentially changing HVAC systems types to radiant, but is anything on conditioned airflow an option in the script to analyze? i’m assuming the base script does not assume perimeter air distribution (slot diffusers) in addition to perimeter heating?

@josh.greenfield ,

Good question. In the past, I was able to model the effects of radiant metal panel perimeter heating systems by combining elements from this version of the Glazing and Winter Comfort Tool with an energy model and this example that shows how to make custom radiant system. Admittedly, you might have to do some manual editing of the OpenStudio model to ensure that both the radiant panel and whatever central heating system are both in the model (or you might be able to use IronBug to set up such a HVAC system at this point). If the radiant panels are the only heating system in the space, though, you wouldn’t have to do any of this.

For the specific winter design day case that I was studying in the climate of Boston, a ceiling-mounted radiant metal panel with 180F water was able to heat double-pane glass to about the same temperature that the window would be with triple pane and without any perimeter heat.

Convectors are a bit of a different animal since (true to their name) they try to heat the window through convective heat transfer in addition to (some) radiant heat transfer. EnergyPlus has pretty robust methods for modeling radiant heat transfer and so the results that I got for the radiant panel were pretty trustworthy. However, for convectors, you would need to do some investigation into:

  1. How much they might change the film coefficients on the interior side of the window. For passive convectors, this is probably not much but, for slot diffusers, the air speed of the output jet will degrade the resistance of the air film and heat the glass surface more.
  2. What temperature the air off of the convector or in the jet is at. With a jet, you probably have a supply air temperature that you are designing to that will help here but it will involve a little more effort to figure it out for a passive convector.

Suffice it to say that, if you can nail down those two parameters, you can come up with an estimate of interior glass temperature using this component that does a steady-state calculation to determine surface temperature. Then you can proceed using the Glazing and Winter Comfort script as you normally would to at least understand a “worse case scenario” of discomfort. Admittedly, convectors would also likely counteract the downdraft that is being modeled in that script but, if you know that the glass is warm enough for people to be comfortable even with the downdraft, you are in the clear.