StefanG's profile - activity

I had no issue in California getting my PE license as a full-time building performance analyst. This might differ from s

The air speed input for thermal comfort calcs is not something you'll find as an energyplus output. This is the local ai

You might be interested in the Rhino/Grasshopper script Butterfly. It is a basic GUI for OpenFOAM and I believe there ar

@poppo92

I'm not sure, but I think the max wind speed is only for closing the windows during high wind events for safety issues. I don't have a good number on hand but I would set as a sufficiently high number to allow natural ventilation to occur most of the times you want it and rely on temperatures to control when the windows open and close.

If you're referring to the indoor velocity for use in thermal comfort calculations, ASHRAE standard 55 lays out the criteria in section 5.3.3. Essentially it's as follows:

• if using natural ventilation, max allowable airspeed is 0.8 m/s
• if occupants have user-controllable fans, the maximum airspeed is 1.2 m/s

Anecdotally I've heard that that above 0.6 m/s there are issues with papers getting thrown around.

The minimum and maximum indoor temperatures describe when the windows are allowed to open, so when the interior temperatures drop below 22C, the windows close. When temperature go above 26C, the windows also close.

In your model, i'm guessing in the summer your indoor temperatures will at some point go above 26C, since naturally ventilated buildings typically will float this high in most climates. The windows all close at this point, but since you still have internal gains and envelope gains which contribute heat to the building, causing the temperature to continue to rise.

Since the windows are closed and there is no HVAC system, there is no way for the building to lose heat, so heat perpetually increases in the space until the climate has cooled enough to allow the building to cool below 26C and your windows are able to open again.

In the winter, your windows stay open until the building drops below 22C, in which case the windows close. The building still loses heat through the envelope however, so the air temperatures inside fall below the 22C threshold.

I would suggest looking into adding controls for the outdoor temperature as well as in the indoor temperature. Maybe switch your 26C limit to the outdoor temperature limit so that the windows are able to be opened in the summer.

Thanks @MatthewSteen, sounds like it's in development for EnergyPlus currently, good to know!

The Washington Energy Code for 2015 has a new prescriptive requirement for providing ventilation via Dedicated Outside Air System (DOAS). http://www.energy.wsu.edu/BuildingEff...

Section 407 of this code defines the baseline or standard HVAC system - for an air-cooled condenser it's packaged rooftop air conditioner unit, with a footnote clarifying that spaces must receive ventilation air through a separate DOAS system. From what I understand, EnergyPlus and OpenStudio are unable to model thermal zones which are connected to more than one air-loop. In that case, it's impossible to model both a central DOAS system with recirculating packaged rooftop air conditioner both connected to a zone in EnergyPlus. Does anyone have a solution to this modeling issue?

I'm trying to implement electrochromic glass in an OpenStudio 1.10 model as switchable glazing under shading controls, but I noticed that the shading controls had no effect on energy performance. After digging into the IDF, I found that the setpoint for solar gain on the windows to activate the switchable glazing was 5,000 W/m2. I have not had this problem previously in OpenStudio 1.9, so it seems that this is a new issue with OpenStudio 1.10. Has anyone else encountered this?

Find my OSM here: https://www.dropbox.com/s/s4wxmjvocli...

Heat pumps work by removing heat from a large space (outside air, or in your case a water loop) and moving it to the indoor space. An air-cooled unit is able to absorb heat from the outside air when providing heating. Your water cooled VRF is absorbing heat from your loop, which then must be made up by the boiler. Essentially it is the boiler that is providing the heating for your building, and the VRF units are just moving that heat around throughout the building, this is why the energy is so much greater. Water-cooled units normally work best with a geo-thermal loop to reject/absorb heat to.

The VRF with DOAS measure in the online BCL would be a good place to start. It will add VRF cassettes to all of your zones, and connect them to condensing units. This measure also creates air-loops to provide moderated temperature outside air to all spaces. It may be helpful to run this measure and look at the VRF section under the "HVAC Systems" tab to see how it's all set up.