Automated Shades for Multi-Family Housing

Not multi-family (though we do have some with manually operable exterior shutter/screens), we have at least two projects with automated exterior blinds, the UCSD BioMedical Research Facility 2 and the RMI Innovation Center, and another in construction. Both use similar exterior blinds guided by cables (Warema, Hunter Douglas and Draper all manufacture), thought their operation and management are different. UCSD: as a high ventilation research lab in a cooling climate, blind management is for 100% glare control – blinds are controlled by a geo-located sun position calcs system and light sensors to override during cloudy/foggy weather. This also eliminates any excess ventilation increases for solar load cooling, but as a lab, the system has excess capacity if needed (like for increased fume hood makeup). RMI: blinds are managed for passive cooling and heating as primary conditioning strategies, which means the control system is based on not only the cloud conditions and known sun position, but also exterior and interior temps to maintain comfort (passive gain only when we need it). In neither case, am I aware that occupancy factors in the controls, but would seem possible if you can let conditions drift and expect the space to be unoccupied on weekends or the like. For UCSD, the energy savings would be relatively trivial, but solar management is a critical energy strategy for RMI. I would need to double check with the MEP, but I’m pretty sure we created a schedule for blind deployment based on conditions, and it would seem depending on the modeling program you could either add this an operable shading device (some might allow rules within the program to control deployment), or you might have to modify the weather file or do other post-processing. System will likely never pay back based on energy savings, but could make a financial case based on reduced/eliminated conditioning systems (like at RMI) – though this would obviously require buy-in from the whole team to make this work – or additional daylight/productivity benefits. Chris Flint Chatto AIA, LEED AP BD+C Principal ZGF ARCHITECTS LLP T 503.863.2324 E chris.chatto@zgf.com 1223 SW Washington Street, Suite 200 Portland, OR 97205 From: D

We did this about twelve years ago.  We used mecho shades, who had the whole system, sensors motorized shades etc.  Worked well.

The energy modeling piece depends on the basis of design product and associated controls. whichever manufacturer selected depending on the control system for the blinds should hopefully be able to produce an 8760 schedule which could be incorporated into the energy model. From a payback standpoint it's possible (though admittedly unlikely) that your  mechanical engineer would be willing to downsize equipment due to reduced peak cooling loads with blinds in place that could result in some first cost savings as well. 
  (forgive me for typos, sent from my phone).

Keep in mind that interior shades don't necessarily reduce cooling loads in spaces; they primarily concentrate that heat in the pocket between the shade and the window.  Due to buoyancy effects, that hot air will spill out of the top of the shade zone and into the space.  This is likely the case in a multi-family designs, so the dwelling unit heat pump would need to remain the same size.  That's not to say that interior shades don't provide some cooling relief, particularly by reducing or eliminating solar radiant heat on occupants.  Alternately, in more commercial environments (e.g. offices), you can design a return from that shade pocket and displace that cooling load to the plenum and back to the cooling coil (same cooling capacity central equipment) and might be able to reduce the size of the zone supply.   Exterior shading devices can actually reduce the cooling load experienced inside the building (both zone and central levels), but introduce their own set of opportunities and challenges architecturally. 

Right on, Patrick.  And then there's the option of electrochromic glazing... though in a residential setting doesn't really achieve privacy goals in residences, but maybe an option for common areas. We've seen some reasonable paybacks for EC glazing since you can actually account for heat gain reductions (and shading system savings). Again, in more of a commercial application.  

The electrochromic glazing is GREAT for reducing cooling loads and peak electrical demand (we have seen 8-10% reductions) - but it actually increases heating energy.  (the shaded glazing blocks solar energy which would benefically heat a building).  Depending on the climate and the fuel use for heating/cooling energy, the use of ECG may have an inverse effect, energy/carbon wise.    My suggestions is that if its being considered, make sure a robust energy modeling effort is completed to understand the full story.

Whatever you do, don't let fully automated window shades justify a high WWR...

One relatively cost-effective strategy can be to use “perimeter extraction” which incorporates a small exhaust duct connection into the head of the window shade roller assembly – MechoShade has a version. The hot air trapped between the shade and glazing gets sucked out before it can infiltrate the space and increase the overall radiant temperature of the interior elements (like floors, walls). This is especially effective in existing buildings with poor performing glazing, but it could work here if you’re able to deploy it without a lot of additional exhaust ductwork. We’ve never done this in a multi-family context to my knowledge, but since multi-family units typically constantly exhaust to a small degree, it may work well, though it would be ideal to have controls on it to turn off the exhaust when the windows are open for instance. I’m not sure exactly how our mechanical engineers have modeled this approach in the past except that I think they’re modifying the SHGC of the windows to account for the fact that the incoming solar gain is being mitigated. Hope this helps in some small way! From: Tate Wa