COLUMN BUILDING SCIENCES smoke and fire guys are PHOTO 4 More Compartmentalization Air Sealing. PHOTO 5 Airtight Electrical Box. Putty pads are used to seal electrical Bottom of walls are sealed fabulously well when boxes airtight. Joint compound is used to complete the seal between on the right page. Run the gypcrete floors are used. the electrical box lip and the cut opening in the gypsum board. compartment demising walls to the underside of the floor above and seal them airtight. It should be happening already (Photo 3). The bottom of the walls are typically sealed with gypcrete (Photo 4). Electrical boxes are sealed with "putty pads" and joint compound is used to and typically defeat measures to PHOTO 6 Weather-Stripped Door. A beautiful thing if you are worried about fires. complete the seal between the box control the stack effect through and the cut opening in the gypsum compartmentalization. Balance board. (Photo 5) and compartment is complicated due to the additive doors are weather-stripped (Photo 6). effect of the stack pressures to the Let's say you achieve fan pressures in the exhaust system compartmentalization. You are not duct risers. Since stack pressures done. Now the mechanical engineer vary with temperature, the flows in can screw it all up by running the exhaust systems also vary with ducts and shafts vertically. Try to temperature. The use of constant FIGURE 5 Unit Ventilation. Do not run ducts and avoid central systems. You can't airflow regulators (devices that shafts vertically. No central systems. You can't make them work.# It is easier to maintain constant airflow across make that work. You need to keep the ducts within each compartment and vent directly to the exterior. make things work by keeping the variations in air pressure) can No complaints from your architects about penetraducts within each compartment mitigate this effect to a degree, tions being ugly. Just deal with it. and venting directly to the exterior but are rarely employed and (Figure 5). No complaints from you require extremely high pressures architects about penetrations being within ducts to effectively operate. ugly. Just deal with it (Photo 7). Apartments on upper levels tend We were here before (Multifamily to be over-ventilated during cold Buildings, ASHRAE Journal, December weather since they are both closer to 2005). Distributed ventilation is the the fans and are most subject to the way to go. Ventilation is provided to stack pressure. each individual unit across exterior Shafts acting as exhaust chases walls, not across interior pressure or containing exhaust ducts are boundaries such as floors. Under difficult to seal effectively and this compartmentalization approach significantly complicate fire ventilation is provided by ventilation and smoke control due to the building management and are systems unique to each unit rather development of complex three typically either on all of the time or than by central systems. dimensional airflow pathways and off all of the time. Units are either In practice rooftop central interstitial pressure fields. all ventilated or all not ventilated- exhaust systems are difficult and Central systems are further resulting in over ventilation in arguably impossible to balance limited as most installations do many units and significantly higher not allow individual unit control- # OK, you can make it work but it is significantly more difficult. energy consumption-or under the central fans are controlled by 54 ASHRAE JOURNAL ashrae.org J U LY 2 0 19https://www.ashrae.org/