It should include the number of people who will actually be in the space, as opposed to the maximum allowed by the fire code or the capacity of the parking lot. Concrete slabs, stone walls or floors, and other massive building elements, when they exchange heat with the ventilation system or the building s exterior, can buffer peak loads and take advantage of cool night temperatures or warm afternoons. We always try to use a passive design approach when the owner is interested in environmental issues, says mechanical engineer Sarah Nicholson. Although the insulating value of a building s walls might seem to be a big factor in determining heat gain, it doesn t matter much for most commercial buildings. That s because cooling load is dominated by internal loads and solar gain.
Insulation does, however, have an impact on winter heating load.
Then temperature differentials between indoor and outdoor air can easily reach 60 or 70 degrees. Roof insulation is crucial, since the sun beats on the roof all day. For large single-story buildings in southern climates, heat transfer through the roof can amount to as much as 30 percent of total cooling load, and higher insulation values are warranted. Engineers as friends Aside from making better design decisions, architects can work with engineers to avoid oversized HVAC systems by expressing interest in the central plant design. If the engineer knows that the architect and the owner want a realistic system, instead of one that guarantees the absolute comfort of occupants, everyone can work together more responsibly.