CEM HVAC and Building Envelope 5

Question 1

In a blower door test, what does a lower ACH50 value indicate?

Accepted Answer

Better building envelope airtightness

Answer

ACH50 is air changes per hour at 50 Pascals of pressure; a lower value means less air leaks through the envelope, indicating a tighter, more energy-efficient building.

Question 2

What is 'chiller staging' and why is it important for energy efficiency?

Accepted Answer

Operating multiple chillers to match load while keeping each near its optimal efficiency point

Answer

Proper staging ensures chillers operate at high part-load ratios where efficiency is greatest, rather than running one chiller at very low load where efficiency degrades.

Question 3

A roof's thermal emittance and solar reflectance index (SRI) are important for which energy strategy?

Accepted Answer

Cool roof implementation to reduce cooling loads

Answer

High SRI roofs reflect solar radiation and emit absorbed heat efficiently, reducing roof surface temperature and cutting cooling loads for the conditioned space below.

Question 4

What is the 'stack effect' and how does it affect building energy use?

Accepted Answer

Buoyancy-driven air movement that increases infiltration in tall buildings during winter

Answer

The stack effect occurs when warm indoor air rises and escapes at the top of a building, drawing cold outdoor air in at lower levels, increasing heating loads particularly in tall buildings.

Question 5

Which measure is most effective for reducing peak cooling demand from solar heat gain through east- and west-facing windows?

Accepted Answer

Adding exterior shading devices such as fins or overhangs

Answer

Exterior shading intercepts solar radiation before it strikes the glass, far more effective than interior shading which allows heat to enter and be trapped between blind and glass.

(CEM) Certified Emergency Manager Practice Test

(CEM) Certified Emergency Manager Practice Test

CEM HVAC and Building Envelope 5