HERS Building Science Principles 5

Question 1

According to building science principles, why is it important to align the air barrier, thermal barrier, and vapor control layer in a building assembly?

Accepted Answer

To prevent misalignment from creating moisture traps and thermal bypasses that degrade performance

Answer

To reduce material costs by combining functions into fewer layers

Answer

To comply with fire code separation requirements between layers

Answer

To ensure that insulation can be inspected by code officials

Question 2

What is 'exfiltration' in the context of building air leakage?

Accepted Answer

Conditioned air leaking out of the building through gaps in the envelope

Answer

Outdoor air leaking into the conditioned space

Answer

Air transfer between floors through penetrations

Answer

The movement of radon gas from the soil into the building

Question 3

In building science, what does the 'Pressure Boundary' of a house define?

Accepted Answer

The continuous plane that separates the conditioned interior from the unconditioned exterior

Answer

The boundary where wind-driven rain pressure is highest on the facade

Answer

The foundation wall depth required to resist hydrostatic pressure

Answer

The interface between duct insulation and the air handler cabinet

Question 4

What is the primary risk of installing a vapor-impermeable material on BOTH sides of a wall assembly?

Accepted Answer

Any moisture that enters the assembly has no drying pathway and can accumulate

Answer

The wall will have too high an R-value for the climate zone

Answer

Wind washing will degrade the insulation performance faster

Answer

The wall will experience thermal bridging through the impermeable layers

Question 5

Which climate-related factor most influences whether a HERS rater recommends a vented or unvented attic assembly?

Accepted Answer

The climate zone, humidity levels, and roof geometry

Answer

Annual heating degree days only

Answer

The local wind speed and prevailing wind direction

Answer

The age of the existing HVAC equipment in the attic

Question 6

What is 'wind washing' in an insulated building assembly and why is it problematic?

Accepted Answer

Air movement through or behind air-permeable insulation that reduces its effective R-value

Answer

Rain water driven by wind across the exterior cladding surface

Answer

The process of pressure-washing exterior surfaces before applying new cladding

Answer

Infiltration of wind-driven debris into attic vents

Question 7

How does the 'stack effect' influence air leakage patterns in a multi-story home during winter?

Accepted Answer

Warm air rises and exits near the top of the house, drawing cold exterior air in at the bottom

Answer

Cold dense air rises and exits at the bottom of the house, pulling warm air in at the top

Answer

Pressure differences are equalized across all floors due to interior air mixing

Answer

The stack effect only applies to commercial high-rise buildings, not residences