HERS Ventilation & Indoor Air Quality 2

Question 1

An HRV (Heat Recovery Ventilator) differs from an ERV (Energy Recovery Ventilator) in that an HRV:

Accepted Answer

Transfers only sensible heat between airstreams without transferring moisture

Answer

An HRV uses a heat exchanger core that transfers only sensible (temperature) energy, whereas an ERV core also transfers latent energy (moisture) between airstreams.

Question 2

In which climate condition is an Energy Recovery Ventilator (ERV) generally preferred over a Heat Recovery Ventilator (HRV)?

Accepted Answer

Hot-humid climates (IECC zones 1-3) where moisture control is critical

Answer

In hot-humid climates, an ERV's ability to transfer moisture from the humid incoming air to the drier exhaust air reduces latent cooling loads, making it preferable over an HRV.

Question 3

A supply-only ventilation system in a hot-humid climate can create which building science concern?

Accepted Answer

Pressurization that drives warm humid air into wall cavities, risking moisture damage

Answer

Supply-only systems positively pressurize the home, which in hot-humid climates can push warm, humid outdoor air into wall assemblies, creating condensation and moisture damage risk.

Question 4

An exhaust-only ventilation system draws outdoor replacement air into the home primarily through:

Accepted Answer

Intentional envelope leakage paths and passive fresh air inlets

Answer

Exhaust-only systems depressurize the home, causing outdoor air to infiltrate through envelope leakage paths and any intentionally installed passive makeup air inlets.

Question 5

What is the typical sensible heat recovery efficiency range for a quality residential HRV unit under rated conditions?

Accepted Answer

70–85%

Answer

Quality residential HRV units typically achieve 70–85% sensible heat recovery efficiency, significantly reducing the energy needed to condition incoming fresh air.

(HERS) Home Energy Rater Certification Practice Test

(HERS) Home Energy Rater Certification Practice Test

HERS Ventilation & Indoor Air Quality 2