Residential Energy Efficiency & Load Calculations Flashcards

A geothermal designer notes that a home has a high window-to-wall ratio on the south facade. How should this affect load calculation?

Answer: Increase both heating and cooling loads due to greater conductive and solar gain area

Large south-facing window area increases winter conductive heat loss and summer solar heat gain, raising both heating and cooling loads.

The 'balance point' of a building is best defined as:

Answer: The outdoor temperature at which internal gains equal heat losses, requiring no heating or cooling

The building balance point is the outdoor temperature at which internal heat gains exactly offset envelope losses, requiring no mechanical heating.

Which of the following insulation locations has the greatest impact on reducing heating loads in a cold climate home?

Answer: Ceiling/attic insulation

Ceiling/attic insulation addresses the largest area of heat loss in most homes and benefits from stack effect and the large temperature differential at the top of the thermal envelope.

In hot-humid climates, latent loads typically represent what approximate percentage of total cooling load?

Answer: 30–50%

In hot-humid climates like the southeastern US, latent (moisture) loads commonly represent 30–50% of total cooling load, making dehumidification a critical design factor.

Which factor is NOT typically included in the internal heat gain component of a residential cooling load?

Answer: Ground loop pump heat rejection

Ground loop pump heat is a system efficiency parameter, not an internal building heat gain source used in Manual J cooling load calculations.

What effect does adding thermal mass (e.g., concrete floors) have on peak cooling load calculations in a well-designed passive solar home?

Answer: It reduces peak cooling load by absorbing and time-shifting solar heat gains

Thermal mass absorbs solar heat during the day and releases it slowly, flattening the peak load curve and reducing the maximum cooling demand.

The Manual S procedure, used after Manual J calculations, is specifically designed to:

Answer: Select properly sized HVAC equipment based on calculated loads and performance data

ACCA Manual S uses the Manual J load results along with manufacturer performance data to select correctly sized heating and cooling equipment.