R-Value Estimator

Estimate wall/ceiling R-value using HVAC data and temperature measurements where internal construction is unknown.

1. Space Information & Temperatures

2. Target Component to Estimate R-Value

Select the type and area of the wall or ceiling whose R-value you want to estimate. The internal construction of this component is assumed to be unknown, and its R-value will be calculated from the energy balance.

If provided, calculates R-value based on surface-to-surface temps.

Required if indoor surface temp is provided.

3. Other Heat Gains & Losses (Assumptions)

Important Assumptions:

  • Internal heat gains (from occupants, lights, equipment) and solar heat gains are assumed to be **zero** for this calculation. For best accuracy, take measurements during periods with no internal activity and no direct sunlight.
  • U-values for **other envelope components (windows, non-target walls/ceilings, floor)** are based on typical default values. This is necessary to balance the energy equation. The accuracy of the estimated R-value depends heavily on how well these defaults represent your building.

To accurately estimate the heat transfer through your target component, we need to account for all other heat flows in the space. These values are used as defaults in the calculation.

Typical: 0.3 (tight) to 1.0+ (leaky) ACH

Areas for Other Envelope Components (Default U-Values Used):

Default Window U-Value: 2.8 W/m²K (Double-pane)

Default Other Walls/Ceilings U-Value: 0.5 W/m²K (Insulated)

Default Floor U-Value: 0.3 W/m²K (Insulated)