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U-Value / R-Value Calculator - Building Envelope (Free) Free Building-Envelope Calculator · U-Value · R-Value · Thermal Resistance · Heat Transfer · HVAC Need to calculate the thermal performance of a wall, roof, floor or other building-envelope assembly? This free U-value / R-value calculator calculates the thermal resistance of individual layers and the overall assembly U-value for a multi-layer construction. Enter each material's thickness and thermal conductivity to see how insulation and other layers affect heat transfer. For building-energy analysis, the envelope is often where the heat-transfer calculation begins. A wall can contain plaster, brick, insulation, concrete, gypsum board, air films and other layers, each contributing a different thermal resistance. Adding those resistances gives the total R-value; the reciprocal of total resistance gives the overall U-value. Figure 1 U value and R value calculation tool FREE U-VALUE / R-VALUE TOOL Calculate Mul...

Every wall, roof and floor in a building is a stack of materials fighting to hold heat in — and one number sums up how well they do it: the U-value. Architects, HVAC engineers and energy assessors live by it, because it sets heat loss, heating-system size, and whether a design passes building regulations. But you can't just add U-values — you have to work in R-values (thermal resistance) , layer by layer, then invert. This free U-value & R-value Calculator does exactly that: build up your wall from inside to outside, add the surface resistances, and get the total R-value and U-value instantly — the proper ISO 6946 way. Figure 1 U Value and R Value Calculator Table of Contents The U-value / R-value Calculator U-value vs R-value The ISO 6946 Method Surface Resistances (Rsi & Rse) Thermal Conductivity (Lambda) R-value vs RSI (Imperial vs Metric) What's a Good U-value? Worked Example Common Mistakes FAQ ...

The PMV / PPD thermal comfort calculator on this page implements the Fanger comfort model exactly as defined in ASHRAE Standard 55 and ISO 7730 — the two internationally recognised benchmarks for evaluating the thermal environment of occupied buildings. Rather than judging comfort from air temperature alone, the model performs a full heat balance on the human body using six variables and returns two indices: the Predicted Mean Vote (PMV) , which places the average thermal sensation on a scale from −3 (cold) to +3 (hot), and the Predicted Percentage of Dissatisfied (PPD) , which estimates how many occupants will be uncomfortable. Figure 1 PMV PPD Calculation steps For HVAC designers, building-performance researchers and CFD analysts, PMV/PPD is the standard post-processing metric that turns a temperature and velocity field into a defensible statement about occupant comfort. This calculator is validated against the worked cases in ISO 7730 Annex D, and it pairs natural...