Formula Used
The calculator converts entered units into consistent SI values. It then applies surface, layer, and bridge adjustments. Final results support practical wall performance comparisons and planning.
How to Use This Calculator
Select a known thermal value or build wall layers. Enter every wall, opening, and design temperature carefully. Then review heat loss, costs, upgrades, and required insulation.
- Choose a calculation mode and preferred units.
- Add each wall or multiply identical wall sections.
- Subtract windows, doors, and other openings.
- Enter temperatures and thermal bridge allowance.
- Build layers or enter a known thermal value.
- Add energy prices and insulation assumptions.
- Calculate, copy, print, or export the results.
Example Material Data
| Material | Typical conductivity | Common thickness |
|---|---|---|
| Mineral wool | 0.037 W/m·K | 50–150 mm |
| Fiberglass insulation | 0.040 W/m·K | 50–200 mm |
| EPS insulation | 0.036 W/m·K | 25–150 mm |
| XPS insulation | 0.030 W/m·K | 25–150 mm |
| Common brick | 0.720 W/m·K | 100–230 mm |
| Reinforced concrete | 1.700 W/m·K | 100–300 mm |
| Gypsum board | 0.170 W/m·K | 9–16 mm |
Published properties vary with density, moisture, and temperature. Confirm project values using reliable manufacturer or code data. Accurate material values improve every thermal calculation and decision.
Assumptions and Limitations
This tool estimates steady, one-dimensional heat transfer through walls. It excludes uncontrolled air leakage, solar gains, and moisture transport. Framing paths and bridge allowances remain simplified engineering adjustments.
- Wall construction is uniform across each entered area.
- Indoor and outdoor temperatures remain constant.
- Surface resistances are user-adjustable engineering assumptions.
- Heating cost uses constant efficiency and energy price.
- Payback excludes financing, maintenance, and price escalation.
Frequently Asked Questions
What does U-value mean?
U-value measures heat flow through one square unit. Lower values indicate stronger resistance to heat transfer. Better insulation usually produces a lower overall U-value.
What does R-value mean?
R-value measures resistance against heat moving through construction. Higher values indicate stronger resistance and improved insulation. The calculator converts supported imperial values into SI units.
Should openings be deducted?
Yes, deduct windows, doors, and other wall openings. Their heat loss should be calculated with separate U-values. This prevents double-counting opaque wall transmission in totals.
Why include surface resistances?
Air films resist heat transfer at wall surfaces. Their values depend on orientation and surrounding airflow. Editable fields support different standards and project assumptions.
How are thermal bridges handled?
The calculator increases U-value using a percentage correction. This provides a simple allowance for junction losses. Detailed projects should use code-based bridge calculations instead.
Can I calculate several walls?
Yes, add separate wall records with different dimensions. Each record can include identical wall quantities and openings. Results show both combined and wall-specific heat losses.
Does the calculator include air leakage?
No, this calculator covers conduction through wall construction. Infiltration and ventilation require separate airflow heat-loss calculations. Combine both values for complete building heating loads.
How is annual cost estimated?
Heat loss becomes energy using selected operating hours. System efficiency converts delivered heat into purchased energy. The energy price then produces estimated heating costs.
What does required insulation thickness mean?
It estimates added thickness needed for the target U-value. The result uses the proposed material conductivity entered. Real designs must consider moisture, fire, and constructability.
Can results replace professional design?
No, results provide planning and educational estimates only. Building codes may require certified methods and product data. Consult qualified professionals for final construction and compliance.